Shear Wall Frame ACECOMS AIT Thailand

7/27/2019 Shear Wall Frame ACECOMS AIT Thailand

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Behavior, Modeling and Design

of Shear Wall-Frame Systems

Naveed Anwar

Asian Center for Engineering Computations and Software, ACECOMS, AIT


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Shear Wall Behavior, Modeling, Analysis and Design AIT - Thailand ACECOM

The Basic I ssues

Modeling and analysis issues

Transfer of loads to shear walls

Modeling of shear walls in 2D

Modeling of shear Walls in 3D

Interaction of shear-walls with frames

Design and detaining issues Determination of rebars for flexure

Determination of rebars for shear

Detailing of rebars near openings and corners

Design and detailing of connection between various commonest of

cellular shear walls


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Shear WallCommon M isconceptions

Due to misleading name Shear Wall

The dominant mode of failure is shear

Strength is controlled by shear

Designed is governed primarily by shear

Force distribution can be based on relative stiffness


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Shear Wall or Column


5/150Shear Wall Behavior, Modeling, Analysis and Design AIT - Thailand ACECOM

Shear Wall or F rame

Shear Wall FrameShear Wall or Frame ?



Shear Wall and Frame Behavior



Shear Wall and Truss Behavior



Shear Wall and Frame

Shear Wall Behavior Frame Behavior



Shear Wall and Frame InteractionInteractionforces



A-1 A-2 A-3 B-4 B-1 B-2 B-3 B-4

Frame and Frame-Shear Wall



Shear Wall and Frame Interaction Frames Deform

Predominantly in a shear mode

Source of lateral resistance is the rigidity of beam-column/slab joints

Shear Wall Deform

Essentially in bending mode

Shear deformations are rarely significant

Only very low shear walls with H/W ratio


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The Basic Behavior of

Shear Walls, Frames and Shear Wall-Frames


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For each 10, 20 and 30 story buildings

Only Shear Wall( Total 3 Cases ) Only Frame( Total 3 Cases ) Only Shear + Frame( Total 3 Cases )

Case Studies: Shear WallFrame I nteracti

Total 3x3 = 9 Cases

C 1 Sh W ll F I t ti


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10 Story Wall D = 26.73 cm

Wall Thickness = 15 cm

Case 1: Shear WallFrame I nteracti



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D = 15.97 cm10 Story Frame

Beam Section = 60 cm x 30 c

Column Section = 50 cm x 50



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20 Story Wall D = 158.18 cm



Case 5 Shear Wall F rame I nteracti


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20 Story Frame D = 27.35 cm

Beam Section = 60 cm x 30 cm

Column Section = 75 cm x 75 c



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Case 8: Shear Wall F rame I nteracti


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30 Story Frame D = 40.79 cm




Case 9: Shear Wall F rame I nteracti


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30 Story Wall and Frame D = 20.87 cm





Shear Wall F rame I nteracti


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Top Floor Deflection Comparison

5.

1412

.

6620

.8715.97 27

.

35

40.

79

26.

73

158.

18

355.

04

0

50

100

150

200

250

300

350

400

0 10 20 30 40

Number of Story

DeflectionatTopFloor(cm)

Frame+Wall

Frame

Wall

Shear WallFrame I nteracti



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Storey Deflection (10 Storey Building)

0

5

10

15

20

25

30

0 2 4 6 8 10 12Story

Deformation(cm)

Wall

Frame



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Shear Wall Frame I nteracti


0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25Storey

Deflection(cm)

Wall

FrameFrame+Wall



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0

50

100

150

200

250

300

350

400

0 5 10 15 20 25 30 35

Storey

Deflectio

n(cm)

Wall

Frame

Frame+W



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D = Force / Stiffness Stiffness = Force / D

Stiffness Frame = 200 / 40.79 = 04.90Stiffness Wall = 200 / 355.04 = 00.56

Stiffness Frame + Wall = 200 / 12.66 = 15.79Stiffness Frame +Stiffness Wall = 4.90 + 0.56 = 5.46

Stiffness Frame +Stiffness WallStiffness Frame + Wall

For the cases considered here (30 story example):

Force=200Deflection = 40.79

Change in Shear Wall Momen


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Shear Wall Moments

for the Coupled System

Change in Shear Wall Momen

Interactionforces

Coupling Element Momen


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Interactionforces

Coupling Element Momen

Shear Wall -F rame Load Distr ibution Curv


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Shear Wall F rame Load Distr ibution Curv

