Evaluation of Pre-stressed Losses in Long-Span Post-Tensioned Bridges

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General Information
Study Number: TPF-5(074)
Lead Organization: California Department of Transportation
Contract Start Date: Apr 01, 2004
Solicitation Number: 772
Partners: CT, ID, NV
Status: Closed
Est. Completion Date:
Contract/Other Number: 59A0420
Last Updated: Jan 13, 2012
Contract End Date: Jun 30, 2011
Financial Summary
Contract Amount: $700,000.00
Total Commitments Received: $80,000.00
100% SP&R Approval: Approved
Contact Information
Lead Study Contact(s): Nathan Newell
nathan.newell@dot.ca.gov
Phone: 916-227-8763
Organization Year Commitments Technical Contact Name Funding Contact Name Contact Number Email Address
Connecticut Department of Transportation 2004 $5,000.00 James Sime 860-258-0309 james.sime@ct.gov
Idaho Department of Transportation 2004 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2005 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2006 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2007 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2008 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Nevada Department of Transportation 2004 $25,000.00 Alan Hilton

Study Description

Post-tensioned box girder bridges are one of our most economical highway design solutions. In 2000, Caltrans began construction on 35 structures of this type, totaling over $88M in construction costs. In the new AASHTO LRFD Specification, the lump sum approximate method for evaluation of losses only applies to spans less than 160 ft (50m), and the refined method for spans less than 240 ft (75m). Research is needed to either confirm the application of these methods to boxgirders and segmental bridges with longer span lengths and higher concrete strengths, or suggest an alternative. If losses in any bridge are over-estimated, excessive camber and improper drainage could result. If losses in the same structures are under-estimated, stresses will be underestimated, and cracking could be excessive - even to the point of failure. If designers must individually investigate this topic for each bridge designed, production will decrease.

Objectives

The overall reearch objective is to asess the time-dependent lump sum and refined prestress loss estimates based ont he current AASHTO LRFD Bridge Design Specifications [3]. Previous or more recent research that shows promise will be reviewed. Changes to the current lump sum and refined prestress loss models will be suggested, if necessary, for application to cast-in-place post-tensioned bridges. The prestress loss models should be assessed by means of long-term field measurements and computer time-step analyses of cast-in-place post-tensioned box girder bridges.

Scope of Work

1) Review previous work, and NCHRP 18-07 "Prestress Losses in Pretensioned High-Strength Concrete Bridge Girders". This effort would in essence repeat 18-07, but for post-tensioned rather than prestressed superstructures.

2) Summarize and comment on current methods for estimating losses in post-tensioned bridges, as they apply to boxgirders, segmental structures, post-tensioned structures that utilize high-strength concrete, and span lengths in excess of present limitations in the AASHTO LRFD Specification.

3) Field-measurements: The study of cast-in-place post-tensioned concrete must be executed in partnership with construction contractors. Measurement devices would be embedded prior to concrete placement. Data would be collected after stressing, dropping of falsework, placement of barriers and wearing surface, and periodically once in service, for two-to-three years. Field measurements will be compared to both approximate lump-sum estimates and those using refined methods per the AASHTO LRFD Specifications, plus any alternative proposed method, for at least three (3) structures of various span lengths.

4) Make design recommendations in the form of proposed changes to the AASHTO LRFD Specifications.

Subjects: Bridges, Other Structures, and Hydraulics and Hydrology

Documents Attached
Title File/Link Type Private Download
Quarterly Report: July - September 2005 3rd_qrtr_rpt_05.pdf Quarterly Progress Report Public
Quarterly Report: April - June 2009 quarterly_report_2009-06-30.pdf Quarterly Progress Report Public
Quarterly Report: January - March 2011 59A0420-3rd QT FY 10-11 Jan 11 - Mar 11.pdf Quarterly Progress Report Public
Quarterly Report: April - June 2010 quarterly_report-Apr-Jun-2010.pdf Quarterly Progress Report Public
Quarterly Report: July - September 2010 quarterly_report-Jul-Sep-2010.pdf Quarterly Progress Report Public
Quarterly Report: October - December 2010 quarterly_report-Oct-Dec-2010.pdf Quarterly Progress Report Public
A Simplified Method for Prediction of Long-Term PreStress Loss in Post-Tensioned Concrete Bridges ssrp_06-21.pdf Report Public

