Evaluation, Repair and Enhancement of Earthquake-Damaged

8NCEE Tutorial on FEMA 306/307/308 1

Evaluation, Repair and Enhancement of Earthquake-Damaged Unreinforced Masonry (URM) Buildings

Brian KehoeWiss, Janney, Elstner Associates, Inc.


Test and inspection procedures

Material Structural Or

Material Property Reinf.Conc.

Reinf. Mas.

URM Test ID Test Type

Crack Location and Size

√ √ √ NDE 1 Visual Observation

Spall Location and Size

√ √ √ NDE 1 Visual Observation

√ √ √ NDE 2 Sounding Location of Interior Cracks or Delaminations

√

√

√

NDE 6

Impact Echo

√ NDE 7 SASW √ √ √ IT 1 Selective Removal Reinforcing Bar Buckling or Fracturing

√

√

NDE 1

Visual Observation

√ √ IT 1 Selective Removal

306: 20


Visual Observation


Impact Echo


Test and inspection procedures (continued)

Material

Structural Or Material Property

Reinf.Conc.

Reinf. Mas.

URMTest ID Test Type

Relative Age of Cracks

√ √ √ IT 2 Petrography

Relative Compressive Strength

√ √ √ NDE 3 Rebound Hammer

Compressive Strength

√ √ √ IT 3 Material Extraction and Testing

Reinforcing Bar Location and Size

√ √ NDE 4 Rebar Detector

√ √ NDE 8 Radiography √ √ NDE 9 Penetrating Radar √ √ IT 1 Selective RemovalStrength of Reinforcing Bar

√ √ IT 3 Material Extraction and Testing

306: 20


Ground Penetrating Radar (GPR)


Test and inspection procedures (continued)

Material

Structural Or Material Property

Reinf. Conc.

Reinf. Mas.

URM Test ID Test Type

Wall Thickness √ √ √ NDE 1 Visual Observation √ √ √ NDE 6 Impact Echo √ √ √ IT 1 Selective Removal Presence of Grout in Masonry Cells

√ √ NDE 2 Sounding

√ √ NDE 6 Impact Echo √ √ NDE 7 SASW √ √ IT 1 Selective Removal Strength of Masonry Units

√ √ IT 3 Material Extraction and Testing

√ IT 4, 5 In Situ Testing

Mortar Strength √ √ IT 1 Petrography √ IT 4, 5 In Situ Testing

306: 20


Tests and investigation guides

Example Test and Investigation Guide. See FEMA 306 pgs. 29-59 for other examples:

• Nondestructive tests

• Intrusive tests


Test and inspection proceduresTest Name and ID

For reference and identification

Test Type Nondestructive or Intrusive Materials Applicability to reinforced concrete,

reinforced masonry, or unreinforced masonryDescription Basic overview of the objectives and scope

of the procedure References Applicable standards, detailed specifications,

or sources of additional information Equipment A summary of the tools, instrumentation, or

devices required Execution General sequence of operations Reporting Requirements

Format for reporting of results

Personnel Qualifications

Skill level and specialized training that may be required

Limitations Restrictions on the level of information that can be gained and advice on the interpretation of results


Pre-existing conditions

Recent cracks • Small, loose edge spalls • Light, uniform color of concrete or mortar within crack • Sharp, uneroded edges

Older cracks • Paint or soot inside crack • Water, corrosion, or other stains seeping from crack • Previous, undisturbed patches over crack • Rounded, eroded edges

306: 22


Repair of damage

FEMA 308


Performance restoration• Select restoration measures for damaged component

• Analyze restored structure for performance objective

• Calculate restored Performance Index = dc*/ dd

*

• Adjust scope of restoration measures until dc*/ dd

* is approximately equal to dc / dd

• Cost of final restoration measures quantifies the effects of the damage on seismic performance


Component Damage Classification Guides

• Component type

• Behavior mode

• Evaluation procedures: Analysis, Observation

• Damage severity: Type, Magnitude

• Property modification factors (λ’s): Stiffness, Strength, Displacement acceptability

• Performance restoration measures

See, for example, 306: 95-106


Repair Guides

Repair Category RC RM URM

RepairID Repair Type

• • • CR 1 Surface coating • CR 2 Repointing

Cosmetic Repair

• • CR 3 Crack injection with epoxy• • SR 1 Crack injection with epoxy • • • SR 2 Crack injection with grout • • SR 3 Spall repair • SR 4 Rebar replacement

Structural Repair

• • • SR 5 Wall replacement • • • SE 1 Concrete overlay • • • SE 2 Composite Fibers

Structural Enhancement

• SE 3 Crack Stitching Notes: Repairs for concrete walls can also be used for concrete frames in infill systems. Repairs for steel frames of infill systems are described in the component repair

guides.

