Experimental research and numerical simulation of a large-span isolated structure considering multi-dimensional input effects

Based on the shaking table test of 1:20 scale structural models of the large-span isolated and non-isolated flat grid structures under the action of horizontal-bidirectional (2D) and three-dimensional (3D) rare earthquake, the dynamic characteristics, including natural vibration frequency, damping ratio, the acceleration and displacement responses are investigated. The results show that the base isolation could significantly prolong the structural vibration periods and increase the damping ratio. The capacity of energy dissipation for the base-isolated structure can also be improved. The horizontal acceleration amplification factors (AAFs) of the structure can be reduced greatly due to the base isolation, which effectively reduces the vertical vibration of the large-span grid. Under the 3D seismic input, the horizontal AAF of each layer is greater than that under the 2D one, which illustrates that the vertical seismic input increases the horizontal dynamic response of the structure. Furthermore, the finite element models of the isolated and non-isolated structures were simulated. The experimental results are in good agreement with the numerical results. The parameter optimization of isolation bearings was conducted by using finite element software. The seismic response of each layer under different shear to weight ratios (μ) was analyzed. It can be found that the parameters of the isolation layer have an optimal range which makes the dynamic response of the structure reach a minimum value under the rare earthquake.