Tall Buildings Initiative
Summary of Case Studies
Farzin Zareian
University of California, Irvine
Quake Summit 2010
San Francisco, Oct 8, 2010
Collaborators
Jack Moehle, Yousef Bozorgnia. UCB
John Wallace, Zeynep Tuna. UCLA
Tony Yang. UBC
Pierson Jones. UCI
Nilesh Shome. RMS
Paul Somerville. URS
Sponsors
California Seismic Safety Commission
California Office of Emergency Services (CalEMA)
FEMA
City of Los Angeles
Objective and Scope
Assess the performance of designed tall buildings
using latest technology
 Development of earthquake ground motions for design
studies.
 Development of building analytical models
 Conduct a large number of earthquake simulations of
tall buildings to develop statistics of engineering
demand parameters
 Perform loss estimation for designed buildings
 Few side studies: simulated vs recorded motions, effect
of vertical component of ground motion, etc.
Sierra Madre
(Cucamonga)
1.5Km, Puente Hills
7.3Km, Hollywood
8.8Km, Raymond
11.5Km, Santa Monica
24.5Km, Elsinore
40.0Km, Sierra Madre
56Km, San Andreas
Challenges in Ground Motion Selection
 Significance of several modes of vibration in response of
the building.
 Similar ground motions for all structures.
 Five hazard levels needs to be looked at:
25, SLE-43, DBE, MCE, OVE)
(SLE-
 A large number of motions are required (we used 15) to
have a reasonable estimate of the dispersion in EDP.
Record Selection and Scaling
Scaling :
 Maximum acceptable scale factor = 5.0
 The scale factor, by which the smallest weighted error
between the target spectrum and the geometric mean
spectrum of a single recording is acquired, is computed.
 Records are matched between Tmin&Tmax at 0.5 & 10.0 sec.
Error
Weight
0.2
Uniform
0.15
0.1
0.05
0
0
0.5
26%
10%
2
3.0
%42
%60
4
6
7.0
Variable
32%
30%
8
10
Period
Response Spectra SLE25 (25 year)
Response Spectra SLE43 (43 year)
Response Spectra DBE (475 year)
Response Spectra MCE (2475 year)
Response Spectra OVE (4975 year)
7 unscaled pairs are from simulated
motions (URS/SCEC)
Response Spectra OVE (4975 year)
2
Rec
Sim
Med
Target
1.5
Sa(T)
1
0.5
0
0
2
4
Period
6
8
10
Building Design and Modeling
Three Building Systems
42-story reinforced
42-story reinforced
40-story steel special
concrete core wall
concrete dual system
moment-frame
After: Zeynep Tuna
42-Story Concrete Core Wall
General Modeling Assumptions
 3D nonlinear dynamic finite element
model (Perform3D).
 Ignored the gravity system.
 Basement walls below grade were
modeled using elastic shear wall elements
(Eeff = 0.8 E)
 Slabs below grade were modeled using
elastic shear shell element (Eeff = 0.25 E)
42-Story Concrete Core Wall
Building Design Comparison
1A: Code
24”
Wall:
24”
1B: PBEE
28”
28”
1C: PBEE+
32”
32”
Strong
Stronger
Strongest
Coupling
beam:
Stronger
Stronger
Strong
1st mode
Period:
T1EW = 5.2 sec
T1EW = 4.8 sec
T1EW = 4.6 sec
T1NS = 4.0 sec
T1NS = 3.6 sec
T1NS = 3.5 sec
After: Tony Yang
42-Story Concrete Core Wall
PEERTBI-1AM
PEERTBI-1BM
MCE
MCE
L43
L43
L38
L38
L38
L33
L33
L33
L28
L23
L18
Floor number [-]
L43
Floor number [-]
Floor number [-]
MCE
PEERTBI-1CM
L28
L23
L18
L28
L23
L18
L13
L13
L13
L8
L8
L8
L3
L3
L3
B3
0
2
4
6
NodeXYZ-ISDRatioH1 [%]
B3
0
2
4
6
NodeXYZ-ISDRatioH1 [%]
B3
0
2
4
6
NodeXYZ-ISDRatioH1 [%]
42-Story Concrete Core Wall
 Structural design:
 Wall thickness:
1A < 1B < 1C
 Wall vertical reinforcement: 1A < 1B < 1C
1C < 1A ~ 1B
 Coupling beam reinforcement:
 Structural period: 1C < 1B < 1A
 Structural response:
 Wall stress safety index: 1B < 1A < 1C
 Coupling beam demand: 1A < 1B < 1C
 Inter-story drift and wall edge strain: 1C < 1B < 1A
After: Tony Yang
Building Design and Modeling
Three Building Systems
42-story reinforced
42-story reinforced
40-story steel special
concrete core wall
concrete dual system
moment-frame
After: Zeynep Tuna
42-Story Concrete Dual System
General Modeling Assumptions
 3D nonlinear dynamic finite element
model (Perform3D).
 Ignored the gravity system.
