TxDOT Bent Cap Research
2
DEVELOPMENT OF STRONG AND SERVICEABLE DETAILS FOR PRECAST, PRETENSIONED BENT CAPS PROJECT OVERVIEW SHEAR AND MOMENT DEMANDS The bent is isolated at inflection points in the cap and exterior column to create the test specimen. The specimen loading is able to create shear and moment demands similar to the prototype. The specimen has a bent cap length of 16 ft and a column height of 8 ft. RESEARCH TEAM Faculty Advisors: Graduate Research Assistants: Undergraduate Student Workers: Dr. Anna Birely (PI) Usha Rani Barooah Nick Danney Dr. John Mander Judong Lee Bryce Martin Kevin Yole Josh Ortiz Benito Soto Sponsored by Texas Department of Transportation, Project 0-6863 PROTOTYPE The prototype bridge is a TxDOT standard I-girder bridge of 66 ft average span length and 40 ft roadway width, similar to the bridge in the photo above. Actuator simulating shear at inflection point Actuators simulating girder loads The use of precast bent caps provide the opportunity for faster construction and increased worker safety. However, the benefits of prestressing for improving strength and serviceability of precast bent caps are still unrealized. This project will develop design recommendations for pretensioned bent caps and demonstrate improved strength and serviceability through experimental testing. The project will also explore the use of a pocket connection (21 inch diameter pipe filled with concrete) between the bent cap and the column in order to improve constructability and interior voids to reduce the weight of the bent caps during transportation and construction. The AutoCAD 3D rendition shows the experimental setup. The two reaction frames provide horizontal stability. The two top vertical actuators represent girder loads. The bottom actuator represents the shear at the point of inflection. Instrumentation will be installed to monitor the strain and displacements during testing. EXPERIMENTAL SETUP
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Transcript of TxDOT Bent Cap Research
DEVELOPMENT OF STRONG AND SERVICEABLE DETAILS FOR PRECAST, PRETENSIONED BENT CAPS
PROJECT OVERVIEW SHEAR AND MOMENT DEMANDS
The bent is isolated at inflection points in the cap and exterior column to create the test specimen. The specimen loading is able to create shear and moment demands similar to the prototype. The specimen has a bent cap length of 16 ft and a column height of 8 ft.
RESEARCH TEAMFaculty Advisors: Graduate Research Assistants:
Undergraduate Student Workers:
Dr. Anna Birely (PI)
Usha Rani Barooah Nick Danney
Dr. John Mander Judong Lee Bryce Martin Kevin Yole Josh Ortiz Benito SotoSponsored by Texas Department of Transportation, Project 0-6863
PROTOTYPE
The prototype bridge is a TxDOT standard I-girder bridge of 66 ft average span length and 40 ft roadway width, similar to the bridge in the photo above.
Actuator simulating shear at inflection point
Actuators simulating girder loads
The use of precast bent caps provide the opportunity for faster construction and increased worker safety. However, the benefits of prestressing for improving strength and serviceability of precast bent caps are still unrealized. This project will develop design recommendations for pretensioned bent caps and demonstrate improved strength and serviceability through experimental testing.
The project will also explore the use of a pocket connection (21 inch diameter pipe filled with concrete) between the bent cap and the column in order to improve constructability and interior voids to reduce the weight of the bent caps during transportation and construction.
The AutoCAD 3D rendition shows the experimental setup. The two reaction frames provide horizontal stability. The two top vertical actuators represent girder loads. The bottom actuator represents the shear at the point of inflection. Instrumentation will be installed to monitor the strain and displacements during testing.
EXPERIMENTAL SETUP
Pocket Connection
Bent capColumn
Corrugated Pipe
Dowel bars
Test Matrix
Specimen Description
1: RCS-16-12 Reinforced concrete for comparison
2: PSS-16-12 Design for prototype bridge
3: PSS-16-24 Less shear reinforcement
4: PSV-16-12 Hollow cross-section for reduced weight
5 T.B.D.
6 T.B.D.
Void Section
Solid Section
In the lab now!
Plan view with misalignment
• A pocket is a large void formed in the bent cap by a corrugated pipe.
• The pocket in the bent cap fits over 6-#11 dowel bars extending from the column.
• Once the bent cap is in place, the void is filled with concrete to complete the connection.
• Pipe acts as confinement and shear reinforcement for joint shear demands.
• Large diameter of the pocket accommodates accidental misalignment of columns.
Placing cap on column
Filling Pocket with ConcreteThe specimen is painted to assist in identifying cracks. The pocket concrete is painted blue.
