Yahya C. Kurama University of Notre Dame Notre Dame, Indiana, U.S.A 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 Technology Yokohama, Japan August 16, 2000

anchorage wall panel unbonded PT steel horizontal joint spiral ELEVATION anchorage wall panel unbonded PT steel horizontal joint spiral reinforcement foundation

LATERAL DISPLACEMENT precast wall gap opening shear slip

BEHAVIOR UNDER LATERAL LOAD base shear, kips (kN) 800 (3558) concrete crushing (failure) PT bar yielding (flexural capacity) effective linear limit (softening) gap opening (decompression) roof drift, % 1 2

BONDED VERSUS UNBONDED BEHAVIOR wall unbonded wall

base shear, kips (kN) 800 (3558) roof drift, % -2 -1 1 2 -800 (-3558) HYSTERETIC BEHAVIOR base shear, kips (kN) 800 (3558) roof drift, % -2 -1 1 2 -800 (-3558)

Unbonded post-tensioned precast walls without supplemental damping OUTLINE Unbonded post-tensioned precast walls without supplemental damping with supplemental damping Unbonded post-tensioned hybrid coupled walls

UNBONDED POST-TENSIONED WALLS WITHOUT SUPPLEMENTAL ENERGY DISSIPATION Analytical Modeling

ANALYTICAL MODEL node truss element constraint fiber element wall model cross-section

BEAM-COLUMN SUBASSEMBLAGE TESTS NIST (1993) N H upper crosshead 7.5 ft (2.3 m) 4.3 ft (1.3 m) lower crosshead

MEASURED VERSUS PREDICTED RESPONSE lateral load, kips (kN) 50 measured (NIST) predicted drift, % -6 6 -50 (222) El-Sheikh et al. 1997

FINITE ELEMENT (ABAQUS) MODEL nonlinear plane stress elements truss elements contact elements

GAP OPENING

FINITE ELEMENT VERSUS FIBER ELEMENT base shear, kips (kN) 1000 (4448) yielding state 500 gap opening state finite element fiber element 0.5 1 1.5 2 2.5 roof drift, %

Seismic Design and Response Evaluation

immediate occupancy collapse prevention base shear design DESIGN OBJECTIVES immediate occupancy collapse prevention base shear design level gr. mt. survival level gr. mt. roof drift

BUILDING LAYOUT FOR HIGH SEISMICITY 8 x 24 ft = 192 ft (60 m) gravity load frame hollow- core panels lateral load frame wall N 110 ft (35 m) S inverted T-beam column L-beam

C L PT bars ap=1.5 in2 (9.6 cm2) #3 spirals fpi=0.60fpu rsp=7% 12 in WALL WH1 CROSS SECTION C L PT bars ap=1.5 in2 (9.6 cm2) fpi=0.60fpu #3 spirals rsp=7% 12 in (31 cm) 10 ft (3 m) half wall length

ROOF-DRIFT TIME-HISTORY 4 2 -2 Hollister (survival) unbonded PT precast wall cast-in-place RC wall -4 10 20 30 time, seconds

WALLS WITH SUPPLEMENTAL ENERGY DISSIPATION U.S. National Science Foundation CMS 98-74872 CAREER Program

viscous damper diagonal brace bracing column floor slab wall VISCOUS DAMPED WALLS viscous damper diagonal brace bracing column floor slab wall

bracing diagonal viscous column brace damper wall panel gap DAMPER DEFORMATION bracing column diagonal brace viscous damper wall panel gap

damper deformation, in (cm) 6 compression tension 5 4 at yielding state Dllp=0.84% floor 3 2 1 -2 (-5) -1 1 2 (5) damper deformation, in (cm)

SURVIVAL LEVEL GROUND MOTION DESIGN OBJECTIVE base shear SURVIVAL LEVEL GROUND MOTION damped system undamped system roof drift

spectral displacement Sd , in (cm) DAMPER DESIGN - WALL WH1 Sa, g 3 Dllp=0.84% MIV=67 in/sec (171 cm/sec) Te = 0.64 sec. xev=3% 2 Teff=0.80 sec. 10% xr=22% 15% 23% 1 30% 40% X 4 8 12 16 (41) spectral displacement Sd , in (cm)

