Performance Based Seismic Design Guidelines for Tall

Buildings and their Applications

Farzad Naeim

1

What is a Tall Building?

•  Overall height as a measure ü Some codes such as ASCE 7 impose limits on

lateral systems to be used based on height •  Aspect ratio as a measure •  Vibration period as a measure •  Prevalence of higher modes in response

as a measure •  No universally accepted definition exists

but you know one when you see one!

2

Should tall buildings be treated like other buildings?

•  Tall buildings are occupied by hundreds if not thousands of people

•  The consequence of failure of tall buildings is much more severe than an ordinary building

•  Codes provide a “one size fits all” approach to seismic design.

•  Tall buildings as small class of specialized structures will perform better during earthquakes if special attention is afforded to their individual characteristics.

•  Prescriptive codes are not equipped with means to distinguish these differences.

3

Why prescriptive codes are not suitable?

•  Because they simply cannot give you what you need. •  Linear analysis is incapable of accurately predicting

collapse and failure which are inherently nonlinear •  The overwhelming majority of construction in United

States and worldwide consists of low-rise buildings

•  Prescriptive provisions are not generally written with tall buildings in mind.

1 to 3 Stories (93%)

14 Stories and Taller (1%)

4 to 13 Stories (6%)

We will examine two guidelines.

ASCE 41and Tall Building Design Guidelines

•  ASCE41 is officially intended for seismic rehabilitation of existing structures

•  However, its component-based performance limits for NDP are routinely referenced by guidelines for performance based design of tall buildings

•  Engineers who believe ASCE 41limits are too conservative, or are not applicable to their project, conduct tests to establish appropriate limits

•  Peer review approval is always necessary for any deviation from ASCE 41

6

Common Performance Objectives

•  SEAOC-99

•  ASCE 41 –  Similar objectives permitted. Emphasis on two events:

•  475 years (10% in 50 years), and •  2,475 years (2% in 50 years)

•  Tall Building Design Guidelines –  Serviceability: 43 years –  Collapse Prevention: 2,475 years

7

Analytical Procedures

•  ASCE-41 permits four types of analyses: 1.   Linear elastic static procedure (LSP) 2.   Linear dynamic procedure (LDP) or response

spectrum analysis 3.   Non-linear static procedure (NSP) commonly

referred to as the push-over analysis, and 4.   Dynamic nonlinear response analysis (NDP).

•  Tall Building Design Guidelines permit only

two: 1.   3D LDP or NDP for serviceability check 2.   3D NDP for all other checks

8

PEER-TBI & LATBSDC Performance Objectives

1.   Serviceable behavior under events having a 50% probability of being exceeded in 30 years (43 year return period) •  building structural and nonstructural components retain

their general functionality during and after earthquake •  Repairs, if necessary, are expected to be minor and

could be performed without substantially affecting the normal use and functionality of the building

2.   A low probability of collapse under events having a 2% probability of being exceeded in 50 years (2,475 year return period) •  Demands are checked for all structural members (lateral

as well as gravity system) •  Claddings and their connections to the structure must

accommodate MCE displacements without failure

1.   Use 2.5% damping instead of 5% damping but permit DCR = 1.5 for deformation controlled members for serviceability.

2.   2011 LATBSDC limits DCR to 0.70 for force controlled members in serviceability check.

3.   2010 PEER requirements for collapse prevention are more elaborate and detailed than 2011 LATBSDC

4.   No minimum base shear capacity requirement

PEER-TBI & LATBSDC Provisions

Design Procedures

•  None of the guidelines tell you how to design •  For example, 2011 LATBSDC states:

ü Use Capacity Design Techniques ü Develop Project-specific Design Criteria, and ü Clearly define where nonlinearity can occur and make sure it

does not occur elsewhere ü Recommends preferred zones of nonlinearity

•  But they do not explain how the engineer is supposed to achieve this design.

11

Source: 2011 LATBSDC ROSE School 2013 12

Evaluation Procedures

•  All guidelines require a three-dimensional detailed mathematical model of the physical structure

•  Realistic estimates of stiffness and damping

•  Expected material properties for ductile elements

•  Specified material properties for brittle elements

13

Source: 2011 LATBSDC Performance Based Seismic Assessment of Tall Buildings – I 14

Effective Stiffness Values for Linear Analysis

Source: 2008 LATBSDC, 2010 PEER ROSE School 2013 15

Effective Stiffness Values for Linear Analysis

Source: 2011 LATBSDC ROSE School 2013 Performance Based Seismic Assessment of Tall Buildings – I 16

Analysis Methods

•  Serviceability: ü  Can use either

1.   Linear Response Spectrum Analyses �  CQC mode combination �  90% mass participation

2.   Nonlinear Response History Analyses •  For MCE (ultimate state) evaluation:

ü  Must use �  Nonlinear Response History Analyses

•  Inherent torsional properties of the structural system should always be considered.

