Transcript 幻灯片 1 - NEES

Effect of Plan Distribution of Energy
Dissipation Devices on Seismic Response of
Soft-Story Wood-Framed Structures
Jingjing Tian, Ph.D. Student
Michael D. Symans, Assoc. Professor
Dept. of Civil and Environmental Engineering
Rensselaer Polytechnic Institute
Technical Session 10 (Wood Structures)
2012 Quake Summit
Boston, MA
July 12, 2012
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Project Team
NEESR-CR: NEES-Soft: Seismic Risk Reduction
for Soft-Story Wood Frame Buildings
John W. van de
Lindt
Michael Symans
Weichiang Pang
University of Alabama
PI, Overall Project Manager
Rensselaer Polytechnic
Institute
Co-PI, Performance-Based
Seismic Retrofit
Co-PI , Advanced Numerical
Modeling
Clemson University
Mikhail Gershfeld
Cal State University,
Pomona
Co-PI, Design of Test Specimens
Xiaoyun Shao
Civil Engineering
Western Michigan Univ.
Co-PI, Hybrid Test Coordinator
Andrei Filiatrault
David Rosowsky
Gary Mochizuki
Ioannis
Christovasilis
Douglas Rammer
David Mar
University at Buffalo
Rensselaer Polytechnic
Institute
Structural Solutions, Inc.
National Tech. Univ. of
Athens
U.S. Forest Products Lab
Tipping Mar
Senior Personnel
Senior Personnel
Senior Personnel
Senior Personnel
Senior Personnel
Senior Personnel
Research supported by National Science Foundation CMMI Grant No. 1041631
(NEESR - Network for Earthquake Engineering Simulation Research)
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Outline
• Seismic response and energy dissipation retrofit
for soft-story buildings
• Energy dissipation retrofit
• Damper type and location
• Displacement amplification system
• Numerical Simulations
• Summary of parametric study of linear
simplified model
• Nonlinear analysis of simplified model
• Summary and Future work
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Seismic Response of Soft-Story Buildings
Soft-Story Buildings:
- Stiffness irregularity due to first story having
large openings in perimeter walls and minimal
interior walls and upper stories having small
openings and many interior walls.
- First story acts as a base isolation system in
that it protects the upper stories through its
flexibility.
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Seismic Retrofit Strategies
• Conventional Retrofit
• Increase stiffness/strength of soft story
• Tends to increase forces transmitted to upper stories
• Thus, need to avoid overstrengthening soft story
• Expected performance level for design earthquake:
Shelter-in-Place (structure serves as shelter
but may have significant damage)
• Performance-Based Retrofit
• Increase damping in first story (and possibly stiffness)
• May increase force transmitted to upper stories
• Expected performance level for design earthquake:
Fully Operational (FO) to Immediate Occupancy (IO)5
Energy Dissipation Retrofit
• Damper Type
• Linear fluid viscous dampers
• Linear: Peak force out-of-phase with peak displ.
• Pure energy dissipation
• Design and analysis procedures exist
• Previously tested in wood structures
• Damper Location
• First story only
• Perimeter walls to increase torsion resistance
• Along both stiff and flexible wall lines
• Displacement amplification system (scissor-jack)
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Damper Displacement Amplification System:
Scissor-Jack Bracing
Model of FVD within
scissor-jack bracing
Fluid Viscous Damper
Source: Hanson and Soong (2001)
Scissor-jack bracing assembly in
"Olympic House and Park Building"
in Nicosia, Cyprus
Simplified Model
- Neglect flexibility of bracing members
- Neglect damper stiffness
- Result: Amplification factor = 4
(based on geometry of narrow garage door
walls used in soft story building model)
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Numerical Simulations
• One-Story Elastic Structure (Review of Main Findings)
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Two-way asymmetric
Linear elastic shear walls; Linear viscous dampers
Uniaxial and biaxial ground motions
Parametric Study (using Matlab) to evaluate effects of damping plan
distribution and damping magnitude
• One-Story Inelastic Structure
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–
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Two-way asymmetric
Nonlinear shear walls; Linear viscous dampers
Uniaxial and biaxial ground motions
Parametric Study (using SAWS2.1 + SAWS2.1-IDA) to evaluate effects of
damping plan distribution and damping magnitude
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Parametric Study of One-Story Linear Elastic
Structure with Energy Dissipation System
Flexible-Edge
EQ-X
Rigid-Edge
- Two-way asymmetric w/rigid diaphragm
- Uniaxial ground motion
- CR & CM Fixed
- CSD Varied
Since a damping system is
added to the inherent
damping (5% assumed in all
modes) with intent of
protecting structural framing
system, structure behavior is
assumed to be linear elastic.
