University of Notre Dame Notre Dame, IN

University of Notre Dame Notre Dame, IN
DESIGN OF LARGE OPENINGS IN UNBONDED POST-TENSIONED PRECAST CONCRETE WALLS Michael G. Allen Yahya C. Kurama University of Notre Dame Notre Dame, IN Good afternoon. My presentation is on the seismic behavior of unbonded post-tensioned precast concrete walls which I have been studying as a part of my Ph.D. work at Lehigh University. Before I begin talking about my research, I would like to give you a brief description of unbonded post-tensioned precast concrete walls and an introduction to their seismic behavior. PCI Convention, Orlando, Florida, September 23-27, 2000

PCI Daniel P. Jenny Research Fellowship University of Notre Dame

anchorage wall panel unbonded PT steel horizontal joint spiral
ELEVATION anchorage wall panel unbonded PT steel horizontal joint spiral reinforcement Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. foundation

gap GAP OPENING BEHAVIOR
Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. gap

UNDER LATERAL LOADS NEAR FAILURE
compression stresses shear stresses Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

POSSIBLE CRACKING 2 5 1 3 4 3 3 Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. 2 5

Develop analytical model Conduct parametric investigation
RESEARCH OBJECTIVES Develop analytical model Conduct parametric investigation Develop design approach I have divided my talk into five distinct sections. First, I will continue describing the behavior of unbonded post-tensioned precast walls, particularly in comparison with conventional concrete systems. Then, I will describe the analytical wall model that we developed to represent this behavior. I will talk about a detailed parametric study of the lateral load behavior of the walls which we conducted using the wall model. A seismic design approach was developed based on the results of this parametric study. Finally, I will present the seismic response of a series of prototype walls from dynamic analyses.

nonlinear plane stress elements truss elements contact elements
FINITE ELEMENT MODEL nonlinear plane stress elements truss elements Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. contact elements

GAP OPENING Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

base shear (kips) 1000 yielding state 500 gap opening state ABAQUS
ABAQUS VERSUS DRAIN base shear (kips) 1000 yielding state 500 gap opening state Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. ABAQUS DRAIN 0.5 1 1.5 2 2.5 roof drift (%)

contact length / wall length 1.0
ABAQUS VERSUS DRAIN contact length / wall length 1.0 ABAQUS DRAIN 0.5 Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. 0.5 1 1.5 2 2.5 roof drift (%)

CLOSED FORM VERIFICATION (Savin 1961) (INFINITE PANEL)
ftx Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

ABAQUS VERSUS CLOSED FORM SOLUTION
ftx (ksi) 1.2 closed form (Savin 1961) 0.6 ABAQUS lo Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. ho 3.0 6.0 ho/lo

PARAMETRIC INVESTIGATION
Wall length Initial concrete stress Opening size I have divided my talk into five distinct sections. First, I will continue describing the behavior of unbonded post-tensioned precast walls, particularly in comparison with conventional concrete systems. Then, I will describe the analytical wall model that we developed to represent this behavior. I will talk about a detailed parametric study of the lateral load behavior of the walls which we conducted using the wall model. A seismic design approach was developed based on the results of this parametric study. Finally, I will present the seismic response of a series of prototype walls from dynamic analyses.

20 feet x 16 feet 15 feet x 16 feet 12 feet x 16 feet
WALL LENGTH 20 feet x 16 feet lp 15 feet x 16 feet Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. 12 feet x 16 feet

INITIAL CONCRETE STRESS lp=20 feet
fci=1.48 ksi (high seismicity) Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. fci=1.08 ksi (medium seismicity) fci=0.68 ksi (low seismicity)

lp=20 feet ho hp=16 feet lo ho lo OPENING SIZE 2 feet (0.13 hp)

Gravity and post-tensioning only Concrete crushing under lateral loads
STAGES OF RESPONSE Gravity and post-tensioning only Concrete crushing under lateral loads I have divided my talk into five distinct sections. First, I will continue describing the behavior of unbonded post-tensioned precast walls, particularly in comparison with conventional concrete systems. Then, I will describe the analytical wall model that we developed to represent this behavior. I will talk about a detailed parametric study of the lateral load behavior of the walls which we conducted using the wall model. A seismic design approach was developed based on the results of this parametric study. Finally, I will present the seismic response of a series of prototype walls from dynamic analyses.

