Analysis Of Earthquake Failure Mode And Global Seismic Capacity For Steel Moment Frame Stuctures

The failure process and global seismic capacity of structures are importantparts of the performance-based earthquake engineering. The failure modes ofstructures can reflect the failure development process and provide a clear directionto improve the global seismic capacity, making the structures meet the appropriateperformance goals under different intensity earthquakes and reduce the loss oflives and property as much as possible. Failure mode of structure is of greatsignificance, and with steel frame structures as the object and the failure modes asthe core, this article concentrated on evaluation methods of structural seismicperformance, the method of analyzing failure development process, theidentification of the structure failure modes and the measures to improve theglobal seismic capacity of structures. The research contents of this article are asfollows:(1) Endurance time method (ETM) is a dynamic time history-based approachfor structural seismic response analysis, which has the characteristic that theground motion intensity increases with time and can be described as ’dynamicPushover analysis’. Endurance time accelerations (ETAs) are developed based onthe Chinese code response spectrum, and ETAs are employed as seismic input of asteel moment frame to evaluate the seismic performance. The structural globalresponse for ETM was assessed based on incremental dynamic analysis (IDA).Using both real ground motions and ETAs as input, the probability of occurrence,yielding sequence and rotation ductility ratio for plastic hinges, is compared. Theinner storey capacity curves of IDA, ETM and Pushover are compared. The resultsindicate endurance time method, has an excellent potential to predict the nonlinearresponse of steel moment frames, which provides a novel approach to quicklyanalyze and evaluate the seismic performance of steel moment frames.(2) The analyzing model updating method sets that the component endshappen bending failure when the end rotation reaches the ultimate rotation andbetween the analysis steps the constraint of bend failure component end isremoved. Using the OpenSees platform, statically indeterminate concept andgeometric constraints analysis are employed to judge whether a structure indynamic analysis becomes a statically indeterminate system. Using real groundmotions, the statistical analysis of structure failure modes and global seismiccapacity analysis are carried out, in which the statically indeterminate criterion isemployed as the structure failure criterion. The results can describe thecharacteristic of the failure mode, which can provide the basis to improve the seismic performance.(3) Based on the concept of uniform damage, a process to achieve theautomatic optimization for the structure in dynamic analysis is developed with theoptimization criterion method using OpenSees platform. Using both real groundmotion and artificial ground motion as input, the optimization processes areimplemented and the effects of optimization are verified. Besides, using ETA asinput, the optimization processes and effect verification for structures in ultimatestates are operated. The results indicate that the process can be used to improve theglobal seismic performance of the structures.