308: 22


Repair Guides (continued)

Repair Name and ID

For reference and identification

Repair Category Cosmetic Repair, Structural Repair, or Structural Enhancement

Materials Applicability to reinforced concrete, reinforced masonry, or unreinforced masonry

Description Basic overview of the objectives and scope of the repair procedure

Repair Materials Typical products used for the repair


Repair Guides (continued)

Equipment A summary of the tools, instrumentation, or devices required

Execution General sequence of operations Quality Assurance

Measures required to achieve satisfactory installation

Limitations Restrictions on the effectiveness of the repair

Standards and References

Applicable sources of further information


Direct method• Investigate damage• Identify components• Determine behavior modes• Determine damage severity• Classify component damage• Determine restoration measures for all

components• Estimate costs

306: 75 307: 199


Investigation of damage

Document Damage:•Inspections and Tests•Pre-existing conditions

Assemble Information:•Damaging Earthquake•Building

Classify Component Damage:•Behavior Mode•Severity

VerificationGather more information and revise assumptions to obtain consistency between damage classification and observations

Identify Components:•Materials•Configuration•Behavior

Component DamageRecords

306: 5


Component types and inelastic mechanisms

Pier and Spandrel Mechanisms

RC5

Weak pier, strong spandrelStrong pier, weak spandrel

RC1

Weakly coupled perforated wall

RC1

RC1

RC3

RC2

RC1

RC3

RC3

RC3

RC2

RC4

306: 13


Component Damage Classification Guides

• Component type

• Behavior mode

• Evaluation procedures: Analysis, Observation

• Damage severity: Type, Magnitude

• Property modification factors (λ’s): Stiffness, Strength, Displacement acceptability

• Performance restoration measures

See, for example, 306: 95-106


Component damage recordComplete for each damaged component

Record damage

Note component types

Note behavior modes

Assign severity

Template

Example 306: 33

306: 28


Direct method limitations

• May overestimate effects of damage on performance in future large events

• May underestimate effects of damage on performance in future smaller events

• No useful information on actual building performance

• Cannot be used for design purposes


FEMA 307 Example

Investigation

Evaluation by Direct Method

Evaluation by Relative

Performance Analysis


FEMA 307 Example — Evaluation

Direct Method • Performance restoration measuresRelative Performance Analysis• Performance objectives• Nonlinear static analysis• Pushover capacity curve and

displacement demand• Modifications for damage• Performance restoration measures






- Prescriptive restoration measures.- Component-by-component.- No assessment of performance.

Direct Method


Component Guides

• By material, component type, & behavior mode

• How to distinguishby observationby analysis

• Damage severitydescriptionmodification factors, λrestoration measures

FEMA Training Seminar Program: Evaluation and Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

306: 96


Performance restoration measures

Direct Method• Cosmetic repairs• Repair coupling beams

Replace heavily damaged coupling beamsInject moderately damaged beams with epoxy






Seismic Hazard

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5 3 3.5

Life Safety - 10%/50 yr

Immediate Occupancy -50%/50 yr

SA(g)

T(s)

306: 96


Investigation of damage

Document Damage:•Inspections and Tests (3.3, 3.8)•Pre-existing conditions (3.4)

Assemble Information:•Damaging Earthquake (3.1)•Building (3.2)

Classify Component Damage:(3.5)•Behavior Mode (5,6,7,8)•Severity (5,6,7,8)

Verification (3.6)

Gather more information and revise assumptions to obtain consistency between damage classification and observations

Identify Components: (2.4,5,6,7,8)•Materials•Configuration•Behavior

Component DamageRecords (3.7)

306: 5


Damaging earthquake - ground motion

Example plot: spectral acceleration contours; building sites

306: 21


Damaging earthquake - site spectrum

Period, T(sec.)

