Transcript Escondido Village Midrises

SCEC Workshop - October 2003
Practical considerations for the future
from a structural engineering
perspective
Craig D. Comartin
Comartin-Reis
Outline



Background on performance-based
engineering
Financial formulation of PBE
Implications for practice

Some important needs
Comartin-Reis
Pacific Earthquake Engineering Research Center
PEER framing equation
Decision variable
annualized loss
performance objective
vDV    G DV DM | dG DM EDP | dG EDP IM | d ( IM )
Damage measure
casualties
capital loss
downtime
Engineering demand
parameter
displacement
drift
Comartin-Reis
Intensity measure
hazard curve
level of shaking
Decision: Should this
building be retrofitted?
Yes, if it is unsafe for
shaking with a 10%
chance of being
exceeded in 50 yrs.
No, if it is safe for
shaking with a 10%
chance of being
exceeded in 50 yrs.
Comartin-Reis
Elements and Components
Returns included in properties
of components A1 and A5
A2
A1
Wall element A
A3
A5
A4
Wall element B
Components
Global Structure
Comartin-Reis
Wall Element A
Component force-deformation tests
deformation
force
Comartin-Reis
Component Behavior and Properties
Force
Backbone
curve
Actual hysteretic
behavior
Deformation
Backbone curve from actual hysteretic behavior
Comartin-Reis
Component Behavior and Properties
Backbone
curve
B
Idealized component
behavior
C
B
D
B, C, D
C, D
E
A
A
Ductile
(deformation controlled)
E
Semi-ductile
A
E
Brittle
(force contolled)
Idealized component behavior from backbone curves
Comartin-Reis
Nonlinear dynamic analysis
Global displacement
D
Story drifts and forces
dij
Component actions
dj
qj
qi
di
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Equivalent single degree of freedom
Static load pattern
Vtotal
Capacity curve
(pushover)
Nonlinear
ESDOF Oscillator
V
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D
Global force-deformation relationship
(Pushover or Capacity Curve)
D
V
TOTAL
Force
Parameter, V
Displacement
Parameter, D
Comartin-Reis
Global Displacement and Damage
Building Damage States
Global
Force
Parameter
Global
capacity
curve
Immediate
occupancy
Life
safety
Collapse
prevention
Performance Levels
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Global
Displacement
Limits, d
c
Performance levels
Performance Level
Collapse
Prevention
Life Safety
Damage
Control
Immediate
Occupancy
Comartin-Reis
Damage State
Down Time
• Severe structural damage
• Incipient Collapse
• Probable falling hazards
• Possible restricted egress
Probable
total loss
• Probable structural damage
• No Collapse
• No falling hazards
• Adequate emergency egress
Possible
total loss
• Slight structural damage
• Life safety attainable
• Essential systems repairable
• Moderate overall damage
2 to 3
weeks
•
•
•
•
Negligible structural damage
Life safety maintained
Essential systems operational
Minor overall damage
24
hours
Spectral representation
Time histories
Comartin-Reis
Elastic spectrum
Nonlinear static analysis
Elastic spectrum
Component actions
dj
qj
qi
di
Story drifts and forces
dij
Capacity curve
(pushover)
Nonlinear
ESDOF Oscillator
D
V
D
Comartin-Reis
Global displacement
Performance point
Intensity
measure
Damage measure
Capacity spectrum method
Global
Force
Parameter,
Sa
Building Damage States
V
dp
Sd
Performance
Point
Coefficient method
V
Global
capacity
curve
delas. dt
d
Inelastic spectrum methods (R, m, T)
3.0
m1
Strength Demand (g)
Collapse
prevention
Global
Displacement
Limits, d
c
m4
m8
1.0
0.0
0.0
1.0
2.0
Period,T (sec.)
Comartin-Reis
Life
safety
Performance Levels
m2
2.0
Immediate
occupancy
3.0
4.0
Engineering demand
parameter
Decision: Should this
building be retrofitted?
No, if it is safe for
shaking with a 10%
chance of being
exceeded in 50 yrs.
Comartin-Reis
Decision: Should the structural
system for this new building be
upgraded?
Yes, if the benefits
of the upgrade
exceed the
additional costs.
