Study On Vertical Seismic Action Of The Diagonal Double-layer Space Grids

The double-layer space grids is a space pole structure of grid shape. It's structure members is disposed according to the certain rule and connected by nodes.It has many advantages,for example large span,large rigidity,good stability,secure and reliant,finer aseismatic performance,extensive adaptability,industrialized ect.After 1976,people adopt double-layer space grids as roof of industry workshop and public building.However,how to perform seismic design of double-layer space grids is still an important problem concerned.Vertical seismic action of the diagonal square pyramid double-layer space grids(DSPG) structure is studied in this paper.DSPG structure'members force are calculated with equivalent sandwich plate .To creat finite element model of DSPG,program to create node,element number and restriction information is compiled. DSPG structure'members force and maximal deflection are calculated with equivalent sandwich plate method and ANSYS,and results show that the method to create DSPG finite element model by ANSYS is correct and the equivalent sandwich plate method to calculate chord force is high accuracy in precision.Equivalent sandwich plate and ANSYS modal analysis are used in the calculation of free vibration. Comparison result show that the study of free vibration property of DSPG adopt ANSYS software is reliable.The dynamic property of DSPG is studied through free vibration analysis of 18 DSPGs and the general rule of DSPG is achieved.The processes and procedures of ANSYS spectrum analysis are given. Through the seismic action analysis of DSPGs onâ…¡ground,we achieve the distribution rule of seismic internal force.The inherent relationship between vertical seismic internal force coefficient and the first vertical frequency is found by researching seismic internal force coefficients of 9 kinds of DSPGs,then practical calculation methods for DSPGs is determined.