Cable Forces Optimization And Multi-Support Random Seismic Response Of Cable-Stayed Bridges

With the improvement of structural analysis,the development of construction technology, and the application of high strength material,cable-stayed bridges have gotten a rapid development since the 50's of the 20th century.For the increase in span and the diversity structural patterns,cable-stayed bridges are competitive against suspension bridges in large span.The cable forces in a cable-stayed brige have a critical effect on the distribution of internal force of the girder and tower,therefore are the key factor to control the whole system. How to adjust the cable forces to make the internal forces of a cable-stayed bridge reasonable is significant in the design.Moveover,in recent years,earthquake disasters frequently occurred all over the world,which threatened the safety of life and property.Long span cable-stayed bridges play an important role in the transportation system.If they had been destroyed during an earthquake,the indirect disaster would bring about more losses of life and property.Therefore,it is essential to keep cable-stayed bridges strong enough during an earthquake.This paper concentrates on these aspects of cable-stayed bridges and more detailed research efforts include:1) The numerical procedures of cable forces optimization of cable-stayed bridges are investigated and discussed.An influence matrix method is developed and the minimum bending energy is taken as a goal function,while the allowable bounds of the cable force and the displacements of elements' nodes are taken as constraints.The analysis is easily fulfilled being transformed into a quadratic programming problem.Cable forces optimization of a practical long-span cable stayed bridge is illustrated and compared.2) Based on the pseudo excitation method(PEM),the multi-support random seismic response of a practical cable-stayed bridge(after cable forces ajustment) is performed due to spatial variation effects of the ground motion,which includes the wave passage,incoherence and site response effects.The influeces of cable forces on the seismic responses are also discussed.3) The bridge structural analysis system BPEM of Dalian University of Technology is developed incorporating the optimization program DOT.The module of cable forces optimization has improved the bridge structural analysis system BPEM.