Displacement-based Seismic Design Method Research On High-speed Railway Continuous Girder Bridge

ABSTRACT:In recent years, the high-speed railway has obtained a rapid development in China. Bridges are taking a bigger percentage of the total length of railways being built whose proportion has reached70%-80%. Since China is a frequently earthquake-attacked nation, seismic response analysis and seismic design research of high-speed railway bridges is becoming very important. In recent decades, examples of earthquake disasters at home and abroad tell us the thought of seismic design that is simply to ensure the safety of lives as the goal and the method based on the strength can no longer apply the new era requirement with the development of our society. The thought of performance-based seismic design is the emphasis of researchs in current field of engineering all over the world. However, results of the study are not widely used in practice or the codes. Nowadays, the railway bridges are designed in terms of Code for Seismic Design of Railway Engineering which has only three levels of seismic requirement. The code does not have specific divisions of performance target levels or the criterion of quantitative indicator, which belongs to the category of seismic method based on the strength. It is imperative to come up with the seismic design method which is suitable for our country’s high-speed railway bridges.In this paper, we take the5-span high-speed railway continuous girder bridge in Tianjin-qinghuangdao passenger dedicated line as the research object. Based on the bridge’s response law and previous research results, the article divides the performance target levels of high-speed railway bridges more specificly with bearing’s damage grade and pier’s displacement ductility coefficient, proposes the seismic design method based on displacement of high-speed railway bridges. So the thought of performance-based seismic design integrates in seismic design of high-speed railway bridges. Main contents and conclusions of seismic studies include:1. Build the finite-element model of5-span high-speed railway continuous girder bridge in SAP2000.2. Seismic effect discipline in longitudinal and lateral directions of the bridge in different earthquake levels are researched.3. Stress contour of the pier’s bottom is studied under different earthquake levels and we get their distribution shapes. The gradients are contrasted and analysed, they are small. Therefore, we are enabled to regard stress contour of the pier’s bottom as a distribution shape of a flat line. In other words, the stress and strain obeys the plain section assumption theory and we choose plastic hinge model to simulate piers’seismic response is feasible.4. Six different seismic performance levels are divided by bearings which have three damage grades according to the definitions and pier’s damage index. Each seismic performance level has its own quantitative indicator requirement.5. Since piers’hysteric energy of high-speed railway bridges is small, the paper suggests a simplified the formula of damage index proposed by Park-Ang, which only use the displacement part.6. The paper proposes the seismic design method based on displacement of high-speed railway continuous girder bridges and gives an engineering design example.