Northridge EQ Motions
- Rinaldi Receiving Station
(strong near-field)
- Newhall County Fire Station
(moderate near-field)
- Canoga Park Station
(moderate far-field)
CM = Center of Mass
CR = Center of Rigidity (located at ex / a  0.2 and ey / d  0.2 ; similar
to location for NEES-Soft test specimen)
CSD = Center of Supplemental Damping (location varies)
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Effect of Plan Distribution on
Max. Inter-story Drift
Flexible-Edge Deformation
- One-story elastic structure (Tnx = Tny = 0.5 sec)
- Uniaxial ground motion (Rinaldi 228)
- Drift normalized w.r.t. value when CSD is at CR
- Fixed damping magnitude: sdx  sdy  10%
Rigid-Edge Deformation
Moving CSD away from CR
and toward CM:
- Reduces drift along flexible edge
(minimizes translation AND torsion).
- Increases drift along rigid edge but
rigid edge drift not main concern.
- Overall, plan-wise distribution of
damping has strong influence
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on structure response
Effect of Damper Magnitude
on Max. Inter-story Drift
- One-story elastic structure
- Uniaxial ground motion (CP 106)
- Drift normalized w.r.t. value when sdx  sdy  10%
- Fixed CSD: esdx / a  0.5
esdy / d  0.5
0%   sdx   sdy  30%
Flexible and Rigid Edge Deformations
Flexible-Edge
Rigid-Edge
Increasing Magnitude of Damping:
- Monotonically reduces drift along
both flexible and rigid edges
(minimizes translation AND torsion).
- Strongest influence is on flexible edge
- Rate of drift reduction largest for small
damping ratios.
- Transmission of damper forces to
wood framing system and into
foundation may impose limitation on
damper magnitude.
EQ-X
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Parametric Study of One-Story Inelastic
Structure with Energy Dissipation System
- Two-way asymmetric w/rigid diaphragm
- Uniaxial ground motion
- CR & CM Fixed
- CSD Varied
EQ-X
Northridge EQ Motions
- Newhall County Fire Station:
NCF90+NCF360
(moderate near-field)
- Canoga Park Station:
CP106+CP196
(moderate far-field)
- 4 walls (one on each side)
- 2 dampers along X- direction,
(one each on north and south sides)
- Wall materials:
Exterior: Horiz. wood sheathing
Interior: Gypsum wall board
SAWS Shear Wall Model:
Hysteretic response
of conventional
structure (no dampers)
subjected to bi-axial
Canoga Park motion.
CM = Center of Mass
CR = Center of Rigidity (located at ex / a  0.2 and ey / d  0.2 ;
similar to location for NEES-Soft test specimen).
CSD = Center of Supplemental Damping (location varies in Y- direction).
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Effect of Plan Distribution
on Max. Inter-Story Drift
- One-story inelastic structure (Tnx = Tny = 0.5 sec)
- Uniaxial ground motion (CP106)
- Fixed total damping magnitude: Damping
coefficient along X- direction is 5 kips-sec/in
EQ-X
esdx / a  0.5
CSD moving
esdy / d  0.5
esdx / a  0.5
CSD moving
esdy / d  0.5
Moving CSD from flexible edge to stiff edge:
- Increases drift along flexible edge (due to both translation AND torsion).
- Reduces drift along stiff edge.
- Overall, damper location (plan-wise distribution) has strong influence on structure response.
- The optimized CSD location is approximately -0.2d in Y- direction (for a range of motions). 13
Effect of Damper Magnitude
on Max. Inter-Story Drift
- One-story inelastic structure
- Uniaxial ground motion (CP 106)
- Damper magnitude for both dampers increased
at same rate from 0 to 5 kips-sec/in.
