Numerical Study on the Effect of Climate Parameters on the Extreme Thermal Gradients in Concrete Box Girders

Abstract

Bridge codes tend to provide general guidance on the thermal gradients acting on bridge decks based on data from historical extreme events that have occurred within a country, without considering the location of the bridge itself. However, the thermal gradient is a function of the climate conditions that occur locally, in the vicinity of the bridge. Thus, a significant number of bridge decks are designed for climate conditions that might not be representative of their locations. The aim of this research is to optimize current guidelines to ensure that thermal gradients are derived based on bridge location. This objective is achieved through the investigation of the relationship that occurs between climate parameters and the resulting thermal extremes. An advanced finite-element platform was used to model the thermal performance of a concrete box girder. Several sets of meteorological data from 18 locations across Canada (representative of different Canadian climate types) were used as input in the thermal models to simulate the temperature distribution within the bridge deck. Upon analysis of the results, it was determined that a correlation exists between the direct normal irradiance (DNI) at a certain location and the resulting thermal differential that occurs between the top and the interior of the cross section. Four categories were defined, with each category representing a range of DNI values and a resulting range of thermal differentials between the top and the interior. To demonstrate the applicability of the established relationship, a case study was performed in which the maximum limit provided by the Canadian Highway Bridge Design Code was investigated across several provinces in Canada.