Modal Pushover Analysis of Spatial Structures Based on the Overall Structural Stiffness Parameter

Abstract:

Due to the three dimensional force transmission mechanism, the application of pushover method for seismic response analysis of spatial structures is limited by the following issues: firstly, the representative nodal load displacement relationship can hardly be specified; secondly, there are no direct interrelationship among structural load, nodal displacement, and support reaction for spatial structures; thirdly, it is difficult to compute the capacity curves of spatial structures. In this paper, static elasto plastic analysis is carried out by using the load patterns generated from the structural vibration modes. Based on the overall stiffness parameter, the load displacement relationship of the modified equivalent single degree of freedom (ESDOF) system of each dominating mode, independent on support reactions, is obtained accordingly. And the equivalent mass of the modified ESDOF system is calculated by utilization of the mode period. Then the newly established ESDOF systems of the dominate modes are adopted in a modified modal pushover analysis (MPA) procedure. Numerical example shows that the modified MPA method, based on the overall structural stiffness parameter, overcomes the problem existing in the establishment of the structural capacity curve for the spatial structures. The computing consumption of the method given in this paper is 10% of the elasto plastic time history analysis (THA) method, meanwhile, in the seismic input direction, the nodal displacement data generated by the proposed method shows a 28% deviation compared with the THA method.