App12_ACI Meshed Slab and Wall Design

8/10/2019 App12_ACI Meshed Slab and Wall Design

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Midas Information Tech nology Co., Ltd.

Autom esh and slab / wall design tutorial

Meshed Slab and Wall Design as per ACI318 11

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

Program Version Gen 2015 (v1.1)

Revision Date 05 Nov 2014
http://en.midasuser.com/http://en.midasuser.com/http://en.midasuser.com/


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Midas Information Technology Co., Ltd.

Autom esh and slab / wall design tutorial Introd uct io n o f Meshed Slab / Wall Design

Step

00

This tutorial is intended to explain how to perform meshed slab and wall design. For this reason, the procedure for general frame design

process were not included.

Element type Member type Strength Check Serviceability Check

Beam element Beam, ColumnBending without axial forceBending with axial forceShear

-

Wall element Wall Bending with axial forceShear -

Plate elementSlab Flexural design (Wood-Armer moment)

Punching shear checkingDeflection Control (Uncracked)

Wall In-plane Stress -

In Gen 2013 (v2.1), meshed slab and wall design as per ACI318-11 has been newly implemented. The following design features as per ACI318-

11 are available in midas Gen.

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Autom esh and slab / wall design tutorial Usage Tip [ Task Pane ]

Step

00

Using the task pane, we can display work procedure, required input items and optional input items foreach analysis and design case. Using the User Defined Task Pane, the user can create a Task Panemanually.For the meshed slab wall design feature, TDF file was provided with the tutorial model files for theusers 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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Autom esh and slab / wall design tutorial Overview

Step

00

9 m 16 m 9 m 23 m

5 m

6 m

7 m

2 m

1 2

. 5 m

Typical Floor Plan

Sectional Elevation

3 m

3 m

3 m

3 m

3 m

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Load Details

Dead Load Self Weight Weight Density: 23.56 kN/m 3

Live Load Pressure Load Shopping areas : 4.0 kN/m2

Office areas : 2.0 kN/m 2

Wind Load X-dir./ Y-dir.

IBC2012 (ASCE7-10)Basic Wind Speed : 85 mile/hExposure Category : CDirectional Factor : 0.85Gust Effect Factor : 0.85

Earthquake Load X-dir./ Y-dir.

IBC2012 (ASCE7-10)Site Class : DImportance Factor : 1.0Response Modification Coefficient (R) : 4.0Maximum Period : 6.0 sec

Step

00 Detai ls of the bu i lding (2)

Applied Load

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St




Step

01

Procedure

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1 File > Open Project

Select flat slab.mgb.

Click [Open] button.

1-1.Openin g the pre-generated mo del f i le

3

Open the pre-generated modelfile.

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Step




Procedure

Node/Element > Mesh >Auto-mesh

Method : Line Elements

Type : Quad + Triangle

Mesh Size : Length : 0.5 m

Material : 1:Grade C4000

Thickness : 1:0.2000

Domain : 1

Select Select by Plane

Select XY Plane

Click edge of the Roofto select Roof as a pictureIso View

Click [Apply]

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1-2. Au to-m esh plan ar area (1)

Generate meshed elements for slabsSpecify meshed area for auto-meshing (Line elements method).

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Step




Procedure

Click > Select elements byidentify

Select Wall > [Add]

Click [Close]

Click [Activation]

> [Activate]

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Step

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Generate meshed elements for wallsSpecify meshed area for auto-meshing (Line elements method).

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Step




Procedure

Step

01 1-2. Au to-m esh plan ar area (3)

Structure > UCS/Plane

User Coordinate System >

X-Z Plan

Origin : 39, 4, 0

Click : [Apply] > [Close]

Structure > UCS/Plane >

Grids > Define Point Grids

dx, dy : 1, 1

Click : [Apply] > [Close]

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Generate meshed elements withopeningSpecify meshed area for auto-

meshing (Nodes method).

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Step




Procedure

Node/Element > Mesh >Auto-mesh

Method : Nodes

Draw as a picture below.

Type : Quadrilateral




Domain >Name : 2

Click [Apply] > [Close]

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Step


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Procedure

Node/Element > Mesh >

Auto-mesh

Method : Planar Elements





Click Select by window

Select as a picture

Domain >Name : 3

Click [Apply]

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p

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Step


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Procedure

Method : Planar Elements





Click Select by window

Select as a picture

Domain >

Name : 4


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Step


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Procedure

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1-3. Def ine Bo und ary Con dit ion

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Select all the bottom nodes of modeland apply the boundary conditionwith drag-and-drop function.

Click Activate All

Toggle off Point Grid

Click Switch to GCS .

