Study On Analytical Method Of Aseismic Performance Of Light Steel Frame Structure

The light steel frame structure with characteristic of good performance and light self-weight is highly receipted by the designers for its merits. The government also approbates the structure system for its energy conservation and environment protection. Because it has these advantages, The light steel frame structure is widely used abroad. And it is spread in our country. Based on the achievement of previous researches, this dissertation focused on the pushover analysis method, weakening section, lateral load, time-history analysis and the capacity spectrum method. The paper emphasized on analytical method of evaluating the structure's aseismic capability. Two approaches, elastic time-history analysis method and static elasto-plastic analysis method, are used in the article. The dynamic analysis method is operated with the Drain-2dx ; the static analysis method is carried out with SAP2000 finite-element software.The recent applications and the developments of pushover analysis were concisely remarked. Several applied methods of pushover analysis to light steel frame seismic performance evaluation and design were summarized.The frame structure linkage model dynamic elasto-plastic time-history analysis program, Drain-2dx, has several features. It is applicable for specially shaped beam frame structure. According to the input function code, it can be used to carry out static elastic analysis, dynamic elastic time-history analysis and dynamic elasto-plastic time-history analysis. It can generate several important files which can be used to evaluate the frame structures aseismic capability, such as inter-floor displacement peak value, acceleration peak value, top layer displacement (relative to bottom-bed) peak value.The capacity spectrum method procedure, the improved capacity spectrum method proposed by Chopra and their comparisons were introduced. The aseismic capability of some examples had evaluated by capacity spectrum method. Two frame structures of 6 and 9stories as the examples are studied. And three earthquake records are selected to calculate the structural seismic response. Taking the results of nonlinear time history analysis as the reference, which can provide the more realistic results for the given earthquake records, the respective estimate results using capacity spectrum method, displacement coefficient method and adaptive spectra-based pushover procedure are compared in detail. Then some valuable conclusions are drawn that: Inelastic static push-over method is an effective simplified computer method with good accuracy and simplicity. For structuresin which the response is characterized by the fundamental mode of vibration, the evaluation results of capacity spectrum method and displacement coefficient method are comparatively precise. The influences of some factors, especially the lateral load patterns, on the analysis results of nonlinear Push-over analysis have been researched in details. The other factors included adaptive lateral patterns, the magnitude of initial base shear force, structural plan asymmetric and the higher mode effects. The research contents involve nonlinear base shear vs. top displacement relationship of Push-over analysis, the distribution of story drifts, the appearance sequence and distribution of structural element plastic hinges. Finally, a frame structure's seismic performance has been evaluated by means of deferent nonlinear static Push-over analysis methods and the analysis results of these methods have been compared. Based on the simplified N2 method and the equal displacement rule, the simplified capacity spectrum method was proposed in the dissertation. The analysis and comparison of some examples had proved that the method was correct.