Prying of a Large Span Base Plate Undergoing a …...ix Figure 4.32: Test 06 Shape of deflection in...

Prying of a Large Span Base Plate Undergoing a Moment

Load Applied by a Round Pier

by

Anastasia Wickeler

A thesis submitted in conformity with the requirements

for the degree of Masters of Applied Science and Engineering

Graduate Department of Mechanical & Industrial Engineering

University of Toronto

© Copyright by Anastasia Wickeler 2017

ii

Prying of a Large Span Base Plate Undergoing a Moment Load

Applied by a Round Pier

Anastasia Wickeler

Masters of Applied Science and Engineering

Graduate Department of Mechanical & Industrial Engineering

University of Toronto

2017

Abstract

Large span base plates with a moment load applied, in any direction, to the centre of the

plate by a round pier are commonly used in the design of anchors for façade access systems.

There is no current method of predicting the behaviour of these large span plates under a

moment load. Six anchor base plate configurations are physically tested. The deflection of

the plate is analysed using digital image correlation (DIC) to track the change in location

of points on the base plates under various applied loads. The shapes are plotted and used

to determine at what point the plates transition from linear to nonlinear deformation. A

method of predicting the moment resistance of the base plates for each test was proposed

and a finite element model for the base plates was analysed and validated using the test

data.

iii

Table of Contents

Chapter 1 Introduction ........................................................................................................... 1

1.1 Safety Anchor Design ................................................................................................................. 1

1.2 Thesis Objectives ......................................................................................................................... 2

1.3 Thesis Organization .................................................................................................................... 4

Chapter 2 Background and Literature Survey................................................................ 5

2.1 Safety Anchor and Davit Base Plate Introduction ............................................................ 5

2.2 Types of Base Plate Connections ............................................................................................ 7

2.2.1 Modelling of Cylindrical Steel Structures to Concrete Foundations .............................. 8

2.2.2 Modelling of Column Base Plates to Concrete Foundations ........................................... 10

2.2.3 Modelling of Beam to Column Bolted Connections ............................................................ 11

2.3 Modelling Issues and Limitations ....................................................................................... 13

2.4 Summary ...................................................................................................................................... 14

Chapter 3 Experimental Setup .......................................................................................... 16

3.1 Introduction to the Experimental Setup .......................................................................... 16

3.2 Test Objectives .......................................................................................................................... 16

3.3 Measuring Techniques and Equipment ............................................................................ 17

3.3.1 Deformation Measurements ........................................................................................................ 17

3.3.2 Strain Measurements...................................................................................................................... 20

3.4 Safety Anchor Configurations and Geometry ................................................................. 22

3.5 Test Frame .................................................................................................................................. 24

3.6 Summary of the Complete Experimental Setup with Equipment ............................ 27

Chapter 4 Analysis of Experimental Testing: Anchor Plates Under Moment Load

...................................................................................................................................................... 30

4.1 Experimental Testing Overview .......................................................................................... 30

4.2 Test 01: Four bolts base plate connection; horizontal load parallel to the

supporting HSS ................................................................................................................................. 30

4.2.1 Test 01 Setup ..................................................................................................................................... 30

4.2.2 Test 01 Strain Gauge Data and Analysis ................................................................................. 31

4.3 Test 02: Four bolts base plate connection; horizontal load at a 45° angle relative

to the supporting HSS ..................................................................................................................... 38

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4.3.1 Test 02 Setup ..................................................................................................................................... 38

4.3.2 Test 02 DIC Data and Analysis .................................................................................................... 39

4.4 Test 03: Four bolts base plate connection; horizontal load perpendicular to the

supporting HSS ................................................................................................................................. 43

4.4.1 Test 03 Setup ..................................................................................................................................... 43


4.5 Test 04: Two bolts base plate connection; horizontal load parallel to the

supporting HSS ................................................................................................................................. 47

4.5.1 Test 04 Setup ..................................................................................................................................... 47


4.6 Test 05: Two bolts base plate connection; horizontal load perpendicular to the

supporting HSS ................................................................................................................................. 50

4.6.1 Test 05 Setup ..................................................................................................................................... 50


4.7 Test 06: Two bolts base plate connection; horizontal load perpendicular to the

supporting HSS ................................................................................................................................. 53

4.7.1 Test 06 Setup ..................................................................................................................................... 53


4.8 Comparison of Different Anchor Geometry Results ..................................................... 58

4.9 Material Properties of the Steel Base Plate ..................................................................... 60

4.10 Moment Resistance of the Base Plates ........................................................................... 62

Chapter 5 Finite Element Analysis ................................................................................... 69

5.1 Finite Element Model .............................................................................................................. 69

5.2 Model Parameters and Constraints ................................................................................... 71

5.3 Finite Element Analysis Stress and Deflection Results Analysis ............................. 72

5.3.1 Test 01 FEA Results......................................................................................................................... 73

5.3.2 Test 02 FEA Results......................................................................................................................... 75

5.3.3 Test 03 FEA Results......................................................................................................................... 78

5.3.4 Test 04 FEA Results......................................................................................................................... 81

5.3.5 Test 05 FEA Results......................................................................................................................... 85

5.3.6 Test 06 FEA Results......................................................................................................................... 87

5.4 FEA Model Conclusions ........................................................................................................... 90

Chapter 6 Conclusions and Recommendations ........................................................... 93

v

6.1 Conclusions ................................................................................................................................. 93

6.2 Recommendations ................................................................................................................... 94

References ................................................................................................................................ 96

vi

List of Tables

Table 4-1: Test 01 Yield Loads at the Strain Gauges .............................................................. 35

Table 4-2: Max. loads in the base plates before permanent deformation occurs ....... 59

Table 5-1: Material properties used in the FEA model ......................................................... 71

vii

List of Figure

Figure 1.1: Anchor system general setup ...................................................................................... 3

Figure 2.1: Anchor with connection bolts embedded in concrete ....................................... 6

Figure 2.2: Anchor with connection bolts wrapped around an I beam section .............. 6

Figure 3.1: Moment Load on Safety Anchor Base Plate ........................................................ 17

Figure 3.2: Example of checkerboard images required for camera calibration .......... 19

Figure 3.3: Glare on base plate due to strain gauges.............................................................. 22

Figure 3.4: Typical anchor currently in production vs. test anchor ................................. 24

Figure 3.5: The six anchor test geometries with load directions (all loads are parallel

to the top plate on the anchor base plate) ................................................................................. 25

Figure 3.6: Test frame with HSS cross-section dimensions and moment resistances

..................................................................................................................................................................... 26

Figure 3.7: Full experimental test setup ..................................................................................... 28

Figure 3.8: Top left: steel plate with scribed lines; bottom right: galvanized steel

plate with scribed lines ...................................................................................................................... 29

Figure 3.9: Steel plate with lines scribed after plate sprayed with blue tool dye paint

..................................................................................................................................................................... 29

Figure 4.1: Test 01 Anchor setup and direction of applied test load ............................... 31

Figure 4.2: Test 01 Strain Gauge Locations ............................................................................... 32

Figure 4.3: Test 01 strain gauge 1 data ....................................................................................... 33




Figure 4.7: Line along which deflection measurements were taken; test load pull the

pier to the right in this image .......................................................................................................... 36

Figure 4.8: Test 01 Deformation under 15kN Load ................................................................ 36

Figure 4.9: Test 01 Deflection at the back of the base plate under 15.5kN load; strain

gauge 4 can be seen on the right of the image and strain gauge 3 on the left .............. 37

Figure 4.10: Test 02 Anchor setup and direction of applied test load ............................ 39

viii

Figure 4.11: Test 02 line along which deformation was measured; test load applied

parallel the red line, to the right of the image .......................................................................... 41

Figure 4.12: Test 02 Failure of the anchor base plate ........................................................... 41

Figure 4.13: Test 02 plot of the change in shape of the base plate along a line on the

side of the plate ..................................................................................................................................... 42


Figure 4.15: Test 03 Maximum deformation in the base plate before the observable

weld failure............................................................................................................................................. 44

Figure 4.16: Test 03 Line on side of plate over which permanent deformation was

measured; horizontal load pulled to the right .......................................................................... 44

Figure 4.17: Test 03 Line at back of plate over which permanent deformation was

measured; horizontal load pulled to the right .......................................................................... 45

Figure 4.18: Test 03 Out of plane deflection at the side of the base plate ..................... 46

Figure 4.19: Test 03 Out of plane deflection at the back of the base plate .................... 47


Figure 4.21: Test 04 Deformation of anchor base plate at 14.0kN load ......................... 49

Figure 4.22: Test 04 Line at which permanent deformation in the base plate was

measured ................................................................................................................................................. 49

Figure 4.23: Test 04 Out of plane deflection along the side of the base plate .............. 50

Figure 4.24: Test 05 Anchor setup and direction of applied load ..................................... 51

Figure 4.25: Test 05 shape of base plate under 10.0kN load; load pulled to the left in

this image ................................................................................................................................................ 52

Figure 4.26: Test 05 Line along which deformation in plate is measured; load pulled

to the left in this image ...................................................................................................................... 52

Figure 4.27: Test 05 Out of Plane Deflection in the base plate .......................................... 53

Figure 4.28: Test 06 Anchor setup and direction of applied load ..................................... 54

Figure 4.29: Test 06 Shape of deflection in the plate with a 10.0kN load; load pulling

the anchor to the left in this image ............................................................................................... 55

Figure 4.30: Test 06 Line on side of plate at which deflection was measured ............ 55

Figure 4.31: Test 06 Out of plane deflection at side of plate ............................................... 56

ix

Figure 4.32: Test 06 Shape of deflection in the plate with a 10.0kN load; load pulling

the anchor to the right in this image ............................................................................................ 57

Figure 4.33: Test 06 Line along the back of the base plate along which deflection was

measured ................................................................................................................................................. 57

Figure 4.34: Test 06 Out of plane deflection at back of plate ............................................. 58

Figure 4.35: Tensile test dogbone dimensions; 1/4" plate thickness ............................. 61

Figure 4.36: Failure of tensile test coupons............................................................................... 61

Figure 4.37: Section properties for a rectangular plate, taken from the Handbook of

Steel Construction [102] ................................................................................................................... 63

Figure 4.38: Test 01 base plate bending lines used for calculating Z .............................. 63






Figure 5.1: FEA mesh .......................................................................................................................... 72

Figure 5.2: FEA constraints and load ........................................................................................... 72

Figure 5.3: Test 01 FEA stress in anchor .................................................................................... 73

Figure 5.4: Test 01 FEA stress in base plate .............................................................................. 74

Figure 5.5: Test 01 FEA out of plate deformation of base plate......................................... 75

Figure 5.6: Test 02 FEA stress in anchor .................................................................................... 76

Figure 5.7: Test 02 physical test image showing plate fracture ........................................ 76

Figure 5.8: Test 02 FEA stress in base plate .............................................................................. 77

Figure 5.9: Test 02 FEA out of plane deformation in base plate........................................ 78

Figure 5.10: Test 03 FEA stress in anchor .................................................................................. 79

Figure 5.11: Test 03 physical test image showing plate fracture ...................................... 79

Figure 5.12: Test 03 FEA stress in base plate ........................................................................... 80

Figure 5.13: Test 03 FEA out of plane deformation in base plate ..................................... 80


Figure 5.15: Test 04 shape of plate under test load of 13.0kN ........................................... 82


x



Figure 5.19: Test 05 image showing crack initiation around weld at the back of the

pier............................................................................................................................................................. 86




Figure 5.23: Test 06 fracture in base plate during experimental testing ....................... 88



1

Chapter 1 Introduction

As high-rise buildings become increasingly complex, creating systems to safely access the

outside of buildings is becoming more challenging. Features such as cascading balconies,

large terraces, and small roof footprints all combined to create difficulties in creating

systems that can access areas on the façade of a building. Façade access is important for

cleaning, repairing and retrofitting buildings as they age.

The challenges posed by modern architecture with respect to larger balconies or complex

building shapes usually results in the need for longer outreach arms on davit systems. The

longer arms increase the moment loads on the base of a machine. These bases must be

designed to withstand higher loads, but still be attached to typical roof structures.

This thesis will focus on the behaviour of safety anchor base plates. These base plates are

currently being designed based on accepted industry standards. The actual behaviour of the

plates under the applied load are not well understood [1]. A deeper knowledge of anchor

base plates would be useful in the design of new equipment for increasingly complex

façade access systems.

1.1 Safety Anchor Design

Safety anchors are used as points in façade access systems to which workers and equipment

are tied when either working suspended off the edge of a structure or close to an area with

a fall hazard. In theory, anchor points may undergo a dynamic load during a fall arrest

situation. To account for this, safety anchors are design to withstand static loads that have

a safety factor of at least 4:1 compared to the maximum expected static load [2]. In addition,

safety anchors are tested on a yearly basis to ensure that they are still acceptable for use.

