tall buildings initiative summary of case studies

Tall Buildings InitiativeSummary of Case Studies

Farzin ZareianUniversity of California, Irvine

Quake Summit 2010San Francisco, Oct 8, 2010

CollaboratorsJack Moehle, Yousef Bozorgnia. UCB

John Wallace, Zeynep Tuna. UCLA

Tony Yang. UBC

Pierson Jones. UCI

Nilesh Shome. RMS

Paul Somerville. URS

SponsorsCalifornia Seismic Safety Commission

California Office of Emergency Services (CalEMA)

FEMA

City of Los Angeles

Objective and Scope

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.

Assess the performance of designed tall buildings using latest technology

1.5Km, Puente Hills7.3Km, Hollywood8.8Km, Raymond11.5Km, Santa Monica24.5Km, Elsinore40.0Km, Sierra Madre56Km, San Andreas

San Andreas

Raymond

HollywoodSanta

Monica

Newport-Inglewood-Rose Canyon

Elsinore (Whittier)

Elsinore (Chino)

Sierra Madre (San Fernando)

Sierra Madre (Cucamonga)Verdugo

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: (SLE-25, SLE-43, DBE, MCE, OVE)

A large number of motions are required (we used 15) to have a reasonable estimate of the dispersion in EDP.

Challenges in Ground Motion Selection

Erro

r W

eigh

t

0

0.05

0.1

0.15

0.2

0 2 4 6 8 10 Period10% %60 30%

26% %42 32%

0.5 3.0 7.0

UniformVariable

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.

Record Selection and Scaling

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)

0

0.5

1

1.5

2

0 2 4 6 8 10

RecSimMedTarget

Period

Sa(T)

Response Spectra OVE (4975 year)

Building Design and ModelingThree Building Systems

After: Zeynep Tuna

42-Story Concrete Core Wall

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)

General Modeling Assumptions


1A: Code

1B: PBEE

1C: PBEE+

Wall: Strong Stronger

Strongest

Coupling beam:

Stronger

Stronger

Strong

1st mode Period:

T1EW = 5.2 secT1NS = 4.0 sec



24”

24”

28”

28”

32”

32”

Building Design Comparison

After: Tony Yang


0 2 4 6B3

L3

L8

L13

L18

L23

L28

L33

L38

L43

NodeXYZ-ISDRatioH1 [%]

PEERTBI-1AM

Flo

or n

umbe

r [-]

MCE

0 2 4 6B3

L3

L8

L13

L18

L23

L28

L33

L38

L43


Flo

or n

umbe

r [-]

PEERTBI-1BM

MCE

0 2 4 6B3

L3

L8

L13

L18

L23

L28

L33

L38

L43


Flo

or n

umbe

r [-]

PEERTBI-1CM

MCE


Structural design: Wall thickness: Wall vertical reinforcement: Coupling beam reinforcement: Structural period:

Structural response: Wall stress safety index: Coupling beam demand: Inter-story drift and wall edge strain:

1A < 1B < 1C1A < 1B < 1C

1C < 1A ~ 1B1C < 1B < 1A

1B < 1A < 1C1A < 1B < 1C

1C < 1B < 1A

After: Tony Yang


After: Zeynep Tuna

42-Story Concrete Dual System

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)

General Modeling Assumptions


2A: Code

2B: PBEE 1C: PBEE+


Wall: Strongest

Strong

Coupling beam:

Strong Strong

1st mode Period:


T1EW = 4.3 secT1NS = 3.9sec

24”

18”

24”

18”

16”36 X 36

42 X 4246 X 46

Columns:36 X 36

42 X 42

46 X 46

Columns:

42-Story Concrete Dual System• Building 2A – Inter-story drifts in H1 direction

0 0.02 0.04In te r-story D rift

0

10

20

30

40

DBE

0 0.02 0.04In ter-story D rift

0

10

20

30

40

MCE


0

10

20

30

40

OVE


0

10

20

30

40

Flo

or L

evel

SLE25

0

10

20

30

40


SLE43

42-Story Concrete Dual System• Building 2B – Inter-story drifts in H1 direction


0

10

20

30

40

DBE


0

10

20

30

40

MCE


0

10

20

30

40

OVE


0

10

20

30

40

Flo

or L

evel

SLE25

0

10

20

30

40


SLE43

Inter-story drifts in H1 direction

-0.03 -0.02 -0.01 0 0.01 0.02 0.03

In ter-story D rift

0

10

20

30

40

Floo

r Lev

el

OVE

-0.03 -0.02 -0.01 0 0.01 0.02 0.03

In ter-story D rift

0

10

20

30

40

Floo

r Lev

el

MCE


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.

42-Story Concrete Dual SystemSummary of findings


After: Zeynep Tuna

Bldg. 3A Bldg. 3B Bldg. 3C

40-Story Buckling Restrained B.F.

General View

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 plate will have full ductility capacity. No cyclic deterioration was modeled

40-Story Buckling Restrained B.F.General Modeling Assumptions

Bldg. 3A Bldg. 3B Bldg. 3C

300K-500K

501K-800K

801K-1200K

KEY:BRB strength [Kips]

NOTE:GRID LINE 2&7N-S DIRECTION


T1NS = 5.3secT1EW = 3.8 sec

T1NS = 6.5 secT1EW= 4.5 sec

T1NS= 5.7 secT1EW = 4.2 sec


MAXIMUM IDR

N-S E-W

E-W N-S

median

%16th and %84th

Individual earthquake

Building 3A4975 (years)

Return Period

OVE

MCE

DBE

SLE43

SLE25

GM set

2475 (years)

475 (years)

43 (years)

25 (years)

MAXIMUM IDR

median


4975 (years)

Return Period

OVE

MCE

DBE

SLE43

SLE25

GM set

2475 (years)

475 (years)

43 (years)

25 (years)

%16th and %84th

N-S E-W

E-W N-S Building 3B

MAXIMUM IDR

median


4975 (years)

Return Period

OVE

MCE

DBE

SLE43

SLE25

GM set

2475 (years)

475 (years)

43 (years)

25 (years)

%16th and %84th

N-S E-W

E-W N-S Building 3C

%Exceedance Of 3% Drift Ratio Safe maximum IDR

considered to be IDR=.03

There were no component failures for the BRBF lateral load system

25%20%15%10%5%0%

OVE MCE DBE SLE43 SLE25

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)

$256/SF$249/SF

$245/SF


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

General Summary1. 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

tall buildings initiative summary of case studies

Documents

year response spectra

year response spectra

year response spectra

year response spectra

designed buildings

year building design

similar ground motions

scaling response spectra