17

P-Δ Inclusion

•  P-Δ effects must be included in all analyses ROOF DRIFT ANGLE vs. NORMALIZED BASE SHEAR

Pushover (NEHRP '94 k=2 pattern); LA 20-Story

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 0.01 0.02 0.03 0.04 0.05

Roof Drift Angle

Nor

mal

ized

Bas

e Sh

ear

(V/W

) P-Delta effect includedP-Delta effect excluded

ROOF DRIFT ANGLE vs. NORMALIZED BASE SHEARPushover (NEHRP '94 k=2 pattern); LA 20-Story

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 0.01 0.02 0.03 0.04 0.05

Roof Drift Angle

Nor

mal

ized

Bas

e Sh

ear

(V/W

) P-Delta effect includedP-Delta effect excluded

Figure courtesy of Prof. Helmut Krawinkler

Modeling Nonlinear Behavior

Figure courtesy of Prof. Prof. Greg Deierlein

19

Modeling Nonlinear Behavior

•  Concentrated plasticity model for beams and columns and fiber elements for walls are most common

•  All other elements and components that in combination significantly contribute to or affect the total or local stiffness of the building should be included in the mathematical model.

•  Axial deformation of gravity columns in a core-wall system is one example of effects that should be considered in the structural model of the building

Figure courtesy of MKA

20

Accidental Eccentricity (AE)

•  2011 LATBSDC ü Consider implications during serviceability evaluation ü Address if significant during MCE evaluation

•  2010 PEER TBI ü Do not need to consider

•  Consideration of AE in nonlinear analyses requires multiple evaluations and little is gained by such time-consuming exercises.

21

Modeling Strength / Stiffness Degradation

•  2010 PEER TBI ü Provides detailed guidelines on four

approved methods for modeling degradation

•  2011 LATBSDC ü Adopts the first two of the detailed

procedures contained in 2010 PEER.

22

2010 PEER TBI Degradation Modeling Options

Figure courtesy of Prof. Helmut Krawinkler

23

Upper Limit on Column Axial Forces

•  Large axial forces reduce available column ductility

•  2011 LATBSDC ü MCE: P < 0.4f’cAg

•  2010 PEER TBI ü MCE: P < balanced load < 0.3f’cAg

24

Soil-Foundation-Structure-Interaction (SFSI)

•  Naeim & Stewart (2008) demonstrated the difficulties of realistic modeling of SFSI in a design environment.

•  2010 PEER TBI has two recommended modeling techniques

•  2011 LATBSDC recommends a single approach for this.

25

2010 PEER TBI Suggested Modeling Techniques for SFSI

2011 LATBSDC

26

Damping

•  A particularly thorny issue ü  In nonlinear analyses most of the damping is

represented by hysteretic behavior of the elements ü Some small additional viscous damping may be

justified for: �  Energy dissipation provided by components

and systems not explicitly modeled �  As necessary to avoid numerical instability

•  2011 LATBSDC ü  Limits viscous damping to 2.5% for both

serviceability and MCE.

•  2010 PEER TBI ü  2.5% for linear serviceability evaluation ü Refers to ATC-72 for nonlinear evaluation

27

Ground Motion Selection and Scaling

•  A minimum of 7 pairs is usually required •  2011 LATBSDC

ü Adopts by reference Chapter 21 of ASCE 7 •  2010 PEER TBI

ü More flexible ü Permits scaling, matching or CMS ü Multiple CMS required if CMS is used, making

this impractical for tall buildings •  Most practicing engineers prefer matching

ü One must be careful as, matched motion contains less record to record dispersion

28

Acceptance Criteria -- Maximum Drift

•  Absolute Maximum Transient Drift Limit ü Serviceability:

� 2011 LATBSDC & 2010 PEER TBI: 0.005 overall

ü  MCE: � 2011 LATBSDC & 2010 PEER TBI:

0.030 max average at any story 0.045 max. interstory drift at any story under any

record

29

Acceptance Criteria -- Maximum Drift

•  Absolute Maximum Residual Drift Limit ü Serviceability:

� 2011 LATBSDC 0.005 overall ü  MCE:

� 2011 LATBSDC and 2010 PEER: 0.010 average max. of time histories

0.015 maximum from any

30

Acceptance Criteria -- Serviceability

•  2011 LATBSDC ü Brittle Actions:

Strength Demand < 0.7*Capacity ü  Ductile Actions:

� Linear Analysis Strength Demand < 1.50 Capacity

� Nonlinear Analysis Can use up to IO limit of ASCE 41

31

Acceptance Criteria MCE

•  2010 PEER and 2011 LATBSDC ü  Ductile Actions:

