®

TILMAN ENGINEERING SOLUTIONS LLC

USER MANUAL & VERIFICATION EXAMPLES

For Structural Engineering Tools Compatible with ETABS®, SAP2000® and CSiBridge®

TILMAN Engineering Solutions LLC October 2019 Slingerlands, NY, USA SAP2000®, ETABS® and CSiBridge® are registered trademarks of Computers & Structures, Inc.

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COPYRIGHT

Copyright ©2019 TILMAN ENGINEERING SOLUTIONS LLC, All Rights Reserved.

Proudly developed in the United States of America.

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DISCLAIMER

THE USER ACCEPTS AND UNDERSTANDS THAT NO WARRANTY IS

EXPRESSED OR IMPLIED BY THE DEVELOPERS OR THE DISTRIBUTORS

ON THE ACCURACY OR THE RELIABILITY OF THESE SOFTWARE

TOOLS. THE USER MUST COMPLETELY UNDERSTAND ALL THE

ASSUMPTIONS MADE AND SHOULD BE ABLE TO INTERPRET THE

RESULTS AND ACCOMMODATE ANY CONDITIONS NOT EXPLICITLY

HANDLED BY THE SOFTWARE TOOLS.

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Table of Contents Chapter 1 Introduction 4

About the Manual ............................................................................................................... 4

Tools Developed by TILMAN ............................................................................................ 4

Tools Compatibility with Older Versions of CSI Products ................................................ 5

Chapter 2 Installation and Licensing 6

Installation Instructions ....................................................................................................... 6

Licensing ............................................................................................................................. 7

Chapter 3 Pile Group Tool 9

About the Tool .................................................................................................................... 9

The Tool “GUI” ............................................................................................................... 11

Analysis of Pile Groups ................................................................................................... 14

Design of Pile Groups ....................................................................................................... 15

Summary of Results ......................................................................................................... 17

Chapter 4 Wall Cracking Tool 18

About the Tool .................................................................................................................. 18

The Tool “GUI” ............................................................................................................... 19

Design Codes ................................................................................................................... 21

Analysis ........................................................................................................................... 23

Summary of Results ......................................................................................................... 24

Chapter 5 Seismic Irregularities Tool 27

About the Tool .................................................................................................................. 27

The Tool “GUI” ............................................................................................................... 28

Appendix A Verification Examples .................................................................................................... 37

Example 1: Pile Group Tool ............................................................................................ 37

Example 2: Wall Cracking Tool ...................................................................................... 41

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Chapter 1

Introduction

About the Manual

The main goal of the tools developed by TILMAN Engineering Solutions LLC is to facilitate the structural

engineer’s tasks and increase work production in the most practical manner. A great deal of engineering

experience, industry feedback and technical know-how have been utilized for the development of these

tools.

Each tool is integrated with various products of Computers and Structures, Inc. using CSI Application

Programming Interface (API). In the current version of the tools, the input parameters can be entered in

either Imperial or Metric SI units. Throughout this manual, we often refer to the integration of these tools

with SAP2000® software developed by CSI but the same discussion applies to the integration with other

CSI products, like ETABS® and CSiBridge®.

Tools Developed By TILMAN

The following tools are currently developed by TILMAN Engineering Solutions LLC:

● Pile Group Tool: This tool automatically connects with CSI Software via API and loads the model

chosen by the engineer. The tool automatically recognizes all restrained or spring supports, and all

load combinations present in the model. The engineer can interactively analyze or design the pile

group at selected joints or at all joints for any set of load combinations selected. The tool

interactively reports the results for the governing case at each joint. Then it can be used to either

analyze or design pile group foundations, using pile capacities defined by the engineer, which can

be different in tension and compression. The tool can also include the self-weight of pile cap in

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design and analysis. A summary of results is available in the GUI also saved to *.txt file for future

reference.

● Wall Cracking Tool: This tool automatically connects with CSI Software via API and loads the

model chosen by the engineer. The tool retrieves all walls and all load combinations present in the

model. Various design codes are available for selection in the GUI. The tool uses the selected code

to calculate the modulus of rupture based on the concrete compressive strength. The original model

is never modified but instead the tool saves the model with its original name but adding

“_cracked.edb” at the end of the file name. It then sets all membrane modifiers to 1, reruns ETABS®

analysis and compares vertical stresses S22 with the modulus of rupture for all selected walls and

load combos. Based on the stress comparison, the tool applies cracked and uncracked modifiers as

selected by the engineer to the corresponding walls. Two types of modifiers are available for

selection Wall Cracking Tool for ETABS: (1) User defined modifiers based on the design codes

independent of wall reinforcement and (2) Program calculated modifiers based on the explicit

method that’s dependent of wall reinforcement. The saved-as model will have those modifiers

automatically assigned. A summary of results is available in the GUI then exported as XML file

and is automatically saved to *.txt file for future reference.

● Seismic Irregularities Tool: This tool automatically connects with CSI Software via API and loads

the model chosen by the engineer. The tool retrieves all seismic load cases present in the model.

Various seismic irregularities checks and calculation of seismic design category are supported

based on IBC/ASCE 7 codes. Go to Chapter 5 for detailed information about this tool.

Tools Compatibility with Older Versions of CSI Products

This set of tools is compatible with multiple versions of ETABS®, SAP2000® and CSiBridge® as indicated

in the products page of TILMAN website. The tools always launch their specific version of CSI products.

Please contact TILMAN Engineering Solutions LLC at support@tilmanllc.com if you need any additional

information on the version of the tool supported and the expected release date of future versions.

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Chapter 2

Installation and Licensing

Installation Instructions

The tools developed by TILMAN Engineering Solutions LLC are available electronically as a full

installation by download from the internet using TILMAN’s website https://tilmanllc.com/products.

Installing these tools does not uninstall any previous versions of the tools. The tools are compatible with

32-Bit and 64-Bit applications of CSI software, can be installed over 32-Bit and 64-Bit operating systems

and are compatible with recent versions of Windows Operating Systems (Windows 10, 8, 7). Step by step

instructions are provided below to download and install the tools:

● Fill up the evaluation request form and download the installation setup file(s) from the ftp link

displayed on the screen after you click “Send Request”.

https://tilmanllc.com/evaluation-request-form

● Run the executable EXE setup file.

● After accepting the licensing terms and conditions, the engineer may either choose the installation

folder or accept the tool’s default location. See Figure 2.1 for Pile Group Tool installation setup

form.

● The installation setup will guide you through the process. The engineer has the option to launch

the tool after the installation is successfully completed.

● To uninstall the tools for any reason, simply go to the tool installation directory and run

uninstall.exe utility.

When running the tool for the first time or if the tool does not find a valid license file, it still runs but on

trial mode. Trial mode cannot be used for engineering production work, it is provided so that the engineer

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can review the features supported and learn all the functionalities before placing an order. All major features

are kept enabled in the trial mode, however, some options are disabled or set to specific values. The

following are the limitations for the trial mode tools:

● Pile Group Tool: Pile capacities and pile spacing are disabled. The default values are used and

cannot be overwritten.

● Wall Cracking Tool: Concrete modulus of rupture is based on a fixed value of concrete

compressive strength and cannot be overwritten.

● Seismic Irregularities Tool: Models with a maximum of 5 stories and 600 point objects can be

analyzed using this tool.

Figure 2.1: Pile Group Tool installation setup form

Licensing

The tools you seek to install or have previously installed from TILMAN Engineering Solutions LLC can

be licensed only on the condition that you agree on the licensing terms and conditions. A copy of the “Tool

License Agreement” is available in the tool’s installation directory on the local machine. The tools are

protected by a licensing system but can still run on trial mode in the absence of a license file (See section

“Installation Instructions” for additional information about the limitations of the trial mode). Follow the

instructions below to complete an order and obtain a license file from TILMAN:

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● Run the tool you downloaded when submitting your evaluation request form as described above

and go to Options > Help > Get Locking Code as shown in Figure 2.2. Use Ctrl+c (no need to

select) to copy the locking code of the PC where you want to install the tool.