Deflected Shape of Shear Wall-F rame I nteractive Syst


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p y

Khan-SbarounisCurves

Comparison of Shears and Moments in the Core wa


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p

4 Different Layouts for Same Function Requirements

30@2

0=60ft

total length of building = 110 ft2

1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

30@2

0=60ft


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

20ft

10 in


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

20ft

10 in

20ft

18-story highshear walls

Type A Type B

Type C


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

20ft

10 in

20ft


Type D

Comparison of : Type A


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30@2

0=60ft


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

Typical Floor Plan- Structure Type A

1

2

3

4

5

6

7

8

28

29

30

31

32

33

34

35

36

22 ft 20 ft

30 ft 30 ft

CL

10 ft

7.5 thick

floor slabs

8' clear heig

between floo

Transverse

section

Corewall

p yp

Comparison of : Type B


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30@2

0=60ft


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

Typical Floor Plan- Structure Type B

1

2

3

4

5

6

7

8

28

29

30

31

32

33

34

35

36

22 ft 20 ft

30 ft 30 ft

CL

10 ft

7.5 thick

floor slabs

8' clear hebetween fl

Transverse

section

Corewall3

0@2

0=60ft


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

20ft

10 in

p yp

Comparison of : Type C


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30@2

0=60ft


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

Typical Floor Plan- Structure Type C

1

2

3

4

5

6

7

8

28

29

30

31

32

33

34

35

36

22 ft 20 ft

30 ft 30 ft

CL

10 ft

7.5 thick

floor slabs

8' clear heig

between floo

Transverse

section

Corewall

30@2

0=60ft


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

20ft

10 in


1

5 @ 20 = 100 ft10 ft

26ft

corewallcorewall

Columnline

1 2 3 4 5 6

CL

2

17

12 in

6ft

in. thickflat plate

20ft

10 in

20ft


p yp


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Comparison of Shears and Moments in the Core wa


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Basic Types of Shear Wal ls


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yp


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Basic Modeling Optionsfor Shear Walls


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Frame Models for Cellular Walls


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Difficult to extend the concept to

Non-planer walls

Core Wall must be converted to

equivalent column and

appropriate rigid elements

Can be used in 2D analysis but more

complicated for 3D analysis After the core wall is converted to

planer wall, the simplified

procedure cab used for modeling

B

H

t

B

H

2t

t

Modeling Walls using 2D Elements


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Walls are subjected to in-plane deformations so 2D elements

that have transnational DOF need to be used A coarse mesh can be used to capture the overall stiffness and

deformation of the wall

A fine mesh should be used to capture in-plane bending or

curvature

General Shell Element or Membrane Elements can be used to

model Shear Walls


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Connecting Walls to Slab


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In general the mesh in the slab should

match with mesh in the wall to

establish connection

Some software automatically

establishes connectivity by using

constraints or Zipper elements

Zipper


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Using Beam-Column to Model Shear Walls


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4-Node plane element may not accurately capture the linear

bending, because constant shear distribution is assumed in

formulation but actually shear stress distribution is parabolic

Since the basic philosophy of RC design is based on cracked

sections, it is not possible to use the finite elements resultsdirectly for design

Very simple model (beam-column) which can also captures the

behavior of the structure, The results can be used directly to

design the concrete elements.


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Modeling Shear Walls Using Beam Elements


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B-1

Single Bracing B-2Double BracingB-3

Column with

Rigid Zones

B-4Columns with

Flexible Zones


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Comparison of Behavior (5 Floors)


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B4

B4

B1

A1

A1

B1


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Effect of Shear Wall Location


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Shear Wall DesignMeshing

Wall Meshing:


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Wall Meshing:

Piers and spandrels where bending deformations aresigni f icant (slender piers and spandrels), need to mesh

the pier or spandrel into several elements

I f the aspect ratio of a pier or spandrel one shell

element is worse than 3 to 1, consider additional meshing

of the element to adequately captur e the bending

deformation


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Shear Wall DesignSpandrel Zones

Spandrels or Headers


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Wall spandrel forces are output at the left and

right ends of wall spandrel Elements

Wall spandrel design is only performed atstations located at the left and right ends ofwall spandrel elements

Multiple wall spandrel labels cannot be assignedto a single area object.

p


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I nteraction Sur face for Shear Walls

P


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Mx

My

Concrete Shear Wall Design


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2D wall pier design and boundary-member checks

2D wall spandrel design 3D wall pier check for provided reinforcement

Graphical Section Designer for concrete rebar location

Graphical display of reinforcement and stress ratios

Interactive design and review Summary and detailed reports including database

formats

Shear Wall - Typical Design Process

1. While modeling define Shear Wall elements


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2. Choose the Shear Wall design code and review

other related preferences and revise them ifnecessary

3. Assign pier and spandrel labels

3. Run the building analysis

4. Assign overwrites

5. Select Design Combos

6. Start Designing Walls


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Avoid Eccentr ici ty in Plan


