Cracked Section Analysis MIDAS GEN

8/9/2019 Cracked Section Analysis MIDAS GEN

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Contents

Step 1: Model overview

Step 2: Load combination

Step 3: Rebar data

Step 4: Cracked section analysis

Slab Deflection Check by Cracked Section nalysis

Midas Information Technology Co., Ltdhttp://en.midasuser.com

Program Version Gen 2010 (v2.1)

Revision Date Nov. 05, 2010
http://en.midasuser.com/http://en.midasuser.com/


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Midas Information Technology Co., Ltd.http://en.midasuser.com

Slab Deflection Check b y Cracked Section AnalysisIntrod uct io n of Deflect ion Check

Step

00

This tutorial has been provided to explain how to check cracking deflection in slabs. For this reason, the procedure for general design

process of slabs and walls are not explained in this tutorial. For the users who are not familiar with the general design of slabs and walls, it is

recommended to review Meshed Slab and Wall Design as per EN1992-1-1:2004 tutorial before going through this tutorial.

In the current version of midas Gen, meshed slab/wall design (ULS and SLS including cracking deflection) are provided as per EN1992-1-

1:2004 only.

Element type Member type ULS (Ultimate Limit State) Design SLS (Serviceability Limit State) Design

Beam element Beam, Column

Bending without axial force

Bending with axial force

Shear

Stress Limitation

Crack Control

Deflection Control

Wall element WallBending with axial force

Shear-

Plate elementSlab

Flexural design (Wood-Armer moment)Punching shear checking

Stress Limitation (considering cracked moment)

Crack ControlDeflection Control (Uncracked, Cracked)

Wall In-plane Stress -

In Gen 2010 (v2.1), cracking deflection check by cracked section analysis has been implemented as perEN1992-1-1:2004.

The following design features are available in Gen 2010 (v2.1).


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Slab Deflection Check b y Cracked Section AnalysisUsage Tip [ Task Pane ]

Step

00

Using the task pane, we can display work procedure, required input items and optional input items for

each analysis and design case. Using the User Defined Task Pane, the user can create a Task Pane

manually.

For the meshed slab wall design feature, TDF file was provided with the tutorial model files for the

users convenience. In order to import the User Defined Task Pane, please follow the procedure below.

1. Go to Task Pane tab in the left panel of the midas Gen window.

2. Click [Task Pane] text from the drop down menu.

3. Click [Import User Defined Page].

4. Select slab desig.tpd file and click [Open] button.

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3

2

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Slab Deflection Check b y Cracked Section AnalysisOverview

Step

01

1 m 9 m 8 m 1 m

5m

6m

5m

1m

1m

Typical Floor Plan

A-A Sectional Elevation

3m

3m

3m

3m

3m

A A

3m

6m


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Slab Deflection Check b y Cracked Section Analysis

Eurocode2-1-1:2004

Beam: Concrete Grade C25/30 Column: Concrete Grade C30/37 Slab: Concrete Grade C25/30

Designation Story Section IDColumn Size

(mm)

Column 1~5F 2 400 x 400

Designation Story Section IDSection Size

(mm)

Girder 1~5F 1 500 x 400

Designation Story Thickness IDThickness

(mm)

1:02 1~5F 1 200

Step

01

Girder section

Column section

Slab thickness

Materials

pplied Code

Detai ls of the bu i lding (1)

Load Details

Permanent

LoadSelf Weight Weight Density: 23.54 kN/m3

V

a

ri

a

b

l

e

L

o

ad

s

Imposed

LoadPressure Load Shopping areas : 4.0 kN/m2

Wind

LoadX-dir./ Y-dir.

Eurocode-1(2005)

Terrain Category : II

Earthquake

LoadX-dir./ Y-dir.

Eurocode-8(2004)

Spectrum Parameters: TYPE 1

Ground Type : B

Importance Factor : 1.0

Appl ied Load

S




Step

01

Procedure

2

3

1 File > Open Project

Select flat slab_CSA.mgb.

