Yungui Li

Several Treatments on Nonconforming Element Failed in the Strict Patch Test

For nonconforming finite elements, it has been proved that the models whose convergence is controlled only by the weak form of patch tests will exhibit much better performance in complicated stress states than those which can pass the strict patch tests. However, just because the former cannot provide the exact solutions for the patch tests of constant stress states with a very coarse mesh (strict patch test), their usability is doubted by many researchers. In this paper, the non-conforming plane 4-node membrane element AGQ6-I, which was formulated by the quadrilateral area coordinate method and cannot pass the strict patch tests, was modified by three different techniques, including the special numerical integration scheme, the constant stress multiplier method, and the orthogonal condition of energy. Three resulting new elements, denoted by AGQ6M-I, AGQ6M-II, and AGQ6M, can pass the strict patch test. And among them, element AGQ6M is the best one. The original model AGQ6-I and the new model AGQ6M can be treated as the replacements of the well-known models Q6 and QM6, respectively.

Four-Node Generalized Conforming Membrane Elements with Drilling DOFs Using Quadrilateral Area Coordinate Methods

Two 4-node generalized conforming quadrilateral membrane elements with drilling DOF, named QAC4 and QAC4M, were successfully developed. Two kinds of quadrilateral area coordinates are used together in the assumed displacement fields of the new elements, so that the related formulations are quite straightforward and will keep the order of the Cartesian coordinates unchangeable while the mesh is distorted. The drilling DOF is defined as the additional rigid rotation at the element nodes to avoid improper constraint. Both elements can pass the strict patch test and exhibit better performance than other similar models. In particular, they are both free of trapezoidal locking in MacNeal’s beam test and insensitive to various mesh distortions.

A Structural Simulation System, Part 1: Interface and Operation

According to the more and more popularity of complex buildings, such as complicated shape building, high-rising building, long-span structure etc., the high performance simulation has become more and more import in the design and construction of building structures. The traditional design software, such as Pkpm, Yjk etc., could not satisfy the above requirements due to the deficiency of computation. On the other hand, the commercial FEA software, such as Abaqus, Ansys etc., although have powerful calculated performance, while they are not convenient for building structure analysis due to the fact that their preprocessors are not suitable for building modeling. Therefor from the civil engineering perspective, a simulation system simultaneously having the advantages of traditional design software and commercial FEA software is very useful even desired to solve the practical engineering problem. In this paper, an integrated simulation system for building structures, or ISSS for short, is presented to satisfy the building engineering requirements for high performance simulation. It is a coalition of the traditional design software and general finite element analysis (FEA) software.