● Visit https://tilmanllc.com/products and add to cart the tool you want to purchase. Proceed to

Checkout and use Ctrl+v to paste the locking code under "Notes" text area available in shopping

Cart > Checkout form.

● TILMAN is committed to respond to all licensing queries 7 days a week. We will email you back

the license file(s) on the same day of processing your order (given that we received the locking

code of your local computer) when submitted before 9 pm EST or in the next morning otherwise.

● Once you receive the “license.txt” file(s) from TILMAN, copy it into the tool’s installation

directory (that is the same folder where the tool’s .exe file is located).

The license file you receive will be standalone, nontransferable and locked to one single computer that

corresponds to the same locking code you sent to TILMAN. Network licensing are not currently supported.

Please contact TILMAN licensing department for additional help on recovering your license if, for any

reason, you lose the PC for which the license was provided.

Figure 2.2: Locking Code from within the tool’s graphical user interface

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Chapter 3

Pile Group Tool

About the Tool

Pile Group Tool is a sophisticated, yet easy-to-use application that seamlessly connects via API with latest

versions of CSI software SAP2000®, ETABS®, and CSiBridge®. The tool is started from the local computer

by either clicking on Windows Start Menu > TILMAN Engineering Solutions LLC > Pile Group Tool or

by double clicking on the Desktop Shortcut > Pile Group Tool.

Pile group analysis and design features are not supported in CSI Software. Post-processing of CSI software

results for pile group analysis can be an extremely hectic and cumbersome task that’s usually done by using

external spreadsheets or tables such as CRSI handbook. These tasks become even more involved when

reactions include both vertical loading and biaxial moments or when the model is revised due to a layout

change that typically alters the foundation loads. Also, the tool can automatically calculate the self-weight

of the pile cap and adds it to the dead load. All these tasks are automated in Pile Group Tool which makes

the results readily available and optimizes multiple interactions with the model in a productive and efficient

manner.

The recommended steps the engineer shall follow after starting the tool: (1) click on Browse button to the

folder where CSI software model file is saved and, for each tool, select the corresponding *.edb file for

ETABS®, *.sdb file for SAP2000® and *.bdb file for CSiBridge®, (2) click Load Model button, the tool

connects with CSI software via API, opens the model and loads all load combinations available in the model

and all joints that possess vertical stiffness into the GUI of the tool, (3) update the input parameters as

applicable to the specific project in the desired units, (4) click on Run radio button to run either an analysis

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or design of the pile groups for the entire project, (5) review the results interactively within the tool, and

(6) display table with the summary of results in any of the selected units.

When running the tool for the first time or if the tool does not find a valid license file, it still runs but on

trial mode. See Chapter 2, section “Installation Instructions” for additional information about the

limitations implemented in the trial mode.

Figure 3.1: Graphical User Interface of Pile Group Tool

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The Tool “GUI”

This section discusses the input parameters that can be specified in Imperial or Metric SI units in the tool

GUI. It also presents the features available in the GUI as shown in Figure 3.1. Items are either a Button,

Textbox, Listbox, drop down Combobox, Radio Button, Checkbox, Groupbox and Panel for drafting etc.

Buttons provide "singleclick" access to commonly used commands. Hovering the mouse pointer over any

of the items in the GUI for a few seconds without clicking or holding down any mouse buttons will display

a brief description of the items’ function. Each of these items is described as follows:

● File- This textbox is filled by using one of the following: (1) click on Browse SDB button, go the

folder where the model is saved and click open, (2) directly type the file path, or (3) copy/paste the

file path into File textbox.

● Browse SDB- Clicking the Browse SDB button displays the Windows Explorer where the engineer

can browse to the folder where the model is located, click on file name with *.sdb extension and

click open.

● Load Model- This button is disabled until Browse SDB button is clicked and the model file name

becomes available in File textbox. Clicking the Load Model button connects the tool with

SAP2000® via API and launches a new instance of the program. When SAP2000® model is loaded

into the tool, all load combinations and joints that possess vertical restraints or springs are

automatically loaded into the GUI.

● Close SAP2000- Clicking Close SAP2000 button will close any SAP2000® instance that’s started

from within the tool, disable Load Model button and the rest of the items in the tool. Note that it

is required to browse to open a new model and click Load Model button again to start a new

instance so that the tool can be used.

● Load Combinations- This listbox is filled after Load Model button is clicked and SAP2000®

model is successfully loaded. The mouse can be used to highlight one or more load combination

from the list by using Ctr+click or to click on Select All or Clear Selection buttons as required. If

the model does not contain any load combination, the tool displays a warning message since the

tool needs at least one load combination to run.

● Joints Unique Names- This listbox is filled after Load Model button is clicked and SAP2000®

model is successfully loaded. The mouse can be used to highlight one or more joint from the list

by using Ctr+click or to click on Select All or Clear Selection buttons as required. Click on Select

button to select and review joints in SAP2000® GUI interactively before running analysis or design.

● Pile Cap- This item consists of a group of input parameters: (1) Thickness of Pile Cap in inches

or cm, (2) Edge Distance from the edge of pile cap to the center of pile in inches or cm, and (3)

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Concrete Weight per Unit Volume in pounds per cubic feet or KN/m3 which are used to calculate

the self-weight of the pile cap. If the engineer doesn’t want to include self-weight of pile cap set

either weight of concrete or pile thickness to zero.

● Pile Capacity- This textbox consists of the pile capacity in kips or KN and are specified as positive

values in both Compression and Tension textboxes. It is permitted to enter a zero value for the

pile capacity in tension. Pile Capacity is disabled for editing when the tool runs in trial mode and

a fixed value of 30 kips (133.45 KN) is internally used in both compression and tension.

● Pile Spacing (center to center)- Pile Spacing is measured in inches or cm from center to center of

piles, specified as Spacing along X, Spacing along Y or equal Spacing for 3 Piles. Angle is the

angle in degrees measured between the vertical axis of the 3 piles group and global Y axis, positive

when the pile cap is rotated counterclockwise as show in Figure 3.2 below. Pile Spacing is disabled

for editing when the tool runs in trial mode and a fixed value of 36 inches (91.44 cm) is internally

used for Spacing along X and Y directions and 42 inches (106.68 cm) for Spacing for 3 Piles.

Figure 3.2: 3-Pile Cap configuration

● Loads Applied- The location of the applied load from pile group centroid is specified as an X

offset and Y offset in inches or cm. The engineer can specify a Scale Factor that scales the axial

loads and biaxial moments as applicable. This is useful when codes allow for increase in pile

capacity for load combinations including seismic or wind load cases. However, the program will

use this factor for all load combinations. The engineer can still select the load combinations that

contain seismic or wind loads only and use for analysis and design.

● Analysis- This groupbox is enabled when the model is first loaded into the tool or when the analysis

radio button is clicked. See the following section for additional information about the analysis

feature.

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● Number of Piles Along X- This textbox, part of Analysis groupbox, is enabled when the

corresponding radio button is clicked. It consists of the number of piles along x direction. This can

be specified as any number between 2 and 30 that is the maximum number of piles that can be

currently plotted in GUI of the tool and a practical limit at which the pile cap may not act as rigid

along x direction.

● Number of Piles Along Y- This textbox, part of Analysis groupbox, is enabled when the

corresponding radio button is clicked. It consists of the number of piles along y direction. This can

be specified as any number between 2 and 30 that is the maximum number of piles that can be

currently plotted in GUI of the tool and a practical limit at which the pile cap may not act as rigid

along y direction.

● Use 3 Piles- This checkbox is enabled when the analysis radio button is clicked. When checked,

the tool will run analysis of 3 piles only with the specified Spacing for 3 Piles.

● Design- This groupbox is enabled when the design radio button is clicked. See the following section

for additional information about the design feature.

