NONLINEAR BEHAVIOR OF BOTTOM PLATE IN CYLINDRICAL LIQUID STORAGE TANKS FOR SEISMIC APPLICATIONS

The paper presents a simplified pseudostatic approach to model the non linear behaviour of the bottom plate in unanchored cylindrical liquid storage tanks for seismic applications. In this paper, the problem of axisymmetric uplift of the bottom plate is studied for tanks supported on both rigid and elastic Winkler foundations. In the analysis, the b ottom plate is modelled by one-dimensional beam and two-dimensional pl ate models. By comparing the results, it is found that the one-dimensi onal beam model gives accurate results acceptable for all practical de sign purposes, in view of the many other uncertainties in the tank upl ift problem. The analysis results also show that the support foundatio n flexibility may have significant effects on the uplift behaviour of the tanks. Based on the axisymmetric uplift results, the paper then pr esents a simple approach to model the seismic partial uplift problem o f unanchored tanks by means of nonlinear springs. Modelling parameters for the nonlinear springs are generated for dynamic uplift response a nalysis. Sensitivities of the uplift behaviour and the nonlinear sprin g modelling parameters to the tank height-to-radius ratio and the soil stiffness are also studied.