step 1: slab deflection check by cracked section analysis ... · pdf fileslab deflection check...

Contents

Step 1: Model overview

Step 2: Load combination

Step 3: Rebar data

Step 4: Cracked section analysis

Slab Deflection Check by Cracked Section Analysis

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

Program Version Gen 2010 (v2.1)

Revision Date Nov. 05, 2010

http://en.midasuser.com/


Slab Deflection Check by Cracked Section AnalysisIntroduction of Deflection 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 element

SlabFlexural design (Wood-Armer moment)

Punching shear checking

Stress Limitation (considering cracked moment)

Crack Control

Deflection Control (Uncracked, Cracked)

Wall In-plane Stress -

In Gen 2010 (v2.1), cracking deflection check by cracked section analysis has been implemented as per EN1992-1-1:2004.

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



Slab Deflection Check by 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

user‟s 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.

1

3

2

4



Slab Deflection Check by Cracked Section AnalysisOverview

Step

01

1 m 9 m 8 m 1 m

5 m

6 m

5 m

1 m

1 m

Typical Floor Plan

A-A‟ Sectional Elevation

3 m

3 m

3 m

3 m

3 m

A A’

3 m

6m




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

Applied Code

Details of the building (1)

Load Details

Permanent

LoadSelf Weight Weight Density: 23.54 kN/m3

V

a

r

i

a

b

l

e

L

o

a

d

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

Applied Load




Step

01

Procedure

2

3

1 File > Open Project…

Select “flat slab_CSA.mgb”.

Click [Open] button.

1-1.Opening the pre-generated model file

Open the pre-generated model file.

2

3




Procedure

Results > Combinations >

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. Automatic generation of load combinations

3

4




Step

02

Procedure

Design >

Meshed Slab/Wall Design >

Serviceability Load

Combination Type

Click [OK]

1

2

2-2. Serviceability load combination type

1

2

Cracking deflection can be checked only for “Quasi-permanent” serviceability load combination type.

Serviceability load combination type is automatically classified if „Auto Generation‟ function has been used to generate load-combinations.

If the user manually defined load combinations, serviceability load combination type must be defined by the user.

If serviceability load combination type is not specified, Slab Serviceability Checking is not performed.

cLCB28 = 1.0D + 0.3LL




Step

02

Procedure

Design >


Slab/Wall Load Combinations

Click [OK]

1

2

2-3. Slab and wall load combinations

Slab/Wall Load Combination

Select the load combinations for

the slab/wall element design.

2Cracked section analysis will be

performed for the “Quasi-Permanent” load combinations selected in Deflection(Cracked) field.

1




Step

02

Procedure

Design >


Serviceability Parameters

Select [All] option.

Select [L/250] option for thedeflection limit.

Click [Apply] button.

1

2

2-4. Slab Serviceability Parameters

Serviceability Parameters

Define deflection limit. Slab

length “L” can be automatically

recognized by the program as a

sub-domain length.

4

Deflection limit is entered as “Span/250” as per the clause 7.4.1 (4) of EN1992-1-1:2004. It will be applied for quasi-permanent load combinations.

2

33

4




Step

03

Procedure

Click [Active by Identifying]icon.

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

Click [Active] and [Close]button.

Design >


Slab/Wall Rebars for Checking

Select “S1” from the “Name” listand check the rebar diameterand spacing.

Select “S2” from the “Name” listand check the rebar diameterand 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. Rebar

data were entered in this model.

4

1

5

2

4

3

5

6

7




Step

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 checkthe 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. Rebar

data were entered in this model.

4

1

5

2

3, 5

4

6

6




Step

04

Procedure

Design >


Cracked Section Analysis Control

Enter “0.01” for Convergence Tolerance

Click : [OK]

1

2

3

4-1. Cracked section analysis control

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

04

Procedure

Design >


Perform Cracked Section

Analysis

1

4-2. Perform cracked section analysis

Perform cracked section analysis

Regardless of the activated

elements, cracked section analysis

is performed for all the slabs which

contains rebar data.

Cracked section analysis is skipped in the following cases:

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

(2) When no rebar data has been entered

(3) When the entered concrete cover is larger than the plate thickness

(4) When no load combinations selected for “Deflection (Cracked)” column in Meshed Slab/Wall Load Combinations dialog box (Design > Meshed Slab/Wall Design > Slab/Wall Load Combinations )




Step

04

Procedure

Design >


Slab Serviceability Checking

Click icon.

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

Click [Active] icon.

Click [Deflection].

Click [Cracked] to check the cracked section analysis results.

Select [Crack Point] option.

Click [Value].

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

1

2

3

4

2

45

5

6

4-3. Check cracking deflection (1)

6

7

8

7

8

3




Step

04

Procedure

Click [Ratio] option.

Click [Apply] button. Cracking deflection ratio comparing to the deflection limit is displayed in the model view.

Click [Design Result] button to check the detailed results.

Check the detailed results in the text file. Effective second moment of area can be checked for dir. 1 and dir. 2 separately.

It also contains deflection limit by sub-domains.

1

2

3


1




Step

04

Procedure

Select [Creep] option.

Select [Value] option.

Click [Apply] to see the long-term cracking deflection.

Click [Close] button.

1

2

3


1

3

2




Members which are expected to crack, but may not be fully cracked, will behave in a mannerintermediate between the uncracked and fully cracked conditions and, for members subjected mainly toflexure, an adequate prediction of behavior is given by the following expression based on the sub clause7.4.3 (3) in EN 1992-1-1:2004. Following factors including the effective second moment of area byelements 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 sectionanalysis.

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

Where,

Step

04

Procedure

[Effective second moment of area ]


where, fctm: mean value of axial tensile strength of concretebc: depth of concrete in compression(Reference: Designers Guide to EN1992-2, Hendy &Smith, thomas telford)




"File Name_CSA.OUT" file contains the following data for each iteration step by elements. Final effectivesecond moment of area can be checked in the final iteration step. This file is provided for the user’sverification of the cracked section analysis results.

Step

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)

Updatedmoment (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)ξ

(dir 1)ξ

(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


step 1: slab deflection check by cracked section analysis ... · pdf fileslab deflection check...

Documents