| The present study investigates three main points of the unanchored large storage tanks by finite element analysis, including structure-foundation contact under static load, elephant foot bulking, and seismic response using FSI(fluid-structure interaction) model. The main objective of this research is to explore scientific numerical simulation modeling solutions of this nonlinear complex system. The three primary innovation points are concluded as follows:1. Based on finite element contact analysis, a novel modeling method called foundation-structure coupling method is presented in order to describe the relation between the stress of the shell-to-bottom joint and the foundation. The stress in tank shell and bottom plate can be easily achieved according to investigating foundation settlement.2. A variety of quasi-static simulation approaches of elephant foot buckling are concluded and further developed. The dynamic model of elephant-foot buckling of unanchored tank is also built on condition that bottom plate is partial pre-uplifted.3. By applying lateral impulsive load on the foundation, there is a new approach of the free vibration response analysis of a structure-fluid interaction system.According to numerical simulation research of the method innovations above, it shows some important results:1. There is a certain relation between the foundation settlement and stress distribution in both tank shell and plate. This relation is applicable in engineering field.2. The mechanism of elephant-foot buckling near the tank base is proved by nonlinear finite element study, which is in accordance with typical codes. It occurs predominantly due to the axial compressive stress in the tank shell, though it is significantly affected by the circumferential membrane stress caused by internal pressure (both hydrostatic and hydrodynamic).3. To solve the natural frequency of the nonlinear FSI system, impulsive excitation method is applied to the finite element modeling. And the frequency spectrum of the FSI system is achieve through Fourier Transform from time domain.4. Additionally, as the ground acceleration, one dimensional sinusoidal resonant wave and three dimensional 1940 El Centro earthquake wave are applied on the foundation. Based on successful simulation of uplifting phenomenon, the mechanism of uplifting is further studied. Qualitative analysis shows the shape of uplifting area, uplifting height and stress level when uplifting happens. And it is proved that uplifting can still happen for 150,000 m~3 liquid storage tank.
|
PDF Full Text Request