4icee-Stmf Goel Prenst

8/7/2019 4icee-Stmf Goel Prenst

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Performance-Based Seismic Design ofSpecial Truss Moment Frames (STMFs)

Shih Shih - - Ho Chao Ho Chao

(Post-Doctoral Research Fellow, University of Michigan, USA)

Subhash C. Goel Subhash C. Goel (Professor, University of Michigan, USA)

Presentation at 4ICEE, Taipei, Taiwan, October 12-13, 2006


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Conventional Truss Moment Frame

Economical for large spansEasy end connections for moment resistanceOpenings for ductwork Smaller story heights


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Plastic Hinges

Special Segment

iF

ih

p

iF

ih

p

Special Truss Moment Frames (Design Criteria: AISCSpecial Truss Moment Frames (Design Criteria: AISCSeismic Provisions 2005, Section 12)Seismic Provisions 2005, Section 12)

withwith XX--diagonal webdiagonal webmembers in special segmentmembers in special segment

without web members in specialwithout web members in specialsegment (Vierendeel type)segment (Vierendeel type)


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Previous Experimental Results (Goel et al., 1991, 1994)Previous Experimental Results (Goel et al., 1991, 1994)


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Current Seismic Design Practice Design Base Shear

V = C e W(I/R)

Elastic Design/Analysis

Drift CheckC d < limit

Prescribed Ductility Detailing

Pushover Assessment

(Works most of the time But not always!)


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Performance-Based Plastic Design (PBPD) Method

1. Design Base Shear

Work-Energy Equation:


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For the given system,

Using Newmark-Hall Inelastic Spectra (R m- ms -T) for E-P SDOF,

Ref: Ref: Housner Housner (1956, 1960) (1956, 1960)

Solution of Work-Energy Equation Design Base Shear

Akiyama (1985)


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Inelastic response spectraInelastic response spectrapp roposed by Newmark androposed by Newmark andHall [1973]Hall [1973]

Energy modification factorEnergy modification factorversus periodversus period


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2. A Seismic Design Lateral Force Distribution Based on

Inelastic State of Structures (Chao, Goel, and Lee; 2006):

Shear Distribution Factor


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p

1( )i i i nF F +=

ih2 ps

L L

i pbr M

pc M pc M

iuw

s L

L

3. Plastic Design Method (for proportioning chord

members in special segment):

External Work = Internal Work

PrePre --Selected Yield MechanismSelected Yield Mechanism


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i LF

ih

iuw

( )ne iV

pc M

/ 2 L

( )c iP

i RF

ih

iuw

( )ne iV

pc M

/ 2 L

( )c iP

/ 2 L

4. Design of Members outside the Special Segments

(Capacity Design Approach):Maximum Expected Shear forcein the middle of special segment:

Exterior Column Tree Interior Column Tree


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Design of Example 9-story STMF:

1. NEHRP 2000 design spectrum.2. Two-level design: Pre-selected target story drift = 2% (under 10% in

50 years hazard); 3% (under 2% in 50 years hazard).3. No R , I , C d , are needed for design since inelastic behavior is accounted for

directly in PBPD.4. Generally no pushover analysis or iteration is required after design.

8's L =


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Relative Story Shear Distributions Obtained fromRelative Story Shear Distributions Obtained fromNonlinear Dynamic Analyses:Nonlinear Dynamic Analyses:


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In SummaryIn Summary 1.1. The new seismic design procedure (PBPD) usingThe new seismic design procedure (PBPD) using

energy and plastic design concepts, and preenergy and plastic design concepts, and pre --selectedselectedyield mechanism and target drift as performanceyield mechanism and target drift as performance

criteria, has been successfully applied to STMF tocriteria, has been successfully applied to STMF toachieve the desired performance objectives, such asachieve the desired performance objectives, such astarget drifts, intended yield mechanism, etc.target drifts, intended yield mechanism, etc.

2.2. R, I,R, I, andand C C d d , are not needed for design since inelastic, are not needed for design since inelasticbehavior is accounted for directly in PBPD.behavior is accounted for directly in PBPD. No iterativeNo iterativeevaluation or refinement, such as by nonlinear staticevaluation or refinement, such as by nonlinear static(pushover) or dynamic analysis after initial design, is(pushover) or dynamic analysis after initial design, isneeded either.needed either.


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