Earthquake Resistance of Modern Masonry Construction - SEAoT

EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

**Earthquake** **Resistance** **of**

**Modern** **Masonry** **Construction**

NSF NEES Small - Group Project

( October 2006 through September 2010 )

Pr**of** . Richard E . Klingner

The University **of** Texas at Austin

klingner@mail.utexas.edu

State Conference

**SEAoT**

Austin , TX

October 31 , 2009

1

Main points

1. Wall - type masonry structures are simple to

design

2. The MSJC Code and Specification is the

technical basis for masonry design in the

US

3. Low - rise masonry structures designed and

constructed according to the MSJC Code

and Specification can resist very strong

earthquakes

2

a dynamic treat . . .

1. Wall - type masonry

structures are simple to design

almost

3 g !

3

4

Steps in simplified design **of**

masonry structures

• starting point for design

• design **of** vertical strips in walls perpendicular

to lateral loads

• design **of** walls parallel to lateral loads

• design **of** lintels

• simplified analysis for lateral loads

• design **of** diaphragms

• detailing

units **of**

concrete or

fired clay

steel

reinforcing

bars

grout

grout

mortar

. . . typical

materials in

reinforced

masonry

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EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

Starting point for wall - type

masonry structures

NO BEAMS OR COLUMNS

( example **of**

direction **of** span )

vertical reinforcement **of**

#4 bars at corners and

jambs

Essential function **of** walls in

resisting gravity loads

bearing walls resist

axial loads ( concentric

and eccentric ) as

vertical strips

Horizontal reinforcement

**of** two #4 bars in bond

beam at top **of** wall ,

and above and below

openings ( two #5 bars

over openings with span

> 6 ft )

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non - bearing walls

resist concentric axial

load as vertical strips

8

Essential function **of** walls in

resisting lateral loads

Effect **of** openings . . .

walls parallel to lateral

forces act as shear

walls

bond beams transfer

reactions from walls to

horizontal diaphragms ,

and act as diaphragm

chords

Effective

Width **of**

Strip A

Strip A

Effective

Width **of**

Strip B

Strip B

Effective

Width **of**

Strip C

Strip C

vertical strips **of** walls perpendicular to

lateral forces resist combinations **of** axial

load and out - **of** - plane moments , and

transfer their reactions to horizontal

diaphragms

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Width A

Width B

Width C

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. . . Effect **of** openings

Design **of** vertical strips in

perpendicular walls

Openings increase original design

actions on each strip by a factor

equal to the ratio **of** the effective

width **of** the strip divided by the

actual width

moments and axial forces due

to combinations **of** gravity and

lateral load

M = P e

Actions in Strip B

⎛ EffectiveWidth B ⎞

= Original Actions

⎜

⎟

⎝ Actual Width B ⎠

M = P e / 2

M wind

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EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

. . . Design **of** vertical strips in

perpendicular walls

Design **of** parallel walls . . .

Φ P n

moment - axial

force interaction

diagram ( with the

help **of** a

spreadsheet )

moments , axial forces and shears

due to combinations **of** gravity

and lateral loads

P

V

M u , P u

h

Φ M n

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. . . Design **of** parallel walls

. . . Design **of** parallel walls

Φ P n

moment - axial

force interaction

diagram ( with the

help **of** a

spreadsheet )

sufficient lateral

capacity comes from

wall density

shearing resistance

V +

n

=

V

m

V

s

M u , P u

16

Φ M n

15

⎡

M

⎞⎤

⎟

⎠⎦

u

'

Vnm

= ⎢4.0

−1.75

⎜ ⎥ An

fm

+ 0. 25

Vu

d ⎟

v

⎣

⎛

⎜

⎝

P

u

Design **of** lintels . . .

. . . Design **of** lintels

( example **of**

direction **of** span )

moments and shears

due to gravity loads

M

V

u

u

w l

=

8

w l

=

2

2

17

neutral axis

A s

shear design : provide

enough depth so that

shear reinforcement is

not needed

d

A

s

flexural design :

M

u

≈ φ f ×0.9 d

y

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EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

Distribution **of** shears to shear

walls . . .

Classical analysis **of** structures

with rigid diaphragms

• classical approach

• determine whether the

diaphragm is “rigid” or

“flexible”

• carry out an appropriate

analysis for shears

• locate center **of** rigidity

• treat the lateral load

as the superposition **of**

a load acting through

the center **of** rigidity ,

and a torsional

moment about that

center

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Simplified analysis **of** structures

with rigid diaphragms . . .

. . . Simplified analysis **of**

structures with rigid diaphragms

V

32 ft

32 ft

4 ft

8ft

8 ft

8ft

4 ft

• consider only the

shearing stiffness ,

which is proportional

to plan length

• neglect plan torsion

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V

32 ft

32 ft

4 ft

8 ft

8 ft

8 ft

4 ft

V =

V

left

right

32 ft

( 32 + 4 + 8 + 4)

( 4 + 8 + 4)

ft

( 32 + 4 + 8 + 4)

=

× V

ft

total

× V

ft

total

2

= V

3

total

1

= V

3

total

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Classical analysis **of** structures

with flexible diaphragms . . .

. . . Classical analysis **of** structures

with flexible diaphragms

• distribute shears according to tributary areas

**of** the diaphragm , independent **of** the

relative stiffnesses **of** the shear walls

32 ft

half half

32 ft

V

4 ft

8 ft

8 ft

8 ft

4 ft

V

V

left

right

1

= V

2

1

= V

2

total

total

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EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

Simplified diaphragm analysis

design for the worse **of** the two cases

2 / 3 V

1 / 2 V

V

32 ft

32 ft

4 ft

8 ft

8 ft

8 ft

4 ft

1 / 3 V

1 / 2 V

Design **of** diaphragms

• Diaphragm shears are resisted by the total

thickness or the thickness **of** the cover

alone ( for non - monolithic diaphragms ) .

