Research On The Response Characteristics Of Large-Span Spatial Hub Structures Under Different Focal Mechanisms Earthquakes

Large-span transportation hubs are public facilities,and their seismic safety is very important.The current"Code for Seismic Design of Buildings"(GB50011-2010)(hereinafter referred to as"Seismic Code")on the seismic design of structures has not yet considered the impact of ground motions with different focal mechanisms.This paper selects two typical large-span spatial hub structures to study characteristics of their seismic responses under the action of ground motions with different focal mechanisms,and proposes ground motion intensity parameters suitable for the seismic design of large-span spatial hub structures.The main contents and results are as follows:(1)Characteristic analysis of ground motion response spectrum with different focal mechanisms.Select 664 ground motions containing 5 focal mechanisms in the PEER seismic database and calculate the response spectrum,and the response spectrum characteristics of ground motions with different focal mechanisms were analyzed by averaging and standardization.The results show that the focal mechanisms that have a greater impact on the peak of acceleration response spectrum are the reverse fault in the near field and the normal fault in the far field;the focal mechanisms that have a greater impact on the peak of the displacement response spectrum are the reverse fault in the near field and the strike-slip fault in the far field;the vertical seismic effects of strike-slip fault,reverse fault in the near-field area,and normal-oblique fault in the far-field area are far greater than the values specified in the“Seismic Code”.(2)Analysis of seismic response characteristics of large-span spatial hub structures under different focal mechanisms earthquakes.The seismic response characteristics of two typical large-span spatial hub structures inputted with different focal mechanisms in the near-field area were studied.The results show that the hub structure is mainly based on the horizontal acceleration or displacement response,and the vertical response is weaker than the horizontal response;the pivot structure whose roof is a pipe truss has the largest response under the action of the reverse-oblique fault,the pivot structure whose roof is a reticulated shell has the largest response under the action of the strike-slip faults;the vertical response of the structure under the ground motion of reverse-oblique fault and strike-slip fault is larger;the interaction between the roof structure and the substructure increases the amplification rate of the seismic response of the structure with increasing height.Compared with the calculation results based on the response spectrum of the"Seismic Code",it is suggested that the seismic action after considering the focal mechanism should be amplified,and the amplification factor should be 1.15.(3)Determination of ground motion intensity parameters suitable for the large-span spatial hub structures.Eleven intensity parameters of 664 ground motions with different focal mechanisms were calculated,and the ground motion intensity parameters were evaluated from the aspects of correlation and validity.The results show that the ground motions intensity of the reverse-oblique faults,strike-slip faults and reverse faults in the near-field area and the strike-slip faults and reverse faults in the far-field area are greater.Compared with the acceleration response,the displacement response of the structure has a better linear fit with the ground motion parameters.Based on the evaluation results of different strength parameters,it is recommended to select the energy density_ρE as the ground motion intensity parameter of the large-span spatial hub structure.