The calculation method of Plastic collapse

• Main Authors: Jhong-Ying Tsai, 蔡忠穎
• Other Authors: 洪宏基
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/50275771346732718859

碩士 === 國立臺灣大學 === 土木工程學研究所 === 104 === In plasticity, limit analysis is a very important topic.The important characteristics of plasticity is "path to path ," and the relationship of load and displacement is "path-related." First, the behavior is elastic until yield occurs, when there will be an "initial yield surface" in the state space. Then, in the plastic stage, the yield surface is evolving in the state space and the so-called “subsequent yield surfaces" are infinite in number, depending upon the load paths. But it will eventually be able to build in the load space a unique "collapse surface," which means that it is path-independent. It is the same collapse surface to which infinitely many different load paths together with different evolving subsequent yield surfaces will eventually reach! Our predecessors, engineers and scholars, have done a lot of discussions, including the use of optimization problem, Karush-Kuhn-Tucker (KKT).conditions, and the setting of different goals, the development of single-objective optimization, and multi-objective optimization, etc. but the biggest drawback is the final formula are too complicated. In view of these, the present thesis focuses on the study of calculating the collapse surface on the load space for trusses and frames. The method developed herein can calculate the collapse surface directly on the basis of the compatibility and equilibrium equations of the structure and also on the algebraic part of the constitutive relations, skipping all subsequent yield surfaces and thereby saving out a lot of complicated calculations. This calculation method may be used for trusses, beams, or frames. In the part of frames, we attempt to consider the axial force and moment interaction in order that the result is more accurate.