Studying Of Added Mass Method For Dynamic Analysis Of Cylindrical Tank

There are many research approaches have been developed for the study of dynamic response on the cylindrical tank under earthquake loading. Finite element method is thought to be one of the more effective and lower cost numerical simulation methods. The fluid-structure interaction problem of cylindrical tank is solved mainly with added mass method. In order to evaluate the safety of cylindrical tank under earthquake loading and to design such tank with more reliability, we challenge a new added mass method with more accuracy, and provide an applicable method for analyzing the dynamic nonlinear behavior of the cylindrical tank.Numerical method is used to simulate the EFB (Elephant Foot Bulging), and comparison is made with dynamic test data. User element (UEL) of ABAQUS has been developed based on the Westergaard added mass technique, and the fluid-structure dynamic interaction in the tank resulting from the earthquake acceleration can be modeled in a simple form. During earthquake acceleration exciting, the liquid filled in the tank will exert transversal pressure on the tank wall. According to Westergaard (1933), the hydrodynamic pressures may be considered to be produced by a certain mass of water moving back and forth with the side wall of the tank, while the remained water is left inactive and not considered. It is discretized to tank shell and water, while only tank shell model is calculated in the numerical simulation. Due to the effect of flexible wall of cylindrical tank, the magnitude and distribution of hydrodynamic pressures is different from that presented in the cylindrical tank with rigid wall. In the case of deformation and oscillation of side wall, we have proposed a new form of distribution of added mass for simulating the hydrodynamic pressure. The direction of response acceleration of the tank wall has been also taken into account for simulating inertia force of added mass with more accuracy.From the simulation, we can study the history of the energy, stress, and strain. The frequency response can also be studied too. According to analyzing the energy balance, we think that the external work done by earthquake loading plays a very important role in EFB of the cylindrical tank.