● Maximum Number of Piles Along X- This textbox, part of Design groupbox, is enabled when the

design radio button is clicked. This is the maximum number of piles in the global X direction for

which the algorithm will try to find a solution. The minimum number of piles is always 2 and the

maximum number of piles that can be specified is 30. That is the maximum number of piles that

can be currently plotted in GUI of the tool and a practical limit at which the pile cap may not act as

rigid along x direction.

● Maximum Number of Piles Along Y- This textbox, part of Design groupbox, is enabled when the

design radio button is clicked. This is the maximum number of piles in the global Y direction for

which the algorithm will try to find a solution. The minimum number of piles is always 2 and the

maximum number of piles that can be specified is 30. That is the maximum number of piles that

can be currently plotted in GUI of the tool and a practical limit at which the pile cap may not act as

rigid along y direction.

● Run- When this button is clicked, the tool runs either analysis or design depending on the

corresponding radio button selection in GUI.

● Selected Joint- Click on this combobox to select the joint to be used for displaying analysis or

design results summary in tool GUI. Click on Select button to interactively review the selected

joint in SAP2000® GUI for which the result summary is being displayed.

● Design Loads for Selected Joint/Combo- This groupbox can be used to scroll, draw and review

results for individual joint and load combination. After clicking on Run button, the engineer needs

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to click on any of the results listed and the tool will display the load combination name, forces (P,

Mx and My) applied to the pile group and the self-weight of pile cap in kips or KN.

● Imperial Units or Metric SI- Click on this combobox to select the units to be used for the input

parameters in the GUI and for the output results. By switching between the units in GUI, the

program will automatically update the input parameters, perform calculations and report results in

the selected units.

● Results for Selected Pile- Once the pile group is displayed in plan view, the engineer can click on

any individual pile to display the demand/capacity D/C ratio as well as the axial force Demand

taken by that specific pile in Kips or KN.

● Governing Results- Governing results are only available after Run button is clicked. When used

for analysis, it will display a summary of the governing results. In this case, the load combination

that produces the highest D/C ratio in any individual pile. When used for design, the governing

results is defined as the least total number of piles that works for all load combinations. If the same

number of piles works for all load combinations, the tool will choose the one with the lower D/C

ratio. For example, if both PC-2x3 and PC-3x2 works with maximum D/C ratios of 0.9 and 0.7,

respectively, then the tool will choose PC-3x2 as it is the more conservative and will have more

room for any pile deviation on the site.

● Results Summary- See the next two sections for detailed information about results summary

displayed in GUI for analysis and design. Note that the two results for the same load combination

correspond to the maximum and minimum demands due to the same multi-step combinations, like

for load combinations include response spectrum, time history cases etc.

Analysis of Pile Groups

Analysis can be used when the number of piles and configuration is known and the engineer wants to check

if the pile group works for selected load combinations and for selected joints. The tool displays the D/C

ratio for each individual pile to help the engineer in deciding to rearrange or change pile capacity as needed.

This section discusses the input parameters required when the analysis radio button is clicked. The tool

currently supports the analysis of PC-3 and larger. PC-3 can be selected for analysis when the engineer uses

the Use 3 Piles checkbox, after which the Spacing for 3-piles and the Angle from global Y axis can be

specified. For other than PC-3, different Number of Piles may be specified along the global X and Y

directions. Spacing along X and Spacing along Y can also be different and may be specified in inches or

cm. Once you input all the parameters required for a specific project, click the Run button to run analysis

for a selected number of joints and load combinations. After analysis is performed, the tool provides a list

of Results Summary for the Selected Joint, Governing Results, Results for Selected Pile and Design

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Loads for Selected Joint/Combo. The Results Summary lists all load combinations included in the

analysis, pile configuration and corresponding maximum D/C ratio. The tool highlights the governing

combination of the list that corresponds to the highest individual pile D/C ratio for the chosen pile

configuration and in addition it reports them under the Governing Results groupbox as shown in Figure

3.3. Clicking on any pile while on plan view will display the Results for Selected Pile, D/C ratio and

Demand in Kips or KN, as well as the corresponding design loads as shown in Figure 3.3.

Figure 3.3: Results summary, governing results at selected joint, results at selected pile and design loads for selected Joint/combo for the analysis of a given Pile Group configuration.

The algorithm assumes that the pile cap is extremely rigid. The program calculates force distribution to

each pile, including self -weight of the pile cap (if required), and biaxial moments. For a joint with fixed

restraints in SAP2000®, the applied loads consist of vertical load as well as biaxial moments and in addition

the engineer may specify X and Y Offset from Pile Group Centroid. The offsets will result on additional

moments that get distributed as axial tension and compression to the piles using statics.

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Figure 3.4: Results summary, governing results at selected joint, results at selected pile and design loads for selected Joint/combo for the design of Pile Group.

Design of Pile Groups

If design radio button is selected, the tool uses a smart optimization algorithm developed by TILMAN to

find the most efficient or governing design. Such design is defined as the minimum number of piles that

works, without overstressing any pile, for all selected load combinations. If a solution cannot be found

within the parameters specified by the engineer, then the program shows a warning indicating that this is

the case. The tool currently supports the design of PC-3 (3 piles) and larger. PC-3 is always included in

design and listed when a design solution works for PC-3. The checkbox to Use 3 piles is disabled when the

Design radio button is clicked but the Spacing for 3-piles and the Angle from global Y axis can still be

specified. For other than PC-3, Maximum Number of Piles may be specified along the global X and Y

directions. Spacing along X and Spacing along Y can also be independently specified in the required units.

Once you input all the parameters required for a specific project, click the Run button to run design for a

selected number of joints and load combinations. After design is performed, the tool provides a list of

Results Summary for the Selected Joint, Governing Results, Results for Selected Pile and Design

Loads for Selected Joint/Combo. The Results Summary for the Selected Joint lists all load combinations

included in the design, corresponding pile configuration with the minimum number of piles that works for

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each load combination, and the maximum D/C ratio for individual pile for that specific configuration. The

tool highlights the governing combination that works for all selected load combination and in addition it

reports them under the Governing Results groupbox as shown in Figure 3.4. The engineer can then click

in any of the configurations from the Results Summary list to review the results graphically. Clicking on

any pile while on plan view will display the Results for Selected Pile, D/C ratio and Demand in Kips or

KN, as well as the corresponding design loads as shown in Figure 3.4.

It is highly recommended that the engineer does not use any envelope type combinations for design as such

combination could be very conservative and may cause wrong design results. In this case, TILMAN

suggests that you explicitly exclude those combinations from the list of selected combinations before

running design.

Like the analysis algorithm, the tool assumes that the pile cap is extremely rigid supported by piles as

support points. See the above paragraph under Analysis of Pile Groups for additional information.

Figure 3.5: Summary of analysis results for Pile Group Tool

Summary of Results

Pile Group analysis and design results become available after analysis or design radio button is selected

and Run button is clicked. Summary of results can be displayed graphically while in the tool’s GUI via

Options > Summary Results command in any of the selected units as shown in Figure 3.5. Also, the

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results are automatically saved in the same folder of the model with the same name of the model file but

ending with “_PileGroupToolResults.txt”. The text file has a note indicating the reason for the duplicate

results that correspond to the maximum and minimum demands due to the same multi-step combinations.

Also, for reference the text file of the summary of results has a date and time stamp documenting the time

when the analysis or design was performed.

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Chapter 4

Wall Cracking Tool

About the Tool

Wall Cracking Tool is a sophisticated, yet easy-to-use application that seamlessly connects via API with

CSI software SAP2000® and ETABS®. The tool is started by either clicking on Windows Start Menu >

TILMAN Engineering Solutions LLC > Wall Cracking Tool or by double clicking on the Desktop

Shortcut > Wall Cracking Tool.

An automatic way of practical modeling cracked concrete walls, as required by most concrete design codes,

is not supported in CSI Software. The engineer is left with two choices to determine whether the shear walls

in the model are cracked or not. The engineer can either assume that all walls are cracked or needs to

compare wall vertical stresses with the concrete modulus of rupture for all load combinations to decide

whether walls are cracked or not. The former is an extremely conservative and uneconomical approach.