Façade access systems are designed so that workers can safely access any area on the

outside of a building. To meet this requirement, safety anchor points are designed so that

2

the loads on the suspension points can be applied in any direction. For this reason, anchor

piers connecting the anchor point to which workers tie off on to the base plate are typically

round. Sections with round cross-sections have the same section properties in all directions,

making them ideal for structures that are required to withstand a load applied in any

direction.

Anchors for use on the exterior of buildings are typically made from structural steel. The

structures are usually galvanized for weather protection. They are commonly fastened to

the building structure by rods embedded in concrete, being bolted to the existing building

structure or by bolts wrapped around steel structural sections used in the framing of

buildings.

1.2 Thesis Objectives

The purpose of this thesis was to analyse the behaviour of base plates under a moment load.

The moment was applied to the centre of the base plate by a round pier welded to the centre

of the plate. How the moment load would be distributed throughout the plate was unknown

(See Figure 1.1 for anchor structure, support locations and applied force location). The

objective of this thesis was to analyse how the anchor base plate behaved under the moment

load and to determine a method of predicting the load at which the anchor base plate will

transition from elastic to plastic deformation. Because the base plate experienced out of

plate bending due to the moment load at the centre of the plate, some sections of the base

plate were loaded in compression and other sections were in tension. How the loads are

distributed was unknown. This thesis explored how the base plate deformed under the

moment load. Out of plane deformations of the base plates were measured, a method

analytically predicting the load at which the base plates start permanently deforming was

proposed and finite element analysis (FEA) was performed to simulate the behaviour of

the anchor system observed during the experimental testing.

3

Figure 1.1: Anchor system general setup

Six different configurations of test anchors were experimentally tested. The test setup was

designed such that the force applied at the top of the anchor point would, as much as

possible, be entirely transferred to the base plate as a moment load. The anchor pier and

supporting structure were designed to be capable of supporting higher loads than the base

plate so that the base plate was the first component of the structure to permanently deform.

The results of the experimental testing were used to propose a method of analytically

calculating the moment resistance of the base plate. There were no methods for analytically

calculating the maximum load an anchor base plate can withstand. Anchor base plates

typically have large spans to accommodate installation on typical roof structures.

Redesigning the configuration of the plate to meet the geometrical limits of previously

studied base plates was not possible.

A finite element model for the base plate was created and compared to the test results for

validation. The model was built to include all necessary components that affected the

behaviour of the anchor base plates. Like with the experimental testing, the finite element

model was designed such that the moment load was concentrated in the base plate.

4

1.3 Thesis Organization

This thesis is divided into four sections. Chapter 2 starts with a background and literature

survey discussing various studies regarding the analysis of structural base plates and

connection plates. Studies were researched that involved both experimental testing

components and finite element modelling. Chapter 3 provides an in-depth explanation for

the design of the experimental test setup for the anchor base plates being studied in this

thesis. A test frame to support the six different anchor configurations was designed and

various measurement methods were explored. This chapter also included details regarding

how deformation in the base plates was measured. This is especially important for

interpreting the results of the experimental testing. The next section, Chapter 4, analyses

the data acquired during the experimental testing. The test was performed as described in

the previous section: Chapter 3. Through the observations in this section, an analytical

method of predicting the moment resistance in the plate was proposed. Chapter 5 discussed

the finite element model of the anchor structure. The model made in this section was

designed to represent the anchor structures tested using the setup described in Chapter 3.

The finite element analysis results in Chapter 5 are also compared with the results of the

analysis in Chapter 4 regarding the experimental testing of the anchor base plates. This

thesis ends with a conclusion for the thesis as a whole and future recommendation.

5

Chapter 2 Background and Literature Survey

2.1 Safety Anchor and Davit Base Plate Introduction

Safety anchors and davits are products commonly used in façade access systems for

building structures. The loading requirements for safety anchors and davits are given based

on building design codes. The products themselves are designed using a variety of sources;

for example, calculations for the strength of anchor bolts in concrete are performed based

on Canadian Standards Association codes (CSA-A32.2 Design of Concrete Structures;

Annex D: Anchorage [3]), the strengths and load resistances of steel components are

determined using the Handbook of Steel Construction, etc. Most components of safety

anchor and davit bases can be modelled analytically or easily tested. The one component,

however, that is difficult to model is the base plate used to connect safety anchor and davit

bases to the building structure.

Base plates for safety anchor and davit bases consist of a square steel plate with a round

steel pier welded in the centre and four connection bolts in the four corners of the plate.

The bolts in the corners of the plate can be fastened to building structures using multiple

methods; they can be embedded in concrete (Figure 2.1), bolted to an existing structure or

the bolts can be wrapped around a beam section (Figure 2.2). The difficulty in modelling

the base plate is predicting how the plate will react when a moment load is applied (in any

direction) by the round pier welded to the centre of the plate.

6

Figure 2.1: Anchor with connection bolts embedded in concrete

Figure 2.2: Anchor with connection bolts wrapped around an I beam section

Current analytical methods for predicting base plate reactions under given loads assume

that the sections of plate extending beyond the pier welded to the base plate acts as a

cantilever and the pressure distribution under the base plates is linear, which results in

conservative base plate designs[1, 4-7]. This is due to the lack of understanding of how

loads and stresses are distributed throughout the base plate and due to the assumptions used

to simplify calculations.

7

Finite element analysis (FEA) has also been used as a means of predicting the behaviour

of base plate connections [8-12]. Given the many factors that affect the reactions of bolted

base plates and connection plates under given loads, FEA models are made and applied to

very specific applications. Base plate behaviour predictions obtained from these models

are specific to base plate connection geometry and loading conditions, therefore the results

cannot be extrapolated and applied to different base plate connections. The accuracy of

finite element (FE) models is confirmed through physical testing of the base plate

connection. Typically, strain and deflection measured during physical testing is compared

to the strain and deflection obtained using FEA [5]. One of the advantages of correctly

representing a model in FEA is that FEA can provide engineering data that is difficult or

impossible to measure during physical testing, such as internal stresses in the connection

plate. Results obtained using FEA have varying degrees of accuracy due to assumptions

made, model accuracy, software limitation etc.

2.2 Types of Base Plate Connections

Although there is no previously performed research specific to the design of safety anchor

and davit base plates, there are other, more commonly used, base plate designs that have

been studied. Previously examined base plates include base plate connections for signposts

[13], column base plate connections to concrete foundations [14-18] , and beam to column

bolted connections. A variety of approaches have been used to model these connection

plates. Studies have analysed base plates through experimental testing [19-24], creating

configuration specific calculations for given loading conditions and base geometries [25],

and used computer simulation models to attempt to predict base behaviour achieved

through physical tests [26-33]. Understanding the successes and failures of previously

modelled base plate connections will help guide the process of creating an accurate FEA

model for the design of safety anchor and davit base plates.

Regarding the creation of FE models to represent base plates, there are some common

features of importance for all the previously studied base plate designs. In the interest of

8

making the FEA efficient, only half of any base plate connection that has a symmetrical

geometry is made and analysed. Mesh sizes are reduced in areas that have large changes in

internal stresses over relatively small areas. These locations include, but are not limited to,

locations where sections are welded to base plates, the segment of bolts that go through the

base plate and around boltholes. Given all the assumptions and variables required in the

representation of base plates using FEA, it is important to thoroughly understand the

capabilities and limitations of FE programs and to have a clear scope and definition of the

design being modelled.

2.2.1 Modelling of Cylindrical Steel Structures to Concrete Foundations

Round hollow structural steel sections welded to square base plates that are bolted to a

concrete foundation are used for several applications. These include traffic sign support

structures, industrial chimneys, wind towers, and cranes.

Typical column base plate to concrete foundation applications are studied for columns with

I and H cross-sections. The use of hollow round steel sections, rather than conventionally

used sections, welded to the base plate affects how the loads are transmitted through the

base plate. Analytical calculations for the design of steel base plates in columns have been

modified and adapted to represent the connection between cylindrical steel structures and

concrete foundations [34, 35].

Traffic sign support structure base plates are square, with four bolt connections in the four

corners of the plate and a round hollow section welded to the centre of the base plate. These

base plates undergo compression loads, moment loads, and torsion loads. The base plates

were originally designed using physical testing. Production companies have stock

configurations of traffic sign base plates and the geometrical configuration of the plates are

kept constant. In order to produce traffic sign base plates with varying geometries, Owens

et al. created standard procedures to analytically model traffic sign base plates [13]. These

procedures operate under the assumption that the mast is sufficiently strong to transfer all

9

loads to the base plate, and the plate has adequate strength for transferring shear and torsion

forces to the bolts. The calculations determine the forces on the four bolts in the corners

of the plate, however separate calculations/analysis must be done to check that the bolts

have adequate strength to withstand any applied loads. To calculate the forces in the bolts,

there is an assumed pressure line location. When a moment load is applied to the base plate,

there is a resulting compression load applied to part of the base plate, and an uplift on the

remaining section of the base plate. The line through the plate that marks the transition

between the compressive and tensile load is the pressure line. For this analysis, the pressure

line is assumed to be perpendicular to the direction of the moment load and tangent to the

round mast. Due to the extensive computational effort required to perform the analytical

calculations, a spreadsheet was created to iteratively solve different base plate designs

within a specific scope. Base plate geometry and loading conditions are inputted into the

program and the minimum plate thickness is then determined.

Hoang et al. (2015) adapted analytical base plate procedures to analyse the connection

between cylindrical steel structures and concrete foundations typically used for industrial

chimneys, wind towers, and cranes [34]. These structures have mast diameters between 2m

and 6m. This analysis utilized the component method to analyse the base plate in the elastic

region of use. The following components were analysed in this application: compression

and bending in the round structural wall, flexion and shear in the base plate, torsion and

bending in the bolts, bending in the repartition plate, and compression in the concrete

foundation.

Both above mentioned analytical methods of analysing the connection between cylindrical

steel structures and concrete foundations employ only analytical means of modelling. They

are geometry specific and the analysis cannot accurately be adapted to represent the

reaction of safety anchor and davit bases under moment loads.

10

2.2.2 Modelling of Column Base Plates to Concrete Foundations

Base plates connecting columns to concrete foundations are an important part of steel

structures in buildings [36-42]. Columns typically support large compressive axial loads,

which result in large compressive loads on the concrete foundation. There are instances,

however, when moment loads are also applied to column bases. Column base plates

undergoing moment and axial loads, versus only axial loads, behave differently with

respect to internal stress distribution and deformation. Literature that specifically examines

the effects of a moment load on column base plates will be the focus of this section.

There are many different configurations of connections between column base plates and

concrete foundations. Geometrical differences include column sections (such as hollow

square section, hollow rectangular sections and W sections (I beams)), plate size (plate

length, width and thickness), and anchor bolt configuration, diameter and embedment

depth. Differences in physical geometries and loading conditions of column base plates

have a large influence on their behaviour.

A variety of FE programs have been used to model different configurations of column base

plates, including commercially available programs such as ABAQUS [43-47] and ANSYS

[48-50], and proprietary programs written by various academic institutions for their own

use, such as FEABOC [51, 52] and SUT_DAM [53]. The success with which column base

plates are modelled is dependent on the complexity of the models and any assumptions

made to simplify the analysis.

Early FE models were very basic due to computer limitations. Krishnamurthy et al. (1989,

1990), using the FEA program FEABOC written by Krishnamurthy, modelled column base

plates under a moment load using 2D and 3D analysis [51, 52]. In the original simplified

model, only the section of the anchor bolt (modelled with a square cross-section) passing

though the base plate was included in the FE model. The assumptions that the influence of

the bolt head and the section of the anchor bolt embedded in the concrete are negligible

yielded inaccurate results when compared to the behaviour of the column base plate during

physical testing. The model was later refined to include the previously omitted sections of

11

the anchor bolt. The improved FE model could qualitatively predict the reaction of the

column base plate under an applied load [51, 52].

As the capabilities of FE programs improve, FE models are capable of modelling column

base plates more accurately and with fewer restrictions due to software limitations. Despite

these advancements, it is still required that assumptions be made when the column base

plate FE model is created. For example, some FE column base plate models assume that

the anchor rods undergo only tensile loads [4], other models constrain the vertical

displacement of the anchor bolts at the end furthest from the base plate, then allow the rest

of the bolt to react accordingly [53]. Seemingly small changes in assumptions and

restraints can greatly influence FE results. With careful analysis and a thorough

understanding of the behaviour of column base plates under a given load, it is possible to

create an accurate FE model defining the behaviour and stress distribution in a base plate.