Comartin-Reis
Engineering demand parameter and intensity measure
Force
Sa
P(IM)
EDP
(displacement)
Pushover curve
T
Range of seismic intensity (IM)
P(EDP)
1.0
10-1
10-2
10-3
10-4
EDP
EDP (displacement) hazard
Comartin-Reis
10-3
10-2
10-1
EDP to damage and loss
Damage
Force
EDP
(displacement)
Pushover curve
Loss
Casualties
Capital loss
Business interruption
EDP
(displacement)
Comartin-Reis
Loss as a function of EDP
Risk and expected annual loss
Loss
($)
P(Loss)
Integrate for expected
annual loss
1.0
EDP
(displacement)
10-1
10-2
10-3
10-4
Loss as a function of EDP
Loss
P(EDP)
Risk of Loss
1.0
10-1
10-2
10-3
10-4
EDP
EDP (displacement) hazard
Comartin-Reis
UC Berkeley – Stanley Hall
Item
Comartin-Reis
Cost
Capital
$160 million
Contents
Business Interruption
$50 million
$40 million annually
UC Berkeley – Stanley Hall
$139K reduction in expected annual losses for
unbonded braces compared to conventional system
$400
($,000)
$300
$207
$200
$100
$113
$188
$143
$0
SCBF
UBB
(conventional braces) (unbonded braces)
Comartin-Reis
Capital/Contents
Business Interruption
UC Berkeley – Stanley Hall
Benefit–cost ratio
(BCR) 2.5
2
5%
discount
1.5
1
0.5
0
1
5
10
20
30
40
50
Building Life (years)
Benefit
Cost
Comartin-Reis
$0.1
$1.2
$0.6
$1.2
$1.1
$1.2
$1.7
$1.2
$2.1
$1.2
$2.4
$1.2
$2.5
$1.2
ATC 58 Performance-based Seismic
Design Guidelines
Federal Emergency Management Agency
FEMA-349
Guidelines for
Performance-based
Seismic Design
Joe’s
Joe’s
Beer!
Food!
Operational
Comartin-Reis
• Multiple Volumes
Beer!
Food!
Immediate
Occupancy
Beer!
Food!
Life
Safety
Collapse
Prevention
– Seismic Performance
Prediction for Buildings
– Performance-based
Seismic Design
– Recommended
Prescriptive Criteria for
Performance-based
Seismic Designs
Traditional traditional questions for
structural engineer
Comartin-Reis
1.
What is your fee?
2.
Does it meet “code”?
Future questions for structural engineers
1. What would be the losses at my facility?
2. What is the return on investment in retrofit?
3. Does it pay to upgrade criteria for new
construction?
4. What is a fair premium for insurance?
5. How does my seismic risk compare with
others I face?
Comartin-Reis
FEMA 440: Improvement of inelastic seismic
analysis procedures
Equivalent Linearization
Displacement Modification
ATC- 40
FEMA-356
Capacity Spectrum Method
(CSM)
Displacement Coefficient
Method (DCM)
Comartin-Reis
Nonlinear response history evaluation database
D
SDOF oscillators
Ground motion records
50 periods of vibration
(0.05s – 3.0s)
20 NEHRP-B
Damping ratio x=5%
20 NEHRP-C
9 levels of relative strength
R = 1 (elastic),1.5, 2, 3, 4, 5, 6, 7, 8
20 NEHRP-D
20 NEHRP-E/F
4 hysteretic behaviors (EPP, SD, SSD, NL)
Comartin-Reis
20 NEAR-FAULT
Maximum displacements
(elastic plus inelastic)
180,000 total
Evaluation of improved procedures
Maximum Displacement, m
T = 0.5s, NEHRP C
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
Mean
Median
MCM
MADRS
Mean +/-
NRHA
0
2
4
6
R
Comartin-Reis
8
10
Evaluation of improved procedures
Maximum Displacement, m
T = 0.5s, NEHRP C
Mean
Mean
Median
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
Median
MCM
MCM
MADRS
MADRS
Mean
+/- s
CM
Mean +/- s
CSM
Mean +/- s
Mean +/-
NRHA
NRHA
NRHA
0
2
4
6
R
Comartin-Reis
8
10
NRHA
CM
CSM
Nonlinear dynamic analysis
Global displacement
D
Story drifts and forces
dij
Component actions
dj
qj
qi
di
Comartin-Reis
Nonlinear static analysis
Elastic spectrum
Component actions
dj
qj
qi
di
Story drifts and forces
dij
Capacity curve
(pushover)
Nonlinear
ESDOF Oscillator
D
V
D
Comartin-Reis
Global displacement
Equivalent single degree of freedom
Static load pattern
Vtotal
Capacity curve
(pushover)
Nonlinear
ESDOF Oscillator
V
Comartin-Reis
D
Multi-degree-of-freedom (MDOF) effects
• Estimate response parameters made using
simplified inelastic procedures.