The latter can be extremely time consuming especially when hundreds of load combinations and walls are

to be checked by post-processing results and manually comparing the stresses. Then the engineer will need

to manually assign the corresponding property modifiers (cracked/uncracked) in ETABS® GUI which can

also be extremely time consuming. These tasks become even more involved when the model is revised due

a layout change that typically alters the location, dimension, stiffness and the lateral load distribution. All

these tasks are automated in Wall Cracking Tool that can produce fast and efficient cracking analysis results

of the original model or after any change to the original model and assign modifiers to the cracked and

uncracked walls based on the modifiers options selected by the engineer.

In a nutshell the steps the engineer needs to follow to analyze any structure in Wall Cracking Tool are:

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● Click on Browse button to the folder where CSI software model file is saved and, for each tool,

select the corresponding *.sdb file for SAP2000® and *.edb file for ETABS®.

● Click on Load Model button, the tool connects with CSI software via API, opens the model and

loads all load combinations available in the model and all shear walls assigned with structural

properties into the GUI of the tool.

● Select the desired units

● Update the input parameters as applicable to the specific project.

● Click on Analyze button, where the model will analyze existing model and output a “cracked”

model with corrected cracking modifiers applied. Refer to the Analysis section below for more

information.

● Display table with the summary of results.

When running the tool for the first time or if the tool does not find a valid license file, it still runs but on

trial mode. See Chapter 2, section “Installation Instructions” for additional information about the

limitations implemented in the trial mode.

The Tool “GUI”

This section discusses the input parameters that can be specified in Imperial or Metric SI units in the tool

GUI. It also presents the features available in the GUI of the tool as shown in Figure 4.1. Items are either

a Button, Textbox, Listbox and drop down Combobox. Buttons provide "singleclick" access to commonly

used commands. Each of these items is described as follows:

● File- This textbox is filled by using one of the following: (1) click on Browse EDB button, go the

folder where the model is saved and click open, (2) directly type the file path, or (3) copy/paste the

file path into File textbox.

● Browse EDB File- Clicking the Browse EDB button displays the Windows Explorer where the

engineer can browse to the folder where the model is located, click on file name with *.sdb

extension and click open.

● Load Model- This button is disabled until Browse EDB button is clicked and the model file name

becomes available in File textbox. Clicking the Load Model button connects the tool with ETABS®

via API and launches a new instance of the program. When ETABS® model is loaded into the tool,

all load combinations available in the model and wall assigned with structural property are

automatically loaded into the GUI.

● Imperial Units or Metric SI- Click on this combobox to select the units to be used for the input

parameters in the GUI and for the output results. By switching between the units in GUI, the

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program will automatically update the input parameters, perform calculations and report results in

the selected units.

Figure 4.1: Graphical User Interface of Wall Cracking Tool-Explicit Method Modifiers Option

● Analyze- This button is enabled after Load Model button is clicked and CSI software model data

becomes available in the tool’s GUI. Refer to section below titled “Analysis” for additional

information on the analysis performed by the tool.

● Close ETABS- Clicking Close ETABS button will close any ETABS® instance that’s started from

within the tool, disable Load Model button and the rest of the items in the tool. Note that it is

required to browse to open a new model, click Load Model button again to start a new instance so

that the tool can be used.

● Load Combinations- This listbox is filled after Load Model button is clicked and ETABS® model

is successfully loaded. The mouse can be used to highlight one or more load combination from the

list by using Ctr+click or to click on Select All or Clear Selection buttons as required. If the model

does not contain any load combination, the tool displays a warning message since the tool needs at

least one combination to run. It is important to note that load combinations may be multi-stepped

producing maximum and minimum responses. When running analysis in SAP2000® wall cracking

tool, it gets the maximum and minimum value of stresses for each load combination that consist of

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response spectrum and time history cases. For ETABS® the behavior is slightly different due to a

current issue in ETABS® API function that retrieves wall stresses. The function does not currently

cover all joint elements created with internal meshing when load combinations include multi-step

loads like, auto seismic, auto wind, response spectrum and time history load cases. To get stresses

at all joints from ETABS® model that may govern the analysis, it is recommended to implement

one of the two workarounds when running ETABS® wall cracking tools: (1) perform

physical/external mesh of walls in lieu of internal meshing. ETABS® default is no meshing for

walls but if you want to mesh the walls, then you shall not use assign > shell > wall auto mesh

options but use edit > edit shells > divide shells command instead, or (2) define your auto seismic

and auto wind load patterns to be applied in one direction at a time so that their corresponding

combinations with gravity loading become single step and the issue mentioned above no longer

persists. The second workaround does not cover load combinations including response spectrum

and/or time history since they are always multi-stepped. In this case, TILMAN recommends using

the first workaround when such load combinations are present in ETABS® model.

● Wall Label (for Stress Check)- This listbox is filled after Load Model button is clicked and

ETABS® model is successfully loaded. The mouse can be used to highlight one or more wall from

the list by using Ctr+click or to click on Select All or Clear Selection buttons as required. Click

on Select button to select and review walls in ETABS® GUI interactively before or after running

analysis for stress check. When program calculated modifiers option is selected, click on Edit

Reinf… button to access Edit Reinforcement form, update wall vertical reinforcement ratio “Rho

(%)”. Rho can be directly inputted in the form, copied and pasted or imported from a text file after

clicking on Load Existing Text File… button.

● Design Code- This combobox includes a wide variety of the latest national and international codes

for the automated values of the modulus of rupture for cracked walls. The selectable codes by this

tool are explained in detail in the next section.

● Modifiers Options- There are two options to select: (1) user defined modifiers that are based on

the design code (ACI and other codes) are mostly appropriate for seismic design but have been

determined to be very conservative specifically for building response to wind loading; user defined

modifiers need to be inputted by the user and are independent of wall vertical reinforcement and

(2) program calculated modifiers that are based on the explicit method as discussed in the paper

published in ACI Structural Journal V.108, No.6 November-December 2011 titled “Lateral

Stiffness of Concrete Shear Walls for Tall Building by Ahmad Rahimian”.

● Uncracked/Cracked Modifiers- The values entered in these textboxes are part of user defined

option and the recommended membrane modifiers f11, f22 and f12 that will be assigned to the walls

23

in the model if they are found to be “uncracked/cracked”. A wall is classified as

“uncracked/cracked” when the maximum vertical stress S22 is lower/higher than the cracking stress

as determined by the selected code. In most cases, only f22 modifier needs to be changed but this

is left to the engineer to decide and interpret the code accordingly.

● Modifiers Upper/Lower Limits- The values entered in these textboxes are the recommended

limits for the membrane modifier f22 with the explicit method. Program calculated modifiers that

are based on wall vertical reinforcement ratio are always calculated to be between the upper and

lower limits.

Design Codes

This tool covers a wide variety of the latest national and international codes for the automated values

of the modulus of rupture for cracked walls as shown in Figure 4.2. The selectable codes are given

below:

ACI 318: fr = 7.5x√(f’c) psi

British BS 8110: fr = 0.6x√(f’c) MPa

Canadian CSA A23.3: fr = 0.6x√(f’c) MPa

Eurocode EC 02:

Strength Classes <=C50/60

fr = 0.3x(2/3)√(fc) MPa

Strength Classes >C50/60

fr = 2.12xlog[1 + (f’c) / 10] MPa

Indian IS 456-2000: fr = 0.7x√(f’c ) MPa

New Zeland NZS 3101: fr = 0.6x√(f’c ) MPa

Australian AS 3600: fr = 0.6x√(f’c ) MPa

Italian NTC 2008:

Strength Classes <=C50/60

fr = 0.3x(2/3)√(fc) MPa

Strength Classes >C50/60

fr = 2.12xlog[1 + (f’c) / 10] MPa

Turkish TS 500: fr = 0.6x√(f’c) MPa

Singapore CP 65:

Strength Classes <=C50/60

fr = 0.3x(2/3)√(fc) MPa

Strength Classes >C50/60

24

fr = 2.12xlog[1 + (f’c) / 10] MPa

Mexican RCDF 2004: fr = 0.53x√(0.8fc) MPa

Figure 4.2: Design Codes supported by Wall Cracking Tool

In addition, the tool provides textboxes for the input of user-defined modulus of rupture in both Imperial

and Metric SI units equals to: Fcr(psi)=A+Bxf’c in psi or MPa where A (psi or MPa) and B (unitless) are

constants. This allows the engineer to use either a constant cracking stress (B=0) or a cracked stress as

function of compressive strength (A=0) or a combination of the two.

