Transcript Post-Tensioned Coupled Shear Wall

Post-Tensioned Coupled Shear Wall Systems
Steven Barbachyn (presenter), M.S., University of Notre Dame
Yahya Kurama, Ph.D., P.E., University of Notre Dame
Michael McGinnis, Ph.D., University of Texas at Tyler
Richard Sause, Ph.D., P.E., Lehigh University
Quake Summit 2012
Boston, MA
Background
• RC coupled shear wall
structures are a commonly
used primary lateral load
resisting system
• Two or more shear wall piers
connected by coupling beams
• Provide large lateral strength,
stiffness, and energy
dissipation
• Current requirements
prescribed in Chapter 21 of
ACI 318-11
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Conventional RC Coupled Walls
wall pier
coupling beam
diagonal
bar groups
wall pier
courtesy, Magnusson Klemencic Associates
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Project Motivation
• Primary concerns:
– Placement of the diagonal bar groups is a major
challenge
– Coupling beams may experience considerable damage
under seismic loading
– Considerable construction and material costs
• Proposed alternative:
– Adapt the widely-used unbonded post-tensioned (PT)
RC floor slab construction method to develop the
coupling forces between the wall piers
– Previous research on use of post-tensioning to couple
RC walls limited to isolated floor-level sub-assemblies
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Main Objectives
• To conduct system-level experimental evaluation of
PT coupled shear wall systems under seismic loading
• To validate analytical models and simulation tools for
these structures
• To develop performance-based engineering design
methodologies and appropriate construction
procedures
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Outline
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•
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Introduction
PT Coupled Shear Wall Design
Analytical Modeling
System-Level Experiments
Summary and Ongoing Work
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PT Coupled Shear Wall System
energy-dissipating (ED)
LOAD
mild
steel
debonded length
anchor at end
of wall pier
left wall pier
unbonded PT
steel in duct
right wall pier
Post-Tensioned
Conventional RC
RCCoupling
CouplingBeam
Beam
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Prototype Structure Design
LAX 90045
SS = 1.50 g
S1 = 0.60 g
Site Class D
I = 1.0
R = 6.0
CS = 0.136
plan view
elevation view
Vtotal = 2191k
Mtotal = 133750k-ft
@ full-scale
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Prototype Structure Design
Vtotal = V1 + V2
Vb,i
Mtotal = Mc + M1 + M2
Mc = (ΣVb,i )Lc
Mc = 0.30Mtotal
M1 = M2 = 0.35Mtotal
V1
V2
M1
Lc
M2
ΣVb,i
V2 / Vtotal = (M2 + Mc ) / Mtotal
(Shen et al. 2006)
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PT Coupling Beam Design
ED steel
Ts=Asfs
ds
Tp=Apfpi
PT strand
dp
a Cs=Asfs’
ds ’
Mbeam = 2Vbeam/Lbeam
MS = 0.30Mbeam
MP= 0.70Mbeam
C=0.85fc’abw
MS = Ts(ds-a/2)+Cs(a/2-ds’)
a = β1c
MP = Tp(dp-a/2)
As
C = 0.85fc’abw = Tp + Ts - Cs
Ap
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PT Coupling Beam Design
• Designed for maximum chord
rotation of, θmax = 9%
• Adapted ACI-ITG 5.2
requirements for unbonded PT
shear walls to design
confinement reinforcement
• Two overlapping hoops (one
small and one large) placed at
beam ends with small spacing
• ¼” notch to initiate crack at ends
• Target maximum strain of 0.5εsu
for debonded length of ED steel
• Shear reinforcement satisfying
Chapter 11 of ACI 318-11
θmax
ED bar
PT steel
large
hoop
small
hoop
wall
beam
¼” notch
cover concrete spalling
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Outline
•
•
•
•
•
Introduction
PT Coupled Shear Wall Design
Analytical Modeling
System-Level Experiments
Summary and Ongoing Work
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Analytical Models
(OpenSees & DRAIN-2DX)
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Fiber Element Wall Pier Model
wall pier
concrete
symmetrical coupled core wall
fiber
discretization
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Analytical Model Validation
Aktan, A. and Bertero, V., 1984
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Prediction of Specimen Response
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Linear Elastic ABAQUS Model
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Outline
•
•
•
•
•
Introduction
PT Coupled Shear Wall Design
Analytical Modeling
System-Level Experiments
Summary and Ongoing Work
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40%-Scale Test Setup at Lehigh
• Bottom 3 stories of 8-story
structure, including
load
tributary floor slabs, being
block
built at Lehigh at 40%scale
• Horizontal and vertical
actuators to simulate
PT slab
forces from upper stories
• Two jacks on each pier
apply service level gravity
loads
reaction frame
foundation
block
C-shaped walls
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Hybrid Simulation
analytical
substructure
8-story
structure
V
typical
N
M
CUT
experimental
substructure
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Slow Hybrid Test under
Reversed-Cyclic Lateral Loads
M = MLW,3 – Σ[Fi(ht-hi)]
CL
M = (T)(z1) + (C)(z2)
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CL
T + C = ΣVb,i
i=4
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3D-DIC Monitoring
με
3’-3”
3’-11”
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15%-Scale Experiments at UT-Tyler
reaction
frame
wall
piers
foundation block
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Summary
1. Post-tensioned coupled wall system for seismic regions
has been designed
2. Aims to address construction and performance issues
in conventional RC coupled walls
3. Analytical models of the new system have been
developed
4. Construction for the first specimen at 40%-scale and
15%-scale is ongoing
5. Multiple 3D-DIC (as well as conventional
instrumentation) will be used to monitor the structural
performance during testing
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Ongoing Work
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•
•
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Construction expected to be completed early Fall 2012
Experiment to be conducted soon after construction is
complete
Construction of second test specimen to commence
late 2012
Post-test analytical studies to be conducted using
validated models
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Community Outreach
Load Frame
Load
Fixtures
Pier 1
Pier 2
Coupling
Beams
Foundation
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Acknowledgments
• Project funded by NSF Grant No: 1041598
– Dr. Joy Pauschke Program Director
• This award is part of the “George E. Brown, Jr. Network for Earthquake
Engineering Simulation (NEES) Research (NEESR)” and the “National
Earthquake Hazards Reduction Program (NEHRP)”
• Material Donations:
– Dayton Superior, Essroc Cement, A.H. Harris Construction Supplies, Hayes
Industries, Sumiden Wire Products Corporation
• Magnusson Klemencic Associates:
– Ron Klemencic, Dave Fields, Joshua Mouras, Amy Haaland
• Lehigh University Faculty/Staff/Graduate Student :
– Dr. Shamim Pakzad, Darrick Fritchman, Gary Novak, Carl Bowman, Michelle Tillotson
• Undergraduate Students:
– Mathu Davis, Amy Breden (REU)
– Michelle Holloway, Michael Lisk (University of Texas at Tyler)
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Questions?
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