, FY 1999, "Thermal Movement Design Procedure for Concrete" (Charles Roeder). Bridges expand and contract due to temperature change. Engineers accommodate this movement with bearings and expansion joints or by deformation of the backfill, piers, and abutments with integral construction. It is important that the magnitude and direction of the design movements be predicted with reasonable accuracy, because extremely large forces can occur if movement is restrained. These forces may lead to severe damage if movement is not properly accommodated through joints and bearings or some form of integral construction. Thermal movements control the design of bearings and expansion joints, and these movements have a significant impact on the economy of the bridge design.
The existing provisions for thermal movement design in the LRFD Bridge Design Specifications were adopted from the AASHTO Standard Specifications for Highway Bridges
. The provisions in this latter document date from the earliest publication of the standard specifications in 1931. The US is divided into two climate zones in these provisions, but no guidance is provided as to what regions of the country constitute cold or mild climates, and no guidance is provided as to how the installation temperature should be defined. Recently a study was completed on the thermal design of steel bridges that provides contour maps for determining design temperatures and rational design equations for installation temperatures and design movements. These new provisions for steel bridges are being considered for adoption by AASHTO.
The objective of this study was to develop contour maps for establishing design temperatures in concrete bridges and design guidelines for determining installation temperatures and design movement for bearings and expansion joints in concrete bridges. The project panel has accepted the final report on this work. Subsequently, data collected outside the NCHRP program was used to supplement the original report. The final report can be downloaded HERE
. (NCHRP Staff: D.B. Beal)