25

Figure 4.3: Analysis Complete status in Wall Cracking Tool

Analysis

The tool saves the model as with the same name but ending with “_Crack.edb” right after the Analyze

button is clicked leaving the original model unchanged. The tool then runs analysis with all membrane

modifiers assigned to wall objects set to 1 while keeping the rest of the modifiers unchanged. The tool will

then scan over all walls, to determine whether the walls are cracked or not by comparing tensional S22 stress

from all load combinations included against the modulus of rupture “Fcr”. For user defined modifiers

options, the tool then applies the uncarcked/cracked modifiers to the walls based on whether S22 is found

less or greater than Fcr, respectively. For program calculated modifiers option (explicit method), the tool

26

always applies the modifiers calculated based on the stress level, cracking stress, wall vertical rebars ratio,

rebars and concrete modulus of elasticity while enforcing the upper and lower limit as input by the user.

The analysis results are then saved in the selected units and can be accessed from GUI, exported to XML

file or by opening the text file as explained next. The tool GUI displays a status message of Analysis

Complete when the tasks are all completed as shown in Figure 4.3.

It is important to note that it is possible for the engineer to apply modifiers in ETABS® GUI using two

different methods. The first method is to define property modifiers while in wall section property and the

second is to assign modifiers to the wall objects. The above analysis covered by Wall Cracking Tool applies

to the modifiers assigned to the wall objects whereas the modifiers defined at the section levels are left

unchanged. Thus, we recommend that the engineer works on models with default modifiers of 1 for wall

section property definition and assign any property modifiers to the wall objects. This can be conveniently

assigned within ETABS® GUI to multiple walls after being selected by the section name. In this case, when

the tool loads ETABS® model, performs analysis as mentioned in the previous paragraph and assigns the

membrane modifiers there will not be double counting for cracking modifiers of the walls.

Important Note: ETABS® allows for a total of eight property modifiers to be changed in a wall element.

However, the ones listed above are only recommended to model a cracked wall that’s also in line with most

code requirements. Generally, f22 stiffness modifier is the only one that needs to be assigned, all others are

either going to not affect the in plane behavior or create unrealistically “weak“ walls. Refer to Verification

Example 2 in Appendix A for additional information.

Summary of Results

Wall cracking analysis results become available after the Analyze button is clicked and analysis run is

completed. Summary of results can be displayed graphically while in the tool’s GUI, or exported as XML

file via Options > Summary Results command in Imperial or Metric SI units as shown in Figure 4.4.

The results are automatically saved to a text file that can be found by browsing to the folder where ETABS®

*.edb model file is saved and opening the text file ending with “_Cracked.txt”. Also, for reference the text

file of the summary of results has a date and time stamp documenting the time when the analysis was

performed.

27

Figure 4.4: Results Summary accessible via Options menu in Wall Cracking Tool

28

Chapter 5

Seismic Irregularities Tool

About the Tool

Seismic Irregularities Tool is a sophisticated, yet easy-to-use application that seamlessly connects via API

with CSI software ETABS®. The tool is started by either clicking on Windows Start Menu > TILMAN

Engineering Solutions LLC > Seismic Irregularities Tool or by double clicking on the Desktop Shortcut

> Seismic Irregularities Tool.

Seismic Irregularities Tool is intended to help the engineer perform common seismic irregularities checks

for building type structures in a fast and efficient way. Post-processing of CSI software results for seismic

irregularities checks can be an extremely hectic and cumbersome task that’s usually done by using external

spreadsheets. All these checks are automated in Seismic Irregularities Tool which makes the results readily

available in tables within the tool and can be also exported to XML/Excel. The tool consists of the following

seismic irregularities checks per ASCE-7/IBC: (1) Torsional Irregularities, (2) Stiffness Irregularities, (3)

Mass Irregularities, (4) Allowable Drifts and (5) Seismic Design Category. All results are reported in

Imperial Units in the current version of the tool.

The recommended steps the engineer shall follow after starting the tool: (1) click on Browse EDB File

button to the folder where ETABS model file is saved and select the corresponding *.edb file, (2) click

Load Model button, the tool connects with ETABS via API, opens the model and loads all seismic loads

available in the model into the GUI of the tool, (3) select the checkbox for the check(s) you want to run, (4)

click on Modify/Show Options for each check and update its corresponding data, (5) click on Run Checks

button for the tool to perform the calculations, (6) click on Results button to review irregularities check

output, (7) click on Save Results as XML which can be later imported into Excel and (8) click on Select

29

X-Direction or Y-Direction Joints on ETABS GUI to graphically review the joints reported in the

tabulated results.

When running the tool for the first time or if the tool does not find a valid license file, it still runs but on

trial mode. See Chapter 2, section “Installation Instructions” for additional information about the

limitations implemented in the trial mode.

Figure 5.1: Graphical User Interface of Seismic Irregularities Tool for ETABS v17

The Tool “GUI”

Torsional Irregularities Check

This check is meant to identify any story in ETABS model with type 1a torsional irregularity or type 1b

extreme torsional irregularities per ASCE-7 10/16 Table 12.3-1. A torsional irregularity is considered to

30

exist when the maximum story drift, including accidental torsion effects, at one end of the structure

transverse to an axis is more than 1.2 times the average of the story drifts of the two ends of the floor.

Similarly, a factor of 1.4 is used to determine extreme torsional irregularity as given below:

Torsional Irregularity exists when: ∆

∆> 1.2

Extreme Torsional Irregularity exists when: ∆

∆> 1.4

And ∆ , ∆ are the maximum story drift and average of the story drifts, respectively.

Figure 5.2: Torsional Irregularities Options form

Click on Modify/Show Options button to access Torsional Irregularities Options form. The data in the

form is organized in the X and Y directions separately. For each direction, seismic load cases, that are

available in ETABS model, are loaded into the list and can be partially or all selected. The engineer needs

to add the selected load cases to the right side table and the tool sorts them under data along X and Y

directions. The engineer can choose to leave “Auto?” option checked or uncheck it for any individual row

of data or for all data. When “Auto?” option is checked, the tool performs the torsional irregularity check

based on the drift of two joints that correspond to the maximum and minimum story drift values. When

“Auto?” option is unchecked, the engineer can choose the two joints which he/she thinks they correspond

to the extreme drift values. The engineer can also specify a cutoff for drift below which the drift is negligible

and not included in the torsional irregularities check. A default value of 0.001 is used by default but the

tool also allows the engineer to choose any user defined value as deemed necessary, this is done to remove

insignificant drift results that constitute of only noise for meaningful results. After all data is ready to be

31

analyzed, click on Apply button to leave Torsional Irregularities Options form followed by clicking on Run

Checks button available in the GUI of the tool.

Figure 5.3: Torsional Irregularities Results form

After seismic irregularities checks are done, click on Results button to review Torsional Irregularities

tabulated results. Similar to the data in options form, the results are organized and reported separately along

X and Y directions. Tabulated results consist of Story, Load Case along corresponding direction, Load Step

number as applicable, Joint 1 and Joint 2 Labels, corresponding Drifts, Maximum/Average Drift Ratio. As

previously mentioned, ratio is compared to 1.2 and 1.4 limits per AISC 7 and, when exceeded, Torsional

and Extreme Torsional Irregularity are flagged, respectively. The engineer can then export the tabulated

results in xml format which can be later imported into Excel. The joints reported in the tabulated results

can be selected from within the tool and displayed in ETABS for visual review of the joints used.

