The Bridge Pounding Analysis Method Using Pseudo Energy Radius Time-Varying Spectrum And Bridge Fragility Analysis

Bridge is one of the most important components of urban lifeline systems. The damage of the bridges in earthquakes may lead to, not only the loss due to the necessary restortion cost of the bridges, but also the loss due to the impact on urban residents’daily trips, assistance activities and urban and regional economy caused by the decreased traffic capacity after an earthquake. The seismic risk analysis, which act as the methodology to quantify the loss, lay its foundation on fragility analysis. However, besides the role it plays in seismic risk analysis, fragility analysis can also help us decide which bridges should be reinforced first and enhance the governments’ability to deal with emergencies. This paper adopt the pushover analysis to carry out the fragility analysis. It is easy to handle and compared with nonlinear time history analysis, it avoid the work from selecting a series of time history of ground motions to conducting complex calculation, thus is less time-consuming. However, it is not applicable to the fragility analysis of irregular bridges and to the situation when the pounding between bridge decks occurs. Thus, the objective in this dissertation is to modify the shortages in the present methodology. The main contents of this dissertation are as follows:1.The theory of pseudo energy radius is introduced and then the concept of pseudo energy radius time-varying spectrum is raised. Also this dissertation gives how a pseudo energy radius time-varying spectrum can be derived from an earthquake evolutionary power spectrum, based on which a methodology to calculate the pounding effects is put forward. The methodology, which can be adopted to calculate the pounding effects between linear single(mutiple)-degree-of-freedom structures, is proper to calculate not only the normal pounding but also the point-to-surface pounding between the bridge decks. The calculation results has an average meaning, which can offer suggestions to designers.2.The pushover analysis is adopted to derive the longitude bridge fragility curves in this dissertation , based on which this dissertation brings up an approach in which a modal pushover analysis will be used for the fragility analysis of irregular bridges. Also an approach based on pseudo energy radius time-varying spectrum is raised to calculate the pounding effects and modify the fragility analysis results of regular and irregular bridges.3.An finite element modal is built in opensees, through which an example is exhibited to explain the procedure to derive the fragility curves of regular and inregular bridges and calculate the pounding effects. Then the relationship between pounding effects and earthquake intensity measure and the gap length between bridge decks is studied.