Research On Seismic Collapse Method Of Frame Structure Based On Stiffness Damage

Under the action of strong earthquakes,the collapse of building structures is often the main cause of casualties and economic losses.Therefore,the research on the seismic collapse of structures is one of the key points that must be paid attention to.Reasonable earthquake-resistant collapse judgment criteria can quantitatively describe the failure of the structure,and can further study the collapse resistance of the structure.At present,a number of criteria for determining the collapse of structures against earthquakes have been proposed at home and abroad,such as: deformation collapse criteria,stiffness collapse criteria,and dual-parameter collapse criteria.In practical applications,the criterion for structural collapse still has limitations,and it is necessary to establish a new criterion for structural collapse.Stiffness,as an index of the ability of a structure or component to resist deformation,can better reflect the seismic characteristics of a structure or component.However,the collapse judgment criterion of rigidity has developed more slowly than other collapse judgment methods,and there are certain problems.Based on the analysis and research on the collapse mechanism and seismic collapse judgment methods of the relevant frame structures at home and abroad,this paper starts with the stiffness of the structure,as the analysis parameter of the structure failure state,and proposes the two-parameter method based on the stiffness improvement and the stiffness damage method respectively.The IDA method studies the seismic collapse resistance of frame structures.The main research contents and conclusions of this paper are as follows:(1)In this paper,stiffness is introduced into the Park-Ang two-parameter model,and a two-parameter damage method based on stiffness improvement and energy is proposed;the stiffness ratio is used as the weight coefficient to obtain the weighting method of the damage of the floor and the overall structure.Pushover analysis of different loading methods for 5-story outer corridor RC frame structure,with the maximum elasto-plastic inter-story displacement angle 1/50 as the analysis state of the structure,using the proposed method to calculate the component,inter-story and structural overall damage index,And compare the Park-Ang two-parameter model and its weighting model.Through analysis and calculation,the following conclusions are drawn: the stiffness and energy-based dual-parameter damage method matching stiffness ratio weighting can more accurately describe the damage of each structural member,layer and the entire structure under earthquake action,and can better compensate for Park-Ang The model does not match the damage value of the elastic and collapsed components.The damage description under the two methods is consistent and uniform,which verifies the feasibility and correctness of the proposed method to a certain extent.(2)This paper proposes an IDA analysis method based on stiffness damage.Take the 7-story inner corridor steel frame structure as the analysis object,draw the IDA curve clusters with the inter-story member stiffness damage and the overall structure stiffness damage as the damage indicators,and the inter-story displacement angle,residual displacement angle,and hysteretic energy as the structure The IDA curve of the dynamic index is compared and analyzed.The study found that the IDA analysis method based on stiffness damage can fully reflect the seismic dynamic characteristics of the structure and can be used as the damage index of the IDA seismic collapse method.The IDA curve based on the stiffness damage of the interlayer members can more accurately describe the failure of each layer,and the IDA method based on the overall stiffness damage of the structure can reduce the risk of overestimating the structural safety of the stiffness criterion.Comparing the IDA curves under different damage indicators,it is found that the IDA analysis method with residual displacement angle and hysteretic energy as damage indicators has a certain degree of redundancy,which overestimates the seismic damage of the structure and can be used as the seismic evaluation of important structures.Analyze the collapse process of the frame structure under different loading modes and different ground motions,observe the hinge path and the degree of plastic failure,and study the collapse mechanism of the frame structure.It is found that due to the randomness of ground motions,the collapse mechanisms are diverse and difficult to qualitatively determine.The structure is designed in the mode of strong column and weak beam,but under the action of strong external load or ground motion,the appearance of the column hinge cannot be prevented.The magnitude of the load borne by the structural members determines the degree of plastic failure.High-rise steel frames are prone to plastic failure due to the ductility of the structure and the obvious P-Δ effect.The degree of dispersion of plastic hinge formation can show the accumulation of seismic energy and the cumulative damage of the structure’s energy consumption to a certain extent.The accumulation of energy consumption has an important influence on the collapse mechanism of the structure.