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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
wall panel
horizontaljoint
unbondedPT steel
spiralreinforcement
foundation
anchorage
ELEVATION
LATERAL DISPLACEMENT
precast wall gap opening shear slip
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)
BONDED VERSUS UNBONDED BEHAVIOR
bonded wall
unbonded wall
HN
HYSTERETIC BEHAVIOR
base shear, kips (kN)
roof drift, %
0 1 2
800(3558)
-800(-3558)
-1-2
OUTLINE
• Unbonded post-tensioned precast walls
–without supplemental damping
–with supplemental damping
• Unbonded post-tensioned hybrid coupled walls
UNBONDED POST-TENSIONED WALLSWITHOUT SUPPLEMENTAL
ENERGY DISSIPATION
Analytical Modeling
ANALYTICAL MODEL
node trusselement
fiberelement
wall model
cross-section
constraint
BEAM-COLUMN SUBASSEMBLAGE TESTS
uppercrosshead
lowercrosshead
4.3 ft(1.3 m)
7.5 ft (2.3 m)
NIST (1993)H
N
MEASURED VERSUS PREDICTED RESPONSE
lateral load, kips (kN)
drift, %
-50 (222)
0
50
-6
measured (NIST)predicted
6
El-Sheikh et al. 1997
FINITE ELEMENT (ABAQUS) MODEL
truss elements
contact elements
nonlinearplane stress elements
GAP OPENING
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
Seismic Design andResponse Evaluation
DESIGN OBJECTIVES
baseshear
roof drift
immediateoccupancy
collapseprevention
designlevel gr. mt.
survivallevel gr. mt.
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
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
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
WALLS WITH SUPPLEMENTAL ENERGY DISSIPATION
U.S. National Science Foundation
CMS 98-74872
CAREER Program
VISCOUS DAMPED WALLS
viscous damper
bracingcolumn
diagonal brace
wall floorslab
DAMPER DEFORMATION
viscousdamper
bracingcolumn
diagonalbrace
wallpanel
gap
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%
DESIGN OBJECTIVEbaseshear
roof drift
SURVIVAL LEVEL GROUND MOTION
damped system undamped system
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%
ROOF DRIFT TIME HISTORY - WALL WH1
dampedundamped
Newhall, 0.66g
-3
0
3
0 20time, seconds
llp=0.84%
llp=0.84%
, %
MAXIMUM ROOF DRIFT - WALL WH1max, %
peak ground acceleration PGA, g
undamped walldamped wall
llp= 0.84%
7
0 0.4 0.8 1.2
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%
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%
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
UNBONDED POST-TENSIONED HYBRID COUPLED WALL SYSTEMS
U.S. National Science Foundation
CMS 98-10067
U.S.-Japan Cooperative Program onComposite and Hybrid Structures
EMBEDDED STEEL COUPLING BEAM
steel beamembedment region
TEST RESULTS FOR EMBEDDED BEAMS
Harries et al.1997
POST-TENSIONED COUPLING BEAM
beam
PT steel
connectionregion
PTanchor
embeddedplate
angle
PT steel
wall region
DEFORMED SHAPE
contactregion
gapopening
COUPLING FORCES
Vcoupling =P z
lb
P
P
Vcoupling
Vcoupling
dbz
lb
RESEARCH ISSUES
• Force/deformation capacity of beam-wall connection region
–beam–angle
• Yielding of the PT steel• Energy dissipation• Self-centering• Overall/local stability
ANALYTICAL WALL MODEL
fiberelement
kinematicconstraint
trusselement
fiberelement
wall beam wall
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
MOMENT-ROTATION BEHAVIOR
0 4 8
1250
2500(3390)
moment Mb, kip.ft (kN.m)
rotationb, percent
Mp
My
ultimatePT-yieldsofteningdecompression
2 6 10
CYCLIC LOAD BEHAVIORmoment Mb, kip.ft (kN.m)
-10 -5 0 5 10 -2500
0
2500(3390)
rotationb, percent
monotoniccyclic
ap and fpi (Pi = constant)
0 4 8 10
2500(3390)
moment Mb, kip.ft (kN.m)
rotationb, percent2 6
1250
PT STEEL AREA
0 4 8 10
2500(3390)
moment Mb, kip.ft (kN.m)
rotationb, percent
1250
2 6
TRILINEAR ESTIMATION
0 4 8 10
1250
2500(3390)
ultimatePT-yieldsoftening
smooth relationshiptrilinear estimate
moment Mb, kip.ft (kN.m)
rotationb, percent2 6
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)
COUPLING EFFECT
0 1 2 3 4roof drift, percent
40000
80000
120000 (162720)
base moment, kip.ft (kN.m)
coupled wall
two uncoupled walls
EXPERIMENTAL PROGRAM
Objectives• Investigate beam M- behavior• Verify analytical model• Verify design tools and procedures
• Beam-wall connection subassemblages
• Ten half-scale tests
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
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
http://www.nd.edu/~concrete
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