� Deformation Demand < ASCE 41-06 CP Deformation Capacity

� Continuous Load Path � Capacity exhausted when it drops below

80% of maximum strength

32

Acceptance Criteria -- MCE

•  2010 PEER ü Brittle Actions:

� Two Groups: �  Critical Actions

�  failure mode pose severe consequences to structural stability under gravity and/or lateral loads

�  Design for mean + 1.3 to 1.5 times SD �  Noncritical Actions

�  Design for mean values �  Use ϕ = 0.75 for shear

•  2011 LATBSDC ü Essentially the same, except uses 1.5 times

mean and ϕ = 1.0

33

R/C Specific Requirements

•  None in 2010 PEER •  Several in 2011

LATBSDC ü Detailing

� The spacing limit of 12 inches of ACI 318 §21.5.3.2 (d) is reduced to 6 inches.

ü High-Strength Concrete

34

Peer Review Requirements

•  Each project needs a Seismic Peer Review Panel (SPRP)

•  SPRP is to provide an independent, objective, technical review of design

•  Paid by the owner but reports to Building Official •  Responsibility for the structural design remains

solely with the EOR •  SPRP is not a plan checking entity •  Minimum of three members with recognized

expertise in relevant fields such as: ü  structural engineering ü  earthquake engineering research ü  performance-based earthquake engineering ü  nonlinear response history analysis ü  tall building design ü  earthquake ground motions, geotechnical engineering,

geological engineering 35

Instrumentation Requirements

•  2010 PEER TBI ü No requirements

•  2011 LATBSDC ü Detailed requirements ü Consistent with CGS / CSMIP

36

A typical tall building instrumented by CSMIP

ROSE School 2013 Performance Based Seismic Assessment of Tall Buildings – I 37

Seismic Instrumentation

CSMIP sensor layout ROSE School 2013 38

Applications

•  Many tall buildings have been designed using these guidelines in Los Angeles, San Francisco, San Diego, and elsewhere

•  Here are some examples ü  Los Angeles:

�  888 Olive �  1133 Olive �  1212 Flower Towers �  Wilshire & Grand �  Metropolis Tower

ü  San Diego �  7th & Ash

ü  San Francisco �  Transbay Tower

39

•  888 Olive Street in downtown Los Angeles ü  34 stories ü  Core wall construction ü  Podium ü  Subterranean levels ü  Basement walls ü  Flat plates ü  Gravity columns

Illustrations and drawings courtesy of Onni Group and Glotman-Simpson

Illustrations and drawings courtesy of Onni Group and Glotman-Simpson

LEVEL 1 0.00'

LEVEL 2 20.00'

LEVEL 3 32.67'

LEVEL 4 45.33'

LEVEL 5 58.00'

LEVEL 6 70.67'

LEVEL 7 83.33'

LEVEL 8 96.00'

LEVEL 9 108.67'

LEVEL 10 121.33'

LEVEL 11 134.00'

LEVEL 12 146.67'

LEVEL 13 159.33'

LEVEL 14 172.00'

LEVEL 15 184.67'

LEVEL 16 197.33'

LEVEL 17 210.00'

LEVEL 18 222.67'

LEVEL 19 235.33'

LEVEL 20 248.00'

LEVEL 21 260.67'

LEVEL 22 273.33'

LEVEL 23 286.00'

LEVEL 24 298.67'

LEVEL 25 311.33'

LEVEL 26 324.00'

LEVEL 27 336.67'

LEVEL 28 349.33'

LEVEL 29 362.00'

LEVEL 30 374.67'

LEVEL 31 387.33'

LEVEL 32 400.00'

LEVEL 33 412.67'

LEVEL 34 425.33'

LEVEL 35 438.00'

LEVEL 36 450.67'

LEVEL 37 463.33'

LEVEL 38 476.00'

LEVEL 39 488.67'

LEVEL 40 501.33'

LEVEL 41 514.00'

LEVEL 42 526.67'

LEVEL 43 539.33'

LEVEL 44 552.00'

LEVEL 45 564.67'

LEVEL 46 577.33'

LEVEL 47 590.00'

LEVEL 48 602.67'

LEVEL 49 615.33'

LEVEL P1 -11.00'

LEVEL P2 -22.00'

LEVEL P3 -33.00'

P5 -45.00'

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

12' -

8"

20' -

0"

11' -

0"

11' -

0"

11' -

0"

PRO

PER

TY L

INE

PRO

PER

TY L

INE

590'

- 0"

33' -

0"

494'

- 0"

96' -

0"

COLOR LEGEND

FLOOR AREA

BUILDING COMMON AREA

STORE AREA

RESIDENTIAL AMENITY

SERVICE AREA

STORAGE

P1 PARKADE

P2 PARKADE

P3 PARKADE

L1 PARKADEL1RESIDENTIALLOBBY

COMMERCIAL/RETAIL STORAGE

STORAGE

STORAGE

BIKE STORAGE

BIKE STORAGE

ELEVATOR

RESIDENTIALAMENITY

RESIDENTIALAMENITY

TOWN HOUSES

STAI

RS

RESIDENTIAL RESIDENTIAL

L2 PARKADE

L3 PARKADE

L4 PARKADE

L5 PARKADE

CHRIS DIKEAKOSARCHITECTS INC.

