Study of Constitutive Law, Collapse Surfaces and Safe Load Domain for Trusses with Softening
Date Issued
2014
Date
2014
Author(s)
Lin, Kuan-Yu
Abstract
In the eld of theory of plasticity, limit analysis is an important topic. Plastic responses
are known to be path-dependent. The greatest advantage of limit analysis is that we can obtain plastic collapse loads directly without prescribing loading paths. In the past, the most common approach is applying mathematical programming to calculating the collapse loads of elastoplastic structures.
Recently, some people use the piecewise linear model to describe the constitutive law of elastoplastic materials, and develop a method via the relationship of evolving yielding surface and collapse mechanism in equilibrium to calculate the collapse surfaces of structures and
to construct the safe domain in load space. But for softening materials, the di cuties of how to describe the constitutive law correctly and the analysis of safe load domain being too conservative are two major problems which need to be improved and studied.
In this thesis, we use a parallel connection of components to describe the constitutive law of a softening member of truss. We make one of the components with the characterisation of negative dissipation, and regard the softening member as a closed system, which still follows the
laws of thermodynamics. With this concept, we can formulate the constitutive law with various mechanical models such as bilinear model of ealstoplasticity or model of perfect elastoplasticity.
For the analysis of safe load domain for a softening structure, we deem using the residual strengthes of softening members to calculate the collapse surface to be too conservative, and there will exist structural interactions between structural members in states of stresses higher than residual strengthes. With these two viewpoints, we use the corresponding displacement space to rede ne the collapse load of a softening structure when unrestricted deformation (plastic ow plateau) takes place, and we nd correct collapse modes and thus expand the safe load domain for softening structures.
Subjects
極限分析
組成律
熱力學定律
軟化
崩塌載重
安全載重空間
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-103-R01521220-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):d773cd2bae4ee84abdaff607e57d66a9