UNBONDED POST-TENSIONING: SEISMIC APPLICATIONS IN CONCRETE STRUCTURAL WALLS
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Transcript of UNBONDED POST-TENSIONING: SEISMIC APPLICATIONS IN CONCRETE STRUCTURAL WALLS
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UNBONDED POST-TENSIONING: SEISMIC APPLICATIONS IN CONCRETE
STRUCTURAL WALLS
Yahya C. Kurama
University of Notre Dame
Notre Dame, Indiana, U.S.A
Tokyo Institute of TechnologyYokohama, JapanAugust 16, 2000
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wall panel
horizontaljoint
unbondedPT steel
spiralreinforcement
foundation
anchorage
ELEVATION
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LATERAL DISPLACEMENT
precast wall gap opening shear slip
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BEHAVIOR UNDER LATERAL LOAD
base shear, kips (kN)
roof drift, %
gap opening(decompression)
PT bar yielding(flexural capacity)
concretecrushing (failure)
effective linear limit(softening)
0 1 2
800(3558)
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BONDED VERSUS UNBONDED BEHAVIOR
bonded wall
unbonded wall
HN
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HYSTERETIC BEHAVIOR
base shear, kips (kN)
roof drift, %
0 1 2
800(3558)
-800(-3558)
-1-2
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OUTLINE
• Unbonded post-tensioned precast walls
–without supplemental damping
–with supplemental damping
• Unbonded post-tensioned hybrid coupled walls
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UNBONDED POST-TENSIONED WALLSWITHOUT SUPPLEMENTAL
ENERGY DISSIPATION
Analytical Modeling
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ANALYTICAL MODEL
node trusselement
fiberelement
wall model
cross-section
constraint
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BEAM-COLUMN SUBASSEMBLAGE TESTS
uppercrosshead
lowercrosshead
4.3 ft(1.3 m)
7.5 ft (2.3 m)
NIST (1993)H
N
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MEASURED VERSUS PREDICTED RESPONSE
lateral load, kips (kN)
drift, %
-50 (222)
0
50
-6
measured (NIST)predicted
6
El-Sheikh et al. 1997
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FINITE ELEMENT (ABAQUS) MODEL
truss elements
contact elements
nonlinearplane stress elements
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GAP OPENING
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FINITE ELEMENT VERSUS FIBER ELEMENT
base shear, kips (kN)
0 0.5 1 1.5 2 2.5
500
1000(4448)
roof drift, %
fiber element
yielding state
gap openingstate finite element
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Seismic Design andResponse Evaluation
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DESIGN OBJECTIVES
baseshear
roof drift
immediateoccupancy
collapseprevention
designlevel gr. mt.
survivallevel gr. mt.
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BUILDING LAYOUT FOR HIGH SEISMICITY
8 x 24 ft = 192 ft (60 m)
110 ft(35 m)
N
hollow-corepanels
gravity loadframe
lateral loadframe
wall
column L-beam invertedT-beam
S
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WALL WH1CROSS SECTION
12 in(31 cm)
10 ft (3 m)
half wall length
#3 spiralssp=7%
PT barsap=1.5 in2 (9.6 cm2)fpi=0.60fpu
CL
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ROOF-DRIFT TIME-HISTORY
-4
-2
0
2
4
0 10 20 30
roof drift, %
time, seconds
Hollister(survival)
unbonded PT precast wallcast-in-place RC wall
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WALLS WITH SUPPLEMENTAL ENERGY DISSIPATION
U.S. National Science Foundation
CMS 98-74872
CAREER Program
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VISCOUS DAMPED WALLS
viscous damper
bracingcolumn
diagonal brace
wall floorslab
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DAMPER DEFORMATION
viscousdamper
bracingcolumn
diagonalbrace
wallpanel
gap
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DAMPER DEFORMATION
floor
damper deformation, in (cm)
1
2
3
4
5
6
-2 (-5) -1 0 1 2 (5)
compression tension
at yielding state llp=0.84%
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DESIGN OBJECTIVEbaseshear
roof drift
SURVIVAL LEVEL GROUND MOTION
damped system undamped system
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DAMPER DESIGN - WALL WH1
spectral displacement Sd , in (cm)
Sa, g
1
2
3
0 4 8 12 16 (41)
Teff=0.80 sec.
