Study On Seismic Performance Of Escalator Truss Based On Finite Element Method

With the development of economy,especially the extensive construction of rail transit,escalator has become a part of people’s daily life.However,although there are frequent earthquakes in China,there is no seismic design code or relevant study for the earthquake resistance of escalator truss.In this paper,the finite element method was used to study escalator truss under the action of earthquake;moreover,the design was optimized to improve the earthquake resistance of escalator.Firstly,ANSYS parametric design language(APDL)was used to establish the finite element model of long-span escalator truss and for static analysis,so as to ensure that its strength and stiffness meet the requirements of national standards and lay a foundation for the subsequent seismic performance studies.Then,seismic analysis was conducted on escalator by equivalent static method in accordance with the foreign current seismic design code for escalators;the response spectrum analysis on escalators was attempted on the basis of the seismic design response spectrum of buildings;dynamic and time-historical analysis of the seismic performance of escalator truss was performed after selecting the actual strong motion recording amplitude modulation.The analysis results in the three groups were compared and mutually verified to ensure the seismic performance of escalator truss.Finally,the structure of escalator truss was optimized.Static analysis and timehistorical analysis of the improved truss structure were carried out one by one by changing the profile specification of the main beam and the thickness of the truss,adopting the double truss,etc.The most cost-effective seismic design and the optimization scheme with optimal seismic performance were selected.Meanwhile,the limitation of equivalent static analysis was verified.The main results are as follows:(1)The longitudinal displacement of the free sliding end of the truss under the action of earthquake was obtained by means of time-historical analysis,and was compared with the pendulum momentum of the floor,finding that the influence of building sway should be mainly considered when designing the lapping amount of the truss.(2)The contrastive analysis of the seismic resistance of several escalator truss models showed that,the seismic design codes for escalators in the United States,Japan and other countries only adopted the equivalent static method;therefore,the safety and reliability of escalators cannot be ensured under the action of rare earthquake,which may lead to misjudgment.The time-historical analysis should be combined for comparative verification,so as to ensure the rationality and reliability of the seismic design of escalator truss.(3)The structure of escalator truss was optimized in various forms.Besides,the time-historical analysis was performed on its seismic response,finding that sometimes the seismic resistance of trusses can be improved by the upgrading of profile specification of the main beam,but not absolutely;the thickening of the inclined section reduces the seismic resistance of the escalator;double truss has the best seismic performance.