Unfortunately, due to the large number of variables (including differences in geometry and

loading conditions), results for a given column base plate configuration cannot be

extrapolated and used to predict the behaviour of different column base plate models.

General, quantitative, trends in column base plate behaviour under moment loading can be

observed when geometric variables are changed. As plate thickness and bolt diameter are

increased, the overall stiffness of the column base plate increases; this affects the internal

stress distribution in the base plate [4, 35, 51-54].

2.2.3 Modelling of Beam to Column Bolted Connections

Beam to column bolted connections are common in steel structures. These connections

usually involve a beam welded to a connection plate. The plate has a series of bolt holes

used to bolt the connection plate to the column, which has matching holes for the bolts.

Typically beam to column bolted connections are subject to a shear load through the

connection bolts. Some connections also experience a bending load on the beam, which

results in a moment load on the base plate [55-61]. The effects of this bending load will

12

cause the connection plate to behave differently compared to a connection plate only

subject to a shear load. There are multiple FE models that have been made to examine the

stress distribution and deflection in connection plates undergoing a moment load.

Finite element models of beam to column bolted connections have been analysed using

many different software packages, such as ANSYS [5, 62] and ABAQUS [6, 63]. With

careful consideration of all the factors involved due to loading conditions and geometries,

these software packages can be used to accurately model the behaviour of beam to column

bolted connections. Again, the geometry of the connection has a large effect on base plate

behaviour such that results cannot be extrapolated beyond a given scope of study for a

beam to column bolted connection analysis.

There are many possible parameters to consider in the design of beam to column bolted

connections, such as whether the end plate extends beyond the beam, beam and column

sections used, bolt grade and diameter, bolt spacing, bolt pretension load, load applied to

beam, connection plate thickness, steel yield strength, co-efficient of friction etc. There are

also assumptions made in the FE models to be able to run the FEA. A common assumption,

which may affect the accuracy of FE models, is that there is no deflection in the column to

which the base plate is attached [3]. Different parameters have varying degrees of influence

on the overall behaviour of beam to column bolted connection behaviour under applied

load. Overall, the two most influential variables are plate thickness and bolt diameter [5,

62].

Plate thickness is important because it affects the rigidity of the connection. This

connection is semi-rigid and changes in rigidity affect the stress and pressure distribution

throughout the connection plate. This in turn affects how the load is distributed to the bolts

[5, 62]. Relatively thicker plates are more rigid, have smaller deflections, and tend to load

the bolts mainly in tension. Plates that are thinner have greater deformations and apply

prying loads to the connection bolts. When a bending load is applied to the connection

plate, part of the plate pulls away from the column to which it is bolted, and a section of

the connection plate pushes against the column. The line dividing these sections of the plate

is called the yield line. The location of the yield line is directly related to how the

13

connection plate distributes the bending load to the bolts and to the deflection of the

connection plate. The location of the yield line cannot be accurately determined through

analytical means; FEA determines the location of the yield line through iterative

calculations [64, 65]. Depending on the thickness of the connection plate, as well as the

diameter and strength of the connection bolts, beam to column bolted connections tend to

fail either due to bolt failure or connection plate failure at the yield line [5, 62].

Bolted connections between beams and columns can have another load at bolt connections

apart from shear and bending forces applied by the beam, such as; bolt pretension forces.

When the bolts are pre-tensioned, an initial tension load is added to the bolts and it affects

the deflection of the connection plate. The compression load added by the washer to the

plate around bolt holes makes it more difficult for the connection plate to slide against the

steel column due to the increase in friction forces [5, 64-66]. When bolt pretension is

considered as part of a FE model, the loading on the connection is done in two steps. First,

the analysis is run with only the bolt tension load. Second, the bending and shear loads are

added to the beam and the simulation is run again.

2.3 Modelling Issues and Limitations

All of the above-mentioned connection plates are analysed for specific base plate

applications and the results cannot be extrapolated to predict the behaviour of safety anchor

and davit base plates. The specific loading conditions and base plate geometries of

previously analysed moment connection in base plates have limited scopes which do not

include the requirements for safety anchor and davit base plate designs.

The geometry and loading of the cylindrical steel structures to concrete foundations are the

most similar to that of safety anchor and davit bases. This is due to the fact that the loads

can be applied in any direction and the mast welded to the base plate is round. The types

of loading on the connection vary depending on the application, and the geometry is only

similar with respect to the section used. Safety anchor and davit base plates are unique in

14

that the length of the base plate is relatively long compared to the diameter of the round

pier. The large space between the pier and bolt locations in the plate will affect the way the

load is distributed through the base plate. Furthermore, the analysis of cylindrical steel

structures to concrete foundations is solely based on analytical calculations which, given

all the assumptions required to solve the calculations, tend to yield conservative base plate

designs. The utilization of FEA to model safety anchor and davit base plates has the

potential to give more accurate results.

With respect to column to concrete connections and beam to column connections, the

structural steel beam sections used are all hollow square sections, hollow rectangular

sections or I beam sections. There was no analysis of the influence of circular hollow steel

structural section on the behaviour of connection base plates. The reason that these

sections, and not circular sections, are used in beams and columns is that the moment or

bending loads acting on these structures are applied in one, predictable direction. These

sections are chosen to be strong in the direction required given the applied loads. Circular

sections are used for safety anchor and davit bases because the given load can be applied

in any direction. Round sections ensure that the strength of the section is the same in every

direction. The square base plate with the connection bolts in the four corners, however,

does not have the same load resistance in every direction. The orientation of the moment

load applied to the base plate will affect how the internal loads are distributed throughout

the plate and how the base plate will deform. An accurate FE model can help determine

the effects of different load directions on the safety anchor and davit base plates.

2.4 Summary

Overall there are many FE models that successfully predict the behaviour of base plates in

different scenarios. Therefore, it should be possible to create a FE model for the analysis

of safety anchor and davit base plates. The results of FEA will have to be compared to

physical testing of safety anchor and davit base plates, as there is no accurate analytical

15

model for the prediction of the reactions of safety anchor and davit base plates under a

moment load.

16

Chapter 3 Experimental Setup

3.1 Introduction to the Experimental Setup

The test setup for the experimental section of this thesis played an important role in

determining the accuracy of the physical testing and the measurements that could be taken

for both the analytical section of the thesis (Chapter 4) and for verifying the FEA model

created in a subsequent section of this thesis (Chapter 5). This chapter explained how the

test was designed to meet the objective of this thesis: analysing the deflection in the anchor

base plates when a moment load was applied to the centre of the plate by a round anchor

pier. It also explored different possible measuring methods that could have been used to

track the change in shape of the base plate. The designed experimental test setup and

selected measurement methods described in this section were used in Chapter 4 in the

discussion of the loads under which the anchor base plates transitioned from elastic to

plastic deformation.

3.2 Test Objectives

The goal of the experimental testing was to analyse the behaviour of safety anchor base

plates under typical loading conditions as required by CSA Z271 [2]. The carbon steel base

plate had a moment load applied through a round pier welded to the plate’s centre. The

plate sat on top of a rectangular steel hollow structural section (HSS) and was held in place

by threaded rods (two or four rods depending on the design) in the corners of the plate. The

threaded rods wrapped around the HSS and bolted through a steel angle section under the

HSS (See Figure 3.1 for anchor setup and moment load location for one of the test

configurations). The base plate was expected to experience out of plane bending and

deflection between the round steel pier and the bolts. The results of the testing were used

17

to determine an analytical method of predicting when the base plates start to undergo

plastic deformation.

Figure 3.1: Moment Load on Safety Anchor Base Plate

3.3 Measuring Techniques and Equipment

3.3.1 Deformation Measurements

In this experiment, the out of plane deflection of a 10” x 10” plate, 3/8” thick, was be

measured. Loads were applied incrementally to the anchor. After each load was applied,

the load was removed and measurements of the plate shape were taken before the next load

increment was applied. This process was repeated after each load increment until the

system started to plastically deform. The data was used to determine when the plate started

permanently deforming. Due to the moment load applied to the centre of the plate through

the round pier, the deflection of the plate was varied throughout the length and width of

the plate. Given the unique configuration and loading of the base plate, it was not possible

18

to accurately predict the behaviour of the plate under the moment load; including the areas

of maximum and minimum deflection, stress and strain. Therefore, when the deflection in

the plate was measured, it was required that the change in location of points over the entire

top surface of the plate be tracked to properly examine the overall change in shape of the

base plates.

There are multiple measuring techniques used to determine changes in position during

tests. The simplest of measurement methods would be to use a ruler for measuring a straight

distance. More accurate tools for length measurements include callipers and point lasers;

these however also could only measure the distance in a straight line. These measurement

techniques would not have been practical for tracking the change in shape of the base

plates. Every point on the plate would have had to have been manually measured at each

load increment. In addition, there would need to be a reference set up to which the point

locations could be measured to track changes in position. The test frame underneath the

anchor base plate and the round pier extending above the anchor base plate further

hampered setting up a reference. When a load was applied to the pier, the pier may also

have deformed and interfered with any reference geometry that was set up for measuring

purposes.

There exist laser scanners that can scan and record the shape of surfaces. However, these

systems and their related software (required for interpreting data) were costly. Since these

systems were outside the budget for this project, a different and more cost-effective

measurement method was found.

Digital image correlation (DIC) is another measuring method that could be used to track

the 3D movement of points [67-73]. It required the use of two or more cameras taking

synchronized images, and then using the images to find the 3D world coordinates of points

seen by both images [74, 75]. The process of translating 2D image coordinates from

multiple cameras into 3D world coordinates is known as triangulation [76-79]. DIC is more

frequently used in experimental mechanics due to its ability to measure displacement both

in-plane and out-of-plane [80-85]. This displacement data can be used to graph the change

in shape of structures due to applied loads.

19

To accurately use DIC, the cameras had to be properly calibrated [86-88]. There were

multiple valid techniques and programs that could have been used for camera calibration

[89-97]. For this experiment, the Camera Calibration Toolbox for MATLAB, written by

Jean-Yves Bouget [98-101], was used to calibrate the cameras. This MATLAB code could

be used to calibrate a pair of cameras. This experiment used four cameras positioned around

the base plate to capture images. The reason for this setup was that it allowed every point

on the base plate to be captured by at least two cameras simultaneously, providing the

ability for every point location on the plate to be determined. The cameras had to be

calibrated in pairs and the data collected from different pairs of cameras was combined to

determine the overall behaviour of the entire plate.

The calibration was performed by taking a series of synchronized images of a checkerboard

pattern that can be seen by the camera pairs (See Figure 3.2 for example of the

checkerboard images taken by one camera). These images were uploaded into the program

and, through a series of functions, the calibration parameters, including focal length,

principal point, skew coefficient, distortions, rotations, and translations, were calculated.

These parameters, along with the pixel coordinates of a point from the left and right

cameras, were then inputted into the triangulation code to calculate the 3D world

coordinates from the point from the point of view of the left and right cameras.

Figure 3.2: Example of checkerboard images required for camera calibration

20

Once the cameras were calibrated, the distance between pairs of points on the

checkerboards was measured using DIC and compared to the distance measured between

these same two points using a calliper. The squares on the grid used for calibrating the

cameras had dimensions of 29.0 mm by 29.0 mm. Using DIC, the average length between

two grid corner points was 29.0 mm, and the standard deviation of this measurement was

0.1 mm. These measurements were taken between the same two points on 152 images,

taken from eight different stereo calibrated camera pairs. The average length measured

between the grid point corners, and the accompanying standard deviation, showed that

using DIC for measuring deformation in the base plates would provide results accurate

enough to analyse the deformation in the base plates.

The 3D world coordinates determined by the Camera Calibration Toolbox for MATLAB

were given from the point of view of the left and right cameras. To extract meaningful data

from these coordinates, a MATLAB code specific to this project was written to translate

and rotate the coordinates. The points on the plate were always measured along a line; this

line became the new x-axis. The new y-axis run perpendicular to the x-axis, on the same

plane as the top surface of the plate. The new z-axis is the out of plane direction

perpendicular to the plate, with up always in the positive direction. The measurements

taken along a line of the plate were plotted to show how the shape and location of the base

plate points changed as the test progressed.

3.3.2 Strain Measurements

Measuring strain (on the order of 10-6) the anchor base plate was another method that could

be used to determine at what load the base plate transitions from plastic to elastic

deformation. Given the accuracy of the DIC measuring technique, it was not possible to

measure the deformation in the plate with enough precision to accurately calculate the

strain in the plate. A precision of approximately 0.00001 mm or more would have been

required to calculate strain based on deformation measurements.

21

Strain gauges adhered to the top surface of the plate could be used to measure the strain

during the experimental testing. Strain gauges were used in the first experimental test. It

was not possible to calculate the force, and therefore the stress, in the locations of the strain

gauge. Therefore, a plot of strain vs. test load at the top of the anchor was used to find the

transition point between linear and non-linear strain reading (elastic vs. plastic

deformation).

