Static Load Test And Travelling-wave Effect On Multi-tower Cable-stayed Bridge With Tie-down Cables

Long-span cable-stayed bridge is one of the most important modern bridge types. As a result of increasing bridge span, deck flexibility and structure complexity, the seismic response analysis of long-span cable-stayed bridge already became one of the most concern problems in bridge engineering field.With the rapid increase of span, multi-tower diagonal cable bridge's stiffness become a Prominent problem.Compare with common cable-stayed bridge,the biggest difference is there's no side cable anchoraging middle tower.It emerge big deviation under load.The middle cross also emerge big deflection.These made cable-stayed more and more flexible.So,the multi-tower diagonal cable bridge which has been built been used some ways to strengthen its overall stiffness.The new type bridge of the multi-tower cable-stayed bridge with Tie-down Cables was performed in this paper.The test and analysis model of the bridge was created by referencing to the actual structure of a Changjiang River bridge. The static mechanical behaviors between the such type bridge and the normal multi-tower cable-stayed bridge was comparatively analyzed by the results of static load test and the finite element analysis. The results showed that the structural system of the cable-stayed bridge with Tie-down Cables can effectively improved the structural rigidity and reduced the bending moment of the main beams, pylons and piers. According to the results, the best scheme about the location and number of Tie-down Cables was proposed in this paper. For the bridge's structural seismic analysis, three keys is the input of earthquake, structure's characteristics and structure's response. Several analysis methods used to calculate the earthquake response of bridges,such as the time-domain approach, the frequency-domain approach, the approximation approach and the mixed approach, are introduced and discussed. The approach of the frequency-domain approach are studied and discussed in this paper.According to the practical bridge data modeling with SAP2000 in this paper, comparative analysis important point of cable-stayed bridge with and without Tie-down cable displacement and force response to find out structure's response under earthquake with tie-down cable by travelling-wave effect and multipoint excitation. Results show that,by travelling-wave effect, the cable-stayed bridge with Tie-down Cables will increase the bending moment of pylons and piers and reduce the bending moment of the main beams; on the the control of the displacement, the cable-stayed bridge with Tie-down Cables will reduce the longitudinal displacement moment of the tower and improve the vertical displacement moment of the main beams;by multipoint excitation, the cable-stayed bridge with Tie-down Cables will increase rapidly bending momentm,shearing force and displacement at important node in the structure.Finally, this paper summarized all the study work and drew some conclusions, besides,the further research problems are indieated.These laws can be used as the basis of seismic design and is useful for directing seismic response analysis of such kind bridge.