- CSD location fixed ( esdy  0.2d ).
esdy / d  0.5
EQ-X
esdy / d  0.5
Increasing Magnitude of Damping:
- Monotonically reduces drift along all wall lines (minimizes both translation AND
torsion). Rate of drift reduction largest at small damper magnitudes.
- Transmission of damper forces to wood framing system and into foundation may
impose limitation on damper magnitude.
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Parametric Study of One-Story Inelastic
Structure with Energy Dissipation System
- Two-way asymmetric w/rigid diaphragm
- Biaxial ground motion
- CR and CM Fixed
- CSD varies
EQ-Y
EQ-X
EQ Motions
- Canoga Park Station
(moderate far-field)
- 22 Far-field EQ records
from ATC-63
- Stronger component applied in
X-direction
- 4 walls (one on each side)
- 2 dampers along X- direction,
(one each on north and south sides)
- 2 dampers along Y- direction,
(one each on west and east sides)
- Wall materials:
Exterior: Horiz. wood sheathing
Interior: Gypsum wall board
SAWS Shear Wall Model:
Hysteretic response
of conventional
structure (no dampers)
subjected to bi-axial
Canoga Park motion.
CM = Center of Mass
CR = Center of Rigidity (located at ex / a  0.2 and ey / d  0.2 ; similar
to location for NEES-Soft test specimen)
CSD = Center of Supplemental Damping (location varies in X- and Y-direction).
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Effect of Plan Distribution
on Max. Inter-Story Drift
- One-story inelastic structure (Tnx = Tny = 0.5 sec)
- Biaxial ground motion (CP106+CP196)
- Fixed total damping magnitude: Damping
coefficient along each direction is 5 kips-sec/in
Conventional
0.77
(0.2,-0.2)
Moving CSD from CR towards, and beyond, CM:
- The maximum structural responses generally decreases (reducing translation AND torsion).
- Damper location (plan-wise distribution) has strong influence on structure response.
- For a range of ground motions, the optimized CSD location is approximately at the coordinate
(0.2, -0.2), which is symmetric with CR about CM.
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Effect of Plan Distribution on
Max. Inter-Story Drift:
Far-Field Ground Motions
CSD location (x,-0.2)
CSD moving in Y
CSD moving in X
CSD moving in X
- One-story inelastic structure (Tnx = Tny = 0.5 sec)
- Biaxial ground motion (22 far-field records)
- Fixed damping magnitude: damping coefficient
along each direction is 2.5 kips-sec/in
CSD location (0.2,y)
CSD moving in Y
Moving CSD from CR towards CM:
- Maximum drift varies non-monotonically.
- Damper location (plan-wise distribution)
has strong influence on structure response.
- Optimized CSD location: X = 0.1~0.2
Y = -0.2~-0.1
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Summary/Conclusions
General Conclusion
Plan distribution of energy dissipation system (location of CSD) has
strong influence on maximum inter-story drift response of both
linear and nonlinear soft-story structures.
Linear Elastic Structure
Minimum inter-story drift of flexible wall lines (critical walls) obtained
when CSD is as far as possible from CR in direction toward CM
(ideally, at corner of structure, although damping cannot
physically be concentrated at a single point).
Nonlinear Structure
- Minimum inter-story drift of flexible wall lines (critical walls)
obtained when CSD is far from CR in direction toward CM but
NOT as far as possible.
- Near-optimal choice for plan distribution of dampers is to position
them such that the CSD is symmetric with respect to the CR about
the CM.
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On-Going/Future Work
Numerical
- Extend parametric analyses to multi-story inelastic structures with different
wall materials (SAWS2.1/SAWS2.1-IDA/Matlab)
- Extend analyses to consider near-field ground motions
- Investigate seismic retrofit consisting of combined stiffening and damping
Numerical/Experimental
- Evaluate performance of damper/stiffening retrofit relative to conventional
(primarily stiffening) retrofits
Experimental
- Real-time hybrid testing of full-scale shear walls with dampers at
University of Alabama
- Hybrid testing of 3-story full-scale building using virtual dampers at NEES-UB
- Shake table testing of 4-story full-scale building using physical dampers
at NEES-UCSD
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QUESTIONS?
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