There were two disadvantages with the use of strain gauges during testing. The first was

that there was no method for precisely predicting which locations on the anchor base plates

would start to yield first. Four strain gauges were used during the first test. They were

located in areas of anticipated higher deflections. Two of the strain gauges showed linear

to non-linear strain data at approximately the same load, the other two strain gauges showed

plastic deformation occurring at distinctly different loads. The problem with using the

strain gauges was that the data may lead to inaccurate conclusions if the strain gauges were

not placed in the correct locations to capture maximum strain areas on the anchor base

plates.

The second disadvantage was that the use of the strain gauges interfered with the images

captured for DIC. The surface preparation requirements for adhering the strain gauges

caused some damage to the grid drawn on the anchor base plates (the grid was used for

tracking the change in location of points on the anchor base plates using DIC). The strain

gauges and adhesive also created areas of glare on the anchor base plates (Figure 3.3).

These negative effects led to the decision that only DIC be used during testing. DIC was

chosen over the use of strain gauges because the deformation measurements were

determined after the testing was complete. Therefore, the test images could be used to

determine the locations of maximum deformation and the measurements at those locations

could be used to determine when the anchor base plate starts plastically deforming.

22

Figure 3.3: Glare on base plate due to strain gauges

3.4 Safety Anchor Configurations and Geometry

There are many possible anchor designs that can be used to meet building code

requirements. The design of an anchor point is influenced by the building on which it is

being installed. Anchors can be embedded into concrete or fastened to the steel structure

of the building. Other engineering teams decide the strength and depth of concrete on a

building and the structural steel sections used in the framing. Designers of safety anchor

points must create anchors that accommodate the designed building structure and comply

with required codes, such as CSA Z271. This code states that the anchorage point must be

able to withstand a load of 11.1kN applied in any direction without permanent deformation

and a load of 22.2kN without fracture of pullout [2].

It was outside the scope of this project to analyze every possible anchor base plate design.

The base plate analysis tested two different, and commonly used, anchor designs. The

typical anchor design off which this analysis was based consisted of a 10” x 10” x 5/8”

base plate with a 4” diameter, ¼” thick, round HSS pier welded to the center and an

anchorage point (onto which the load would be applied) welded to the top of the anchor

23

pier. The differences in the two designs used for experimentation was that one design was

fastened to the building structure by bolts in the four corners of the base plate and the other

base plate was secured by two bolts in opposite corners of the base plate.

The focus of this test was to analyze the behaviour of the safety anchor base plates with a

moment load applied to the center of the base plates by the round HSS pier. To transfer

the entire load to the plate, the rest of the test system was designed to withstand loads

larger than the expected test loads. The thickness of the 4” diameter pier was increased

from ¼” to 5/16”, which is the largest readily available thickness for the outside diameter

of HSS. This thicker section increased the moment resistance of the pier from 15.0kN to

18.2kN.

The anchor point onto which the test load was applied was also modified to withstand

larger loads without deforming. A typical anchor point can have loads applied in any

direction. The anchors used in this test had one predetermined load direction. A ¾” steel

rod with a length of 30 mm between support points was the hook up point for the load in

the test. According to beam diagram calculations for a beam fixed at both ends –

concentrated load at center (Beam Diagram and Formula 16 in the Handbook of Steel

Construction [102],this anchor point should be able to withstand a force of 370kN applied

at the rod’s center.

The final deviation from the typical safety anchor design was the base plate thickness. The

anchor base plate thickness was reduced from 5/8” thick to 3/8” thick. The thinner plate

was used so that lower loads would be required to obtain larger deformations in the anchor

base plates. See Figure 3.4 for an image of a typical anchor design used and the test anchor

design.

24

Figure 3.4: Typical anchor currently in production vs. test anchor

3.5 Test Frame

Safety anchors are typically installed on roofs and balconies of high-rise buildings. They

can be embedded in concrete or fastened to the steel structure of the building. This

experiment was designed to represent a safety anchor that had been fastened to a steel

structure. The safety anchor bases were bolted around rectangular hollow structural steel

sections (HSS).

A test frame was designed to support the bolted anchor base and hook up location for the

applied horizontal force on the anchor point. One single test frame was built to

accommodate testing of both anchor geometries. Typical anchors can be loaded in any

direction; therefore, three tests per anchor geometry were performed to examine the effects

of different applied moment directions to the deformation in the anchor base plates. All the

loads were applied horizontally (parallel to the top surface of the anchor base plate) to

maximize the moment on the plate. The three load directions were: horizontal force parallel

25

to the supporting HSS, horizontal force perpendicular to the supporting HSS and horizontal

force on a 45° angle relative to the supporting HSS. Two anchor geometries and three load

directions resulted in a total of 6 tests. Top views of the six test anchor geometries and

loading directions can be seen in Figure 3.5.

Figure 3.5: The six anchor test geometries with load directions (all loads are parallel to the top plate on the anchor base plate)

26

The horizontal load on the anchor point was applied by a tirfor or a chain pull. The tirfor,

or chain pull, was supported on the other end by an anchor point on a trolley located at the

centre of the test frame on a vertical square HSS. The trolley on the centre HSS could be

moved down as testing proceeds and the anchor pier starts deflecting; this was done to keep

the applied load horizontal.

The strength of the pier on the anchor base plate had already been increased within the

limits of commercially available sections with the required outside diameter. The test frame

dimensions did not have the same restrictions as the pier, therefore they were designed to

withstand moment loads much larger than expected test loads.

According to the moment resistances of the HSS sections in the test frame, the test frame

was able to withstand a moment of 87.3kNm before plastically deforming. See Figure 3.6

for the moment resistances of the main frame sections. The maximum moment load that

the anchor design could withstand given the pier moment resistance is a moment of 18.2kN,

therefore the test frame was designed to withstand a load 4.8 times greater than the

maximum test load the pier can withstand before deforming. This was determined based

on the moment resistances of the HSS sections used in the test frame, beam deflection

calculations and weld calculations. All relevant data and equations used were found in the

Handbook of Steel Construction [102].

Figure 3.6: Test frame with HSS cross-section dimensions and moment resistances

27

As mentioned above, the test anchors were fastened to the test frame by either two or four

bolts wrapped around the HSS of the test frame. A325 threaded steel rods were bolted

through the anchor base plates on the top side of the HSS and went through steel angles

(angle dimensions of 3”x3”x1/2”, two angles for the four bolt bases and one angle for the

two bolt bases) on the underside of the HSS. The holes in the angles were the same size

and distance apart as the bolt holes in the anchor base plates being tested. One nut was

used on either end of the threaded rod and hand tightened to hold the test anchors in place.

No washers were used. Washers were omitted because they covered more of the base plate,

which interfered with the camera images of the base plate and, in turn, would limit the

locations at which the deformation can be measured.

3.6 Summary of the Complete Experimental Setup with

Equipment

The completed, assembled, setup of the experimental testing can be seen in Figure 3.7.

Between the anchor point in the test anchor and the hook up point in the centre of the test

frame were a dynamometer and a tirfor or manual chain pulley hoist. The dynamometer

showed the magnitude of the load being applied to the anchor point, and the tirfor or manual

chain pulley hoist provided the power/mechanical advantage that enabled the load to be

applied to the system. The maximum load on the dynamometer was 50kN, and the load

increments on the dynamometer scale were 0.5kN. The tirfor used in Test 01 had a two-

ton (imperial tons; 2 ton = 4000 lbs = 17.76kN) capacity and the manual chain pulley hoist

had a maximum capacity of five metric tons (49.05kN).

28

Figure 3.7: Full experimental test setup

The four cameras used for DIC are mounted on their own frame. The camera frame was

kept independent from the test frame so that the locations of the cameras were not disturbed

when the load was applied to the test anchors. If the placement of the cameras was

compromised, then the calibration of the cameras would be affected and any measurements

taken with DIC would be inaccurate.

The cameras used for this testing were FLIR Systems; model number CM3-U3-31S4M-

CS. The cameras were connected to a laptop via USB cables and they were wired for

synchronized image capturing. The Flycap software was used to capture the images and

the synchronized triggering of the cameras was controlled through a C+ program. The

lenses used were from Edmond Optics. There were two different lens models used: 12mm

C series lenses and 12mm UC series lenses. Both lens types were similar and no difference

in performance was observed in the data collected through DIC.

The cameras used were monochrome and had a resolution of 2048x1536 pixels. The high

resolution and contrast in the monochrome images were essential for accurate DIC data.

Some sample pictures taken of steel plates before testing showed glare in some of the

images. It was also difficult to see the scribed grid on the plate. To aid with the visibility

of the etched lines and to lessen the glare on the plate, blue tool dye paint was sprayed onto

the plates before the grid was drawn. Tool dye paint was sprayed onto the metal plate in a

29

very thin layer, had a matte finish and provided a better contrast in the images. See (Figure

3.8) and (Figure 3.9) for images (taken from the same camera) of a scribed plate without

and with blue tool dye paint, respectively.

Figure 3.8: Top left: steel plate with scribed lines; bottom right: galvanized steel plate with scribed lines

Figure 3.9: Steel plate with lines scribed after plate sprayed with blue tool dye paint

30

Chapter 4 Analysis of Experimental Testing: Anchor

Plates Under Moment Load

4.1 Experimental Testing Overview

This section analysed the deformation of the six base plate configurations when a moment

load was applied to the centre of the plate. The testing was done using the test setup and

methods described in Chapter 3. The measured results for each test configuration were

discussed separately. Analysis for each test discussed the measured deflection of the anchor

base plate (or measured strain gauge data in test 01) and the load at which the anchor base

plates start plastically deforming. Finally, an analytical method of predicting the point at

which permanent deformation occurred was proposed. The discussed results were also used

in the next section, Chapter 5, to verify the proposed finite element model.

4.2 Test 01: Four bolts base plate connection; horizontal load

parallel to the supporting HSS

4.2.1 Test 01 Setup

As discussed in the previous chapter, the test anchor in this experiment was fastened to the

test frame by four bolts, in the four corners of the anchor base plate, wrapped around the

supporting HSS. The load on this anchor was parallel to the top face of the anchor base

plate, and parallel to the length of the supporting HSS. (See Figure 4.1 for Test 01 anchor

and direction of applied load).

31

Figure 4.1: Test 01 Anchor setup and direction of applied test load

4.2.2 Test 01 Strain Gauge Data and Analysis

As discussed in Chapter 3: Experimental Setup, section 3.2.2, the first test performed was

documented using both strain gauges and camera images. Unlike the following tests, in this

test the horizontal load applied to the anchor point was increased in increments and the

load was never removed. The reasoning for this was that the cycles of applying and

removing the load repeatedly may have interfered with the strain gauges. Therefore, the

strain gauge data, and not the DIC data, was used for determining the transition point from

linear to non-linear deformation. The strain gauge locations can be seen in Figure 4.2.

32

Figure 4.2: Test 01 Strain Gauge Locations

The strain gauges in this test measured the microstrain (strain x10-6) in four different areas

of the plate. Since there was no way of determining the stress in these four locations

throughout the test, the strain measurements were plotted against the applied horizontal

load at the top of the anchor pier. From these graphs, the load at which the base plate

transitions from linear to nonlinear deformation was then determined. The load vs. strain

graphs for strain gauges 1, 2, 3 and 4 can be seen in Figure 4.3, Figure 4.4, Figure 4.5,

and Figure 4.6 respectively. There was an attempt made to measure the strains in the

locations of the strain gauges using DIC. Unfortunately, the DIC was not precise enough

to accurately measure strain. The measured strains varied greatly (and not linearly at any

point during the testing) such that it was decided that the analysis based on the DIC

measurements will focus on deformation rather than strain.

33

Figure 4.3: Test 01 strain gauge 1 data


0

5

10

15

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35Hori

zonta

l F

orc

e on A

nch

or

Poin

t (k

N)

Strain x10e-3 (in compression)

Test 01: Strain Gauge 1 Data

Measured test

strain

0

5

10

15

0 0.5 1 1.5 2 2.5 3 3.5

Hori

zonta

l F

orc

e on A

nch

or

Poin

t (k

N)

Strain x10e-3 (in tension)


Measured test strain

0.2% offset strain line

Series3

34



0

5

10

15

0 0.5 1 1.5 2 2.5 3

Hori

zonta

l L

oad

on A

nch

or

Poin

t

(kN

)

Strain x10e-3 (in tension)


Measured test

strain0.2% offset

strain line

0

5

10

15

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8Hori

zonta

l L

oad

on A

nch

or

Poin

t (k

N)

Strain x10e-3 (in compression)


Measured test

strain0.2% offset

strain line

35

On the load vs strain graphs, an offset line with the slope of the linear region of the

graph was drawn at strain 2e10-6. From where this line intersects with the measured

strain data, the test load at which plastic deformation begins was determined. The

loads at which the plates start to nonlinearly deform at each strain gauge are

summarized in Table 4-1.