Torsional Irregularities Results also list the values of amplification of accidental torsional moment at each

floor, Ax, using the following equation:

𝐴𝑥 = (𝛿

1.2 × 𝛿)

32

Stiffness Irregularities Check

This check is meant to identify any type 1a stiffness-soft story irregularity or type 1b stiffness-extreme soft

story irregularity, per ASCE-7 10/16 Table 12.3-2, by comparing the lateral stiffness of individual stories.

There are two methods discussed in Volume I of the IBC Structural/Seismic Design Manual (developed by

the Structural Engineering Association of California, SEAOC). The first method is based on the lateral

stiffness properties which is often complex to evaluate. The second method, recommended by SEAOC, is

implemented in this tool by comparing values of drift ratios due to prescribed seismic lateral forces. To

compare displacement rather than stiffness, the reciprocal of the limiting percentage ratios of 70% and 80%

for soft story (60% and 70% for extreme soft story) shall be used. In terms of calculated drift ratios, the

following conditions are checked:

Soft Story exists when: 0.7 × ∆ > ∆ 𝑜𝑟 0.8 × ∆ > × (∆ + ∆ + ∆ )

Extreme Soft Story exists when: 0.6 × ∆ > ∆ 𝑜𝑟 0.7 × ∆ > × (∆ + ∆ + ∆ )

Where ∆ is the story drift ratio at level i, ∆ is the story drift ratio at one level above level i and so on.

Story stiffness ratio for the roof (top story) is not computed.

Figure 5.4: Stiffness Irregularities Options form

Click on Modify/Show Options button to access Stiffness Irregularities Options form. Similar to Torsional

Irregularities Options, seismic load cases and corresponding data are organized along X and Y directions.

33

The engineer can choose to leave “Auto?” option checked or uncheck it for any individual row of data or

for all data. When “Auto?” option is checked, the tool performs stiffness irregularities check based on user’s

selection under “Options For Auto”. This option can be either “Use Maximum Drift” or “Use Average

Drift”. Maximum drift option uses the maximum story drift in stiffness irregularity calculations. Average

drift option uses the average of maximum and minimum drift values. When “Auto?” option is unchecked,

the engineer can choose the joint that corresponds to the maximum drift values which he/she wants to use

in stiffness irregularities check. After all data is ready to be analyzed, click on Apply button to leave

Stiffness Irregularities Options form followed by clicking Run Checks button available in the GUI of the

tool.

Figure 5.5: Stiffness Irregularities Results form

After seismic irregularities checks are done, click on Results button to review stiffness irregularities

tabulated results. Similar to the data in options form, the results are organized and reported separately along

X and Y directions. Tabulated results consist of Story, Story height in inches, Load Case along

corresponding direction, Load Step number as applicable, Joint 1 and Joint 2 Labels, Joint Selection type,

(100%, 80%, 70% and 60%) of Drift ratios, Average of Drift Ratio for the three stories above the considered

level, Extreme Stiffness Irregularity and Stiffness Irregularity. Ratios are compared per above equations,

and when exceeded, soft and extreme soft story are flagged, respectively. The engineer can then export the

tabulated results in xml format which can be later imported into Excel. The joints reported in the tabulated

results can be selected from within the tool and displayed in ETABS for visual review of the joints used.

34

Allowable Drifts Check

IBC code and ASCE 7 reference standards place limits on the design story drift per ASCE 7-10/16, Table

12.12-1. The maximum story drift needs to be calculated based on the design seismic displacement and not

the elastic response as given below:

∆= (𝛿 − 𝛿( ) )

Where ∆ is the inelastic drift, Cd is the displacement amplification factor, I is the importance factor, 𝛿

and 𝛿( ) are the elastic displacements at level x and the level underneath it.

Figure 5.6: Allowable Drifts Options form

Click on Modify/Show Options button to access Allowable Drifts Options form. Similar to Torsional

Irregularities Options, seismic load cases and corresponding data are organized along X and Y directions.

The engineer can choose to leave “Auto?” option checked or uncheck it for any individual row of data or

for all data. When “Auto?” option is checked, the tool performs allowable drifts check based on the

maximum story drift. When “Auto?” option is unchecked, the engineer can choose the joint that corresponds

to the maximum drift values which he/she wants to use in allowable drifts check. Since the lateral system

may be of a different type in each direction, the engineer can input different values for the allowable story

drift and the deflection amplification factor. The engineer can also check the option to reduce the allowable

35

drift by the redundancy factor as required by code for special moment frames in high seismic design

categories. After all data is ready to be analyzed, click on Apply button to leave Allowable Drifts Options

form followed by clicking Run Checks button available in the GUI of the tool.

After seismic irregularities checks are done, click on Results button to access Allowable Drifts Results

form. Similar to the data in options form, the results are organized and reported separately along X and Y

directions. Tabulated results consist of Story, Story height in inches, Load Case along corresponding

direction, Load Step number as applicable, Joint 1 Label, Joint Selection type, Inelastic Drift in inches,

Maximum Drift Limit and Drift Check. Inelastic drifts are compared with the maximum limit per ASCE 7-

10/16 Table 12.12-1, and when exceeded, the drift check is flagged accordingly. The engineer can then

export the tabulated results in xml format which can be later imported into Excel. The joints reported in the

tabulated results can be selected from within the tool and displayed in ETABS for visual review of the joints

used.

Figure 5.7: Allowable Drifts Results form

36

Mass Irregularities Check

This check is meant to identify any type 2 weight (mass) irregularity, per ASCE 7-10/16 Table 12.3-2, for

a story in ETABS model with an effective mass that is more than 150 percent of the effective mass of any

adjacent story. This requirement does not apply to the roof (top floor) when it is lighter than the story below.

After Run Checks is performed, the tool performs the necessary calculation to obtain story mass. Having

excessive meshing in walls and floors can have significant effect on the running time of mass irregularities

check in ETABS v17. Click on Results button to access Mass Irregularities Results form. Tabulated results

consist of Story and its Mass in Kip-s2/in. When the ratio of story mass is more than 150 percent of any of

the adjacent stories, that story is flagged with mass irregularity and reported as such in the Mass

Irregularities Results table. The engineer can then export the tabulated results in xml format which can be

later imported into Excel.

Figure 5.7: Mass Irregularities Results and Seismic Design Category Results form

Seismic Design Category

Structures are assigned to Seismic Design Category based on their building risk category and the spectral

response acceleration coefficients SDS and SD1, irrespective of the fundamental period of vibration of the

37

structure. Each structure shall be assigned the most severe seismic design category in accordance with

ASCE 7-10/ASCE 7-16, Table 11.6-1 and -2 of Section 11.6.

After Run Checks is performed, click on Results button to access Seismic Design Category Results form.

Two codes are currently supported in this tool per ASCE 7-10 and ASCE 7-16, Section 11.6. In the form,

the engineer needs to select the seismic coefficients and the tool reports the seismic design category

accordingly.

38

Appendix A

Verification Examples

Example 1

DESCRIPTION

Pile Group Tool, compatible with SAP2000®, ETABS®, and CSiBridge®, are checked for the analysis of

3-piles cap supporting column above with axial vertical load, P, and biaxial moments, Mxx and Myy applied

simultaneously. In addition, axial vertical load is assumed to be applied at ex and ey eccentricities from the

pile group centroid. Imperial units are selected for this example.