Click Select by Plane

and Select XY Plane

Select any node at the bottom

of model

Works Tab in the Tree Menu

Click Boundaries>Supports>

Type 1 [1111110]

Drag & Drop to the model

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r g

rop

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Step


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Procedure

Tree Menu > Work >

Domain1 [1] > Double Click

Load > Static Loads >

Pressure Loads

Load Case Name : LL

Direction : Local z

Loads : P1 : -4.0kN/m 2


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2-1. Press ur e load s (1)

6

Apply floor loads.

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Step


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Procedure

Structure > Building > Control

Data > Building Generation

Number of Copies : 4

Distance(Global z) : 3 m

Operations : Click [Add]

Check off Copy NodeAttributes option.

Click [Select All] icon

Click [Apply]

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2-2. Bu ildin g generatio n

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Step


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Procedure

Structure > Building > Control

Data > Stroy

Click [Auto Generate Story Data]button

Click [OK]

Click [Close]

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2-3. Au tom atic generat ion o f the s to ry d a ta

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Step


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Procedure

Load > Seismic > Response

Spectrum Data > Response

Spectrum Functions

Click [Add]

Click [Design Spectrum]

Design Spectrum :

IBC2012(ASCE7-10)

Click [OK]

Click [OK]

Click [Close]

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2-7. Respon se spectrum func t ions

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Step


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Procedure

Results > Combinations >

Concrete Design >

Auto Generation

Select Design Code as

ACI 318-11

> Click [OK]

> Click [Close]

Perform Analysis

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2-9. Au tom atic generat ion of lo ad com binat ions

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Step

0 3 1 C l d i


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Autom esh and slab / wall design tutorial 03

Procedure

Design > Design > RC Design >

Design Code

Select Design Code as

ACI318-11 >

Click [OK]


Column Design

Click [Select All] and then[Update Rebar] button.

Sorted by : Member >

Check the design results >

click [Close]

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3-1. Colum n design

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Step

03 3 2 M dif l b d


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Procedure


Modify Column Rebar Data

Select SECT 2-1 in the list.

Check the rebar data.

Rebar data can be modified inthis dialog box.

Click [Add/Replace] > [Close]

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3-2. Modify colu m n rebar da ta

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Step

04 4 2 Design criter iafor rebar


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Procedure

Design > Design >

Meshed Design >

Design Criteria for Rebar

Check off [Basic Rebar for Slab] .

For Slab Design :

Dir. 1 : 0.03 m, 0.03 m

Dir. 2 : 0.05 m, 0.05 m

Click [OK]

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4-2. Design criter ia for rebar

Specify rebar sizeEnter the standard sizes ofrebars used in the design of

reinforcement for slab/wallelements.

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Basic rebar option is usefulwhen the engineer wants toassign the identical rebar to theentire slabs and checks theadditional rebar amount.

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Step

04 4 3 Ac tiveIdent ity


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Procedure

View > Activities >

Active Identity

Click : Story > ROOF

Check : +Below

Click : [Active] > [Close]

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4-3. Ac tive Ident ity

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A h d l b/ lld i i l

Step

04

4-4 Slabflexu raldesig n(2)


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Procedure

Design > Design >

Meshed Design >

Slab Flexural Design

Select [Avg. Nodal] .

Click [Design Result]

Click [Design Force]

Click [Update Rebar]

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Produce the detail flexuraldesign results of slab elementsin a text format.

Produce the flexural designforces of slab elements in atabular format.

Update the rebar quantity for each slab element. The updatedrebar data is used for strengthverification.

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4 4. Slab f lexu ral desig n (2)

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Autom eshandslab/walldesigntutorial

Step

04 4-4.Slabflexu raldesig n(3)


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Procedure

Design > Design >

Meshed Design >


Check [Resistance Ratio]

Load Cases/ Combinations

: ALL COBMINATION

Select [Avg. Nodal] .

Check [Dir.1]

Click [Apply]

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The ratio of the design momentto the moment resistance whenthe designed rebar spacing isapplied.

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4 4. Slab f lexu ral desig n (3)

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Autom eshandslab/walldesigntutorial

Step

04 4-4. Slab f lexu ral desig n (5)


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Procedure

Design > Design >

Meshed Design >


Check [Wood Armer Moment]

Load Cases/ Combinations

: ALL COBMINATION

Check [Dir.1]

Click [Apply]

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Display the Wood Armer Moments in contour.

g ( )

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Autom eshandslab/walldesigntutorial4-4. Slab f lexu ral desig n (6) Step

04


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Procedure

[Design strength of

flexural member]

g ( )

Doubly Reinforced:

1. Design Strength

Flexural strength of meshed slab is calculated based on the doubly reinforced beam design method.