ROOF DRIFT TIME HISTORY - WALL WH1 3 damped Newhall, 0.66g undamped Dllp=0.84% Dllp=0.84% -3 20 time, seconds

MAXIMUM ROOF DRIFT - WALL WH1 Dmax, % 7 undamped wall damped wall Dllp= 0.84% 0.4 0.8 1.2 peak ground acceleration PGA, g

MAXIMUM ROOF DRIFT - WALL WP1 Dmax, % 7 undamped wall damped wall Dllp= 1.14% 0.4 0.8 1.2 peak ground acceleration PGA, g

MAXIMUM ROOF DRIFT - WALL WP2 Dmax, % 7 undamped wall damped wall Dllp= 1.47% 0.4 0.8 1.2 peak ground acceleration PGA, g

MAXIMUM ROOF ACCELERATION - WALL WH1 amax, g 0.5 1 1.5 2 0.4 0.8 1.2 peak ground acceleration PGA, g undamped wall damped wall

UNBONDED POST-TENSIONED HYBRID COUPLED WALL SYSTEMS U.S. National Science Foundation CMS 98-10067 U.S.-Japan Cooperative Program on Composite and Hybrid Structures

EMBEDDED STEEL COUPLING BEAM embedment region steel beam

TEST RESULTS FOR EMBEDDED BEAMS Harries et al.1997

POST-TENSIONED COUPLING BEAM PT anchor connection region wall region beam PT steel angle embedded plate PT steel

DEFORMED SHAPE contact region gap opening

COUPLING FORCES Vcoupling P z db P lb Vcoupling P z Vcoupling = 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

truss element kinematic constraint fiber element fiber element ANALYTICAL WALL MODEL wall beam wall truss element kinematic constraint fiber element fiber element

BEAM-WALL SUBASSEMBLAGE F L8x8x3/4 W18x234 PT strand lw = 10 ft lb = 10 ft (3.0 m) lw = 10 ft fpi = 0.5-0.7 fpu ap = 1.28 in2 (840 mm2)

MOMENT-ROTATION BEHAVIOR moment Mb, kip.ft (kN.m) 2500 (3390) Mp My 1250 ultimate PT-yield softening decompression 2 4 6 8 10 rotation qb, percent

CYCLIC LOAD BEHAVIOR moment Mb, kip.ft (kN.m) -10 -5 5 10 -2500 2500 5 10 -2500 2500 (3390) rotation qb, percent monotonic cyclic

ap and fpi (Pi = constant) 4 8 10 2500 (3390) moment Mb, kip.ft (kN.m) rotation qb, percent 2 6 1250

PT STEEL AREA 4 8 10 2500 (3390) moment Mb, kip.ft (kN.m) 4 8 10 2500 (3390) moment Mb, kip.ft (kN.m) rotation qb, percent 1250 2 6

TRILINEAR ESTIMATION 4 8 10 1250 2500 (3390) ultimate PT-yield 4 8 10 1250 2500 (3390) ultimate PT-yield softening smooth relationship trilinear estimate moment Mb, kip.ft (kN.m) rotation qb, percent 2 6

W18x234 ap = 0.868 in2 (560 mm2) fpi = 0.7 fpu PROTOTYPE WALL 82 ft 12 ft 8 ft 12 ft 82 ft (24.9 m) fpi = 0.7 fpu (3.7m 2.4m 3.7 m)

COUPLING EFFECT 1 2 3 4 roof drift, percent 40000 80000 120000 1 2 3 4 roof drift, percent 40000 80000 120000 (162720) base moment, kip.ft (kN.m) coupled wall two uncoupled walls

Beam-wall connection subassemblages Ten half-scale tests EXPERIMENTAL PROGRAM Beam-wall connection subassemblages Ten half-scale tests Objectives Investigate beam M-q behavior Verify analytical model Verify design tools and procedures

ELEVATION VIEW (HALF-SCALE) L4x7x3/8 W10X100 PT strand strong floor lw = 5 ft lb = 5 ft (1.5 m) lw = 5 ft fpi = 0.7 fpu ap = 0.217 in2 (140 mm2)

Large self-centering capability Softening, thus, period elongation 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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