UNDER GRAVITY AND POST-TENSIONING ONLY
Asf Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

DESIGN PREDICTION C T Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. C

Asf (predicted/ABAQUS) ALL CASES
1.5 1.0 lp=10 feet (fci=0.68 ksi) lp=20 feet (fci=1.48 ksi) 0.5 lp=15 feet (fci=0.44 ksi) lp=20 feet (fci=0.67 ksi) lp=15 feet (fci=0.68 ksi) lp=20 feet (fci=0.34 ksi) lp=20 feet (fci=0.68 ksi) 2.0 4.0 ho/lo

UNDER LATERAL LOADS AT FAILURE
xcr compression stresses shear stresses Tmax1 Vmax1 Vmax3 Vmax4 Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. Tmax3 Tmax4

CRITICAL SECTION IN TOP CHORD
xcr Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

LARGE OPENING VERSUS SMALL OPENINING
xcr xcr Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. small opening large opening

CRITICAL PANEL REGIONS AND SECTIONS
xcr 1 2 3 4 Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

FREE BODY DIAGRAMS FOR SECTIONS 1, 2, AND 3
top chord 1 2 Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. 2 3 side chord

Asl IN SECTION 1, lp = 20 feet, fci = 1.55 ksi ho/hp = 0.125
10 20 0.25 0.5 lo/lp Asl (in2) ABAQUS Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. predicted

Asl IN SECTION 1, lp = 20 feet, fci = 1.55 ksi lo/lp = 0.1
As (in2) 20 10 ABAQUS Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. predicted 0.25 0.5 ho/hp

10 20 0.25 0.5 ho/hp Asl (in2) ABAQUS Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. predicted

10 20 0.25 0.5 ho/hp Asl (in2) ABAQUS predicted Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

10 20 0.25 0.5 lo/lp Asl (in2) ABAQUS predicted Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

Ast IN SECTION 1, lp = 20 feet, fci = 1.55 ksi ho/hp = 0.25
40 0.25 0.5 lo/lp Ast (in2) ABAQUS predicted Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

Ast IN SECTION 1, lp = 20 feet, fci = 1.55 ksi lo/lp = 0.3
40 20 ABAQUS Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections. predicted 0.25 0.5 ho/hp

10 20 0.25 0.5 lo/lp Asl (in2) ABAQUS predicted Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

Ast IN SECTION 3, lp = 20 feet, fci = 1.55 ksi ho/hp = 0.25
10 20 0.25 0.5 lo/lp Ast (in2) ABAQUS predicted Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

Ast IN SECTION 3, lp = 20 feet, fci = 1.55 ksi lo/lp = 0.3
10 20 0.25 0.5 ho/hp Ast (in2) ABAQUS predicted Typically, there is a connection at each floor level and at the base. The wall panels are held together using post-tensioning bars or strands. The post-tensioning bars are smooth, greased, and are placed in oversize ducts such that bond cannot develop between the bars and the wall panels. The bars are anchored to the wall panels at the roof and at the base. This type of construction, which is new in a seismic system, is called unbonded post-tensioned construction. Spiral reinforcement is provided to confine the concrete, particularly in the base panel. Concrete confinement is necessary in unbonded post-tensioned precast concrete walls where large concrete strains develop as a result of gap opening along the horizontal connections.

CONCLUSIONS Parametric Investigation
Top chord and side chord under lateral loads Critical sections “Large” versus “small” openings Panel length Initial stress Top Chord As lo/lp and ho/hp , longitudinal steel  As lo/lp and ho/hp , transverse steel  I have divided my talk into five distinct sections. First, I will continue describing the behavior of unbonded post-tensioned precast walls, particularly in comparison with conventional concrete systems. Then, I will describe the analytical wall model that we developed to represent this behavior. I will talk about a detailed parametric study of the lateral load behavior of the walls which we conducted using the wall model. A seismic design approach was developed based on the results of this parametric study. Finally, I will present the seismic response of a series of prototype walls from dynamic analyses.

CONCLUSIONS (CONTINUED)
Side Chord As ho/hp , longitudinal steel  As lo/lp , transverse steel  Design Approach Utilizes equilibrium of critical panel regions Can be used to predict the ABAQUS results; and To design the longitudinal and transverse reinforcement in the top and side chords I have divided my talk into five distinct sections. First, I will continue describing the behavior of unbonded post-tensioned precast walls, particularly in comparison with conventional concrete systems. Then, I will describe the analytical wall model that we developed to represent this behavior. I will talk about a detailed parametric study of the lateral load behavior of the walls which we conducted using the wall model. A seismic design approach was developed based on the results of this parametric study. Finally, I will present the seismic response of a series of prototype walls from dynamic analyses.

Finalize design for lateral loads
REMAINING WORK Finalize design for lateral loads Experimental verification (Lehigh Tests) I have divided my talk into five distinct sections. First, I will continue describing the behavior of unbonded post-tensioned precast walls, particularly in comparison with conventional concrete systems. Then, I will describe the analytical wall model that we developed to represent this behavior. I will talk about a detailed parametric study of the lateral load behavior of the walls which we conducted using the wall model. A seismic design approach was developed based on the results of this parametric study. Finally, I will present the seismic response of a series of prototype walls from dynamic analyses.

University of Notre Dame Notre Dame, IN

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