04

Design Strength Required Strength

(Nominal Strength) U

1 ' ( ')n s y M A f d d

2 ( ') ( )2n s s ya

M A A f d

1 2( ) [ ' ( ') ( ') ( )2n n n s y s s ya

M M M A f d d A A f d

where,( ')

0.85 s s y

ck

A A f a

f b

Cross Section Strain Strength

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Autom esh and slab / wall design tutorial 4-4. Slab f lexu ral desig n (7) Step

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g

Procedure

[Design strength of

flexural member]

2.Strength reduction factor

Strength reduction factor needs to be calculated based on the tensile strain in extreme tension steel.

04

Design Strength Required Strength

(Nominal Strength) U

Strength reduction factor is uniformly applied as 0.9 in midas Gen.

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Autom esh and slab / wall design tutorial 4-4. Slab f lexu ral desig n (8) Step

04


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Procedure

[Design strength of

flexural member]

3. Minimum reinforcement of flexural members

5. Minimum Spacing LimitRebar spacing shall not be less than the smaller of 3*slab thickness and 18in.

4. Maximum reinforcement of flexural members

, 0.002 s min A bh for 40 y f ksi or 50 ksi

, 0.0018 s min A bh for 60 y f ksi

,

0.0018 60000 s min

y

A bh f

for 60 y f ksi

Above limitation is applied in midas Gen. If fy > 60ksi, As,min is the smaller of 0.0014 and .0.0018 60000

y

bh f

In midas Gen, maximum rebar ratio is limited as 75% of balanced rebar ratio as per Appendix B10.3.3.

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Step

04 4-4. Slab f lexu ral desig n (9)


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Procedure

[Wood Armer Moment]

From the analysis results, following plate forces about the local axis are calculated- m x x - m y y - m x y In order to calculate design forces in the reinforcement direction, angle and will betaken as following figure:

x, y: local axis of plate element1, 2: reinforcement direction: angle between local x-direction and reinforcement direction 1: angle between reinforcement direction 1 and reinforcementdirection 2

Firstly, internal forces (mxx, myy and mxy) are transformed into the a-b coordinate system.

6. Required Moment Strength calculated from Wood Armer moment

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Step

04 4-4. Slab f lexu ral des ign (10)


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Procedure

[Wood Armer Moment]

Then, Wood-Armer moments are calculated as follows:

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Step

04 4-5. Slab sh ear check ing (1)


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Procedure

Design > Design >

Meshed Design >

Slab Shear Checking


Click [Apply]

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Slab Shear CheckingProduce the two-way shear(punching shear) check results atthe supports of slab elements or atconcentrated loads and the one-way shear check results along theuser-defined Shear Check Lines.

Code Method FEM Method

3Produce the detail punchingshear design results of slabelements in a text format. If theplate elements of a certaincritical perimeter are selected inthe model view, the detailresults will include the punchingshear results of the selectedelements. If none of the elementhas been selected, the mostcritical results will be plotted inthe detail result text output.

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Autom esh and slab / wall design tutorial 4-5. Slab sh ear check ing (3) Step

04


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Procedure

[Punching Shear Check(By CODE)]

In this method, the program takes the axial force in the column supporting the slab as the shear force (V u).The basic control perimeter is taken at a distance d/2 from the column face (as shown in the diagram below).

Punching shear perimeter for calculating concrete shear strength

Maximum Shear Strength by Concrete (ACI318-11 11.1.3.1)

6n ck oV f b d

2c ck oV f b d

In midas Gen, the above limitation is applied when slab thickness is larger than 200mm.

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04


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Procedure


2. Shear strength of reinforcement, Vs

In midas Gen, required rebar area is calculated by Vs = Vn- Vc .Shear rebar spacing limit and minimum shear rebar area are not applied.

v y s

A f d V

s

,min 4 s ck wV f b d

Shear rebar spacing limit

0.5 s d

0.75 6

0.50 6

u ck

u ck

d for f s

d for f

2 g d

Minimum Shear Rebar Area

1

2 c u cV V V

,min 0.75 w

v ck y

b s A f

f (50 ) /w yb s f but shall not be less than .

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04


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Procedure


Unbalanced moment between a slab and column by flexure

3. Required Shear Strength, Vu

Unbalanced moment between a slab and column by eccentricity of shear

(1 )v f

1 2

1

1 (2 / 3) / f

b b

Factored shear stress

( )u v u AB

f ABc c

V M cv

A J

( )u v u AB

f CDc c

V M cv

A J

Case A. Exterior column Case B. Interior column

Case C. Exterior column Case D. Conner column

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Step



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Procedure

[Punching Shear Check(By FEM)]

In these methods (The FEM Method), the Shear force along the critical section is taken and divided by the effective depth to calculate shear stress.Therefore there is no need to calculate (Beta), to consider moment transferred to the column.