 Basement walls below grade were
modeled using elastic shear wall elements
(Eeff = 0.8 E)
 Slabs below grade were modeled using
elastic shear shell element (Eeff = 0.25 E)
42-Story Concrete Dual System
Building Design Comparison
2B: PBEE 1C: PBEE+
2A: Code
Columns:
18”
24”
36 X 36
42 X 42
16”
18”
42 X 42
24”
46 X 46
Wall:
Coupling
beam:
1st mode
Period:
Columns:
36 X 36
Strongest
Strong
Strong
Strong
T1EW = 4.5 sec
T1EW = 4.3 sec
T1NS = 4.0 sec
T1NS = 3.9sec
46 X 46
42-Story Concrete Dual System
• Building 2A – Inter-story drifts in H1 direction
Floor Level
SLE25
SLE43
MCE
DBE
OVE
40
40
40
40
40
30
30
30
30
30
20
20
20
20
20
10
10
10
10
10
0
0
0
0
0
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
42-Story Concrete Dual System
• Building 2B – Inter-story drifts in H1 direction
Floor Level
SLE25
SLE43
MCE
DBE
OVE
40
40
40
40
40
30
30
30
30
30
20
20
20
20
20
10
10
10
10
10
0
0
0
0
0
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
0
0.02 0.04
Inter-story Drift
42-Story Concrete Dual System
 Inter-story drifts in H1 direction
OVE
40
40
30
30
Floor Level
Floor Level
MCE
20
20
10
10
0
0
-0.03
-0.02
-0.01
0
0.01
Inter-story Drift
0.02
0.03
-0.03
-0.02
-0.01
0
0.01
Inter-story Drift
0.02
0.03
42-Story Concrete Dual System
Summary of findings
 Overall behaviors of the two building designs are quite
similar.
 Median inter-story drift ratios (max ≈ 2%) are all well
below established limits.
 Wall shear stresses and strains are slightly higher in the
code-based design.
 Column axial forces in the code-based design are twice as
high as those in the PBD.
Building Design and Modeling
Three Building Systems
42-story reinforced
42-story reinforced
40-story steel special
concrete core wall
concrete dual system
moment-frame
After: Zeynep Tuna
40-Story Buckling Restrained B.F.
General View
Bldg. 3A
Bldg. 3B
Bldg. 3C
40-Story Buckling Restrained B.F.
General Modeling Assumptions
 PERFORM3D
(version 4.03) structural analysis software by
Computers and Structures Inc. was used for the nonlinear
time history analysis.
 The
only nonlinear element employed in the model is the
Buckling Restrained Brace element. (Ry = 1.1, ω = 1.25, and
β = 1.1.)
 The
brace components in the model have a maximum
deformation capacity of (20εy)
 Gusset
 No
plate will have full ductility capacity.
cyclic deterioration was modeled
40-Story Buckling Restrained B.F.
Building Design Comparison
Bldg. 3A
Bldg. 3B
Bldg. 3C
KEY:
BRB strength [Kips]
300K-500K
501K-800K
801K-1200K
NOTE:
GRID LINE 2&7
N-S DIRECTION
T1NS = 5.3sec
T1NS = 6.5 sec
T1NS= 5.7 sec
T1EW = 3.8 sec
T1EW= 4.5 sec
T1EW = 4.2 sec
Return
Period
GM set
4975 (years)
OVE
2475 (years)
MCE
475 (years)
DBE
43 (years)
SLE43
E-W
N-S
Building 3A
N-S
median
%16th and %84th
25 (years)
Individual
earthquake
SLE25
MAXIMUM IDR
E-W
Return
Period
GM set
4975 (years)
OVE
2475 (years)
MCE
475 (years)
DBE
43 (years)
SLE43
E-W
N-S
Building 3B
N-S
median
%16th and %84th
25 (years)
Individual
earthquake
SLE25
MAXIMUM IDR
E-W
Return
Period
GM set
4975 (years)
OVE
2475 (years)
MCE
475 (years)
DBE
43 (years)
SLE43
E-W
N-S
Building 3C
N-S
median
%16th and %84th
25 (years)
Individual
earthquake
SLE25
MAXIMUM IDR
E-W
40-Story Buckling Restrained B.F.
%Exceedance Of 3% Drift Ratio
25%
20%
15%
$249/SF
$256/SF
$245/SF
10%
5%
0%
OVE MCE DBE SLE43 SLE25
 Safe maximum IDR
considered to be IDR=.03
 There were no
component failures for
the BRBF lateral load
system
 Building 3C did not exceed the safe IDR in any of the ground
motions, was considered to perform the best.
 Building 3A generally performed better than the
performance based design (Building 3B)
Basic Assumptions for Loss Calculations
Based on inter-story drift and floor acceleration results only.
Similar components in all buildings.
The EDPs from nonlinear time-history analysis are used
directly for loss calculations without any fitting as done
commonly for loss estimations.
After: Nilesh Shome
After: Nilesh Shome
General Summary
1. Performance of 9 tall buildings at five hazard levels
were evaluated: Three lateral load resisting systems X
Three design guidelines.
2. The progress in reduction in estimated loss from CBD
to PBD+ designs shows the a general success in
proposed design guidelines for tall buildings.
3. On going efforts:
 Loss estimation methodology
Thank You