Thermal field characteristic analysis of steel box girder based on long-term measurement data

Thermal loads are important factors that affect the serviceability of long-span bridges. In this paper, the distribution characteristics and statistical features of thermal field in flat steel box girder are presented based on long-term field measurement data collected by the structural health monitoring system (SHMS) permanently installed on the Runyang Suspension Bridge (RSB). Firstly, the daily variations as well as seasonal ones of measurement temperature and temperature differences in the box girder cross-section are summarized. Secondly, employing a combined probability distribution model defined by the weighted sum of one Weibull distribution and one normal distribution, the probability density function (PDF) of each temperature difference is formulated. Thirdly, making use of the extreme value analysis, the extreme temperature differences are predicted with a return period of bridge design working life and compared with the expected values in British standard (BS EN 1991-1-5, 2003). Finally, the critical temperature difference models in cross-section are proposed for thermal stresses calculation according to correlation analysis. The results provide a clear understanding of thermal field in flat steel box girder bridges and have reference values for structural design and evaluation.