Lecture 11 Performance Based Evaluation

Masonry Structures, lesson 11 slide 1

Seismic Design and Assessment ofMasonry Structures

Seismic Design and Assessment ofMasonry Structures

Lesson 11: Performance-Based Seismic Evaluation and Rehabilitation of

Masonry Buildings

Notes Prepared by:Daniel P. Abrams

Willett Professor of Civil EngineeringUniversity of Illinois at Urbana-Champaign

October 25, 2004


NEHRP Guidelines

first national consensus document for rehabilitationperformance-based designductility-based rehabilitationdisplacement-based analyses

For free copy of FEMA 356 call:1-800-480-2520

FEMA 273, FEMA 356


Performance Based Rehabilitation

costbasic safety objectives

probability ofexceedance in 50 years

increasingreliability

2%10%

20%50%

increasingperformance

collapse

life safety

immediate occupancy

operability


NEHRP Provisions and Guidelines

Seismic Hazard Maps

Sa

T0.2To To 1.0


Scope of Masonry Chapter

Existing, rehabilitated or new masonry lateral-force resisting elements.Clay and concrete masonry, hollow clay tileUnreinforced and reinforced masonry.In-plane and out-of-plane elements.See Simplified Rehabilitation or Nonstructural chapters for parapets, cladding or partition walls.


Performance of Brick Veneer

brick veneer


Masonry Partition Walls


Contents MitigationABC Good Morning America


Immediate Occupancy

IO

0.0

0.5

1.0

0.25 0.50 0.75 1.00

First Story Drift, %

Bas

e Sh

ear /

Wei

ght

1.5


Life Safety

IO

0.0

0.5

1.0

0.25 0.50 0.75 1.00


Bas

e Sh

ear /

Wei

ght

1.5

LS


Collapse Prevention

CPIO

0.0

0.5

1.0

0.25 0.50 0.75 1.00


Bas

e Sh

ear /

Wei

ght

1.5

LS


Performance Indices for Masonry

Immediate Occupancy

minor cracks 0.1%

Life Safety extensive cracksno dislodgment of units

0.3%

Collapse Prevention

extensive cracksdislodgment of unitsnoticeable offsets

0.4%

wall drift levels*expected damage

dam

age

cont

rol

limite

d sa

fety

* with bed-joint sliding mechanism


Enhancement Options

infilled openingsenlarged openingsshotcrete


Enhancement Options

repointingbraced and stiffened wallsgrouted collar jointsreinforced cores

surface coatings

prestressed cores


Behavior of Non-Retrofitted Pier


Ferrocement Surface Coating


Fiber Reinforced Polymer


Reinforced Shotcrete


Reinforced Cores

#3 or #5 bar

-10

-8

-6

-4

-2

0

2

4

6

8

-3 -2 -1 0 1 2 3Drift %

Late

ral L

oad

[kip

s]

8F7F1F


Reticulated Reinforcement


Reticulated Reinforcement

Displacement

Forc

e


Analysis Procedures

Linear Static ProcedureNonlinear Static ProcedureLinear Dynamic ProcedureNonlinear Dynamic Procedure


Linear Static Procedure

V=C1C2C3SaW

C1= interpolate between 1.0 and 1.5 for T=0.1 and To

C2= from Table 3-1 for framing type 1C3= 1.0 for non-bearing wallSa = spectral accelerationW = weight of building


Forc

e

Deflection

Linear Static Procedure – FEMA 356

QCE

k

∆y

kQCE

y =∆

∆i

y

iim

∆∆

=

Vb

ECE QQm ≥κ

QCE

QE

∆y ∆i

io = immediate occupancyls = life safetycp= collapse prevention


Bed-Joint Sliding

Deformation-controlled action

nmebjs AvV =

Vbjs

ECE QQm ≥κ

expected strength


Rocking

Deformation-controlled action PCE

L

h

Vr

⎟⎠⎞

⎜⎝⎛=

hLP9.0V CEr α

ECE QQm ≥κ

PCE

L

h

Vr


LSP Acceptability Criteria

(Multiply m factors by 2 for secondary elements for Life Safety (LS) and Collapse Prevention (CP))

EUDCE QQQm =≥κ

Bed-joint sliding 1 3 4

m factors for primary elementsIO LS CP

Rocking 1.5 heff/L>1 3.0 heff/L>1 4.0heff/L>1


Force-controlled action

Diagonal Tension

00.1hL0.67 for <<

dt

andtdt 'f

f1hLA'fV +⎟⎠⎞

⎜⎝⎛=

VdtP = faA

ECE QQm ≥κ

lower bound value


Toe Crushing

Force-controlled action

⎟⎟⎠

⎞⎜⎜⎝

⎛−⎟

⎠⎞

⎜⎝⎛=

m

aCLtc 'f7.0

f1hLPV α

VtcPCL

ECE QQm ≥κ

lower bound value


Modeling and Acceptability Criteria

drift

forc

e CP

d

e

cCP

LS

0.75d

LS0.75e

primary walls

secondary walls

Nonlinear Static Procedure


NSP: Acceptable Drifts

(Multiply drifts by 2 for secondary elements for LS and CP)