• Compare with results obtained by nonlinear
dynamic analysis
Comartin-Reis
from Aschheim 2002
Overturning Moments— Weak-story 9-story frame
2% Drift
Floor
9th
9th
8th
8th
7th
7th
6th
6th
5th
5th
4th
4th
3rd
3rd
2nd
2nd
Weak—2 %
1st
0
50000
100000
150000
4% Drift
Floor
Weak—4 %
1st
200000
0
50000
Overturning Moment (kips-ft)
Mean
Min
Max
SD SD
Comartin-Reis
Median
100000
150000
200000
Overturning Moment (kips-ft)
First Mode
Rectangular
Adaptive
Inverted Triangular
Code
SRSS
Multimode
from Aschheim 2002
Potential simplified NDP
4% Drift
Floor
1. Do NSP analysis to estimate
global displacement.
9th
8th
7th
2. Select one (few?) response
histories and scale to result in
same global displacement.
6th
5th
4th
3rd
3. Use results to evaluate MDOF
effects.
2nd
1st
0
50000
100000
150000
200000
Overturning Moment (kips-ft)
Comartin-Reis
Factors that may reduce response
of short period buildings
1. Neglecting ascending branch of design spectra
2. Short, stiff buildings more sensitive to SSI
3. Radiation and material damping in supporting
soils
4. Full and partial basements
5. Incoherent input to relatively large plan
dimensions
6. Concentrating building masses at floor and
roof levels
Comartin-Reis
geotechnical components
of foundation
structural components of
foundation
Infinitely rigid foundation and soil
ug= free field motion (FFM) with
conventional damping
a) Rigid base model
ug= free field motion (FFM) with
conventional damping
b) Flexible base model
ug= foundation input motion (FIM)
with conventional damping
Kinematic interaction
(high T-pass filter)
Adjust for foundation
damping
ug= foundation input motion (FIM)
with system damping including
foundation damping
foundation input motion (FIM) with
conventional damping
free field motion (FFM) with
conventional damping
Kinematic interaction
(high T-pass filter)
free field motion (FFM) with
conventional damping
c) Kinematic interaction
Comartin-Reis
d) Foundation damping
Example building for SSI effects
100’-0”
160’-0”
8” R/C wall – 20’L
typical
Plan
20’-0”
Roof
10’-0”
typical
2nd
1st
3’D
Footing 26’L x 3’B x 1.5’t
Comartin-Reis
Elevation @ wall
Section @ wall
SSI example
Sa
1.60
FFM @ 5%
1.40
1.20
FIM @5% adjusted for kinematic
SSI
FIM @12.5% adjusted for
foundation damping
1.00
0.80
0.60
0.40
0.20
0.00
0
Comartin-Reis
0.5
1
Period (sec)
1.5
Example building
(displacement modification procedure)
Procedure Cap
Current
Improved
Comartin-Reis
yes
yes
no
no
Base
fixed
flexible
fixed
flexible
fixed
fixed
flexible
flexible
SSI
dy
T
Sa
R
C0
C1
d
mu
no
yes
no
yes
0.1
0.2
0.1
0.2
0.1
0.1
0.2
0.2
0.14
0.21
0.14
0.21
0.14
0.14
0.21
0.21
1.5
1.5
1.5
1.5
1.5
0.8
1.5
0.8
3.8
3.8
3.8
3.8
3.8
2.0
3.8
2.0
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.5
1.4
3.4
2.4
2.6
1.6
1.7
1.3
0.5
1.1
1.2
1.8
0.9
0.3
1.3
0.5
5.0
5.4
11.8
9.2
8.8
2.9
6.6
2.6
Effects of Foundations on Performance
Foundation stiffness and strength affect
various structural components differently.
High forces
cause shear
wall damage
D, small
Foundation
yielding and
rocking protects
shear wall
Large
displacements
cause frame
damage
D, large
Small
displacements
protect frame
from damage
Stiff and Strong Foundation
Flexible and Weak Foundation
Stiff and strong is not always favorable;
nor is flexible and weak always conservative.
Comartin-Reis
Pier load tests
D ate: 4-O c t -200 1
L oc ation :
U C B er k eley
B er k eley , C A
T es t S ha ft A 2-2 5:
24" O D
~25- ft P ene trat io n
T e s t P ie r A 2- 2 5 Un d e r D y na m ic a n d S t a ti c L o ad s
700
Dynamic
600
Load (kips)
500
Static
400
300
P LT - D y na m ic
S tatic
200
Conventional estimates based on
unconfined compression strength
100
0
0 .0 0 0
0 .1 0 0
0 .2 0 0
0 .3 0 0
0 .4 0 0
D isp. (in )
Comartin-Reis
0 .5 0 0
0 .6 0 0
0 .7 0 0
0 .8 0 0