Spectral Acceleration, Sa

0.5 1.0 1.5

Sa at T=0.3sec from Figure 3-3

Sa at T=1.0 sec from Figure 3-4

PGA atT=0 sec from Figure 3-2

Sa = (Sa at T=1.0)/ T

306: 18


Bearing wall buildings

Section

Elevation

Floor and roof loadssupported on wall

Concrete or masonrybearing wall

Portion of vertical load may becarried by beam/slab/columnframing

306: 11


Infilled frame buildings

Section

Elevation

Floor and roof loadssupported by steel orconcrete frame

Concrete or masonryInfill panels

Essentially all verticalload carried by frame

Note:Reinforced concrete panelswell-anchored to boundary membersbehave similar to bearing walls

306: 11


Elements and Components

A2

A3A1 A5

A4

Global Structure Wall Element A

Components

Returns included in propertiesof components A1 and A5

Wall element A Wall element B

306: 9


Component types for RC wallsComponent Type Description

RC1: Cantilever Wall or Stronger Wall Pier

Stronger than beam or spandrel elements that may frame into it so that nonlinear behavior (and damage) is generally concentrated at the base, with a flexural plastic hinge or shearfailure. Includes isolated (cantilever) walls. If the componenthas a major setback or cutoff of reinforcement above the base, this section should be also checked for nonlinear behavior.

RC2: Weaker Wall Pier

Weaker than the spandrels to which it connects, characterized by flexural hinging top and bottom, or shear failure

RC3: Weaker Spandrel or Coupling Beam

Weaker than the wall piers to which it connects, characterized by hinging at each end, shear failure, sliding shear failure

RC4: Stronger Spandrel

Should not suffer damage because it is stronger than attached piers. If this component is damaged, it should probably be re-classified as RC3

RC5: Pier-Spandrel Panel Zone 306: 78






Relative Performance Analysis is Based on the Nonlinear Static Procedure, NSP.

(Push-Over Analysis)

V

∆

∆

V


3D Computer Analysis Model

Coupled Wall

Beam Elements Representing Solid Wall

Beam Elements Representing Floor Slab

Nodes Where Lateral Loads are Applied 307: 205


Coupled Wall – Frame Model

R ig id E n dO f f s e t

N o d e

C o lu m n E le m e n t

C o u p l in g B e a mE le m e n t

C o lu m n E le m e n tR e p r e s e n t in g W a l l P ie r

307: 204

Rigid end offsets model the joint legions


Coupled Wall – Shell Model

Column18 inch

Column18 inch

Wall12 inch Coupling

Beam


FEMA 356 Component ModelingShear Walls — Initial Stiffness

• Flexural (Uncracked): 0.8 Ec Ig• Flexural (Cracked): 0.5 Ec Ig• Shear: 0.4 Ec Aw

Coupling Beams — Initial Stiffness• Flexural: 0.5 Ec Ig• Shear: 0.4 Ec Aw


SAP 2000 Element Modifications






FEMA 356 Component Properties

Shear Wall Coupling Beams

050

100150200250300

0 0.005 0.01

Rotation

Forc

e

IO LSp CPp

LSs CPs

IO: Immediate Occupancy

LS: Life SafetyCP: Collapse

Preventionp: primarys: secondary


Pre-event pushover curve

0

2,000

4,000

6,000

8,000

10,000

0 0.5 1 1.5 2

Roof Displacement (Inches)

Ba

se

Sh

ea

r (k

ips

) Pushover curve

Bilinear idealizedcurve


Displacement Demand

By the FEMA 356 Nonlinear static procedure, calculate displacement demand using the coefficient method.

24πe

t 0 1 2 3 aTC C C C Sδ =Coefficient method:

356: 3-21


Seismic Hazard

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5 3 3.5

Life Safety - 10%/50 yr

Immediate Occupancy -50%/50 yr

SA(g)

T(s)

306: 96



0

2,000

4,000

6,000

8,000

10,000

0 0.5 1 1.5 2

Roof Displacement (inches)

Ba

se

Sh

ea

r (k

ips

) Pushover curve

Bilinear idealizedcurve

dd life safety


Damaging Earthquake

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 0.5 1 1.5 2 2.5 3Period (Sec.)