Click [Open] button.

1-1.Openi ng the pre-generated model fi le

Open the pre-generated modelfile.

2

3

St




Procedure

Results > Comb inations >

Concrete Design tab

Click [Auto Generation]

button.

Click [OK], and [Close] button.

Click icon to perform an

analysis.

1

Step

02

2

3

2

3

4

2-1. Au tomatic generat ion of lo ad com binat ions

3

4

Step




Step

02

Procedure

Des i gn >

Meshed Slab /Wal l Des ign >Serv iceabi l i ty Load

Combinat ion Type

Click [OK]

1

2

2-2. Serviceabi l i ty load c ombinat ion type

1

2

Cracking deflection can be checkedonly for Quasi-permanentserviceability load combination type.

Serviceability load combinationtype is automatically classified ifAuto Generation function has beenused to generate load-combinations.

If the user manually defined loadcombinations, serviceability loadcombination type must be definedby the user.

If serviceability load combinationtype is not specified, SlabServiceability Checking is not

performed.

cLCB28 = 1.0D + 0.3LL

Step




Step

02

Procedure

Des i gn >

Meshed Slab /Wal l Des ign >

Slab /Wal l Load Combinat ions

Click [OK]

1

2

2-3. Slab and wall load combinat ion s

Slab/Wall Load Combination

Select the load combinations for

the slab/wall element design.

2Cracked section analysis will beperformed for the Quasi-Permanent load combinationsselected in Deflection(Cracked)field.

1

Step




Step

02

Procedure

Des i gn >

Meshed Slab /Wal l Des ign >

Serv iceabi l i ty Parameters

Select [All] option.

Select [L/250] option for thedeflection limit.

Click [Apply] button.

1

2

2-4. Slab Serviceabil i ty Parameters

Serviceability Parameters

Define deflection limit. Slab

length L can be automatically

recognized by the program as asub-domain length.

4

Deflection limit is entered asSpan/250 as per the clause 7.4.1(4) of EN1992-1-1:2004. It will beapplied for quasi-permanent load

combinations.

2

33

4

Step




Step

03

Procedure

Click [Active by Identifying]icon.

Select [Story], [4F], [+Below]options.

Click [Active] and [Close]button.

Design >

Meshed Slab/Wall Design >

Slab/Wall Rebars for Checking

Select S1 from the Name listand check the rebar diameter and spacing.

Select S2 from the Name listand check the rebar diameter and spacing.

Click [Close]

1

2

3

3. Check rebar data

Check rebar data

Cracked section analysis can

be performed for the elements

which contain rebar data. Rebardata were entered in this model.

4

1

5

2

4

3

5

6

7

Step




p

03

Procedure

Click [Display] icon.

Click [Design] tab and check on[Sub-Domain Rebar Direction]options.

Click [Apply] button and checkthe rebar direction and subdomains.

Check on [Meshed Slab RebarData] option.

Click [Apply] button and check

the rebar data for each element.

Check off [Sub-Domain RebarDirection] and [Meshed SlabRebar Data] option. Click [OK]button.

1

2

3

3. Check rebar data

Check rebar data

Cracked section analysis can

be performed for the elements

which contain rebar data. Rebardata were entered in this model.

4

1

5

2

3, 5

4

6

6

Step


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p

04

Procedure

Design >


Cracked Section AnalysisControl

Enter 0.01 for ConvergenceTolerance

Click : [OK]

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2

3

4-1. Cracked sect ion analysis co ntrol

Cracked section analysis control

As the program use the updated

effective second moment of area

during the cracked section analysis,convergence criteria and iteration

numbers needs to be entered.

2

3

Step


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Slab Deflection Check b y Cracked Section Analysis04

Procedure

Design >


Perform Cracked Section

Analysis

1

4-2. Perform cracked sect ion analysis

Perform cracked section analysis

Regardless of the activated

elements, cracked section analysis

is performed for all the slabs whichcontains rebar data.

