Seismic Response And Stability Analysis Of Long-Span Truss Cable-Stayed Bridges

In China, earthquake zone are widespread and more earthquakes happened. The bridge engineering have an important part in traffic engineering,which as the throat of traffic. Once the birdge engineering damaged in the earthquakes, it will lead to another huge lost. Only if we recognize the long-span bridges response which is under the earthquake effect, we can reducing the effect of earthquakes on bridge and carry out the seismic design as better as we can. So researching on the large span bridges’seismic response has a very important significance.This paper take Tongling Yangtze river bridge as example to analysis the the bridge seismic response. The cable-stayed bridge have a great advantage, which span in the range of400m to1000m. This structures usually use floating or semi-floating system, and there are not binding on the longitudinal direction, which make the stucture has a longer first-order vibration period. Such structures can use its own swing to dissipate energy, which also can reduce the seismic response of the main tower. However, due to its special boundary conditions, its main beam will have a greater longitudinal displacement under the external force. Lacking of effectively design will lead to large collisions between the main bridge and the approach span. So in engineering, we also set dampers between the tower and the beam to reduce the beams’longitudinal displacement.It is difficult in long span bridge’s construction. Construction of state structural stability is also an important part. Analysising of structural stability correctly and avoiding unreasonable design can provide a reference to stuctures construction.This paper take the cable-stayed bridge whose main span is630m as an example, to analysis the stucture’s seismic response, and analysis its stuctural stability.The paper’s main work are:(1) Describes the way of creating the finite element model. Take the software ANSYS as a tool, to introduce the key parts of stucture into finite element modeling, such as caisson foundation and pile foundation;(2) The paper analysis this bridge dynamic behavior by taking pile foundation into consideration, for the long span bridge’s seismic design. From the result we can see that the pile-soil-structure effect on the seismic response of structures have non-negligible impact. Whether to consider the pile-soil-structure interaction effects, depending on the construction site geological conditions and other factors.(3) The quality of modal participation factor is important for the modal superposition method. Using the single point spectrum analysis method for the bridge’s seismic response. As the cable-stayed bridges’the first vibration period is longer, which is beyond the use of standardized response spectrum, so in this paper we discusses some correction of standardized response spectrum. Using this correction method, we calculate the bridge response spectrum.and compared the result with the results of single point response spectrum.(4)Doing the dynamic time history anlasis, and compare the result with the single point spectrum analysis’s result. Considering the traveling wave effect, and analysising structure’s response by different seismic velocity.(5) Analysis the stability of the bridge at the different Construction period, such as Single-tower status, the double cantilever state, the single-cantilever state, Operating state. To provide a reference for construction safety.