TIME HISTORY ANALYSIS OF ELASTO-PLASTIC SEISMIC RESPONSE OF A SUBWAY STATION STRUCTURE WITH ARCHED CROSS SECTION BASED ON FIBER MODEL

Time history analysis of elasto-plastic seismic response of a single-layer three-span subway station with arched cross section and island platform has been carried out using finite element software MSC.Marc by means of static-dynamic coupling analysis method based on unified viscous-spring artificial boundary. A fiber model program THUFIBER is used to simulate the structure. The results show that both the middle positions of arched roofs of side spans and top positions of columns have strong responses to the horizontal acceleration and displacement. The columns take greater internal forces than other members of the structure under horizontal seismic loads, which implies that the columns are the most disadvantageous positions of seismic bearing. Compared with the bottom of the column, the top of it takes a similar axial force but a greater moment, thus it may be crushed first under strong seismic loads. The arched shape top roof takes a smaller moment and a relatively greater axial force, so the structural form with arched cross section has a more reasonable and advantageous stress state than that with rectangular cross section. The results also show that for the aseismic analysis and design of underground structures, the peak ground displacement relative to bedrock (PGRD) seems to be a more reasonable and efficient design parameter of ground motion than the design basic acceleration of ground motion.