The Seismic Response Analysis Of Long-Span Composite Beam Cable-Stayed Bridge

In this paper,optimization of dead load cable tension and seismic response analysis of a cable-stayed bridge were investigated by the engineering background of Wangdong Yangtse River Bridge,which is the China's longest cable-stayed bridge with composite beam.Dynamic analysis was processed.Both response spectrum and time history analysis to the bridge had been done.The main work was as follows.(1)The development history of the cable-stayed bridge with concrete-steel beam was reviewed firstly,it was concluded that this kind of bridge had a better static and dynamic performance than the steel and concrete cable-stayed bridge.The seismic response analysis of long-span cable-stayed was of great significance in reality,and a summary of several major analytical methods had been done.In order to get a precise result,the applicable condition of each method should be considered.(2)A finite element model of the Wangdong Yangtse River Bridge was established in ANSYS,allusion to the chararacteristics of a combined girder with concrete plate and steel webs.Different types of element were employed according to the mechanical characteristics of three basic members: towers,cables and girders.(3)Zero displacement method,minimum bending strain energy method and first order method were applied to the optimization of dead load cable tension.The first order analysis method-an effective method,with more comprehensiveness,and better distribution of internal force were showed in result.(4)Fixed model and lumped-mass-model had been analyzed and compared in this paper,it had been concluded that the pile-soil-structure interaction had significant influence on the dynamic characteristics.(5)Response spectrum analysis of the cable-stayed bridge had been done,by inputting response spectrum curve along the longitudinal,transverse and two type of combined ground motion(longitudinal and vertical,transverse and vertical).It was indicated that vertical earquake had a considerable effect on the axial force,longitudinal moment and displacement.(6)The result of the geometrical nonlinear time history of the bridge showed that the longitudinal seismic response of cable-stayed bridge was the critical factors of anti-seismic design,and vertical earquake should be taken into consideration.The structural internal force time history and displacement time history had also showed that,the cable-stayed bridge was one kind of long-period structure.(7)The soil-pile interaction was equivalent to a serious of springs placed in parallel based on “m” method.The effect of pile-soil-structure interaction on Wangdong Yangtze River Bridge was investigated in time-history analysis.It was showed that the dynamic response of the tower may be underestimated.(8)The seismic response reduction of Wangdong Yangtze River Bridge by adding fluid viscous dampers was invested.The main analysis is the parametric sensitivity of damping coefficient.The investigation indicated that the adding fluid viscous dampers can significantly reduce the structural displacement response as well as the tower moment.