The Temperature Fields Of Curved Bridges With Steel Box Girder And Their Effects

In the construction of urban infrastructure, the application of the curved steel box girder bridge of small and medium span has become much more universal. Steel material has properties including light weight, low heat capacity and significant temperature expansion coefficient, and consequently, the maximum temperature difference within the bottom of steel box beam could reach roughly 30℃ under sunshine condition,with nonlinear vertical distribution cross the transverse section. Due to nonuniform temperature field, structure weight and offset load from overweight vehicles, the bearing of curved steel box girder bridges tends to be subjected to tension or disengaging, thus causing overturning and requiring specially designed countermeasures. This paper investigates a three-span curved steel box girder bridge located in Hangzhou, China, for the research on temperature field and its effects on this bridge, and the following tasks are carried out:(1) With field measurement and numerical simulation of temperature field of the girder, this paper proposed the temperature field pattern based on the temperature difference of bottom an top beds with an e-based exponential function by fitting.This temperature pattern is then used to make numerical simulations of the disengaging displacement due to temperature variation which are then compared to the measured results. Thus the precision and validity of the derived pattern can be verified.(2) Based on the derived temperature pattern, we analyze the temperature effects on overturning stability of curved steel box girder bridges. Through analysis of the supporting reaction variation under temperature loads, structure weight, and offset vehicle load, we determine the overturning pattern of the bridge with the center line of the two middle bearings as rotational axis, and discuss the designing countermeasure concerning overburden pressure and bearing setup adjustment.Then, apply the method of this paper to other bridges of the same category, evaluate the temperature effects on overturning stability and suggest solutions to the problems.(3) We study the temperature effects on fatigue performance of the curved steel box girder bridge according to the temperature pattern. By using the hot spot stress method, we evaluate the effect of temperature loads on fatigue lifetime of the bridge. We discover that the temperature loads will significantly increase the average stress in the vulnerable parts of the bridge and thus greatly reduce its fatigue lifetime. As a result, we suggest that in the future design and construction of curved steel box girder bridges, such temperature effects on fatigue performance must be thoroughly considered.