Shaking Table Experimental Research On Collapse Processing Of Domes Under Multi-Support Excitations

As an important branch of long-span spatial structures, latticed shells is the most widely-used structure at present. For our country is located in a region with severe earthquake hazards, researchers were dedicated to conduct systematic studies on collapse mechanism of latticed shells under intensive earthquake. While the theoretical researches achieve immense outbreaks, which is insufficient to verify and explore the failure mechanism of latticed shells on experimental perspectives. Therefore, in this paper, the dynamic performance of domes under multi-support excitations is investigated through shaking table tests. And finite element method is applied to reveal the collapse process of models under seismic excitations.The main contents and conclusions are illustrated as follows:(1) Two scale models were strictly designed and manufactured according to similarity theory and topology of prototype. The span and height of models were 23.4m and 11.7m respectively. Normally designed Model 1 possessed uniform stiffness except bottom was reinforced. Model 2 was manufactured from Model 1 with two weak parts embedded on purpose and was expected to respond differently with Model 1 under same seismic excitations. The responses of the structures under different working conditions were observed in the experiment by increasing PGA of seismic waves gradually. The results indicated that two testing models both collapsed suddenly because of special boundary conditions, plasticity region of models and plastic area of beam section were fully developed during the failure process. Due to weak parts made purposely, beams in weak part zones went to failure firstly and the zones were destroyed severely before collapse. Therefore, abrupt-changed stiffness should be prohibited during engineering design.(2) Target self-power spectral density function and mutual-power spectral density function were applied to produce four coherent seismic waves. And spectrum analysis was used to prove the accuracy and rationality of the waves which would be applied in subsequent numerical simulation and seismic input. By the large mass method in ANSYS, time history analysis under multi-support excitations was carried out for testing models with geometric nonlinearity and material nonlinearity in consideration. And structural response was obtained. Simulation results indicates that when the large mass is set to 104～108 times the self weight of the model, the accuracy of the structural seismic response analysis under multi-support excitation can be assured.(3) Birth-death element technique was applied to simulate the changing structural system and boundary conditions of testing models caused by element failures during collapse process. Different testing model stages including elastic state, plastic state and collapse were displayed. Testing schemes and numerical models were proved to be reasonable by comparing theoretical deformation with experimental deformation.