Bridge Temperature Profiles Revisited: Thermal Analyses Based on Recent Meteorological Data from Nevada

Abstract

Temperature profiles for bridge design were developed and introduced into current bridge design specifications after soffit cracking in prestressed concrete bridges was attributed to nonlinear temperature distribution through the superstructure depth. The profiles in the specifications are based on average conditions over wide geographical areas of the United States. As a consequence, the desert climate of the southwestern portion of the United States, with high solar radiation and extreme daily temperature differentials, could be expected to cause larger thermal gradients than those recommended in the specifications. In this study, thermal gradients in representative concrete box girder and composite steel bridge superstructures were calculated by heat flow analysis using long-term meteorological data recorded at two weather stations in Reno and Las Vegas, Nevada. This study is believed to be the first to use continuously collected weather data to allow analysis of temperature variation at any point in the season. For both types of superstructures, the calculated temperature difference between the top surface and an internal layer was typically 10°C larger than the corresponding value in the current design temperature profile, suggesting that the current profile is unconservative. Furthermore, for concrete superstructures, the shape of the calculated temperature profile was better represented by a fifth-order curve than the current multilinear thermal gradient. For composite superstructures, the temperature in the steel girder (which was almost uniform over its depth) was significantly higher than that given in the design profile.