Diaphragm moments are resisted by

diaphragm chords ( bond beams ) .

V = w L / 2

L / 2

M = w L 2 / 8

25

w

26

. . . Details

• wall - diaphragm connections

• design **of** lintels for out - **of** - plane loads

between wall - diaphragm connections

• connections between bond beam and walls

• connections between walls and foundation

2. The MSJC Code and

Specification is the technical

basis for masonry construction

in the US

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**Masonry** Design Codes in the US

Technical

Organizations

MSJC

develops

provisions

ANSI process ( balance **of** interests , letter ballots ,

resolution **of** Negatives , public comment )

Industry

Groups

MSJC

Code

model codes

reference

ICC

those

( International

provisions

Building Code )

NEHRP

Other Model

Codes

( NFPA )

ASTM

( Material

Specifications )

MSJC

Specification

( QA ,

materials ,

execution )

3. Low - rise masonry structures

designed and constructed

using the MSJC Code and

Specification can resist very

strong earthquakes

local authorities

adopt those

model codes Building Code

( legal standing )

( contract between society and the designer )

( part **of** a civil

contract

between owner

and contractor )

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EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

Seismic design **of** masonry is

state -**of** -the -art

important results so far

• NSF -NEES small -group

project

• October 2006 through

September 2010

• involves four universities

plus masonry industry

• headed by UT Austin

31

• low-rise reinforced concrete masonry buildings

with clay masonry veneer ( meeting MSJC

Code and Specification for SDC D ) resist

earthquakes above MCE without collapse

• seismic response **of** buildings and veneer is

generally consistent with performance

expectations

• seismic response is well predicted by nonlinear

dynamic analysis and static design tools

32

what’s coming

project objectives

• project objectives

• project participants

• seismic response **of** low - rise buildings

• reinforced concrete masonry with clay

masonry veneer

• experimental and analytical work

• key observations

• important points

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• performance - based design **of** new masonry

and masonry veneer

• study seismic performance **of** masonry veneer and

veneer connectors

• examine inelastic behavior **of** low - rise reinforced

concrete masonry structures

• propose refinements to performance - based design

provisions for new masonry and masonry veneer

• educate the pr**of**ession and the public

34

project participants

structures studied

• University **of** Texas at Austin

• Richard E . Klingner , Seongwoo Jo ( GRA )

• University **of** California at San Diego

• Benson Shing , Hussein Okail ( GRA )

• Washington State University

• Char Grimes , Katherine Keane , David McLean

• North Carolina A&T State University

• Mark McGinley , Eric Johnson ( GRA )

• Help from masonry industry

35

• backing system **of**

wood-stud frames or

reinforced concrete

masonry ( CMU )

• clay masonry veneer

( attached to backing

system using

connectors ) improves

esthetics and thermal,

acoustic and water -

penetration resistance

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EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

masonry veneer connectors

seismic response

• wood - stud frames

• corrugated connectors

• rigid connectors

• reinforced concrete masonry

• adjustable connectors

• tri-wire connectors

37

• in - plane CMU

walls govern the

seismic response

**of** the building

• in - plane veneer

slides and rocks

• out -**of**-plane

veneer acts as

added mass

direction **of**

shaking

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reinforced concrete masonry

with clay masonry veneer

experimental work ( 1 )

• experimental work

• analytical work

• key observations

• important points

• quasi - static tests **of**

wall segments

( UT Austin )

• shaking - table tests **of**

wall segments

• shaking - table tests **of**

complete structure

in - plane

out - **of** -

plane

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experimental work ( 2 )

experimental work ( 3 )

• quasi - static tests **of**

wall segments

• shaking - table tests **of**

wall segments

( UCSD )

• shaking - table tests **of**

complete structure

out -**of** -plane

in - plane

• quasi - static tests **of**

wall segments

• shaking - table tests **of**

wall segments

• shaking - table tests **of**

complete structure

( UCSD )

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EARTHQUAKE RESISTANCE OF MODERN MASONRY CONSTRUCTION

Richard E. Klingner, University **of** Texas at Austin

**SEAoT** Annual Meeting Austin, Texas October 29-31, 2009

analytical work ( OpenSees )

a construction treat . . .

• develop nonlinear analytical models for each

element

• reinforced concrete masonry

• clay masonry veneer

• veneer connectors

• predict quasi - static and shaking - table

response

• refine models using quasi - static and shaking

- table results ( in progress )

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a dynamic treat . . .

response sequence . . .

almost

3 g !

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• Design - basis earthquake

• PGA 0.67 g : no damage

• Maximum considered earthquake ( MCE )

• PGA 1.01 g : no damage

• PGA 1.68 g : flexural cracking **of** walls

• PGA 1.79 g : rocking and sliding **of** in - plane veneer

• PGA 2.69 g : sliding **of** in - plane CMU

• PGA 2.69 g : damage to CMU and veneer

46

important results so far

Main points

• low-rise reinforced concrete masonry buildings

with clay masonry veneer ( meeting MSJC

Code and Specification for SDC D ) resist

earthquakes above MCE without collapse

• seismic response **of** buildings and veneer is

generally consistent with performance

expectations

• seismic response is well predicted by nonlinear

dynamic analysis and static design tools

47

1. Wall - type masonry structures are simple to

design

2. The MSJC Code and Specification is the

technical basis for masonry design in the

US

3. Low - rise masonry structures designed and

constructed according to the MSJC Code

and Specification can resist very strong

earthquakes

48

8