Study On Seismic Response Characteristics Of Large-Span Column-Free Atrium Subway Station

With the rapid development of China’s rail transit,the use of underground space by subway and other rail transit is increasing and the construction technology of subway sections and stations has become one of the hot issues in the international research.In this context,the column-free atrium station structure was born.It combines the station hall floor and platform floor into a whole,cancels structural column placement and breaks closed space interface.It improves the mobility of passengers,creates a wide open space vision and creates a wide and bright space vision.However,its dynamic response characteristics under earthquake action are different from those of traditional stations,and the stress characteristics and damage characteristics are more complex.Based on a large-span column-free atrium subway station in Chengdu,the seismic performance of large-span column-free atrium subway station is studied in this paper.Firstly,the seismic performance of each typical section of the column-free atrium subway station is calculated by the reaction displacement method,and the stress characteristics and weak parts of each typical section under the earthquake load are analyzed.Then,a three-dimensional ground-station coupling model is established to carry out time-history analysis,and the seismic dynamic response characteristics of large-span column-free atrium subway station under different seismic loads are further analyzed.Then,the shaking table test is designed and carried out on the basis of theoretical analysis.Finally,a structural optimization scheme is proposed and its seismic performance optimization effect is analyzed.The main achievements are as follows:(1)The seismic analysis of each typical section of column-free atrium subway station is carried out by reaction displacement method.It is found that the most unfavorable position of column-free atrium station is the connection between the side wall and the bottom plate,followed by the connection between the side wall and the middle plate of the open section,and the stress on the atrium section is more unfavorable than that on the non-atrium section.The external fire passageway has little effect on the seismic performance of the structure,but the entrance and exit have great effect on the seismic performance of the structure.The traditional seismic measures of arch tie rod construction and triangular air duct structure are not suitable for large-span column-free atrium subway station.(2)The seismic analysis of column-free atrium subway station under various seismic loads by time-history analysis shows that the most unfavorable position of column-free atrium subway station is the junction of side wall and bottom plate,followed by the junction of atrium corner,side wall,roof and middle plate,and the force of open section is more unfavorable than that of non-atrium section.Moreover,the non-atria between the two atria are affected by the atria on both sides.The acceleration amplification coefficient of each measuring point has nothing to do with the seismic load intensity,and the extreme values of principal stress and dynamic internal force are positively correlated with the seismic load intensity.The distribution of dynamic internal forces on both sides of the column-free atrium subway station presents an antisymmetric law about Z axis.The rationality of the reaction displacement method is verified and the calculation results of the reaction displacement method are too conservative.(3)By time history analysis method on the intensity of seismic load without pillar atrium subway station under the seismic analysis,further defined the atrium without column force characteristic and the weak link of the subway station,and among them,the dangerous parts of side wall plate border,atrium corner,side wall between the roof and side wall plate boundary,the atrium is the atrium paragraphs force,the atrium period between the two atrium force also is bad,The distribution of dynamic internal force is antisymmetric about Z axis;The acceleration amplification coefficient of each monitoring point has nothing to do with the seismic load intensity,and the extreme values of principal stress and dynamic internal force are positively correlated with the seismic load intensity.The rationality of the reaction displacement method is verified and the calculation results of the reaction displacement method are too conservative.(4)Based on the reaction displacement method,time history analysis method and shaking table test,a structural optimization scheme is designed to optimize the size and the connection form between side wall and bottom middle plate.After the structural optimization,the force at the junction of side wall and bottom plate decreased obviously,while the force at other parts increased slightly,and the overall force of the structure was better.