Zareian Building

Response of TBI case study buildings

ANALYSIS OF STEEL BUILDING

Pierson Jones & Farzin Zareian

May 7th, 2010

IntroductionIntroductionThree Building Systems

Structural and Earthquake Engineering

40-story BRBF building

� 40-story Buckling Restrained Braced Frame (Bldg. III)

� Three designs by Simpson Gumpertz&Heger, Inc.

� Building III-A Code-based Design (IBC 2006 and not considering the maximum height limit, )

� Building III-B Performance-based Design (LATBSDC)

� Building III-C Performance-based Plus Design

� Perform 3D models provided by designer for Building III-B and III-C.

Building Information

• 2007 California Building Code

• ASCE 7.05 Standard for Minimum Design Loads for Buildings and Other Structures. (SDS = 1.145, SD1 = 0.52, R = 7)

•AISC 360.05 Spec. for Steel Buildings

•AISC 341.05 Seismic Spec.

•ACI 318-08 Building Code Requirements for Reinforced Concrete

Code Based Design

�Layout is identical to Code Based Design except that 2 bays of bracing have been removed (in the lower stories of the perimeter braced frames in the N-S)

�BRB member sizes have been reduced.

� Designed to meet the LATBSDC seismic design guidelines

Performance Based

Design

�Layout is identical to Performance Based Design except that outriggers are added to mitigate serviceability level design requirements.

�Designed to meet the Guidelines for PEER Seismic Design of Tall Buildings

Performance Based

Design Plus

General Comparison

Bldg. III-A Bldg. III-B Bldg. III-C

elevation

PINNED CONNECTION (801-1200K BRACES)

BOLTED CONNECTION (501-800K BRACES)

BOLTED CONNECTION (301-500K BRACES)TYPICAL COLUMNS, BRACES, AND CONNECTIONS

CONCRETE FILLEDBOX COLUMN

FROM 18” SQUARE TO 60” SQUARE

fc’=10,000 psi

Bldg. III-A Bldg. III-BBldg. III-C

Comparison of BRB strength along similar grid lines

300K-500K

501K-800K

801K-1200K

KEY:BRB strength [Kips]

NOTE:GRID LINE 2&7N-S DIRECTION

�PERFORM3D (version 4.03) structural analysis software by Computers and Structures Inc. was used for the nonlinear time history analysis.

� 3-D models of the building are subjected to 2-component ground motions.

�The only nonlinear element employed in the model is the Buckling Restrained Brace element.

General Modeling

�Columns and Beams were modeled with elastic elements. Elastic behavior was verified in these elements by monitoring their demand-capacity ratios and ensuring that they remained in the elastic range.

�Models that included the gravity frame were developed but did not significantly change the seismic demands.

�The perimeter shear walls were modeled with elastic wall elements with 50% of the gross stiffness and 40% of elastic shear modulus to account for cracked section properties. Diaphragm assumed rigid

General Modeling

BRBF Typical Bay-connection details

Assumption – gusset plate will have full ductility capacity.i.e. the connections are well engineered and will behave as pins even under severe ground motions.

BRBF Typical Bay – modeling details

Elastic Column element, equivalent steel cross section used (axial, torsional, and bending stiffness modified to account for concrete)

BRBF “brace” element, nonlinear. Connections modeled as pins.

BRBF “stiff endzone”30% length linear elastic bar

Elastic Beam Element with pinned connections to columns

Rigid panel zone

BRBF Modeling

Backbone curve for BRBF. Image source: Simpson Gumpertz and Heger

•Buckling-restrained braces were modeled using a built-in model in Perform 3D software with Ry = 1.1, ω = 1.25, and β = 1.1.•30% of the length of buckling-restrained braces are considered as “End Zone”•The brace components in the model have a maximum deformation capacity of (20εy) as determined by SGH.•If this capacity is exceeded during the time-history analysis, the analysis stops•No strength or stiffness degradation

Building III-A Modal Properties (E-W)

0

5

10

15

20

25

30

35

40

-1 -0.5 0 0.5 1Mode Shape Value

Sto

ry N

um

ber

Mode 1 Mode 2 Mode 3

Building III-A Modal Properties (N-S)

0

5

10

15

20

25

30

35

40


Sto

ry N

um

ber


Mode Number 1 2 3 4

Period 3.80 1.27 0.69 0.48

Mass Part. 0.72 0.17 0.05 0.02

Mode Number 1 2 3 4

Period 5.25 1.48 0.77 0.51

Mass Part. 0.57 0.24 0.09 0.04

Building III-A Modal Properties (E-W)

0

5

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15

20

25

30

35

40


Sto

ry N

um

ber


Building III-A Modal Properties (N-S)

0

5

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15

20

25

30

35

40


Sto

ry N

um

ber


Mode Number 1 2 3 4

Period 3.80 1.27 0.69 0.48

Mass Part. 0.72 0.17 0.05 0.02

Mode Number 1 2 3 4

Period 5.25 1.48 0.77 0.51

Mass Part. 0.57 0.24 0.09 0.04

Modal Properties: Building III-A

N-S E-W

�Dominance of flexural mode of vibration in N-S and E-W.

