DESIGN OF LARGE OPENINGS IN UNBONDED POST-TENSIONED PRECAST CONCRETE WALLS
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Transcript of DESIGN OF LARGE OPENINGS IN UNBONDED POST-TENSIONED PRECAST CONCRETE WALLS
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DESIGN OF LARGE OPENINGS IN UNBONDED POST-TENSIONED PRECAST CONCRETE WALLS
Michael G. Allen
Yahya C. Kurama
University of Notre Dame
Notre Dame, IN
PCI Committee Days, Chicago, Illinois, April 14-15, 2000
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1998 PCI Daniel P. Jenny Research Fellowship
University of Notre Dame
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ELEVATION
wall panel
horizontaljoint
unbondedPT steel
spiralreinforcement
foundation
anchorage
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GAP OPENING BEHAVIOR
gap
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UNDER LATERAL LOADS AT FAILURE
compression stresses
shearstresses
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CRACKING
1
2
2
3
3
4
5
5
3
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RESEARCH OBJECTIVES
• Develop analytical model
• Conduct parametric investigation
• Develop design approach
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FINITE ELEMENT MODEL
truss elements
contact elements
nonlinearplane stress elements
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GAP OPENING
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STAGES OF RESPONSE
• Gravity and post-tensioning only
• Lateral loads
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UNDER GRAVITY AND POST-TENSIONING ONLY
Asf
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DESIGN PREDICTION
T
C
C
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0 2.0 4.0
ho/lo
1.0
lp=10 feet (fci=0.68 ksi)lp=15 feet (fci=0.44 ksi)lp=15 feet (fci=0.68 ksi)lp=20 feet (fci=0.68 ksi)
lp=20 feet (fci=1.48 ksi)lp=20 feet (fci=0.67 ksi)
lp=20 feet (fci=0.34 ksi)
1.5
Asf (predicted/ABAQUS)ALL CASES
0.5
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UNDER LATERAL LOADS AT FAILURE
compression stresses
shearstressesTmax
xcr
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CRITICAL SECTION
xcr
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LARGE OPENING VERSUS SMALL OPENINING
small opening large opening
xcr xcr
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PANEL REGION TO BE ANALYZED
xcr
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FREE BODY DIAGRAM
V1
Ncr
Nlc
Mcr
Mlc
Vtop
Vlc
NtopNgrav
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FREE BODY DIAGRAM
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MOMENT AT CRITICAL SECTION, Mcr
ho/hp = 0.125
-8
0
8
0.25 0.50lo/lp
V1Vtop
Vlc
Mlc
Nlc
Ngrav
Ntop
M / Mcr
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MOMENT AT CRITICAL SECTION
V1Vtop
Vlc
Mlc
Nlc
Ngrav
Ntop
-8
0
8
0.25 0.50lo/lp
M / Mcr
ho/hp = 0.375
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MOMENT AT CRITICAL SECTION
-8
0
8
0.25 0.50ho/hp
M / Mcr
lo/lp = 0.1
V1Vtop
Vlc
Mlc
Nlc
Ngrav
Ntop
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MOMENT AT CRITICAL SECTION
V1Vtop
Vlc
Mlc
Nlc
Ngravity
Ntop
-8
0
8
0.25 0.50ho/hp
M / Mcr lo/lp = 0.4
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PREDICTED VERSUS ACTUAL MOMENT
-3
-2
-1
0
Mcr (104 kip-in)
ABAQUS (Vtop)predicted (Vtop)ABAQUS (Vlc)predicted (Vlc)
lo/lp = 0.3
0.25 0.50ho/hp
Ncr
Mcr
Vtop
Vlc
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ABAQUS (Vlc)
PREDICTED VERSUS ACTUAL MOMENT
-3
-2
-1
0
Mcr (104 kip-in)
ABAQUS (Vtop)predicted (Vtop)
predicted (Vlc)
ho/hp = 0.25
0.25 0.50lo/lp
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PREDICTED VERSUS ACTUAL MOMENT
ABAQUS (Ntop)
1
2
3
Mcr (104 kip-in)
ABAQUS (Mlc)predicted (Mlc)
predicted (Ntop)
ho/hp = 0.25
0.25 0.5lo/lp
0
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PREDICTED VERSUS ACTUAL MOMENT
ABAQUS (Ntop)
1
2
3
Mcr (104 kip-in)
ABAQUS (Mlc)predicted (Mlc)
predicted (Ntop)
lo/lp = 0.3
0.25 0.5ho/hp
0
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TOTAL Mcr
1
2
3
Mcr (104 kip-in) ho/hp = 0.375
0.25 0.50lo/lp
ABAQUSpredicted
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TOTAL Mcr
1
2
3
Mcr (104 kip-in) lo/lp = 0.3
0.25 0.50
ho/hp
ABAQUSpredicted
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TOTAL Ncr
ho/hp = 0.25
0.25 0.50lo/lp
ABAQUSpredicted
-400
0
400
Ncr (kip)
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TOTAL Ncr
lo/lp = 0.3
0.25 0.50ho/hp
ABAQUSpredicted
-400
0
400
Ncr (kip)
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Asf IN TOP CHORD
3
6
0.25 0.50
lo/lp
ABAQUSpredicted
ho/hp = 0.25Asf (in2)
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Asf IN TOP CHORD
lo/lp = 0.3
ABAQUSpredicted
3
6
0.25 0.50
ho/hp
Asf (in2)
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Asf (predicted/ABAQUS)TOP CHORD
0
1
3
1.5 3 ho/lo
2
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Asf IN LEFT CHORD
3
6
0.25 0.50
Asf (in2)
ABAQUSpredicted
lo/lp
ho/hp = 0.25
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Asf IN LEFT CHORD
0
2
4
6
0 0.1 0.2 0.3 0.4 0.5
ABAQUS
predicted
lo/lp=.3
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Asf IN MIDDLE CHORD
3
6
0.25 0.50
ho/hp
Asf (in2)
lo/lp = 0.3
ABAQUSpredicted
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Asf (predicted/ABAQUS)LEFT CHORD
0
1.5
3
1.5 3 ho/lo
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CONCLUSIONS
Analytical Model• ABAQUS model developed for walls with openings• ABAQUS results compare well with DRAIN-2DX results and closed form
results
Parametric Investigation• Gravity and post-tensioning loads only
• As fci increases, steel requirement increases significantly
• As ho increases, steel requirement decreases, especially for longer walls
• As lo increases, steel requirement increases, especially for shorter walls
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CONCLUSIONS
Design Approach
• Utilizes a strut-and-tie model
• Can be used to predict the ABAQUS results; and
• To design the reinforcement above the openings
– Asc to prevent cracking
– Asf to minimize crack widths
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REMAINING WORK
• Finish design for lateral loads
• Experimental verification (Lehigh Tests)