Direct secant estimation of limit behaviour of framed structures

Yu, Xiao (2010) Direct secant estimation of limit behaviour of framed structures. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (21MB)

Abstract

A direct secant method used to predict the plastic limit load of framed structures is presented in this thesis. Instead of using classical techniques, it utilizes two or more purely elastic analyses to predict the limit load. Secant rigidity of structures is modified based on the result of the first purely elastic analysis. Iterative reanalyses are performed until convergence is reached. By selecting the peak bending moment, potential plastic hinges are listed. The result can be used to predict the plastic limit load as well as the collapse mechanism. The limit load calculated by the direct secant method is compared to the solution of other traditional analyses, where applicable. Generally, the direct secant method is an attractive alternative for evaluating the limit load of framed structures. The results are a significant improvement over traditional methods which are illustrated in the thesis. Similar idea is applied on frame stability analysis. After the first purely elastic analysis, two preliminary and empirical methods for analyzing stability are suggested. Factor C and factor β are investigated to evaluate the critical load. This thesis investigates large deflection by using similar idea inspired from the direct secant method used for analyzing frame stability. Factor η is investigated and used to analyzing the large deflection. -- The method is executed by ANSYS software using APDL routines. The problems solved include: Portal frames, Two-bay Single-storey frame, Two-bay Two-storey frame as well as Multistorey Frame Subject to Concentrated and Distributed Loads. The results from the above analyses compare with other traditional methods closely, and the error is no more than 5%, thus demonstrating the usefulness of the direct secant method.

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