Spe

ctra

l Acc

eler

atio

n (g

)

5% Damp10% Damp20% Damp

Spec

tral

Acc

eler

atio

n (g

)



0

2,000

4,000

6,000

8,000

10,000

0 0.5 1 1.5 2

Roof Displacement (inches)

Ba

se

Sh

ea

r (k

ips

)

Pushover curve

Bilinear idealizedcurvede

8NCEE Tutorial on FEMA 306/307/308 53FEMA Training Seminar Program: Evaluation and Repair of Earthquake Damaged Concrete and Masonry Wall Buildings

Time

Pre-eventState

OriginalPerformanceDamage State

PerformanceEarthquake dd

a) Building without prior earthquake damage

IntermediateDamage State

DamagingEarthquake

PerformanceDamage State ( ' )

dd'de

b) Building with prior earthquake damage

306: 3

308: 11






306: 66


LS = Life Safety

CP = CollapsePrevention

A

B C

D E E'D'

C'B'

A'

RD

IO = Immediate Occupancy

Undamaged Component Damaged Component

IO' = IO - RDLS' = λD

LS - RD

CP'= λDCP - RD

designates primary components designates secondary components

b) Component deformation limits

P S

S

S

S

P P

P P P

S 306: 67


Earthquake Damage – Solid Wall

RC1M

Isolated Wall, Foundation Rocking, Insignificant Damage

307: 232


Earthquake Damage – Coupled Wall

307: 223


Component Classifications

RC1N RC1N

RC3H

RC3H

Damage Severity

ModerateHeavyInsignificant


Post-Earthquake Modifications

Element BehaviorMode

Severity ModificationFactors

Pier PierRocking

Insignificant λk=1.0λQ=1.0λD=1.0

CouplingBeam

PreemptiveDiagonalShear

Moderate λk=0.5λQ=0.8λD=0.9

CouplingBeam

PreemptiveDiagonalShear

Heavy λk=0.2λQ=0.3λD=0.7


Damaged Component Properties

0

50

100

150

200

250

0 0.002 0.004 0.006 0.008 0.01 0.012

Rotation (radians)

Shea

r (k

ips) Heavy Damage

Moderate Damage


Comparison of Pre-Event and Post-Event Performance

0

1,000

2,0003,000

4,000

5,000

6,0007,000

8,000

9,000

0 0.5 1 1.5 2

Roof Displacment (Inches)

Bas

e Sh

ear (

kips

)

Pre-eventPost-event


Performance Comparison

• Capacity versus Demand (C/D)Capacity based on displacement limits for critical componentDemand based on target displacement using design earthquake

• Compare pre-event capacity to demand• Compare post-event capacity to demand• Difference in C/D ratio is an indication of

amount of loss of performance


Comparison of Pre-Event and Post-Event Performance

dd and dd’dc’

dc

0

1,000

2,0003,000

4,000

5,000

6,0007,000

8,000

9,000

0 0.5 1 1.5 2Roof Displacment (inches)

Base

She

ar (k

ips)

Pre-eventPost-event


Performance Loss

Displacement Capacity

Displacement Demand

Performance Index

LS IO LS IO LS IO Pre-Event

1.00 0.60 1.68 0.97 0.60 0.62

Post-Event

0.75 0.52 1.68 0.97 0.45 0.53



Direct Method • Performance restoration measuresRelative Performance Analysis• Performance objectives• Nonlinear static analysis• Pushover capacity curve and displacement

demand• Modifications for damage• Performance restoration measures



Direct Method:- Prescriptive restoration measures.- Component-by-component.- No assessment of performance.

Relative Performance Analysis:- Devise measures to restore performance

ability (Displacement Demand/Capacity) for performance levels of interest



Relative Performance Analysis• Nonstructural repairs• Various alternatives could be tried

to restore structural performance. Choose repair of coupling beams.

Replace heavily damaged coupling beamsInject moderately damaged beams with epoxy



0

50

100

150

200

250

300

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

Rotation, Radians

She

ar, K

ips

0

50

100

150

200

250

300

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

Rotation, Radians

She

ar, K

ips

Moderate

Heavy

Force-displacement for coupling beams:

a) Pre-event

b) Post-event

307: 207



0

50

100

150

200

250

300

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

Rotation, RadiansS

hear

, Kip

s

Moderate

Heavy

0

50

100

150

200

250

300

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

Rotation, Radians

She

ar, K

ips

Force-displacement for coupling beams:

b) Post-event

c) Replacement Coupling Beam with Diagonal Reinforcement

307: 207


FEMA 307 Example — EvaluationDirect Method • Performance restoration

measuresRelative Performance Analysis• Performance objectives• Nonlinear static analysis• Pushover capacity curve and

displacement demand• Modifications for damage• Performance restoration

measures


Questions

Documents

Evaluation, Repair and Enhancement of Earthquake-Damaged