Research On The Relation Between The Binds And Seismic Response Of Long-span Suspension Bridge And Push-over Analysis Of The Tower

Suspension bridge is one of the optimal selections of long-span bridge. There is no case that the suspension bridge was destroyed in the earthquake before, but partially damaged frequently. AiZhai Bridge is different from the general suspension bridges because one of the two towers of AiZhai Bridge is approximately double to the other, so do the side spans. And the stiffening girder isn't bound to the towers. It is worth to make further study on the effect of suspension bridge seismic performance that caused by the joint of the suspension bridge. Taking the AiZhai Bridge as the sample, the seismic performance is studied in this thesis. The main research work is summarized as follows:1. This thesis introduces the seismic design theory, especially the displacement-based seismic design philosophy and earthquake-resistant appraisal based on the static push-over analysis. The program named FDXLX.FOR is compiled according to the segmented catenary theory, which is used to calculate the main cable line shape and the initial strain. Accurate coordinates and initial stress of the fulfilled bridge are obtained through the associative calculation of the program and the common structure analyses procedure ANSYS. The computed model is created for the seismic analysis.2. The influence on the dynamical character of the stiffening girder, main cable and towers caused by the center buckle is analyzed. The dynamical character of the bridge in the condition of no central buckles, flexible central buckle and rigid central buckle is checked. Parametric analysis is deduced of the area of the oblique cord of the flexible central buckle and the initial rigidity. And the effect on the seismic response due to the buckle is studied.3. The effect on the natural vibration frequencies, the displacement and the internal force of the main section of the bridge due to the rigidity of the end flexible fixing of the stiffening girder are studied systematically. The results indicate that the longitudinal drift frequency of the stiffening girder is in linear relationship with the Brigg's logarithm of the rigidity of the flexible fixing when the latter is between 4×106N/m and 4×109N/m. Suitable end binds of the beam can reduce the end displacement of the beam in the earthquake largely, which take little effect on the displacement on the tower and inner force. 4. The effect on the dynamic response of the bridge is compared due to the vertical earthquake and the traveling-wave effect. It is shown that the former causes the increase of the vertical displacement at midspan and the latter leads to the increment of displacement on the top of the tower. Both should be considered in the course of the seismic analysis of the suspension bridge.5. The transversal static push-over of the tower is analyzed for the first time. The curve on the top transversal displacement of the tower and the total horizontal shear force are obtained to invert to the energy spectrum. The design acceleration spectrum according to the Vidic model is reduced to getting the inelastic demand spectrum, and then the earthquake-resistance performance is evaluated.