MIV=67 in/sec (171 cm/sec)
X
ev=3%
10%
15%23%
30%40%
llp=0.84%Te = 0.64 sec.
r=22%
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ROOF DRIFT TIME HISTORY - WALL WH1
dampedundamped
Newhall, 0.66g
-3
0
3
0 20time, seconds
llp=0.84%
llp=0.84%
, %
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MAXIMUM ROOF DRIFT - WALL WH1max, %
peak ground acceleration PGA, g
undamped walldamped wall
llp= 0.84%
7
0 0.4 0.8 1.2
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MAXIMUM ROOF DRIFT - WALL WP1
7
0 0.4 0.8 1.2
max, %
peak ground acceleration PGA, g
undamped walldamped wall
llp= 1.14%
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MAXIMUM ROOF DRIFT - WALL WP2
7
0 0.4 0.8 1.2
max, %
peak ground acceleration PGA, g
undamped walldamped wall
llp= 1.47%
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MAXIMUM ROOF ACCELERATION - WALL WH1amax, g
0
0.5
1
1.5
2
0.4 0.8 1.2peak ground acceleration PGA, g
undamped walldamped wall
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UNBONDED POST-TENSIONED HYBRID COUPLED WALL SYSTEMS
U.S. National Science Foundation
CMS 98-10067
U.S.-Japan Cooperative Program onComposite and Hybrid Structures
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EMBEDDED STEEL COUPLING BEAM
steel beamembedment region
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TEST RESULTS FOR EMBEDDED BEAMS
Harries et al.1997
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POST-TENSIONED COUPLING BEAM
beam
PT steel
connectionregion
PTanchor
embeddedplate
angle
PT steel
wall region
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DEFORMED SHAPE
contactregion
gapopening
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COUPLING FORCES
Vcoupling =P z
lb
P
P
Vcoupling
Vcoupling
dbz
lb
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RESEARCH ISSUES
• Force/deformation capacity of beam-wall connection region
–beam–angle
• Yielding of the PT steel• Energy dissipation• Self-centering• Overall/local stability
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ANALYTICAL WALL MODEL
fiberelement
kinematicconstraint
trusselement
fiberelement
wall beam wall
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BEAM-WALL SUBASSEMBLAGE
W18x234PT strand
L8x8x3/4
ap = 1.28 in2 (840 mm2)
lw = 10 ft lb = 10 ft (3.0 m) lw = 10 ft
F
fpi = 0.5-0.7 fpu
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MOMENT-ROTATION BEHAVIOR
0 4 8
1250
2500(3390)
moment Mb, kip.ft (kN.m)
rotationb, percent
Mp
My
ultimatePT-yieldsofteningdecompression
2 6 10
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CYCLIC LOAD BEHAVIORmoment Mb, kip.ft (kN.m)
-10 -5 0 5 10 -2500
0
2500(3390)
rotationb, percent
monotoniccyclic
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ap and fpi (Pi = constant)
0 4 8 10
2500(3390)
moment Mb, kip.ft (kN.m)
rotationb, percent2 6
1250
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PT STEEL AREA
0 4 8 10
2500(3390)
moment Mb, kip.ft (kN.m)
rotationb, percent
1250
2 6
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TRILINEAR ESTIMATION
0 4 8 10
1250
2500(3390)
ultimatePT-yieldsoftening
smooth relationshiptrilinear estimate
moment Mb, kip.ft (kN.m)
rotationb, percent2 6
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PROTOTYPE WALL
W18x234
ap = 0.868 in2
(560 mm2)
12 ft 8 ft 12 ft
82 ft(24.9 m)
fpi = 0.7 fpu
(3.7m 2.4m 3.7 m)
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COUPLING EFFECT
0 1 2 3 4roof drift, percent
40000
80000
120000 (162720)
base moment, kip.ft (kN.m)
coupled wall
two uncoupled walls
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EXPERIMENTAL PROGRAM
Objectives• Investigate beam M- behavior• Verify analytical model• Verify design tools and procedures
• Beam-wall connection subassemblages
• Ten half-scale tests
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ELEVATION VIEW (HALF-SCALE)
W10X100PT strand
L4x7x3/8
ap = 0.217 in2 (140 mm2)
lw = 5 ft lb = 5 ft (1.5 m) lw = 5 ft
strong floor
fpi = 0.7 fpu
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CONCLUSIONS
• Unbonded post-tensioning is a feasible construction method for reinforced concrete walls in seismic regions
• Large self-centering capability• Softening, thus, period elongation• Small inelastic energy dissipation• Need supplemental energy dissipation in high seismic regions
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http://www.nd.edu/~concrete