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Or


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Design of Shear Walls


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10

Axial Stresses in Cellular Walls

Biaxial Bending


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2

5


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I nteraction Sur face - Biaxial

The surface is

generated by

+P

A c ross -sec tion of

interaction surface a

Un-safe


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changing Angle and

Depth of Neutral Axis

+

- My

+ My

- Mz

Pu

Safe

Un safe

=

=

=

=

=

=

.. .),(

1

....,

1

...),(1

.. ..,1

.. .),(1

...,1

1213

121

2

121

1

i

n

iii

x yy

i

n

i

ii

x y

x

x y

n

i

iiz

xyxAxdydxyxM

yyxAydydxyxM

yxAdydxyxN


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Single Cell Walls


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Designing as Axial Zones


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Axial Zones for Box Wall


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Shear Design of Pier

Determine Concrete shear

capacity Vc


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capacity, Vc

Check if Vc exceeds the limit, ifit does, section needs to be

revised

Determine steel Rebars for

Vs=V-Vc

Check additional steel for

seismic requirementspL


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Shear Design for Spandrel

h

sL

Determine Concrete shear

capacity, Vc

Ch k if V d th li it if


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toprd

botrd

ac

h

st

Elevation

Section

Check if Vc exceeds the limit, if

it does, section needs to be

revised

Determine steel Rebars for

Vs=V-Vc

Check additional steel forseismic requirements

ACI Equations for Spandrel Design

sscLWc dtfRV

= 2

Basic Concrete Shear Capacity


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cu

cns VV

VVV ==

sscLWs dtfRV 8sy s

sv

df

VA =

Concrete not to Exceed the limit

Area of Steel Computed as

Check for minimum steel and spacing etc.


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Effect of Rebar LayoutMoment Capacity for 1% Rebars

a) Uniform Distribution


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b) Concentrated Bars

Max M= 380

Max M= 475Nearly 25% increase for same steel

Wall Section Place more reinforcement at

the corners and distribute

the remaining in the middle


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portion Confine the Rebars at the

corners for improved

ductility and increased

moment capacity

Provide U-Bars at the

corners for easier

construction and improved

laps


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Slenderness

of Columns

Complexity in the Column DesignLoading

P Mx

My

Load Complexity


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Shape

Length

V.Lon

g

Long

Short

P

P Mx

Most Simple

Problem

ShapeComplexity

Slenderness

What is Slenderness Effec

P

Moment

Amplification

CapacityP

e


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I

II

Column Capacity (P-M)

M

Reductio

II : Mc = P(e + D

Long Column

D =f(Mc)C

I. Mc = P.e

Short Column

P

e

C


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Larger Sway Moment

Larger Non- Sway MomentFinal

Design

Moment

ACI Moment Magnif ication Summary


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ssnsnsm MMM =

1

75.01

1)

5.1

0.1

1

1)

0

=

D

=

c

us

s

cu

us

P

Pb

thenIf

lVP

a

C

u

m

ns

PP

C

75.01

=

Moment

2

2

)(

)(

U

C

Kl

EIP

=4.0

2

14.06.0 =

M

MC

m


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More about CmFactorM1

M1M2M2


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M1= -M M1 = 0 M1 =M M1 =0

M2 = M M2 = M M2 = M M2 = M

1

2

1 =M

M0

2

1 =M

M1

2

1 =M

M0

2

1 =M

M

M2 M1 M1 M2

Cm = 1.0 Cm = 0.6 Cm = 0.2 Cm = 0.6


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Determination of Stif fness EI

gC

d

sesgC

IE

IEIEEI

b

=

4.0

1

2.0

h

Ab

yb


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Attempt to include,

Cracking, Variable E, Creep effect Geometric and material non linearity

Ig = Gross Moment of Inertia

Ise = Moment of Inertia of rebars

bd = Effect of creep for sustained loads. = Pud/Pu

d

or b= 1

12

3bhIg =

= 2. bbse yAI

b


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BS Moment Magn i f icat ion

Basic Equation for Slender Columns


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uim NaMM =

Initial Moment form

elastic analysisMadd, Additional

moment due to

deflection

Kha au b=

Calcu lat ion of Deflect ion au

Load correction factor

Column Dimension

along deflection

Length Correction Factor


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1

=

baluz

uz

NN

NNK

2

2000

1

=b

leab

Smaller dimension

Effective Length = blo (From Table 3.21 and 3.22)

Length Correction Factor

Applied column load

Axial Capacity for M = 0

Axial capacity at balanced

conditions

yscccuuz fAAfN 95.045.0 =

Some Special Cases


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M

PV

M


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Shear Wall Frame ACECOMS AIT Thailand

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