The Numerical Analysis Of Large Scale Egg-shaped Digester Under Static Loads

With the rapid development of the computer and construction, the egg-shaped digesters being a new type of structure are used more and more widely. Because of the large cubage, the special configuration and the various kinds of loads, the determination of the digesters'shape , the analysis of deformations and internal stress of the digesters are the most important in the initial design phase.The shell and solid elements are adopted respectively in the models of the egg-shaped digesters under ANSYS software. In shell-element model, the egg-shaped digesters are established using ANSYS Parametric Design Language, and the problems of the continuously changing thickness of the wall and the conjunction of different element types are solved. In the solid-element , the process of the modeling is convenient . But the program is designed using APDL in the course of calculate the internal force of the solid element. The deformation and the internal forces of the two different types of models are according to each other on the whole.The prestress is replaced by equivalent pressure which is applied to the wall of the digester in the shell-element model; on the other hand, in the solid-element the prestress is simulated by using the initial strain of the steel bar. Both two methods can achieve the reasonable distributing of the internal force on the wall of the egg-shaped digester.Finally through calculating the egg-shaped digesters which have the same cubage and regular change of dimension, the relationship between the internal force and the controlled dimension of the digester is attained. And the effect of the two different buried conditions that one is the depth that the digester buried controlled at the boundary of the egg-shaped wall and the bottom taper, the other is the depth changing with R/H to the internal force is got. The advice of the determination of the principal size in initial design phase is proposed.