Table 4-1: Test 01 Yield Loads at the Strain Gauges

Strain Gauge # Yield Load (kN)

1 4.2

2 4.2

3 8.4

4 5.7

Table 4-1 shows that the locations of strain gauges 1 and 2 on the plate started

plastically deforming under the same load of 4.2kN. The measured strain at gauge 1

was negative, therefore this section of the plate is being compressed. Strain gauge 2

gave positive strain readings, meaning that section on the plate was being deformed

through a tension load. At strain gauges 3 and 4 the steel plate started yielding at

higher loads than the other two strain gauges, 8.4kN and 5.7kN respectively. Strain

gauge 3, like strain gauge 2, gave positive strain readings and was also therefore in

tension. Strain gauge 4, like strain gauge 1, had negative strain gauge reading,

meaning this section of the plate was also being compressed along the length of the

strain gauge.

The two strain gauges that reached yield strain first during testing were both on the

font half of the plate (the side over which the load was being applied). This is

interesting to note because at the end of the test, the largest deformation was visible

at the back end of the plate. Deformation measurements were taken along the line on

the anchor image shown in Figure 4.7 using DIC. The plot of the out of plane

deformation along this line at a 15.0kN load compared to zero load can be seen on

Figure 4.8.

36

Figure 4.7: Line along which deflection measurements were taken; test load pull the pier to the right in this image

Figure 4.8: Test 01 Deformation under 15kN Load

There are multiple possible reasons why the strain gauges closest to the areas of

maximum deflection started yielding at a higher load. Linear strain gauges were used

in this experiment, meaning only unidirectional strain was measured. However, it can

be seen in the test images that the base plate experienced multidirectional

deformation and would therefore have strain in the plate acting in multiple

directions. A rosette style strain gauge could have been used to measure the plane

strain in the plate. However, this would not have been able to measure the strain in

the plane orthogonal to the plate surface, which would likely be important given the

observed out of plane deformation. A rosette strain gauge would also be larger than

a liner strain gauge. The larger gauge would obscure more of the area that was being

photographed for the purposes of DIC measurements. Finally, a rosette strain gauge

37

would not solve the issue of attempting to predict where the strain gauges must be

located to measure the largest strains in the plate. The fact that two of the linear strain

gauges used measured compressions strains and the other two linear strain gauges

measured tension strains shows that the distribution of the load and strains in the

base plate changes abruptly over the surface of the plate.

Figure 4.9: Test 01 Deflection at the back of the base plate under 15.5kN load; strain gauge 4 can be seen on the right of the image and strain gauge 3 on the left

Strain gauge 3, shown in Figure 4.9, was positioned between the pier and the

anchoring bolt. This strain gauge exhibited linear strain deformation up to a load of

8.4kN on the anchor pier. This was the last section of the plate to start permanently

deforming. Strain gauge 4, also shown in Figure 4.9, started to record nonlinear strain

readings after a load of 5.7kN of the top of the anchor pier. What was interesting about

strain gauge 4 was that the strain in this area was negative, therefore the plate was

being compressed in this area along the direction of the linear strain gauge. If this

strain gauge were in the same area, but oriented at 90° relative to its current position,

it may have been able to capture the strain around the section of the plate at the back

38

of the base that was bending and the strain reading would likely have been positive

rather than negative.

Given the variation in strain measurements at the four plate locations, it was possible

that plastic deformation may have started at an even lower applied load at different

locations on the plate. For the purposes of further analysis, it was assumed that plastic

deformation in the plate started when a horizontal load of 4.2kN was applied to hook

up point on the top of the anchor pier.


at a 45° angle relative to the supporting HSS

4.3.1 Test 02 Setup

This test anchor was fastened to the test frame by four threaded rods in the four

corners of the anchor base plate. The width of the supporting HSS was 6” and the pier

of the anchor was centred on the supporting HSS. The test load was horizontal

(parallel to the top surface of the base plate) and oriented at a 45° angle relative to

the supporting HSS. See Figure 4.10 for an image of the anchor and test load direction.

39


4.3.2 Test 02 DIC Data and Analysis

As previously discussed, this test and the subsequent tests in this analysis were

analysed using only the data from DIC. Images were taken of the base plate at a staring

load of 0.5kN. This was used as the baseline for comparing any subsequent

deformation during testing. When the horizontal force was applied, the load was held

constant while the cameras were capturing images of the base plate. After each new

load increment was applied, the force was removed and images were captured at the

starting base load of 0.5kN. This was repeated until plastic deformation occurred in

the plate; at that point it was deemed unnecessary to track the plastic deformation in

the plate once the steel started to yield.

To determine whether the anchor was plastically deforming, a laser was set up to

track the movement of the anchor pier. The laser was attached to the camera frame,

directly opposite to the side of the pier on which the horizontal force was being

40

applied. In each test, the laser measured a point on the centre of the pier a couple of

inches away from the top of the pier. The distance measured by the laser was taken

at each load increment and at each point in the test when the load was released. If

there was no significant increase between the lengths measured by the laser when

the test load was released, data was collected for the loaded and unloaded anchor

plate at each test increment. Slight changes in the pier location (on the order of 2-

3mm) between tests were not considered permanent deformation. These changes in

pier location could be attributed to the anchor shifting or the steel settling around the

weld location. It was decided that although constantly applying and releasing the load

on the anchor was time consuming, it would be better to have collected more data

than necessary to be cautious, rather than assume plastic deformation had occurred

at a given point only to determine later through the image analysis that no permanent

deformation had yet begun.

To track the changes in the shape of the plate, a line along which to track the change

in displacement of points on the plate was chosen. This line can be seen in Figure 4.11.

This section of plate was chosen because it was the longest continuous line on the

plate that intersected the bend line at which the largest deformation occurs before

failure. See Figure 4.12 for an image of the test anchor after failure; this anchor base

plate cracked around the weld at a load of 28kN. The anchor plate ultimately failed

around the back edge of the weld between the pier and the anchor plate. Before the

ultimate failure occurred, the plate bent between the pier and the back bolt.

Measurements along the red line in Figure 4.11 were able to capture this bending.

41

Figure 4.11: Test 02 line along which deformation was measured; test load applied parallel the red line, to the right of the image

Figure 4.12: Test 02 Failure of the anchor base plate

The location of the grid points located on the line in Figure 4.11 were determined in

MATLAB, using the Camera Calibration Toolbox for MATLAB written by Jean-Yves

Bouget [98-101]. The change in the out of plane location of the plate along the line in

Figure 4.11 was plotted in Figure 4.13. The location of the points plotted were determined

using the images taken after each load increment was released. The graph therefore shows

the permanent change in location of the point along the plotted line.

42

Figure 4.13: Test 02 plot of the change in shape of the base plate along a line on the side of the plate

In Figure 4.13 the change in shape after various loads are applied, then released, can

be seen. The bold line shows the initial location of all the point at the minimum

baseline load of 0.5 kN. The line showing the location of points after the 7.5 kN load

was applied then released is similar in shape to the initial line, it is just rotated slightly

around the centre in the clockwise direction. The shape of the next line, measured

after the release of the 7.75 kN load, had a different shape compared to the previous

two lines. The points between -15mm and 70mm along the plate have a peak and the

points past 70 mm start to dip down relative to the rest of the points. This trend

became more pronounced after the release of the 8.75 kN, 9.25 kN and 10.0 kN loads

respectively. Given the change in shape of the plate between the application 7.5 kN

and 7.75 kN loads, it was determined that the plate permanently deforms between

these two loads.

43


perpendicular to the supporting HSS

4.4.1 Test 03 Setup

In this test, the anchor base plate was secured to the HSS of the test frame by four

bolts, in the four corners of the base plate, wrapping around the HSS. The horizontal

test load on this anchor was applied in a direction perpendicular to the length of the

supporting HSS. See Figure 4.14 for anchor setup and load direction.



In this anchor configuration, the deformation was tracked along two separate lines.

In Figure 4.15 the deformation of the base plate can be seen. This image was captured

at a test load of 24.0 kN. This was the last captured image before cracking was

observed around the weld at a load of 36.0kN. There is large observable deformation

44

at the side and back edges of the plate. The deformation at both these locations was

measured and used to determine at what load the base plate transitions from linear

to nonlinear deformation. This first line on which the permanent deformation at

various loads was examined was along the entire length of plate, from back to front,

2 ½" away from the side edge of the plate (See Figure 4.16). The second line was at

the back of the plate between the two back bolts, 2” away from the edge of the plate

(See Figure 4.17)

Figure 4.15: Test 03 Maximum deformation in the base plate before the observable weld failure

Figure 4.16: Test 03 Line on side of plate over which permanent deformation was measured; horizontal load pulled to the right

45

Figure 4.17: Test 03 Line at back of plate over which permanent deformation was measured; horizontal load pulled to the right

Figure 4.18 plots the gradual change in shape of the base plate after various test loads

were released. Again, the bold line was the shape of the measured line with the

application of the baseline load of 0.5 kN. After the 6.5 kN was removed, it was

observed that the anchor had rotated around a point approximately 180 mm away

from the back of the plate. The general shape of the plate between the 0.5 kN and 6.5

kN loads remained the same. After the removal of the 7.0 kN load, a slight curve in the

back section of the plate was observed. Following the application and removal of the

subsequent loads of 7.5 kN and 8.0 kN, the curve in the back of the plate became more

pronounced. Therefore, according to this plot, permanent deformation begins

between the applied loads of 6.5 kN and 7.0 kN.

46

Figure 4.18: Test 03 Out of plane deflection at the side of the base plate

The change in shape of the plate between the two back bolts is shown in Figure 4.19.

In most of the graphs plotted from the DIC data, many of the lines depicting the shape

of the plate after the test load increments were released overlap, creating messy and

confusing plots. Many of the unnecessary lines were removed so that only the data

relevant to the transition from linear to nonlinear deformation was shown. In this

analysis, the plotted points after various loads did not often overlap, therefore more

points where kept on the graph. The points depicting the change in shape of the back

of the base plate (along the line drawn on the back of the plate in Figure 4.17) move

up slightly between load increments starting at a load of 4.0 kN up until 6.5 kN. This

shows that there was a slight shift in the location of the plate; the overall shape of the

plate remained the same. This means that there was no bending in the plate and it

was not plastically deforming. Starting after the load of 7.0 kN, the centre of the line

on the plate can be seen to have curved upwards. This means that starting at the 7.0

47

kN load the back section of the plate started to plastically deform. This curve becomes

more pronounced as the load increments were slowly increased.

Figure 4.19: Test 03 Out of plane deflection at the back of the base plate

The data collected from the line on the side of the plate and the line on the back of the

plate both agree that plastic deformation began between the loads of 6.5 kN and 7.0

kN.

4.5 Test 04: Two bolts base plate connection; horizontal load

parallel to the supporting HSS

4.5.1 Test 04 Setup

In this test, the anchor was secured to the supporting HSS by two bolts, in opposite

corners of the base plate, wrapped around the HSS and bolted to a supporting angle

on the bottom of the HSS. The HSS was 8” wide and the pier of the anchor was centred

on the supporting section. The horizontal load was applied in a direction parallel to

the supporting HSS (see Figure 4.20).

48



Figure 4.21 shows how the anchor base plate was deformed under an applied

horizontal load of 14.0kN on the anchor hook up point. In this figure, there is visible

a bend line on the front section of the plate at the edge of the weld between the anchor

pier and base plate. To capture the bending at this line, the DIC measurements were

taken along the line depicted in Figure 4.22.

49

Figure 4.21: Test 04 Deformation of anchor base plate at 14.0kN load

Figure 4.22: Test 04 Line at which permanent deformation in the base plate was measured

The plot showing the change in shape of the plate along the line in Figure 4.22 after

various loads were removed can be seen in Figure 4.23. In this plot, the bold line

represents the initial shape and position on the plate under the 0.5 kN initial load. The

next line in the graph above the bold line shows the shape and location of the line on

the plate after the 5.0 kN load had been removed. This line shows that the plate shifted

slightly, but given that the shape of the line remains the same, the plate was still

undergoing elastic deformation. The line showing the shape of the plate after the 5.25

kN load was removed started to show more of a curve in the shape of the plate.

Therefore, it was at this load that the plate started plastically deforming. This curve

50

became more pronounced after the application of the 5.75 kN load, as shown on the

graph. In this test, the base plate started permanently deforming between the loads

of 5.0 kN and 5.25 kN.