IO LS CP

Drifts for Primary Elements

Bed-Joint Sliding 0.1% 0.3% 0.4%

Rocking 0.1% 0.3 heff/L% 0.4 heff/L%


Example Building

• URM clay-unit masonry• two-wythe brick walls• constructed prior to 1960• located in St. Louis• total roof dead load = 60 kips• symmetrical structure• soil class B• case A: no testing, visual exam• case B: testing and inspection

Problem: check adequacy of pier for BSO and suggest

rehabilitation scheme if necessary.

Problem: check adequacy of pier for BSO and suggest

rehabilitation scheme if necessary.

URM pier

32’-0”24’-0”

4’-0”

4’-0”

8’-0”

4’-0” wood roof joists

URM bearing wall

7.63”

direction of earthquake


1.0

1

1v

1

1Xa B

SFBSS ==

Seismic Demand: LSP

Sa

T

S

1

1Sa

S1vo S

SBSFBSFT ==

To

S

Sa

S

XSa B

SFBSS ==

Fa= Fv= 1 for site class B

BS = B1 = 1 for 5% damping 0.2To


Seismic Demand: LSP

S1 SS To C1 C2 C3 Sa V/W

St. Louis

seconds 129.0)feet12(020.0hCT 43

43

t ===

BSE-1 10% /50 yearsLife Safety

BSE-22% /50 yearsCollapse Prevention

0.05g 0.18g 0.278 1.42 1.30 1.00 0.18g 0.332sec.

0.18g 0.58g 0.310 1.43 1.50 1.00 0.58g 1.244sec.


Lateral Force Distribution

8’-0”

4’-0”

30.0 + 2(31.8/4) = 45.910.6

5.4

Weights (kips)

total weight per shear wall = 61.9 kips

60.0 kips

31.8 kips

10.6 kips

2.7 kips

2.7 kips


Pier Strength: Case A, no tests

governs

Vme= 27psi f’me= 900 psi from default values

kips89.9)"48x"63.7)(ksi027.0(AvV nmebjs ===bed-joint sliding:

kips38.2)5.0)(kips29.5)(0.1(9.0hLP9.0Veff

CEr ==⎟⎟⎠

⎞⎜⎜⎝

⎛α=

rocking:

psi4.14)"48("63.7

lbs5290fa == psi5636.1

f'f mem ==

kips54.2)563(7.0

4.141)5.0)(kips29.5)(0.1('f7.0

f1hLPV

m

a

effCLtc =⎟⎟

⎠

⎞⎜⎜⎝

⎛−=⎟⎟

⎠

⎞⎜⎜⎝

⎛−⎟⎟

⎠

⎞⎜⎜⎝

⎛α=

toe crushing:

PG = 5.29k

QCE

8’-0”

4’-0”


Pier Strength: Case B

Vte = 150 psi from shove tests f’me = 2000 psi from prism tests

kips2.23)"48x"63.7)(ksi0635.0(AvV nmebjs ===

bed-joint sliding:

kips38.2)5.0)(kips29.5)(0.1(9.0hLP9.0Veff

CEr ==⎟⎟⎠

⎞⎜⎜⎝

⎛α=

rocking:

kips60.2)1250(7.0

4.141)5.0)(kips29.5)(0.1('f7.0

f1hLPV

m

a

effCLtc =⎟⎟

⎠

⎞⎜⎜⎝

⎛−=⎟⎟

⎠

⎞⎜⎜⎝

⎛−⎟⎟

⎠

⎞⎜⎜⎝

⎛α=

toe crushing:

psi5.635.1

)psi4.14psi150x75.0(75.0vme =+

=PG = 5.29k

QCE

8’-0”

4’-0”

governs


Acceptability Criteria UDCE QQm ≥κ

Case A:ok kips3.10kips7.10)kips38.2)(75.0(6Qm CE >==κ

Case B:ok kips3.10kips3.14)kips38.2)(00.1(6Qm CE >==κ

kips3.10)5.0)(kips9.61(332.0QUD ==BSE-1

m = 6 for Life Safety


Acceptability CriteriaUDCE QQm ≥κ

BSE-2 kips5.38)5.0)(kips9.61(244.1QUD ==

m = 8 for Collapse Prevention

Case A:NG kips5.38kips3.14)kips38.2)(75.0(8Qm CE <==κ

Case B:NG kips5.38kips0.19)kips38.2)(00.1(8Qm CE <==κ


Rehabilitation Option 1

Enlarge pier width:

'8.10)'0.4(3.145.38L ==

Case A, Check CP:ok kips5.38)kips43.6)(75.0(8Qm CE ==κ

5’-5”

QCE

new

PG = 5.29k

8’-0”

4’-0”old

(Eq. 7-4)

kips43.6

)'0.8'8.10)(kips29.5)(0.1(9.0

hLP9.0Veff

CEr

=

=

⎟⎟⎠

⎞⎜⎜⎝

⎛= α

Check:



Prestress pier:

kips24.14)kips29.5(3.145.38P ==

Required prestressing force = 14.24 - 5.29 = 8.95 kips

PG = 5.29k

8’-0”

4’-0”

Pstress = 8.95k

Case A, Check CP:ok kips5.38)kips41.6)(75.0(8Qm CE ==κ

(Eq. 7-4)

kips41.6)5.0)(kips24.14)(0.1(9.0

hLP9.0Veff

CEr

==

⎟⎟⎠

⎞⎜⎜⎝

⎛= αCheck:



Reinforce:

Consider as reinforced masonry pierper Sec. 7.4.4 8’-0”

4’-0”

2 - No. 4 bars


Damage to Out-of-Plane Walls

1886 EarthquakeCharleston, South Carolina

1994 Northridge Earthquake, Hollywood


Out-of-Plane Walls

Flexural cracking limits IODynamic stability for LS and CP

1-story bldgs 20 16 13

Pk

multistory bldgs1st story 20 18 15top story 14 14 9

all other walls 20 16 13

dynamic stability ok if h/t < table values

Wall types SX1 < 0.24g 0.24g < SX1<0.37g 0.37g<SX1<0.5g


Masonry Infills

URM Infill, Tangshan, PRC URM Infill, Campania, Italy


Masonry Infills

Static Cyclic Tests of URM infillsUniversity of Illinois

-300

-200

-100

0

100

200

300

-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3

Lateral Drift, %

Infil

l She

ar S

tres

s, p

siIn

fill S

hear

Str

ess,

psi

Lateral Drift, %


Infill Damage Patterns

crack pattern, large-scale static test

crack pattern, half-scale dynamic test


Frame-Infill Systems


In-Plane Masonry Infills

Stiffness

H

inf

meinf

rEatk =

a

rinfinf

4.0col1 r)h(175.0a −= λ

41

infcolfe

infme1 hIE4

2sintE⎥⎦

⎤⎢⎣

⎡ θ=λ


In-Plane Masonry Infills

Strength

vieniineCE fAVQ ==

ECE QQm ≥κ


m Factors for Masonry Infills

Example:Life Safety

Table 7-6

ine

fre

VV

=β

0.30.7

1.3inf

inf

hL

m

2.0

1.00.5

4.0 6.08.0

3.55.2

7.0

6.03.0 4.5

page 7-20


Out-of-Plane Infill Strength

Pres

sure

, psf

Center Deflection / Height %


Out-of-Plane Infills

low moderate highseismicity seismicity seismicity

IO 14 13 8LS 15 14 9CP 16 15 10

Table 7-8: maximum h/t ratios for which no analysis is necessary



If arching action is prevalent:

CP for 3% andIO for %2

th002.011

th002.0

h 2

inf

inf

inf

inf

inf

inf

<

⎟⎟⎠

⎞⎜⎜⎝

⎛−+

⎟⎟⎠

⎞⎜⎜⎝

⎛

=∆

hinf

∆inf



If arching action is prevalent:

2.11.7 Sec. per load

144x

th

'f75.0qQ

inf

inf

2minCL

<

⎟⎟⎠

⎞⎜⎜⎝

⎛λ

==


Undesirable InterventionsMaintain deformation controlled mechanisms

– do not change rocking to shear mechanism with coatings, overlays, shotcrete or reinforcement

– do not change bed-joint sliding to diagonal tension with brittle coatings or overlays

Alter force controlled mechanisms – enlarge openings to promote rocking

– lighten gravity loads to piers to avoid toe compression


Concluding Remarks

• Systematic rehabilitation of masonry buildings.

• Guidelines are first performance-based provisions for masonry structures.

• Judgement of engineer is essential for proper application of Guidelines.


Famous Last Words

Infrequent events will not happen tomorrow….

1886 Charleston, South Carolina 2001 Gujarat

Lecture 11 Performance Based Evaluation

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f aavdtll f

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