Evaluation of Pre-stressed Losses in Long-Span Post-Tensioned Bridges

General Information
Study Number: TPF-5(074)
Lead Organization: California Department of Transportation
Contract Start Date: Apr 01, 2004
Solicitation Number: 772
Partners: CT, ID, NV
Status: Closed
Est. Completion Date:
Contract/Other Number: 59A0420
Last Updated: Jan 13, 2012
Contract End Date: Jun 30, 2011
Financial Summary
Contract Amount: $700,000.00
Total Commitments Received: $80,000.00
100% SP&R Approval:
Contact Information
Lead Study Contact(s): Nathan Newell
nathan.newell@dot.ca.gov
Phone: 916-227-8763
Commitments by Organizations
Organization Year Commitments Technical Contact Name Funding Contact Name Contact Number Email Address
Connecticut Department of Transportation 2004 $5,000.00 James Sime 860-258-0309 james.sime@ct.gov
Idaho Department of Transportation 2004 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2005 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2006 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2007 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Idaho Department of Transportation 2008 $10,000.00 Matt Farrar Mike Santi 208- 334-8450 mike.santi@itd.idaho.gov
Nevada Department of Transportation 2004 $25,000.00 Alan Hilton

Study Description

Study Description

Post-tensioned box girder bridges are one of our most economical highway design solutions. In 2000, Caltrans began construction on 35 structures of this type, totaling over $88M in construction costs. In the new AASHTO LRFD Specification, the lump sum approximate method for evaluation of losses only applies to spans less than 160 ft (50m), and the refined method for spans less than 240 ft (75m). Research is needed to either confirm the application of these methods to boxgirders and segmental bridges with longer span lengths and higher concrete strengths, or suggest an alternative. If losses in any bridge are over-estimated, excessive camber and improper drainage could result. If losses in the same structures are under-estimated, stresses will be underestimated, and cracking could be excessive - even to the point of failure. If designers must individually investigate this topic for each bridge designed, production will decrease.

Objectives

The overall reearch objective is to asess the time-dependent lump sum and refined prestress loss estimates based ont he current AASHTO LRFD Bridge Design Specifications [3]. Previous or more recent research that shows promise will be reviewed. Changes to the current lump sum and refined prestress loss models will be suggested, if necessary, for application to cast-in-place post-tensioned bridges. The prestress loss models should be assessed by means of long-term field measurements and computer time-step analyses of cast-in-place post-tensioned box girder bridges.

Scope of Work

1) Review previous work, and NCHRP 18-07 "Prestress Losses in Pretensioned High-Strength Concrete Bridge Girders". This effort would in essence repeat 18-07, but for post-tensioned rather than prestressed superstructures.

2) Summarize and comment on current methods for estimating losses in post-tensioned bridges, as they apply to boxgirders, segmental structures, post-tensioned structures that utilize high-strength concrete, and span lengths in excess of present limitations in the AASHTO LRFD Specification.

3) Field-measurements: The study of cast-in-place post-tensioned concrete must be executed in partnership with construction contractors. Measurement devices would be embedded prior to concrete placement. Data would be collected after stressing, dropping of falsework, placement of barriers and wearing surface, and periodically once in service, for two-to-three years. Field measurements will be compared to both approximate lump-sum estimates and those using refined methods per the AASHTO LRFD Specifications, plus any alternative proposed method, for at least three (3) structures of various span lengths.

4) Make design recommendations in the form of proposed changes to the AASHTO LRFD Specifications.

Subjects: Bridges, Other Structures, and Hydraulics and Hydrology

Title File/Link Type Private
Quarterly Report: July - September 2005 3rd_qrtr_rpt_05.pdf Quarterly Progress Report Public
Quarterly Report: April - June 2009 quarterly_report_2009-06-30.pdf Quarterly Progress Report Public
Quarterly Report: January - March 2011 59A0420-3rd QT FY 10-11 Jan 11 - Mar 11.pdf Quarterly Progress Report Public
Quarterly Report: April - June 2010 quarterly_report-Apr-Jun-2010.pdf Quarterly Progress Report Public
Quarterly Report: July - September 2010 quarterly_report-Jul-Sep-2010.pdf Quarterly Progress Report Public
Quarterly Report: October - December 2010 quarterly_report-Oct-Dec-2010.pdf Quarterly Progress Report Public
A Simplified Method for Prediction of Long-Term PreStress Loss in Post-Tensioned Concrete Bridges ssrp_06-21.pdf Report Public

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