Cracked section analysis is skippedin the following cases:

(1) Mat foundation type plateelements specified in Define SubDomain dialog box (Model >Domain > Define Sub Domain).

(2) When no rebar data has beenentered

(3) When the entered concrete cover islarger than the plate thickness

(4) When no load combinationsselected for Deflection (Cracked)

column in Meshed Slab/Wall LoadCombinations dialog box(Design > Meshed Slab/WallDesign > Slab/Wall LoadCombinations )

Step


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Procedure

Design >


Slab Serviceability Checking

Click icon.

Select [Story] and [3F] in the list.

Click [Active] icon.

Click [Deflection].

Click [Cracked] to check thecracked section analysis results.

Select [Crack Point] option.

Click [Value].

Click [Apply] and check theresults in the model view.

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2

45

5

6

4-3. Check crack ing deflection (1)

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7

8

3

Step


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Procedure

Click [Ratio] option.

Click [Apply] button. Crackingdeflection ratio comparing to thedeflection limit is displayed in themodel view.

Click [Design Result] button tocheck the detailed results.

Check the detailed results in thetext file. Effective second moment

of area can be checked for dir. 1and dir. 2 separately.

It also contains deflection limit bysub-domains.

1

2

3


1

Step


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Procedure

Select [Creep] option.

Select [Value] option.

Click [Apply] to see the long-termcracking deflection.

Click [Close] button.

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1

3

2

Step


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Members which are expected to crack, but may not be fully cracked, will behave in a manner

intermediate between the uncracked and fully cracked conditions and, for members subjected mainly to

flexure, an adequate prediction of behavior is given by the following expression based on the sub clause

7.4.3 (3) in EN 1992-1-1:2004. Following factors including the effective second moment of area by

elements for each iteration step can be checked in "File Name_CSA.OUT

file which is automaticallygenerated in the same folder as a model file has been saved after performing the cracked section

analysis.

Therefore Ieff (effective second moment of area) can be calculated from the following equation.

Where,

04

Procedure

[Effective second moment of area ]


where, fctm: mean value of axial tensile strength of concrete

bc: depth of concrete in compression

(Reference: Designers Guide to EN1992-2, Hendy &

Smith, thomas telford)

Step


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"File Name_CSA.OUT" file contains the following data for each iteration step by elements. Final effective

second moment of area can be checked in the final iteration step. This file is provided for the users

verification of the cracked section analysis results.

04

Procedure

[File name_CSA.OUT file]


element no.I_effective

(dir_1)

effective I

(dir_2)

I_fully cracked

(dir 1)

I_fully cracked

(dir 2)I_uncracked cracked moment

dc

(dir 1)

dc

(dir2)

Updated

moment (dir1)

updated

moment (dir 2)

No. Ieff_x Ieff_y Icr_x Icr_y Ig Mcr Dc_x Dc_y MO_x MO_y

334 1.22E-04 6.67E-04 7.76E-05 0.00E+00 6.67E-04 1.71E+04 3.34E-02 0.00E+00 1.89E+04 4.49E+03

n (Es/Ec)Rebar Area

(dir 1)

Rebar Area

(Dir 2)

Effective depth

(dir 1)

Effective depth

(dir 2)

(dir 1)

(dir 2)

I_eff / I_cracked

(dir 1)

I_eff / I_cracked

(dir 2)

Final

effective I (dir 1)

Final

effective I (dir 2)

n(Es/Ec) AS_X AS_Y DD_X DD_Y XI_X XI_Y RATIO_X RATIO_Y RATIO_X*Ig RATIO_Y*Ig

6.35E+00 7.54E-04 7.54E-04 1.50E-01 1.50E-01 5.91E-01 0.00E+00 1.82E-01 1.000000 1.22E-04 6.67E-04

Cracked Section Analysis MIDAS GEN

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