Figure 4.23: Test 04 Out of plane deflection along the side of the base plate



4.6.1 Test 05 Setup

In this test, the anchor was fastened to the supporting HSS by two anchor bolts

wrapped around the support structure and fastened to an angle under the HSS. The

supporting HSS was 8” wide and the centre of the anchor was centred on the

supporting HSS. The horizontal load was applied at a direction perpendicular to the

length of the supporting HSS (See Figure 4.24).

51

Figure 4.24: Test 05 Anchor setup and direction of applied load


The shape to which this anchor base plate deformed can be seen in Figure 4.25. The

previous anchor test 04 (Figure 4.20) had a similar setup; the difference in the two

tests was that the load direction was rotated by 90° relative to the supporting HSS in

the two tests. In the previous test the front of the base plate was bent at a line

perpendicular to the load direction and tangent to the weld. In this test, there was

also a clear bending line in the plate. It was also perpendicular to the applied load

direction and tangent to the weld. The differences in the deflection in this test

compared to the previous test was that the bend line was at the back of the pier

instead of the front, and that the plate was bending in the opposite direction. To

52

capture the change in shape of the plate, the deformation measurements were in

relatively the same location as the previous test, as can be seen in Figure 4.26.

Figure 4.25: Test 05 shape of base plate under 10.0kN load; load pulled to the left in this image

Figure 4.26: Test 05 Line along which deformation in plate is measured; load pulled to the left in this image

The measurements of the point locations along the line in Figure 4.26 are shown in

Figure 4.27. The bold line was the initial shape of the plate along the line under the

baseline load of 0.5 kN. After the load of 5.25 kN was applied and released, the base

53

plate shifted by rotating in the counter clockwise direction. The overall shape of the

line remained similar to that of the initial plate shape, which means the plate had

shifted slightly, but no plastic deformation had occurred in the plate. After the 5.5 kN

load was applied and released the shape of the plate changed slightly. The back

section of the line in the plate started to curve upwards. This shows that after the 5.5

kN was applied, the plate started to permanently deform.

Figure 4.27: Test 05 Out of Plane Deflection in the base plate



4.7.1 Test 06 Setup

For this test, the anchor was fastened to the supporting HSS by two bolts, in two

opposite corners of the plate, wrapped around the 8” wide HSS and bolted through an

54

angle. The horizontal load was applied at an angle of 45° relative to the supporting

HSS.

Figure 4.28: Test 06 Anchor setup and direction of applied load


The deflection in the base plate for this test can be seen in Figure 4.29 and Figure

4.32; note that the applied horizontal load was being pulled in opposite directions in

these two pictures. Both images were taken with an applied load of 10.0 kN. Once the

load was increased to 10.5 kN, the base plate started to fracture along the weld line

in the section of the weld closest to the back bolt. Since the deflection within the plate

was not symmetric about any axis, the deflection along two lines was analysed. One

line was on the side of the plate, as shown in Figure 4.30, and the other line was at the

back of the plate as shown in Figure 4.33.

55

Figure 4.29: Test 06 Shape of deflection in the plate with a 10.0kN load; load pulling the anchor to the left in this image

The nut on the threaded rod at the back of the plate blocks part of the grid on the plate

from the view of the cameras. For this reason, the line of points being measured using

DIC did not run the entire length of the plate. This was true for both sets of

measurements taken for this anchor configuration. Both lines of points intersected

the areas of bending shown in Figure 4.29 and Figure 4.32 thus only measuring the

location of points along partial lines of the plate should not have affected the quality

of the results.

Figure 4.30: Test 06 Line on side of plate at which deflection was measured

56

The plot of point locations measured at the side of the plate drawn along the line in

Figure 4.30 can be seen in Figure 4.31. The bold line showed the original shape of the

line being analysed. The line showing the shape after the application and release of

the 5.25 kN load was similar in shape to the original line. The line showing the out of

plane deflection after the release of the 5.5 kN load started to show the plate curving

upwards at the back of the plate. The curves seen on the graph showing the out of

plane deflection after the 6.25 kN, 6.75 kN and 7.75 kN loads showed that the amount

of deflection continued to increase as the load increases. This means that the anchor

base plate started permanently deforming between the application of the 5.25 kN and

5.5 kN loads.

Figure 4.31: Test 06 Out of plane deflection at side of plate

57

Figure 4.32: Test 06 Shape of deflection in the plate with a 10.0kN load; load pulling the anchor to the right in this image

Figure 4.33: Test 06 Line along the back of the base plate along which deflection was measured

Figure 4.32 shows how the back of the base plate deformed under loading. The

unbolted back corner lifted and the back section of the base plate closest to the nut

started to bend. This was reflected in the points measured along the line drawn in

Figure 4.33. The graph in Figure 4.34 shows the progression of the out of plane

deformation after various loads. The bold line shows the location of the points along

the line at the baseline load of 0.5 kN. The next line was plotted after the release of

the 5.25 kN; it was slightly raised, but the shape remained similar. The plot of the line

58

after the 5.5 kN load was released started to change shape and curved slightly on the

right of the graph; this was the side of the line of points being measured that is closer

to the bolt at the back of the plate. As higher loads were applied and released, the

curve on the right side of the graph became more pronounced and the section of plate

on the left side of the graph rose upwards as was anticipated from Figure 4.32. The

data plotted in this graph showed that plastic deformation occurred between the

application of the 5.25 kN and 5.5 kN loads. This agreed with the deflection of the line

plotted in Figure 4.31.

Figure 4.34: Test 06 Out of plane deflection at back of plate

4.8 Comparison of Different Anchor Geometry Results

Table 4-2 shows the maximum recorded loads on the anchor measured before the

onset of plastic deformation. Test 01 determined this from the strain gauge that was

the first to start showing nonlinear behaviour (in this test both strain gauges 1 and 2

have the same, lower load). Test 02 through Test 06 determined this based on the

deformation of the plate measured though DIC. The loads in the table were the highest

recorded loads before the plate started to permanently deform. However, given the

load increments applied to the top of the anchors, the anchor may have resisted

59

slightly higher loads then those recorded before permanently deforming. The

maximum moment loads in the table were determined by multiplying the horizontal

test for by the vertical distance between the load hook up point and the base plate

(0.675 m).

Test Max. Horizontal Load (kN)

Moment Load in Centre of Plate (kN m)

Test 01

4.2 2.84

Test 02

7.5 5.06

Test 03

6.5 4.39

Test 04

5.0 3.38

Test 05

5.25 3.54

Test 06

5.25 3.54

Table 4-2: Max. loads in the base plates before permanent deformation occurs

60

It is interesting to note, in Table 4-1, that the three different test load directions on

the two-bolt anchor experience similar yield loads whereas the four bolts anchors all

yield at different loads. It can be argued that because the yield load for the first test

was determined using strain gauges, and the second and third test were analysed

using DIC it was difficult to compare the yield loads between those tests. However,

given the difference in yield loads between the second and third test, the effected of

load direction affected the yield load limit in the four-bolt anchor configuration more

than the two bolts anchor system.

4.9 Material Properties of the Steel Base Plate

Since the anchor base plate was the part of the system that was being analysed, it was

important to find the material properties of the steel used to make the base plate. The

grade of steel used for the plate was 300W. There are standards that dictate the

minimum strength of the steel; however, it would have been inaccurate to assume

that the plate was made to the minimum strength specified by the standard.

Three coupon samples of the base plate were tensile tested to determine the yield

strength and ultimate strength of the steel (See Figure 4.35 for coupon dimensions).

The yield strength was especially important for predicting the moment resistance of

the base plate. When performing the FEA analysis, young’s modulus was also

required. This was determined using the stress-strain graph results from the tensile

test.

61

Figure 4.35: Tensile test coupon dimensions; 1/4" plate thickness

The tensile tests were performed by Engineering Material Research. The dimensions

of the tensile samples are shown in Figure 4.35. The plate thickness was originally

3.8” (9.53mm). To accommodate the machines used for testing, the plate sample was

thinned down to ¼” (6.35mm). The average yield stress and ultimate strength was

372MPa and 543MPa respectively. The fractured test coupons can be seen in Figure

4.36.

Figure 4.36: Failure of tensile test coupons

62

4.10 Moment Resistance of the Base Plates

The anchor base plate was designed to be the weakest part of the system. The other

sections of the anchor and test frame were designed to be stronger, rigid and to

transfer the moment load to the anchor base plate. For this reason, it was assumed

that the entire horizontal force applied during test was transferred, as a moment load,

to the base plate. There is no current way of calculating the moment resistance of the

plate under the moment loading conditions. By observing the areas at which the plate

bent, a method of calculating the moment resistance for each specific anchor plate

was proposed.

The moment resistance of a section was calculated by multiplying a section’s elastic

section modulus (Z) by the yield strength of the material (Fy). The elastic section

modulus for a rectangular plate is shown in Figure 4.37. Since the base plate analysed

in this testing did not undergo pure bending, calculating Z=b*d2/4 will not give a

section modulus that would result in a correct moment resistance. If Z were

calculated along the 10” length of the plate, Z=254 mm*9.53 mm2/4= 5757 mm3, then

multiplied by the yield strength, Mr=5757 mm3*372 MPa= 2.14 kNm, then the

calculated moment resistance of the plate would be 2.14kNm. Table 4-2 shows that

the lowest moment that any of the anchor configurations started plastically

deforming was 2.84 kNm. This was higher than the moment resistance calculated

along the length of the plate.

63

Figure 4.37: Section properties for a rectangular plate, taken from the Handbook of Steel Construction

[102]

A new method of calculating the moment resistance for each test configuration was

proposed. A section modulus for each plate configuration was found based on the

locations of bending in the plate. The lengths of the bend location were combined and

used as the variable b in the equation Z=b*d2/4, used for calculating the elastic section

modulus, as shown in Figure 4.37. In Figure 4.38 through to Figure 4.43, the grid lines

drawn on the base plates are ½” apart; the same spacing as the grids scribed onto the

anchor base plates for the experimental testing.

Figure 4.38: Test 01 base plate bending lines used for calculating Z

64

Figure 4.38 shows the approximate lines at which the base plate bent during testing.

The four straight lines were approximately 2 ½” long each, and the two-curved

section combined were approximated at 1/3 the circumference of the outside weld

circle. Under these assumptions, Z was calculated as 10.3x103mm3 and the moment

resistance was 4.39 kNm. The maximum moment on the plate before the onset of

plastic deformation was 2.8 kNm according to the strain gauge analysis. This

calculated moment resistance was higher than the maximum moment in the base

plate before plastic deformation. However, this anchor configuration yielded at a

relatively low load compared to the other five tests, especially the two other tests that

tested four-bolt anchor base plates. When compared to the yield strengths of the

other two four-bolt anchor base tests, 4.39 kNm moment resistance in the base plate

was reasonable.


The bending lines on the test 02 anchor base plate were drawn on Figure 4.39. The

straight line had a length of 233 mm, the two smaller quarter circles had radii of 55

mm and the larger quarter circle at the back of the base plate had a radius of 116 mm.

The radius of 55 mm around the bolt holes was assumed because the arc of the circle,

assuming the centre of the circle was at the corner of the base plate closest to the bolt

hole, touched the outside of the bolt hole furthest from the corner of the plate to which

65

the hole was closest. The radius of 116 at the back of the base plate had similar

reasoning. In this case, with the centre of the arc positioned at the back corner of the

base plate, the outer edge of the arc touched the edge of the weld around the pier.

Using these lengths to determine Z, a moment resistance of 4.98kNm was calculated.

The tests measured using DIC determined between which horizontal loads on the top

of the anchor pier the plate starts to permanently deform. Test 02 started plastically

deforming between the loads of 7.5kN*0.675m=5.05kNm and

7.75kN*0.675m=5.23kNm. The calculated moment resistance of 4.98kNm was lower,

but very close, to the moment calculated while the plate was still elastically deforming

This showed that the calculated moment resistance in the plate was reasonable and

slightly conservative.


Figure 4.40 shows the lines along which test 03 bends. The four short straight lines

on the right side of the plate were approximated as 2 ½” long each, and the two round

sections combined were assumed to be 1/3” the circumference of the outside weld

line. This gave a moment resistance of 4.39 kNm. This was the same as the moment

in the plate at the last recorded load before permanent deformation:

6.5kN*0.675m=4.39kNm.

66


Test 04 shown in Figure 4.41 had a bending line at the front of the anchor pier that

was 233 mm long and two quarter circles with radii of 55mm each around the bolts.

Using these lengths, the moment resistance of the base plate was calculated to be 3.43

kNm. This fell between the moment given by the load before the onset of plastic

deformation (5.0kN*0.675m=3.38kNm) and the load at which plastic deformation

was first observed (5.25kN*0.675m=3.54kN).


