cracked section analysis midas gen
TRANSCRIPT
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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
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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.
1
3
2
4
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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
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Slab Deflection Check b y Cracked Section Analysis
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
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Slab Deflection Check b y Cracked Section Analysis
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
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Slab Deflection Check b y Cracked Section Analysis
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
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Slab Deflection Check b y Cracked Section Analysis
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
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Slab Deflection Check b y Cracked Section Analysis
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
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Slab Deflection Check b y Cracked Section Analysis
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
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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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Slab Deflection Check b y Cracked Section Analysis
p
04
Procedure
Design >
Meshed Slab/Wall Design >
Cracked Section AnalysisControl
Enter 0.01 for ConvergenceTolerance
Click : [OK]
1
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 >
Meshed Slab/Wall 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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Slab Deflection Check b y Cracked Section Analysis04
Procedure
Design >
Meshed Slab/Wall 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.
1
2
3
4
2
45
5
6
4-3. Check crack ing deflection (1)
6
7
8
7
8
3
Step
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Slab Deflection Check b y Cracked Section Analysis04
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
4-3. Check crack ing deflection (2)
1
Step
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Slab Deflection Check b y Cracked Section Analysis04
Procedure
Select [Creep] option.
Select [Value] option.
Click [Apply] to see the long-termcracking deflection.
Click [Close] button.
1
2
3
4-3. Check crack ing deflection (2)
1
3
2
Step
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Slab Deflection Check b y Cracked Section Analysis
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 ]
4-3. Check crack ing deflection (3)
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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Slab Deflection Check b y Cracked Section Analysis
"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]
4-3. Check crack ing deflection (4)
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
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