Research On Mechanical Behavior Of Box Girder With Corrugated Steel Webs Of Cable Stayed Bridge

The bridge on Zhenshui Road in Xinmi City is the first inclined-tower cable stayed bridge without back stays of box girder with corrugated steel webs in China, which has advanced design concept. The domestic number of similar bridges is relatively fewer, so it is necessary for profound research on its mechanical property.Combined with the related theory, large-scale finite element analysis software was used to establish equivalent beam-cable and solid model of the main bridge. Mechanical property of the main bridge and box girder with corrugated steel webs was studied. The main research contents and conclusions are as follows:Static behavior was studied by establishing equivalent beam-cable model. The results show that the maximum longitudinal displacement locates on the top of the inclined-tower, the maximum axial force locates in the root of the tower. Axial compressive force of the main girder decreases gradually from the location of the main pier to it of the secondary pier. The maximum axial compressive force of the main pier is at the bottom. The cable force peak is less than design value, and its variation is relatively smaller. The main bridge design is reasonable, which reflects superiority of the structure.Dynamic behavior was studied by establishing equivalent beam-cable model. The model was motivated by seismic wave from three orthogonal directions and displacement and internal force response of key nodes in the main bridge were calculated. Auxiliary piers were added to the model to research its impact on the dynamic property of the main bridge. The results show that bending moment peaks of the mid-span node, tower-beam consolidation point and secondary pier-beam consolidation point along three directions decrease significantly. Axial force peaks of three key nodes of the main girder and the top of piers reduce dramatically.Static behavior of box girder with corrugated steel webs was studied by establishing solid model. Vertical shearing stress of corrugated steel webs changes slightly along the height of box girder. Vertical deflection of corrugated steel webs is larger than that of concrete slabs at the same cross section. Concrete slabs undertake some vertical shearing force. Longitudinal strain of corrugated steel webs is extremely small, whose deformation is not in accord with the whole cross section.Based on analysis of the solid model, the main span simplified spatial finite element model of the box girder was established. Unit load was applied on the center of the top slab to calculate critical buckling stress of box girder with corrugated steel webs, which is compared with various buckling stress calculated from theoretical equation. The main geometrical parameter dimensions were changed to study their effect on shear buckling property of box girder with corrugated steel webs. The results show that horizontal length of the straight section shouldn’t be too long in order to prevent the structure from local buckling instability. Enlarging horizontal folding angle appropriately can prevent the structure from global buckling instability, but its design also needs to consider the height of webs. Web thickness should be increased, which can improve buckling resistance of the structure, especially local buckling instability resistance.The main conclusions above can provide certain theory guidance for similar engineering practice in the future.