Agency TRANSPORTATION DEPT

Contractor University of Minnesota

SWIFT Contract Number 63675

Project Name Effect of temperature on PC strand stress during c

Project Number (if applicable) 99008w102

Summarize purpose of the contract, including why it was necessary: During fabrication of prestressed concrete bridge girders, the strands are pretensioned in the precasting bed prior to casting the concrete. Because the beds are fixed length, changes in temperature affect the mechanical stress in the strands. Currently, the strand stress is adjusted during tensioning to account for the difference in temperature between strand pull and the temperature of the concrete at placement. It is believed that temperatures may increase to the hydration temperature (e.g., 160 degrees Fahrenheit) prior to bonding. The implication is that the strand may undergo larger losses in prestress, prior to bonding, that currently are not accounted for in design. The purpose of this project is to determine the losses associated with thermal effects during girder construction. The project involves instrumentation of prestressed girders during construction with thermistors and strain gages to separate the thermal and mechanical strain components. In addition, segments of girders may be cast and detensioned at early ages to try to determine the time at which bonding occurs with the strand. Variables to be investigated in the study include the difference in temperature between strand pull and bond.

Project Duration

Start Date Sun, 06/14/2015 - 00:00

Original end date Thu, 12/31/2015 - 00:00

Actual end date Thu, 12/31/2015 - 00:00

Did project finish on time? Yes

Total billable hours utilized (if applicable) {Empty}

Contract Amounts

Original contract: $132345.00

Amendments $0.0

Contract total $132345.00

Did project finish within budget? Yes

What was the funding source? State Research Program & Federal Funds

Is this a sole source contract? No

If this was a single source contract, explain why the agency determined there was only a single source for the services (if applicable) {Empty}

Evaluator Name Dave Dahlberg

Evaluator Email Address Dave.Dahlberg@state.mn.us

Evaluate the contractor's timeliness Satisfactory

Evaluate the contractor's quality High quality

Evaluate the contractor's cost Satisfactory

Evaluate the contractor's overall performance Satisfactory

Would you engage the contractor's services again? Yes

Describe any negative action taken during the duration of this contract (i.e., termination, pursuit of suspension, etc.): None

Please rate the overall experience with the contractor 4 - satisfied