SCALE: 1/32" = 1'-0"OLIVE ST. MIXED-USE DEVELOPMENT817 - 825 Hill St. & 820 S. Olive St., Los Angeles, CA

SECTIONAugust 26th, 2013 A306Design Development

1/32" = 1'-0"A2011 Section 9

42

43

LEVEL 1 0.00'

LEVEL 2 17.33'

LEVEL 3 30.00'

LEVEL 4 42.67'

LEVEL 5 55.33'

LEVEL 6 68.00'

LEVEL 7 80.67'

LEVEL 8 93.33'

LEVEL 9 106.00'

LEVEL 10 118.67'

LEVEL 11 131.33'

LEVEL 12 144.00'

LEVEL 13 156.67'

LEVEL 14 169.33'

LEVEL 15 182.00'

LEVEL 16 194.67'

LEVEL 17 207.33'

LEVEL 18 220.00'

LEVEL 19 232.67'

LEVEL 20 245.33'

LEVEL 21 258.00'

LEVEL 22 270.67'

LEVEL 23 283.33'

LEVEL 24 296.00'

LEVEL 25 308.67'

LEVEL 26 321.33'

LEVEL 27 334.00'

LEVEL 28 346.67'

LEVEL 29 359.33'

LEVEL 30 372.00'

LEVEL 31 384.67'

LEVEL 32 397.33'

LEVEL 33 410.00'

LEVEL 34 422.67'

LEVEL 35 435.33'

LEVEL 36 448.00'

LEVEL 37 460.67'

LEVEL 38 473.33'

LEVEL 39 486.00'

LEVEL 40 498.67'

LEVEL 41 511.33'

LEVEL P1 -12.00'

LEVEL P2 -23.92'

LEVEL P3 -35.84'

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"12

'-8"

12'-8

"17

'-4"

12'-0

"11

'-11"

11'-1

1"

W. 12TH STREET ALLEY

PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

GARBAGE

PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

RES. LOBBY

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

MECH.

MECH.

PARKING

PARKING

RES.AMENITY

HELIPAD

EXISTINGOFFICE BUILDING

TOWER 1BEYOND

PRO

PER

TY L

INE

PRO

PER

TY L

INE

PODIUMCOURTYARD

LEVEL 1 0.00'

LEVEL 2 17.33'

LEVEL 3 30.00'

LEVEL 4 42.67'

LEVEL 5 55.33'

LEVEL 6 68.00'

LEVEL 7 80.67'

LEVEL 8 93.33'

LEVEL 9 106.00'

LEVEL 10 118.67'

LEVEL 11 131.33'

LEVEL 12 144.00'

LEVEL 13 156.67'

LEVEL 14 169.33'

LEVEL 15 182.00'

LEVEL 16 194.67'

LEVEL 17 207.33'

LEVEL 18 220.00'

LEVEL 19 232.67'

LEVEL 20 245.33'

LEVEL 21 258.00'

LEVEL 22 270.67'

LEVEL 23 283.33'

LEVEL 24 296.00'

LEVEL 25 308.67'

LEVEL 26 321.33'

LEVEL 27 334.00'

LEVEL 28 346.67'

LEVEL 29 359.33'

LEVEL 30 372.00'

LEVEL 31 384.67'

LEVEL 32 397.33'

LEVEL 33 410.00'

LEVEL 34 422.67'

LEVEL 35 435.33'

LEVEL 36 448.00'

LEVEL 37 460.67'

LEVEL 38 473.33'

LEVEL 39 486.00'

LEVEL 40 498.67'

LEVEL 41 511.33'

LEVEL P1 -12.00'

LEVEL P2 -23.92'

LEVEL P3 -35.84'PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

RES. LOBBY

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

ELEV.

MECH.

MECH.

RES.AMENITY

HELIPAD

RES. LOBBY

PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

PARKING

PRO

PER

TY L

INE

W. 12TH STREET EXISTING ALLEY

PRO

PER

TY L

INE

CHRIS DIKEAKOSARCHITECTS INC.

SCALE: 1/32" = 1'-0"FLOWER ST. MIXED-USE DEVELOPMENT1212 S. Flower Street, Los Angeles, CA

BUILDING SECTIONSAugust 26, 2013 A305DESIGN DEVELOPMENT

1/32" = 1'-0"A2011 TOWER 2 BUILDING SECTION

1/32" = 1'-0"A2012 TOWER 1 BUILDING SECTION

44

Thank you!

45