Thermal response in Florida bridges

Reinforced and prestressed concrete bridges are subjected to non-linear temperature
variations leading to complex thermal stresses which vary continuously with time. Though
these stresses are often comparable with those produced by live and dead loads, little
guidance is given in bridge design codes on how these stresses are accurately computed.
The objective of this project is to study the response of Florida bridges in the extreme
thermal environment The project is divided into the following four tasks
i) Computer modeling of the bridge and estimation of the thermal response.
ii) Field measurements of temperatures in typical bridges.
iii) Comparison of observed and estimated data.
iv) Suggestions and/or revisions to the existing thermal stress allowances in the code.
A computer software FETAB was used to model and analyze the thermal response
of several bridge cross sections. Two single cell box girder bridges, located at the 1-595
and US-441 interchange, Fort Lauderdale, were instrumented with thermocouples and
vibrating wire strain gages. The predicted temperature variations were found to compare
fairly well with those measured in the field. Though the analytical values vary a little from
the actual field data, emphasis was given to gain insight into the problems associated with
the thermal effects in concrete bridges. Suggestions were made for revision of existing
design code provisions for improved design of bridges.