Seismic Analysis Of Long-span Bridges Subjected To Multi-component And Multi-support Earthquake Excitations

The seismic behavior of long-span bridge (LSB) under multi-support excitations is the focused problem in engineering and academic area. Several factors, such as characteristic, propagation process, environment, lead to the situation that there are not reasonable ways to input seismic waves to LSB. Therefore, it is meaningful to conduct the research about the input mode of seismic waves and its influencing factors. Theoretical knowledge of multi-support excitations and the method about how to select reasonable numerical model are mainly studied in the paper. And the effects that are taken by simple-support excitation in one-way, multi-support excitations in one-way, simple-support excitation in multi-way, multi-support excitations in multi-way of LSB are mainly discussed in the paper. In addition, two main factors that influence multi-support exaction are briefly introduced in the paper: one is the select of seismic waves, the other is wave velocity. The method and conclusions are as follows:1 The cause of seismic damage of LSB are discussed and summarized, and the research status of influencing factors of multi-support excitations is introduced.2 Three important factors---input mode of seismic waves, numerical mode and solution method of equations are elaborated in detail.3 The computational and refined model of Niulanjiang Bridge are built with the finite element software ABAQUS, and the dynamic analysis of Niulanjiang Bridge is conducted, and then compare the results with measured data in order to get the advantages and disadvantages and application scope of two methods.4 The refined model of Niulanjiang Bridge is built, and then the seismic response analysis under different situations is conducted: simple-support excitation in one-way, multi-support excitations in one-way, simple-support excitation in multi-way, multi-support excitations in multi-way. Additionally, the influence of the selection of seismic waves and velocity are discussed.The conclusions are as follows after analysis: the easier of the model, the smaller number of elements, and the less of cost calculation. The stable results can be got but not exact. This is the first process of qualitative analysis; if the model is complex, there will be a large number of elements and higher cost calculation, and the computational process is unstable. But the results are relative precise, and can be used in local analysis or global analysis; the displacement and bending moment are bigger under multi-support excitations than under simple-support excitation; the displacement and bending moment are bigger in multi-way than in one-way. The influence is different under different seismic waves, and the conclusion of seismic behavior of LSB under various seismic waves is the same with single seismic waves. The difference of seismic behavior of LSB under seismic waves with different velocity is noticeable different.