Figure 4.42 shows the locations at which the base plate in test 05 bent. The line at the

front of the plate was 233 mm long, the radius of the larger quarter circle at the back

67

of the plate was 116mm. These lengths combined resulted in a moment resistance of

3.51 kNm. This calculated moment resistance for the plate was slightly lower than the

moment in the plate at the last measured horizontal load before the base plate started

to permanently deform: 5.25kN*0.675m=3.54kNm.


In test 06 the base plate bent along the two lines shown in Figure 4.43. The vertical

line on the right side of the plate was 254 mm long and the quarter circle at the bottom

left corner of the plate had a radius of 116 mm. These lengths combined resulted in a

calculated moment resistance in the plate of 3.69 kNm. This fell in between the

moment in the plate at the last recorded load experiencing elastic deformation at

5.25kN*0.675m=3.54kNm and the load at which the base plate started plastically

deforming at 5.5kN*0.675m=3.71kNm.

The moment resistances calculated according to the bend lines observed during

testing resulted in moment resistances that were either slightly lower than the last

recorded moment loads before the base plate started plastically deforming or they

were in between the moment loads that marked the transition from elastic to plastic

deformation. The only exception was the moment resistance predicted for the first

test anchor. The reason for the discrepancy between the accuracy of this prediction

compared to the other five anchor configurations was that this base plate yielded at

68

a lower load according to the strain gauge data; the other five tests used DIC data for

determining the onset of plastic deformation. Unfortunately, this DIC data is not

available for the first test. Overall, the moment calculations for the six specific test

configurations predicted moment resistances more accurately that the typical

moment resistance calculation in Figure 4.37 for a rectangular section.

69

Chapter 5 Finite Element Analysis

Finite element analysis (FEA) is an important and powerful tool used to predict the

behaviour of structures under given loads. For this analysis, the FEA software ANSYS was

used for the computer modelling and simulations. This chapter discusses how a FEA model

was created to predict the stress and deformation of the anchor base plates tested in Chapter

4. The data collected during the experimental testing was used to validate the accuracy of

the FEA.

5.1 Finite Element Model

The focus throughout this thesis project was analysing the behaviour of anchor base plates.

This still held true for the computer modelling. The six test configurations that were

experimentally tested were the same base plate configurations that were simulated in

ANSYS. However, when building the computer model, it was not necessary to includes all

the test components that were required for the physical testing. The more components that

were included in an FEA, the longer the run time for the simulation and the greater the

computational cost. In this model, all the necessary components that will affect the anchor

base plates were included and the rest of the parts used in the experimental testing were

omitted.

A short piece of HSS, a few inches longer that the base plate, acted as a base for the

modelled anchor. The test frame was designed to withstand much higher loads than the

base plate, therefore it was assumed that the support HSS did not move during testing. By

adding a fixed constraint to the HSS section, this fixed support was modelled without

needing to model the entire frame. The same HSS section dimensions were used as the

section dimension of the supporting HSS on the test frame.

70

The rods and nuts holding the corners of the base plate were also partially included in the

model. This simulation was run at the maximum loads each anchor withstood before

plastically deforming. This leads to the assumption that, if the anchor bolts do deform, the

deformation will be negligible. To increase the efficiency of the model, only a short section

of the bolts was modelled.

The pier was kept in this model, but anchor point at the top of the pier to which the

horizontal force was applied was removed. In the model, the load was applied to the top

face of the round HSS pier. The pier was lengthened so that the top of the section was the

same distance away from the top surface of the plate as the centre of the anchor point was

during physical testing. This was done so that the moment load on the centre of the base

plate resulting from the applied load on the top of the anchor pier was the same in the FEA

model as it was during the experimental testing.

Failure in the test anchors during experimental testing occurred typically around the weld

between the pier and the anchor plate. This suggests that the weld is an important part of

the anchor design. Therefore, the full ½” weld between the pier and plate was included in

the ANSYS model.

The material properties for the base plate were inputted to be the strength values determined

in the tensile testing of the base plate metal. Grade 300W steel was used for the plate. This

grade must have a minimal yield strength of 300MPa; from the tensile testing, the base

plate was determined to have a yield strength of 372MPa, which is much higher than

expected. Since the base plate was the focus of the analysis it was important to have

accurate materials properties, rather than use assumed minimum values for the grade of

steel used. To control the maximum allowable stress in the base plate, the 300W plate

material was set to behave under bilinear isotropic hardening conditions. The HSS pier and

rectangular support sections were designed to withstand much higher loads than the steel

base plate. For this reason, the materials properties for the round HSS pier and the

rectangular HSS support were assumed to be the minimal values for these section according

to the Handbook of Steel Construction [102]. See Table 5-1 for the steel material properties

used in the FEA model. If the maximum stresses were concentrated in the base plate, the

exact material properties for the other sections were not required. These sections were

71

strong enough that they should transfer all the loads to the base plate. If they fulfilled this

purpose, their exact properties were not going to affect the stress in the base plate.

Section Yield Strength

(MPa)

Ultimate Strength

(MPa)

Young’s Modulus

(MPa)

Base plate 372 543 190 000

Pier HSS 317 450 200 000

Rectangular HSS 350 450 200 000

Table 5-1: Material properties used in the FEA model

5.2 Model Parameters and Constraints

Since the experimental testing was performed with incremental loads being held on the

anchor, the static structural analysis model in ANSYS was used for the setup.

The top face of the rectangular supporting HSS was set as a fixed support. This was done

because in the experimental testing the test frame was designed to be able to withstand

loads significantly higher than the maximum loads applied to the anchor during testing.

The nut and rod were also assumed to not deform before the onset of plastic deformation

in the plate. For this reason, the nuts and rods in the model were set as rigid bodies; this

means that they were not permitted to change shape during the computer analysis. The

stresses in rigid bodies were not computed and the bodies were not meshed; this allowed

the model to be solved quicker during analysis. In ANSYS, rigid bodies were not permitted

to have their surfaces constrained with a fixed support. Therefore, a remote displacement

constraint was applied to the bolts and all the coordinate directions and rotation angle

displacements were set to zero. This essentially meant that the nuts and bolts were fixed in

place. The force on the system was applied to the top surface of the anchor pier. The

magnitude of the applied force was set to the maximum load applied before plastic

deformation of each test configuration and the direction of the load was set to be the same

72

as that in the experimental testing (as summarized in Table 4-2). The mesh in the model

can be seen in Figure 5.1 and the force and constraints can be seen in Figure 5.2.

Figure 5.1: FEA mesh

Figure 5.2: FEA constraints and load

5.3 Finite Element Analysis Stress and Deflection Results

Analysis

The FEA results focused mainly on the stress and deformation calculated in the base plate.

For all six anchor geometries that were modelled, the location of maximum stress in the

system was always in the base plate. This result was anticipated because all the other

components were overdesigned for the expected test load. In addition, the anchor base plate

was made thinner than typically used for anchor base plates so that the locations at which

the plate bends could be easily seen and studied with smaller test loads required within the

system.

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Since the experimental testing focused mainly on measuring the deflection in the base

plate, the FEA results for deflection were compared to the measured deflection within the

plate at the areas of maximum deformation. The areas of maximum stress were compared

to the areas in the plate that fractured when the system failed.

5.3.1 Test 01 FEA Results

As seen in Figure 5.3, the largest stress concentrations were concentrated in the base plate

and the weld connecting the pier to the base plate. The welded area between the pier and

plate experienced the highest moment loading. This moment load was then dispersed

throughout the plate.

Figure 5.3: Test 01 FEA stress in anchor

Figure 5.4 shows the stress distribution in just the base plate. The 300W grade plate had a

yield strength of 372 MPa. The maximum stress calculated by the FEA model was 362

MPa in the plate. This high stress occurred only in a small section of the plate close to the

two back bolt holes. Interestingly, the section of the base plate where the strain gauges

74

showed yielding in the plate at the lowest test loads was the section of the plate that has the

lowest stress values according to FEA. This discrepancy suggested that either the model or

the experimental testing did not accurately capture the behaviour of the base plate under

the moment load.

Figure 5.4: Test 01 FEA stress in base plate

Figure 5.5 shows the out of plane directional deformation in the anchor base plate. The

fact that both the stresses in Figure 5.4 and the deformation in Figure 5.5 had a

concentrated area of stress and deformation, respectively, centred around the edge of the

weld at the back of the pier agrees well with the information learned during the

experimental testing. It was at this location that the plate failed and started to fracture (well

after the onset of plastic deformation).

75

Figure 5.5: Test 01 FEA out of plate deformation of base plate

The maximum out of plane deformation shown in Figure 5.5 was 0.44 mm. The change in

position of this area measured using DIC was 0.31 mm. The point at which deformation

was measured was on the centreline of the plate, 2” away from the back edge of the plate,

between the loads of 2.22 kN and 4.44 kN. In this simulation, the maximum deformation

was predicted to be slightly larger than the measured deformation.


In this simulation, the maximum stress was predicted to be 545 MPa, which is close to the

ultimate stress of 543 MPa, and is shown in Figure 5.6 by the areas in red. The red area

around the weld was in the location of the plate that fractured when the system failed

(Figure 5.7). The other red location, by the back bolt, was obscured from view by the bolt

during physical testing. This made the location difficult to observe during testing. Looking

at the deformation of the plate and back bolt in Figure 5.7 taken after the plate fractured,

76

it can be reasonably assumed that there was a high stress concentration surrounding the

back bolt location on the base plate.


Figure 5.7: Test 02 physical test image showing plate fracture

77


The location of maximum stress and deformation shown in Figure 5.8 and Figure 5.9,

respectively, corresponded with the location of fracture around the weld where this anchor

geometry failed. The stresses along the line (shown in Figure 4.11) where the deflection

measurements were taken to determine at what load the plate transitioned from linear to

non-linear behaviour all fell in an area of the base plate that demonstrated stresses within

the yield strength of the material (according to FEA and the test material properties of the

base plate). This demonstrated that the distribution of the stresses in the plate determined

with the finite element model agreed with the experimental test results. Due to the weld

(around which the grid drawn on the plate used for DIC was slightly obscured) and the nut

on the threaded rod, DIC measurement that tracked the deformation of the plate could not

be taken at the areas that showed the maximum stress. If strain gauges were used during

experimental testing rather than DIC, the strain gauges could not be used close enough to

the weld in the heat affected zone of the base plate and the nut still obscured the area around

the bolt hole so that a strain gauge could not have been attached to the base plate in that

location either.

78

Figure 5.9: Test 02 FEA out of plane deformation in base plate

The maximum out of plane deformation predicted by FEA and shown in Figure 5.9 was

0.75 mm. The deformation measured by DIC at a point 3” to the left and 3” up from the

bottom right of the plate shown in Figure 5.9 gave a deformation of 2.46 mm between the

loads of 0.5 kN and 7.5 kN. The larger deformation measured from the experimental testing

could have been due to the plate possibly rotating rigidly around the supporting HSS. Also,

the FEA model did not consider the fact that there was a heat affected zone around the weld

that may have affect the deformation, stress levels and distributions, in the plate.


Figure 5.10 shows that a maximum stress of 553 MPA in this anchor geometry occurred

at the back of the plate around the edge of the weld and around the back two bolt holes.

The maximum stress location around the weld occurred in the area of the base plate that

fractured when the anchor plate failed, and the two bolt locations at the time of failure

experienced large deflections (See Figure 5.11). From the shape of the deformed plate, it

79

could be concluded that the plate was being pulled in tension between the area of high

stress around the weld and the bolt locations.


Figure 5.11: Test 03 physical test image showing plate fracture

80


The areas of maximum stress shown in Figure 5.12 on the base plate occurred in areas of

the plate that could not be monitored during the physical testing using either DIC or strain

gauges. The stresses calculated by FEA in the plate along the areas of the plate that were

analysed and used to determine the load at which the plate started plastically deforming in

the experimental test results remained under the yield strength of 372MPa.


81

The predicted maximum out of plate deflection of the plate determined by FEA was 0.69

mm (see Figure 5.13). This was much smaller than the deflection of 5.85 mm measure in

the centre of the plate, 2” away from the back of the plate, using DIC. The larger deflection

measured in the experimental testing could again be due to shifting of the entire anchor and

the effect of the heat affected zone around the weld that was not accounted for in the finite

element model.


The FEA stress results for this anchor, seen in Figure 5.14, showed that the area of

maximum stress occurred at the front of the plate and around the bolt holes. During the

experimental testing, a bend line was observed along the front edge of the weld where the

base plate was being compressed and the threaded rods were bent as the moment on the

pier caused the plate to deform and pull the rods in towards the centre of the plate (see

Figure 5.15). These experimental test observations suggested that the areas of maximum

stress in the base plate, given as 445 MPa, occurred in the areas of max stress shown in

Figure 5.14.