Building III-B Modal Properties (E-W)

0

5

10

15

20

25

30

35

40


Sto

ry N

um

ber


Building III-B Modal Properties (N-S)

0

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20

25

30

35

40


Sto

ry N

um

ber


Mode Number 1 2 3 4

Period 4.49 1.50 0.81 0.56

Mass Part. 0.74 0.16 0.04 0.02

Mode Number 1 2 3 4

Period 6.47 1.77 0.88 0.58

Mass Part. 0.64 0.22 0.07 0.03

Building III-B Modal Properties (E-W)

0

5

10

15

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25

30

35

40


Sto

ry N

um

ber


Building III-B Modal Properties (N-S)

0

5

10

15

20

25

30

35

40


Sto

ry N

um

ber


Mode Number 1 2 3 4

Period 4.49 1.50 0.81 0.56

Mass Part. 0.74 0.16 0.04 0.02

Mode Number 1 2 3 4

Period 6.47 1.77 0.88 0.58

Mass Part. 0.64 0.22 0.07 0.03

Modal Properties: Building III-B

N-S E-W

�Dominance of flexural mode of vibration in N-S and a balance between the flexural and shear mode in the E-W.

Building III-C Modal Properties (E-W)

0

5

10

15

20

25

30

35

40


Sto

ry N

um

ber


Building III-C Modal Properties (N-S)

0

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15

20

25

30

35

40


Sto

ry N

um

ber


Mode Number 1 2 3 4

Period 4.17 1.39 0.74 0.51

Mass Part. 0.73 0.17 0.05 0.02

Mode Number 1 2 3 4

Period 5.74 1.64 0.80 0.54

Mass Part. 0.67 0.20 0.06 0.03

Building III-C Modal Properties (E-W)

0

5

10

15

20

25

30

35

40


Sto

ry N

um

ber


Building III-C Modal Properties (N-S)

0

5

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15

20

25

30

35

40


Sto

ry N

um

ber


Mode Number 1 2 3 4

Period 4.17 1.39 0.74 0.51

Mass Part. 0.73 0.17 0.05 0.02

Mode Number 1 2 3 4

Period 5.74 1.64 0.80 0.54

Mass Part. 0.67 0.20 0.06 0.03

Modal Properties: Building III-C

N-S E-W

�Dominance of flexural mode of vibration in N-S and a balance between the flexural and shear mode in the E-W.

Representative Results

MAXIMUM IDR

N-S E-W

E-W N-S

median

%16th and %84th

Individual

earthquake

Building III–A

4975 (years)

Return

Period

OVE

MCE

DBE

SLE43

SLE25

GM set

2475 (years)

475 (years)

43 (years)

25 (years)

MAXIMUM IDR

median

Individual

earthquake

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 III–B

MAXIMUM IDR

median

Individual

earthquake

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 III–C

median

Individual

earthquake

MAXIMUM ACCELERATION [g]

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 III–A

median

Individual

earthquake


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 III–B

median

Individual

earthquake


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 III–C

N-S E-W

GM set: OVE

MAXIMUM IDR

Simulated vs. recorded ground motions

E-W N-S

T1 = 3.8T2 = 1.3

T1 = 5.3T2 = 1.5

simulated ground motions

%16th and %84th

mean

recorded & scaled ground motions

0

0.5

1

1.5

0 1 2 3 4 5 6 7 8 9 10

(Sa

(T)/

g [5

% c

riti

ca

l da

mp

ing

]

Period (T)

Matched Spectra for TBI (OVE, 3 & 0.1, 7 & 0.6)

Target Spectrum

Median Spectrum

Indv. SpectrumRec./Scaled

Indv. SpectrumSimulated

N-S E-W

GM set: OVE

MAXIMUM IDR


E-W N-S

T1 = 4.9T2 = 1.5

T1 = 6.5T2 = 1.8


%16th and %84th

mean


0

0.5

1

1.5

0 1 2 3 4 5 6 7 8 9 10

(Sa

(T)/

g [5

% c

riti

ca

l da

mp

ing

]

Period (T)


Target Spectrum

Median Spectrum



GM set: OVE

MAXIMUM IDR


N-S E-W

E-W N-S

T1 = 4.2T2 = 1.4

T1 = 5.7T2 = 1.60

0.5

1

1.5

0 1 2 3 4 5 6 7 8 9 10

(Sa

(T)/

g [5

% c

riti

ca

l da

mp

ing

]

Period (T)


Target Spectrum

Median Spectrum




%16th and %84th

mean


%Exceedance Of 3% Drift Ratio

� Safe maximum IDR considered to be IDR=.03

� All of the analysis completed -- there were no component failures for the BRBF lateral load system

25%

20%

15%

10%

5%

0%

OVE MCE DBE SLE43 SLE25

� Building III-C did not exceed the safe IDR in any of the ground motions, was considered to perform the best.

� Building III-A generally performed better than the performance based design (Building III-B)

$256/SF

$249/SF

$245/SF

� Behavior of Building III-C is different from Buildings III-A and III-B (different structural system)

� Stiffer building (III-A) observes larger acceleration and smaller deformation compared to other two buildings.

� No collapse was indicated

� Building III-B appeared to be the one with higher probability of exceeding the drift limit of 3% in MCE and OVE hazard levels. Building III-A exceeded the limit only at the OVE level.

Summary

Zareian Building

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