Study On Temperature Effect And Long-Term Temperature Fatigue For Box-Girder Of Concrete Cable-Stayed Bridge

Under temperature change in the sunshine, inner of reinforced concrete box-girder bridge will produce non-uniform temperature field which leads to the appearance of thermal stress field. In the summer day of solar radiation, concrete box girder will appear large temperature tensile stress and temperature compressive stress, if the design is unreasonable, it easily emerges the temperature cracks. Meanwhile, the stress amplitude caused by temperature can not be ignored during the summer day of solar radiation. Currently, most of the studies are about non-uniform temperature field and thermal effect of the bridge, but no further discussion of the effect of temperature stress on the fatigue life of the bridge. It is necessary to study the longterm fatigue effect of temperature stress on bridge.This article is based on the Yingde Beijiang concrete cable-stayed bridge as the engineering background. Depending on the separation model of the total solar radiation intensity by Erbs, it chooses the summer daily average maximum and minimum temperature to establish a two-dimensional box beam section model by a large general finite element software ANSYS, leading to numerical simulation of temperature field of concrete box girder. According to the result of analysis, the moment of the most unfavorable temperature field whose position is below the top of the roof 0.05 m is consistent with the actual data, meanwhile the curve shape of the temperature distribution along the inner web from the top to the bottom matches the index curve shape of the temperature distribution depending on the design specification of China railway bridge. The two conclusions explain that the model can simulate the temperature field of concrete box-girder in summer. According to the results of temperature stress analysis, the article chooses 2 key positions whose temperature stress and stress amplitude are largest. The varied curve of the temperature stress of the key position in the summer day is used as the load spectrum. According to the Miner linear criterion and the fatigue life S-N curve equation of rebar and concrete, the fatigue life of the bridge is analyzed. According to the analysis results, the fatigue performance of fully prestressed concrete beams is superior to that of the finite prestressed concrete beams, and steel corrosion will weaken the fatigue life of concrete bridge.