Research On The Seismic Performance Of Bridge With High Piers And Long Spans Using Incremental Dynamic Analysis

In recent years, many earthquakes occurred in the western areas of China, which have resulted in the damage of many bridges, causing the seismic research workers pay close attention to it. Located in the mountains, and with the influence of topography and other factors, the bridges in the western areas of China presented the characteristics of long spans and high piers. Those irregular bridges are beyond the range of the current seismic design code at home and abroad, for example, the Guidelines for Seismic Design of Highway Bridges (JTJ/T B02-01-2008) applied to the bridges the pier height of which are less than40m and a span of which are less than150m.The seismic responses of irregular bridges with high piers are quite different from the traditional regular bridges, but most of the existing achievements at home and abroad are built on the basis of the low pier bridges, and researches on the bridges with high piers can’t catch up with the need of Practical Engineering. Based on this background and hunan province science and technology plan (Number2011FJ3242), combined with performance-based seismic design ideas, the seismic performance researches on the high pier bridge structures by the mean of Incremental Dynamic Analysis are carried out. Generally speaking, the main contents and conclusions are as follows:(1) In this article, a large number of domestic and foreign literature are consulted, and the seismic design theory development history of the bridges is reviewed, then the theory of the performance-based seismic design and the current seismic research on irregular bridges with high pier are summarized; and most important, the basic framework and mentality of the seismic performance assessment based on the IDA are formed.(2) Taking a continuous rigid frame bridge for example, the elastic-plastic finite element dynamic analysis model is built using the software of OpenSees.(3) First, through the incremental dynamic analysis of the structure of single vibration, this paper gains stress-strain hysteresis curve of concrete, steel bars under the action of earthquake stress; By means of the various performance parameters of the response curve and single vibration IDA curve, studies the damage indicators applying to high pier structures. The research illustrates that the control section curvature can soundly measure damage states of high pier structures.(4) Selects15ground motion records from the database of the Pacific earthquake research center (PEER) to perform the incremental dynamic analysis, forms IDA-based seismic performance evaluation curves and risk assessment curves, and evaluates structural seismic performance from many different perspectives. The results show that the incremental dynamic analysis is an effective evaluation method of seismic performance of the structure, and IDA-based assessment curves can clearly reflect the structural seismic performance.(5) Points out the limitation of traditional formulas of the displacement, studies the process of the formation of the plastic hinges of high pier structures and the calculation method of the plastic area length; based on the characteristics of the maximum curvature distribution of high piers within seismic cycle, proposes calculation formula that suits displacement curves of high piers. The results demonstrates that the formation of plastic hinges in high pier structures is in accordance with that of traditional low piers, the plastic hinge length can apply the equivalent calculation formula of the plastic hinge length within low piers, the proposed displacement calculation formula is identical with the results of practical IDA analysis.