82


Figure 5.15: Test 04 shape of plate under test load of 13.0kN

83


The areas of maximum stress on the plate shown in Figure 5.16 were not analysed with

the use of DIC. It was not possible to collect image data at these locations because of the

interference on the grid pattern by either the nuts or the weld. The line along which

deflection was analysed ran parallel to the supporting HSS and as close to the weld as

possible (see Figure 4.22). Along this line over which DIC measurements were taken to

observe the point at which plastic deformation began, the stresses in the plate were less

than the yield stress of 372 MPa. This showed that, in the area measured by the test, both

the FEA model and the experimental testing agreed that there was no plastic deformation.

84


The back corner in this plate experienced the largest deflection. This was shown both in

the experimental testing (Figure 5.15) and in the FEA result (Figure 5.17). In FEA, under

a load of 5.0 kN, the predicted deformation was 4.13 mm. From the experimental test data

at this load, the deformation was measured to be 10.96 mm. This value was measured at

½” down and ½” to the left from the top right corner of the plate. Using DIC it was difficult

to accurately select a point on the edge, and especially on the corner edge of the plate. The

plate does not form a perfect right angle between the top and side surfaces of the plate;

therefore, the perception of the edge location may change between different cameras that

captured the image of the base plate at different angles. The discrepancy between the FEA

and experimentally measured deformation may be due to shifting of the plate during

testing; the bottom surface of the base plate and the top surface of the supporting HSS may

not both have been perfectly flat. Welding the pier onto the base plate may have slightly

deformed the base plate. The 3/8” thick base plate was only slightly larger that the ½” weld

size. The edges of the plate were observed to angle upwards slightly after the pier was

welded to the plate compared to the shape of the plate before welding. The discrepancy

between deformation in the test compared to the discrepancies in tests 1, 2 and 3 may have

85

been larger because there were fewer bolts holding the base in place. This geometry relied

more on the strength of the anchor base plate and less on the fasteners.


In this anchor base configuration, there was a bolt holding down the back corner of

the plate. The areas of maximum stress were in the back of the plate between the weld

and the plate, in the area closest to the bolts, and around the bolt hole (see Figure

5.18). This anchor configuration showed a large tension on the back of the plate. This

agreed with the way in which the base plate deformed during testing (see Figure

5.19).


86

Figure 5.19: Test 05 image showing crack initiation around weld at the back of the pier


The maximum stress on the plate given by the FEA was 530 MPa. This was larger than the

yield strength (372MPa) of the plate, but below the ultimate strength of 543 MPa. In Figure

5.20 the areas in red show where the stress exceeded 372 MPa. Again, these areas of high

stress occurred in places of the plate that were difficult to analyse during the experimental

testing. The line on the plate along which the deformation was tracked using DIC runs

along the plate perpendicular to the supporting HSS on the outside of the pier (see Figure

87

4.26). Along this area of the plate, the stress remained below the 372MPa limit. Therefore,

this FEA model did not contradict the measured experimental data.


The area of maximum deformation in the FEA model shown in Figure 5.21 agreed with

the bend location observed in the experimental testing in Figure 5.19. The maximum

deformation according to FEA was 0.77 mm and according to the DIC data the deformation

was 2.18 mm. The DIC measurement was taken between the loads of 0.5 kN and 5.25 kN

and was taken 4” to the left and 2” up from the bottom right corner of the plate shown in

Figure 5.21.


The final anchor configuration tested had the least symmetric geometry, and therefore

demonstrated an unsymmetrical stress distribution (see Figure 5.22). There were areas of

high stress around both bolt holes; with more stress around the back bolt hole than the

front. There were also two locations of high stress around the weld. The larger

88

concentration occurred at the section of weld closest to the back bolt. Between this section

of stress and the area around the back bolt hole the plate was being pulled in tension. The

other area of high stress around the weld was shown at the front of the anchor where the

pier was applying a compressive load on the base plate. These regions of high stress agreed

with the deformation and fracture observed in the base plate during physical testing (see

Figure 5.23).


Figure 5.23: Test 06 fracture in base plate during experimental testing

89


The maximum stress in the plate determined by the FEA in Figure 5.24 was 481 MPa.

These locations occurred in areas that could not be analysed with DIC or strain gauges.

The DIC results measured the change in shape of two lines on this plate. One line was 2”

away from the bottom edge of the plate and the other was 2” away from the right edge of

the plate shown in Figure 5.24. The lines on the plate can be seen in Figure 4.30 and

Figure 4.33. These areas of the plate showed stresses below the yield stress of the plate.

The results of the FEA for the stresses in the plate matched the data collected during the

experimental testing of this anchor configuration.

90


The maximum deformation shown the in FEA model of the plate occurred at the back

corner of the plate that was not bolted. The predicted out of plane deformation in Figure

5.25 was 3.18 mm and the measured deformation using DIC was 7.59 mm. The reasoning

for this discrepancy was the same as discussed in previous tests. It was interesting to note

that there was no deformation in the plate at the front of the pier. When the plate started to

permanently deform, a bend line was seen along the front of the plate, tangent to the front

tip of the weld area (see Figure 5.23). It was possible that the deformation in this area only

starts to occur once the plate had started yielding between the pier and the back bolt (also

a location of bending that can be seen in Figure 5.23). Once the back sections of the base

plate started to permanently deform, more of the load was dispersed to the front of the

plane, creating a second line of bending at the front of the plate.

5.4 FEA Model Conclusions

Overall, the finite element model results agreed reasonably well with the data

collected during experimental testing in Chapter 4. The highest stresses in the FEA

were in the base plate. This was as expected because the anchor pier and support HSS

91

were designed to withstand larger loads than the base plate. The maximum stress

concentrations around the pier in the weld occurred at areas that ultimately failed in

the experimental testing at higher loads. The stress around the bolt holes was

concentrated at bolts that deformed significantly by the end of the tests.

Some of the stresses predicted were higher than the yield stress of the plate. However,

these predicted areas of high stress were at or below the ultimate strength and were

in areas of the plate for which stress could not be measured. It was possible that these

stresses were present during physical testing. There were several reasons some of

the high stress areas could not have been analysed in the physical testing. The areas

around the bolts were obscured by the nut on the top of the rod. The nut prevented

DIC readings being taken for deflection around the bolt holes; the omission of

washers under the nut was done to prevent further obstruction on the plate around

the area of the threaded rods. The nut also prevented strain gauges from being

adhered to these areas to measure the strain around the bolt holes. The other area of

high stress was around the weld connecting the pier to the base plate. Strain gauges

cannot be used in this area of the plate because of the heat affected zone created by

the weld. The weld also obscured parts of the grid scribed in the blue tool dye paint.

The grid was used to select the point used for DIC analysis of the base plate. In the

areas where the grid was ruined by the welding, DIC reading could not be taken.

Most of the deformation results predicted by FEA were smaller that the measured

deformation using DIC at the same loads as those applied in the finite element model.

There were multiple reasons which, acting together, can explain this discrepancy. The

first was that the anchor may have shifted and settled once the load was applied to

the top of the anchor pier. The anchor plate and HSS support may not have been

completely flat, leading to the rotation of the anchor plate between the load

increments applied before plastic deformation. This was especially likely given the

lines plotted from the DIC results in the experimental testing analysis confirm this

phenomenon. In multiple tests, the line along which points were measured retained

its overall shape, but the location shifted (either up, down or rotated) before the onset

of permanent deformation. This shift may have explained the relatively large

92

displacement measured during testing versus the deformation predicted by FEA.

Another phenomenon that affected the physical testing was the fact that the plate

deformed slightly around the heat affected weld area during the welding process. The

addition of heat in the centre of the plate caused the edges of the plate to tilt upwards.

A relatively large weld (1/2”) was used on the 3/8” plate so that the weld, like the

pier and supporting HSS, was overdesigned for anticipated test loads. The fact that

the weld was overdesigned was further supported by the fact that the fracture in the

system often occurred through the base plate at the edge of the welded section.

Recommendations for the improving the model to better reflect measured test data

includes adding the heat affected zone around the weld as part of the model. This area

had a stress concentration in all the models and many of the base plates failed in this

area during experimental testing. Another suggestion would be to include more of the

components that were removed to simplify the model. These include the anchor hook

up point, a longer section of the supporting HSS, the full length of the threaded anchor

rods and the angles underneath the supporting HSS used to fasten the anchor to the

test frame. Adding these items to the model may result in FEA deflection predictions

closer to the measured deflection from the experimental testing.

93

Chapter 6 Conclusions and Recommendations

6.1 Conclusions

There were two different anchor models studied: one was fasted to the supporting HSS

with four threaded rods wrapped around the support structure and the other was fastened

to the HSS by two threaded rods wrapping around the HSS. Since the anchor must be able

to withstand a load applied in any direction, three different load directions were tested for

each anchor.

The test frame performed as was expected. No deformation was observed in the test frame.

As test loads increased, the angle of the pier changed as the plate started to bend. However,

the pier itself underwent no visible deformation. The threaded rods holding the anchor to

the supporting system did undergo visible deformation. This deformation was observed to

only have started after the plate started yielding and bending out of shape. Therefore, it was

concluded that since this deformation only began after the permanent deformation of the

base plate began, that the bending in the threaded rods did not affect the DIC results used

to determine when the base plate started plastically deforming.

The use of DIC for measuring the deformation of the plate was an effective method for

analyzing the deflection of the anchor base plates under a moment load. The greatest

advantage of this measurement method was that the location of points on the plate can be

measured after the test was finished. This allowed the areas of maximum deflection to be

observed before the measurements were taken. Using the MATLAB program for DIC

analysis provided a strong platform for processing and presenting the collected data.

Every component of the test setup functioned as expected. In the future, this setup could

continue to be used for further testing. This can include different anchor configurations

which could include variables such as plate thickness, base plate span, pier diameter, bolt

diameter and different materials. Through further analysis using this test setup, the variable

in the anchor design could be optimized for multiple applications.

94

The load at which the base plates started permanently deforming was spread over a wider

range for the four-bolt anchor, ranging from 4.2 kN to 7.5 kN. The two-bolt anchor plates

started plastically deforming in a range of 5.0 kN to 5.5 kN. The two-bolt fastening system

was generally weaker. This is to be expected as there were fewer bolts holding the anchor

base plate in place. The fact that the base plates started plastically deforming at similar

loads in all directions showed that the two-bolts anchor configuration was less sensitive to

the direction of the applied load.

Most of the anchors tested experienced fracture in the plate around the outside edge of the

weld. The one exception was test 03; this anchor had no bolt on the back half of the plate

and therefore no large tension load between the weld area and a bolt hole. For the other

five anchor configurations, a crack formed in the base plate at the edge of the weld in the

closest area to any bolts being pulled in tension. For the anchor bolts with two threaded

rods under tension loads, the cracks formed in two locations, then eventually joined in the

center. The area of the plate under the anchor pier was stiffened by the presence of the pier.

Around the pier, the ½” weld also provided additional strength. Therefore, the section of

plate at the outside of the weld became a weak spot in the structure and, consequently, the

area in the plate that fractures when the structure ultimately fails.

The FEA model proposed agreed with the data collected during the experimental analysis.

The maximum predicted stresses were shown to be in the areas of the plate that ultimately

failed. The deflection in the FEA model was smaller in general than the measurements

measured during the physical testing. This was likely due to the plate shifting and from the

base plate deforming after the pier was welded to the center.

6.2 Recommendations

The analysis of anchor base plates in this thesis provides a start to understanding the

behaviour of large span plates undergoing moment loads applied to the center of the

plate through round piers. To get a more comprehensive understanding of these base

plates, more configurations of plates should be tested. As base plate thicknesses are

95

increased the system becomes more rigid. It would be interesting to test thicker

plates to determine if the plate thickness affects which areas of the plate deform.

The tests performed gave an idea of where the base plates should deform. In future

tests, the grid can potentially be drawn with points closer together in areas that are

suspected to be of higher interest. This will provide more plot points, which can lead

to more accurate data.

Further work on the FEA model to include the effects of the head affected zone around

the weld area could help to obtain more accurate deformation predictions. Another

improvement to the model could be to include more of the components from the

experimental test setup that were excluded in the model.

The finite element model was shown to predict that the areas of high stress were seen

in areas for which deflection and strain could not be measured. If a method could be

found to measure the behaviour of the base plates in these areas, that would be

helpful in determining the validity of the finite element model. One possible solution

could be welding the pier to the plate before spraying the anchor base with the blue

tool dye paint and scribing the grid. It would be more difficult to draw the grid in this

case, but it may be possible to take DIC deformation closer to the welded area on the

plate.

96

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