INPUT PARAMETERS

Pile Cap Geometry:

Spacing between piles=48 inch

Angle from y-axis=0

Pile cap thickness=36 inch

Area of pile cap= 44.75 ft2

Edge distance=24 inch

39

Figure A1.1: Pile cap plan view of PC-3 used in Pile Group Tool Pile Capacity:

In compression=300 Kips

In tension=45 Kips

Loadings; reactions imported from SAP2000:

P=347.77 Kips

Mxx =1.25 Kft

Myy =10.83 Kft

Input in Pile Group Tool:

Concrete weight=150pcf

Eccentricity ex=8 inch

Eccentricity ey=-12 inch

FEATURES VERIFIED

Verification of Pile Group Tool’s analysis include:

Demand in each pile

D/C ratio in each pile

ANALYSIS OF RESULTS

Independent results in this table are taken from SAP2000® software developed by Computers and

Structures, Inc. and hand calculations (presented below) that are based on the NCEES practice problems

for the SE exam. In SAP2000®, high property modifiers are applied to the pile cap to simulate the rigid

assumption of pile cap assumed in both Pile Group Tool and hand calculations.

40

Output SAP2000 Hand Calculations

Pile Group Tool

% Difference

vs SAP2000 Vs Hand Calcs

Demand in pile P1 (kips)

133.660 132.93 132.94

0.54% 0.01%

D/C ratio in Pile P1

0.446 0.443 0.44

1.26% 0.68%

Demand in pile P2 (kips)

12.320 11.59 11.59

6.30% 0.00%

D/C ratio in Pile P2

0.041 0.039 0.04

2.67% 2.50%

Demand in pile P3 (kips)

221.940 223.39 223.4

0.65% 0.00%

D/C ratio in Pile P3 0.740

0.745 0.74 0.03% 0.68%

Table A1.1: Summary of verification example results from SAP2000®, hand calculations and Pile Group Tool

HAND CALCULATION

The following equations represent the x and y coordinates of the vertices (piles) of an equilateral triangle

with respect to the coordinate system passing through the pile group centroid.

Piles location w.r.t pile centroid:

𝑋 = . 𝑎. √3. 𝐶𝑜𝑠𝑖𝑛𝑒(30 − 𝑎𝑛𝑔𝑙𝑒) 𝑌 = . 𝑎. √3. 𝑆𝑖𝑛𝑒(30 − 𝑎𝑛𝑔𝑙𝑒) Eq. 1

𝑋 = − . 𝑎. √3. 𝐶𝑜𝑠𝑖𝑛𝑒(30 + 𝑎𝑛𝑔𝑙𝑒) 𝑌 = . 𝑎. √3. 𝑆𝑖𝑛𝑒(30 + 𝑎𝑛𝑔𝑙𝑒)

𝑋 = − . 𝑎. √3. 𝑆𝑖𝑛𝑒(𝑎𝑛𝑔𝑙𝑒) 𝑌 = − . 𝑎. √3. 𝐶𝑜𝑠𝑖𝑛𝑒(𝑎𝑛𝑔𝑙𝑒)

Where “a” is the side length of the equilateral triangle connecting the 3 piles=spacing between the piles;

and “angle” is the measure of the angle from the vertical axis when the pile cap is rotated.

Loading at pile centroid accounting for eccentricities (moment sign follows right hand rule) and pile cap

self-weight:

P=347.77+20.15=367.92 Kips

Mx0=Mxx-P.ey =1.25Kft-347.77Kips x (-12 inch)/(12 inch/ft)=349.02 Kft

41

My0=Myy+Pex =10.83Kft+347.77Kips x (8 inch)/(12 inch/ft)=242.68 Kft Demand:

𝐷 @ 𝑃𝑖𝑙𝑒 𝑃 = −.

∑+

.

∑ Eq. 2

D/C Ratio:

𝐷/𝐶 @ 𝑃𝑖𝑙𝑒 𝑃 =( )

Eq. 3

Where C is the pile capacity in compression when Di is positive and the pile capacity in tension when Di

is negative.

The following table summarizes the hand calculations performed. The coordinate system is centered at

the pile group centroid.

Pile X coordinate

(in) Y coordinate (in)

Demand (Kips) D/C Ratios

P1 24.00 13.86 132.93 0.4431 P2 -24.00 13.86 11.59 0.0386 P3 0.00 -27.71 223.39 0.7446* ∑x2 1152 ∑y2 1152

*: This value is reported in Results Summary as the maximum D/C ratio

Table A1.2: Hand Calculations for Pile Demand Capacity Ratio following Equations 1, 2 and 3

CONCLUSION

Pile Group Tool results show a good comparison with the independent results obtained from SAP2000®

and the hand calculations. The small difference between SAP2000® and both Pile Group Tool and hand

calculation is due to the assumptions of rigid cap vs modified stiffness for the pile cap in SAP2000® model.

PICTURES

Below pictures are captured from Pile Group Tool’s graphical user interface and results saved in the text

file that can also be accessed via Options > Results Summary.

42

Figure A1.2: Demand/Capacity ratio at pile P1 and P2

Figure A1.3: Demand/Capacity ratio at pile P3 and summary of results

43

Example 2

DESCRIPTION

Wall Cracking Tool, compatible with SAP2000® and ETABS®, is checked for the cracking analysis of

shear walls subjected to axial and lateral loading. The shear wall is part of a 10-story building with a floor

to floor height of 12ft. The need of performing explicit stress analysis of shear walls is studied through a

parametric comparison of different analyses: (1) all walls are uncracked (unconservative), (2) all walls are

cracked (extremely conservative), and (3) strict modeling of cracked/uncracked walls based on stress

analysis using two different modifiers options: user defined independent of wall reinforcement and

program calculated explicit method dependent of wall reinforcement and other items as explained next.

By the end of this example, the engineer will have a clear understanding on the importance of strict

modeling of cracking and the practical reasons to use Wall Cracking Tool. Imperial units are selected for

this example.

INPUT PARAMETERS

Wall Geometric Properties:

Height =120 ft

Thickness=12 inch

Length of wall=288 inch

Distance form centroid to extreme fiber=144 inch

I= 23,887,872 in4

Wall Material Properties:

Concrete compressive strength= 4000 psi

Ec= 3,604,996 psi

G=1,502,081.7 psi

Applied Loading:

100 kips lateral load at top of wall

3.6 kips/ft (self-weight per unit height of the wall= 24ftx1ftx150pcf)

FEATURES VERIFIED

Verification of Wall Crack Tool’s analysis include:

44

Comparison of wall stresses with cracked stresses as per ACI 318 code

Correct application of cracked stiffness modifiers when required

Two different options for application of modifiers: user defined and program calculated

explicit method

Figure A2.1: ETABS® uncracked model for a shear wall with a display of applied lateral loads and lateral displacement response (all stiffness modifiers are set to 1)

ANALYSIS OF RESULTS

Hand calculations and analysis output from both ETABS® and Wall Cracking Tool for ETABS are

compared to study the level of cracking required in shear walls. Specifically, a comparison is presented for:

(1) shear walls with no cracked modifiers, (2) shear walls with user defined cracked modifiers applied to

walls at all story levels, (3) shear walls with strict modeling of cracked modifiers (user defined vs program

calculated) based on stress analysis, and (4) Wall Cracking Tool and its capability for performing a

complete stress analysis followed by an automatic application of stiffness modifiers using two different

options (user defined vs program calculated).

Hand calculations compared with ETABS® output and structural response of an updated model after using Wall Cracking Tool

1) Assuming all shear walls are not cracked

a) Hand calculation of lateral displacement at top of the wall due to lateral loading using

structural mechanics formulation of a cantilever wall while accounting for both flexural

and shear deformations:

45

∆= + Eq. 4

∆=(100 ∗ 1000 ∗ (120 ∗ 12)

3(3604996)(23887872)+

100 ∗ 1000 ∗ 120 ∗ 12 ∗ 144

2 ∗ 1502081.7 ∗ 23887872

∆= 1.15 + 0.04=1.19 inches

b) Lateral displacement at top of shear wall as obtained from ETABS®, with all stiffness

modifiers are set to 1, is presented in Figure A2.1. It is shown that the maximum lateral

displacement is reported equal to 1.1903 inches.

