Study On Response Modification Factor For The Steel Grid Box Frame Structure Based On Seismostruct

The response modification factor is a key parameter to determine the design seismic force in the force-based seismic design method and the performance-based seismic design method,which is closely related to the bearing capacity and ductility of the structure.However,the current seismic design code of our country implies the same fixed value for the response modification factor of different structural systems of different materials.The steel grid box frame structure is a new structure system with excellent aseismic performance.In order to study the response modification factor for the steel grid box frame structure and its influence factors,the four typical steel grids box frame structures of three,six,nine and twelve layers,and the finite element models were established and verified based on SeismoStruct in this dissertation.Then,Adaptive pushover analysis method,conventional pushover analysis method and IDA method are adopted to calculate the capacity of response modification factor for the steel grid box frame structure in the collapse prevention state.The effects of different analytical methods,the number of the structural layers and infill walls on the response modification factor for the steel grid box frame structure are studied.The main conclusions are as follows:(1)Based on the results calculated through IDA method,the adaptive pushover analysis method will overestimate the response modification factor for the steel grid box frame structure,while conventional pushover analysis method will underestimate the response modification factor of the steel grid box frame structure.when studying the response modification factor for this structure,it is suggested that using traditional pushover analysis method when the structure is below 9 layers and using the adaptive pushover analysis when the structure is not less than 6 layers to reduce the calculation error and shorten the calculation time.(2)With the increase of the number of the structural layers,the response modification factor variation law got from the adaptive pushover analysis method is consistent with the response modification factor got from the IDA method,while the response modification factor variation law got from conventional pushover analysis method is different with the response modification factor got from the IDA method.According to the results got from the IDA method,the response modification factors for the steel grid box frame structures increase gradually with the increase of the number of the structural layers,thus the influence of the number of the structural layers should be considered in the rational value of the correction factor of this structural system in the seismic design code.(3)According to the results of the IDA method,the typical steel grid box frame structure of 3-12 layers designed based on 8 degrees seismic fortification,its values of capacity of response modification factor,structural ductility reduction factor and structural overstrength factor for the steel grid box frame structures suggested to be 5,1.6 and 3 in the critical collapse state.In the response modification factor for the steel grid box frame structure,the proportion of structural overstrength factor is much larger than that of structural ductility reduction factor.(4)The effect of the infill wall on the steel grid box frame structures mainly lies in the improvement of structural overstrength,then the response modification factor improved.The difference of filling rate also affects the degree of the improvement of the response modification factor.