Robust estimation of limit loads of plates using secant rigidity

Abstract

A robust method for the estimation of limit loads of structures has been adopted for plate structures. It involves the use of modified secant rigidity. The method makes use of repeated linear elastic analyses to predict limit behavior. The results from an initial elastic analysis are used to obtain the principal moments. A suitable yield criterion (such as Tresca or Von Mises) in terms of generalized forces is used. A set of equivalent moments is then computed for the plate. This is used to modify the secant rigidity of the plate. The modified structure is re-analyzed iteratively until convergence is reached. The moment distribution from the convergent analysis shows the collapse mechanism for the plate. The average of the equivalent moments along the collapse (or yield) lines of the plate is scaled to the plastic moment capacity of the section to obtain the limit load factor. The method has several advantages in comparison to other traditional methods. -- This method has been implemented on ANSYS software using APDL routines. Problems solved include: simply supported and fixed square and circular plates with uniform and concentrated loads, plates with irregular boundary conditions and shapes as well as continuous plates with checkerboard loading. The results from the above analyses match analytical results very closely, thus demonstrating the usefulness of the method used.