Seismic Performance Analysis Of MDOF System Based On Hysteresis Characteristics

Code for seismic design of buildings in China only for a few important building collapse resistance design offers suggestions,however,there is no strict norms and standards about general structure of the building.After suffering larger earthquake disasters in some areas,a large number of frames happened the phenomenon of global collapse.Therefore,it is necessary for the general buildings to study deeply on improving the capacity of collapse resistance,so as to realize the goal of "no collapsing with strong earthquake".At present,it is necessary to have two aspects to evaluate the seismic capacity of the MDOF system:one is the evaluation of the seismic performance of the structure;the other is the assessment of the structural collapse resistance.These two aspects fully reflect the performance-based design of seismic design,but in the assessment of structural seismic capacity will involve a large number of complex nonlinear analysis problems,it is necessary to spend a lot of time,thereby increasing the seismic design cycle.Therefore,the influence of non-linear constitutive relation of material on nonlinear analysis is found out.Working out a simplified assessment of seismic capacity in order to minimize the time and effort spent on the analysis and evaluation,having a good engineering practical significance.In this paper,the seismic performance of the structural system is studied as follows:(1)This paper introduces the nonlinear analysis model and the constitutive nonlinear model,summarizes two non-linear structural analysis methods wich is commonly used:incremental dynamic analysis(IDA)method and static elasto-plastic analysis(Pushover)method,the basic principles of the two methods are explained,the advantages and disadvantages of the two methods are compared.The analysis method of structural collapse fragility and the criterion of collapse judgment are introduced.(2)Based on OpenSees finite element analysis software,the finite element analysis model is established,and 23 different amplitude waves are input.The IDA curve of MDOF system is calculated and the characteristics of IDA curve described.Then,drawing the collapse probability curve of the MDOF system,based on 50%collapse probability corresponding structural collapse resistance index is concluded.The influence of different hysteresis characteristics(ductility coefficient,strengthening coefficient,softening coefficient and hysteresis)on the anti-seismic collapse ability of the structure is analyzed by using the "control parameter"principle.(3)A simplified method for assessing seismic capacity of structures is proposed.Using Pushover method with different loading mode,based on the capability spectrum analysis,the performance point is obtained.According to the performance point and then converted into the floor displacement,the use of different loading mode of the Pushover method to assess the results of the seismic performance evaluation accuracy.The MDOF system is transformed into the equivalent SDOF system,and the collapse of the equivalent degree of freedom is analyzed,reducing the computational complexity of complex MDOF system.(4)By comparing the anti-seismic collapse ability index of the prototype structure,the accuracy of the method is verified by the method of simplified analysis of the MDOF system to the equivalent SDOF system.In this method has a certain accuracy under the premise,and then can be introduced to reliability of the seismic capacity of the reliability of the assessment method.