Figure A2.2: ETABS® cracked model for a shear wall showing lateral displacement response (stiffness

modifiers f22 is set to 0.35)

2) Assuming all shear walls are cracked using 0.35Ig per ACI 318 Section 10.10.

a) Hand calculation of lateral deflection at top of wall due to lateral load

∆=𝑃𝐿

3𝐸𝐼 ∗ 0.35+

𝑃𝐿𝑐

2𝐺𝐼

∆=1.15

0.35+ 0.04 = 𝟑. 𝟑𝟐𝒊𝒏

46

b) Lateral displacement at top of the wall as obtained from ETABS®, after assigning stiffness

modifiers for f22 = 0.35 in all walls, is presented in Figure A2.2. It is shown that the

maximum lateral displacement is reported equal to 3.333 inches.

3) Strict calculations of wall stresses to determine the locations at which shear walls need to be

modeled as cracked. User defined cracking modifiers per ACI 318 Section 10.10. where 0.35 Ig

(flexural) are assigned to the walls that have maximum tensile stress S22 higher than 7.5√f’c. Also,

hand calculations for program calculated cracking modifiers (function of wall reinforcement) based

on the explicit method are presented:

a) User defined modifiers: Hand calculation of maximum axial stresses vs limiting cracking

stress for a load combination of 0.8*Axial load+1*Lateral load:

Axial load at 3rd level =0.8* 3.6Kips/ft*(7 levels*12ft/level) =241.92 kips

Axial load at 4th level =0.8* 3.6Kips/ft*(6 levels*12ft/level) =207.36 kips

Moment due to lateral load at 3rd level =100Kips*84ft=8400 kip-ft

Moment due to lateral load at 4th level =100Kips*72ft=7200 kip-ft

Axial stress at extreme fiber of the wall due to combined loading at 3rd level:

𝑆 = − Eq. 5

𝑆 =241.92 ∗ 1000

288 ∗ 12−

8400 ∗ 1000 ∗ 12 ∗ 144

23887872

𝑆 = 70-607.6= -537.6psi (tension)> 7.5√f’c =474psi=> Cracked, F22 modifier =0.35

Axial stress at extreme fiber of the wall due to combined loading at 4th level:

𝑆 =𝑃

𝐴−

𝑀𝑐

𝐼

𝑆 =207.36 ∗ 1000

288 ∗ 12−

7200 ∗ 1000 ∗ 12 ∗ 144

23887872

𝑆 = 60-520= -460 psi (tension) < 7.5√f’c =474psi=> Uncracked, F22 modifier=0.7

b) Program calculated modifiers (explicit method): Hand calculation of cracking

modifiers that depend on wall vertical reinforcement, maximum axial tensile stress,

concrete, rebars’ elastic modulus and the modulus of rupture is shown below:

𝜆 = = =.

(1 − 𝜌) + 𝜌 Eq. 6

Fcr=474psi; Es=29000ksi; and Ec=3605 ksi

47

Level

ft/f’c

𝜌 (%)

𝜆 = 𝐹 𝑚𝑜𝑑𝑖𝑓𝑖𝑒𝑟 % Stiffness Gain

Explicit Method

vs User Defined

Explicit Method

By Hand (Eq. 6)

User Defined

(Wall Cracking Tool)

Explicit Method

(Wall Cracking Tool)

1 0.204 0.47 0.503 0.35 0.503 44%

2 0.171 0.44 0.630 0.35 0.630 80%

3 0.152 0.4 0.738 0.35 0.7 100%

4 0.132 0.34 0.882 0.35 0.7 100%

5 0.113 0.27 1.089 0.7 0.7 0%

6 0.094 0.25 1.409 0.7 0.7 0%

7 0.074 0.25 1.940 0.7 0.7 0%

8 0.055 0.25 2.950 0.7 0.7 0%

9 0.036 0.25 5.413 0.7 0.7 0%

10 0.023 0.25 9.977 0.7 0.7 0%

Table A2.1: Comparison of stiffness modifiers calculated based on hand calculation, user defined and program calculated (explicit method function of wall reinforcement)

Figure A2.3: Vertical stress S22 due to load combination Comb1=0.8D+1.0Lateral as obtained from ETABS® model

48

c) Vertical stress S22 contours, plotted at wall elevation from ETABS® model, is presented in

Figure A2.3. It is clearly shown from the stress contour plots that all walls below the 4th

level are cracked while all walls above are uncracked. Table A2.1 shows cracking

modifiers that are dependent of wall reinforcement for the explicit method using both hand

calculations and Wall Cracking Tool and compared with the user defined modifiers that

are independent of reinforcing. Percent gain of stiffness is also reported in Table A2.1

when comparing modifiers from the user defined method vs the explicit method for the

cracked walls.

Figure A2.4: Lateral displacement response of ETABS® model after being run through Wall Cracking Tool using user defined modifiers (independent of reinforcement)

4) Figure A2.4 and Figure A2.5 show lateral displacement response of ETABS® model after it is

passed through Wall Cracking Tool’s stress analysis using modifiers options of user defined and

explicit method, respectively, after which the tool instantaneously applies the corresponding

modifiers. For this example, user defined modifiers (uncracked= 0.7 and cracked = 0.35) are

applied to the uncracked walls above the 4th level and cracked wall below the 4th level respectively.

An upper limit modifiers of 0.7 are enforced to all walls when the modifier option is based on the

49

explicit method. It is shown that lateral displacement at the top of the building is about 2.97 inches

and 1.89 inches, for the user defined and the explicit method, respectively.

Figure A2.5: Lateral displacement response of ETABS® model after being run through Wall Cracking Tool using modifiers based on the explicit method (dependent of reinforcement)

CONCLUSION

Based on the stress analysis presented above, Wall Cracking Tool results show a good comparison with

the independent results obtained from ETABS® and the hand calculations. It is demonstrated that for the

user defined modifiers options, walls below the 4th level are to be modeled as cracked walls (with f22

modifier of 0.35) while walls above need to be modeled uncracked. In addition, when using Wall Cracking

Tool, the modifiers are automatically and instantaneously assigned to the walls based on selected code

without the need to post-process any results.

Per Figure A2.6, when the model is run with the strict cracking assumptions using the user defined

modifiers, the lateral displacement at the top of the wall is about 2.97 inches that is about 11% less than

the one calculated using the conservative approach (3.33 inches). When the model is run with the strict

cracking assumptions using the program calculated modifiers based on the explicit method, the lateral

displacement at the top of the wall is about 1.89 inches. This is about 43% less than the one calculated

50

using the conservative fully cracked approach and 36% less than the lateral displacement from the user

defined options. This difference shows the importance of using the modifier options based on the explicit

method which tends to be more significant on taller buildings.

Figure A2.6: Lateral displacement response of ETABS® model for uncracked, fully cracked and strict cracking application via Wall Cracking Tool based on user defined modifiers and modifiers from explicit method. Figure A2.7 shows multiple plots of the modifiers calculated per Eq.6 for the explicit method with varying

stress level (normalized with compressive strength of 4000 psi for illustration purposes) and different wall

vertical reinforcement ratios. The upper and lower limits are also plotted to show the importance of using

varying modifiers of the explicit method in lieu of the constant user defined modifiers. For this example,

when the tensile stress is between 0.12*f’c and 0.25*f’c, the modifiers from the user defined method must

be taken as 0.35 (cracked) while the modifiers from the explicit method varies between 0.35 to 0.7 which

can be as high as 100% gain in stiffness. Depending on the wall reinforcing ratio and concrete compressive

strength, this gain can be also significant for highly stressed walls.

51

Figure A2.7: F22 modifier using Eq. 6 vs normalized axial tensile stress w.r.t concrete compressive strength of 4000 psi for different reinforcement ratios.

0.000.100.200.300.400.500.600.700.800.901.001.101.201.301.401.501.601.701.801.902.002.102.202.30

0 0.1 0.2 0.3 0.4 0.5

λ =F22Modifie

r

ft/f'c

F22 Modifier vs Normalized Wall Stress ft=S22 w.r.t f'c

rho=0.25 rho=0.5 rho=1 rho=2

rho=3 rho=4 Lower Limit Upper Limit