(There are 4 plate elements intersecting at nodes. The nodes are marked by nomenclature of Grid Lines. As the center node is denoted by B2 , B on x-Axis and2 on Y-Axis)

When slab is defined as the plate element, the program calculated stresses only at the nodes, in the analysis. So we have the stresses at B1, B2, C2 etc. (seethe figure above) are calculated by the program.

Case 1 - To calculate stresses at the critical section that is u1 in the given figure, for example we take the point P in the figure which lies in a straight line. Thestress at B1 and B2 are known. The values at these nodes are interpolated linearly to find the stress at point P .

Case 2- Now if the point lies in the curve such as the point Q, then the software will divide the curve into 6 parts. At each point such as Q a tangent whichintersects B1-B2 and C2-B2.The value of stresses at T and V are determined by linear interpolation of stresses which are known at for T (at B1 and B2) and forV (at C2 and B2). After knowing stresses at T and V the stress at Q is determined by linear interpolation of stresses at T and V.

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Step



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Procedure

[Punching Shear Check(By FEM)]

(Method 1: Average by elements.)In this method the stresses at all the critical points is determined. The critical points divide the critical sectioninto segments. The average value for all these segments is determined by dividing the stresses at the two endsof the segment by 2. After determining the average value for each segment, the maximum average valuefrom all of the segments is reported as the Stress value for the critical Section.

a,b are stresses at the segment ends.Average value for the segment will be (a+b)/2, and such average value for each segment is determined.

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Step

04 4-6. Servic eabili ty param eter


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Procedure

Design > Design> RC Design >

Serviceability Parameter

Select All

Click [Apply]

Unselect All

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Slab deflection is verified as per the clause 9.5.3 of ACI318-11. This deflection limit can be entered bythe user in Serviceability Parameter.

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Step

04 4-7. Slab servic eabili ty c heck ing


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Procedure

Design > Design >

Meshed Design >

Slab Serviceability Checking

Check [Uncracked] and Active

Long-term Deflection and Check

[Creep] .

Select [Ratio]


Click [Apply]

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Calculate the deflection for theuncracked section and compareit with the allowable deflection.Deflection for the crackedsection is not supported in thecurrent version.

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Autom esh and slab / wall design tutorial 4-8. Wall d esig n (1) Step

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Procedure Wall Design

Wall design forces and tension reinforcements are obtained in an element subject to in-plane orthogonal stress.

The tension reinforcement in an element subject to in- plane orthogonal stresses Edx , Edy and Edxy can be calculated as shown below.Compressive stresses should be taken as positive, with Edx > Edy , and the direction of reinforcement should coincide with the x and y axes.

where, x and y are the geometric reinforcement ratios, along the x and y axes respectively.

In locations where Edy is tensile or Edx Edy 2Edxy , reinforcement is required. The optimum reinforcement, indicated by superscript , andrelated concrete stress are determined by:

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Reference: Nielsen, M.P., Limit Analysis and Concrete Plasticity, Second Edition, CRC Press, USA, 1999

Wall design using wall element is also supported in midas Gen.

Autom esh and slab / wall design tutorial 4-8. Wall d esig n (2) Step

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Procedure Wall Design

Minimum reinforcement for vertical and horizontal rebar is considered in accordance to ACI318-11, 14.3.2 and 14.3.3. Maximum ratio of of verticalreinforcement are applied as 0.04 and it can be modified in Design > Concrete Design Parameter > Limiting Maximum rebar Ra tio.

[Minimum ratio of vertical reinforcement area] [Maximum ratio of vertical reinforcement area]

0.04

[Minimum ratio of horizontal reinforcement area]

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Step

04 4-8. Wall d esig n (3)


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Procedure

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View > Activities > Active All

Design > Design >

Meshed Design >

Wall Design

Check [As_req(m^2/m)]

Select [Avg. Nodal]

Select [Resistance Ratio]

Click [Apply]

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Wall DesignPerform the flexural designresults for wall elements incontour.

Display the area of therequired reinforcement.

Wall design is performedbased on ACI318-11. 2

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Step

04 4-8. Wall d esig n (4)


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Procedure

Design > Design >

Meshed RC Design >

Wall Design


Click [Design Force]

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Documents

App12_ACI Meshed Slab and Wall Design