Strength behavior and collapse of spatial-reticulated structures under multi-support excitation

Under strong shocks, long-span spatial-latticed structures may collapse due to dynamic instability or strength failure. The elasto-plastic dynamic behaviors of three spatial-latticed structures, including two double-layer cylindrical shells and a spherical shell used for the 2008 Olympic Games in Beijing, were quantitatively examined under multi-support excitation (MSE) and uniform support excitation (USE). Numerical analyses described several important parameters such as the peak acceleration and displacement responses at key joints, the number and distribution of plastic elements, and the deformation of the shell at the moment of collapse. Results of the analysis revealed the features and the failure mechanism of the spatial-latticed structures under MSE and USE. In both scenarios, the double-layer reticulated shell collapsed in the overflow mode, collapse was governed by the number of invalid plastic elements rather than the total number of plastic elements, and the collapse of the structure began with damage to certain local regions near the supports. By comparing the numbers and distributions of the plastic members under MSE to those under USE, it was observed that the plastic members spread more sufficiently and the internal forces were more uniform under MSE, especially for lower apparent velocities in soils. Due to the effects of pseudo-static displacement, the stresses in members near supports under MSE were higher than those under USE. These regions are prone to failure during earthquakes and deserve special attention in the seismic design of reticulated structures.