Second-order analysis of imperfect light-weight and composite structures

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Second-order analysis of imperfect light-weight and composite structures

 

Author: Fong, Man
Title: Second-order analysis of imperfect light-weight and composite structures
Degree: Ph.D.
Year: 2012
Subject: Composite construction.
Composite materials.
Structural design.
Building, Iron and steel.
Concrete construction.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Civil and Structural Engineering
Pages: xxviii, 251 leaves : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2507340
URI: http://theses.lib.polyu.edu.hk/handle/200/6501
Abstract: Recently published and popular national design codes such as the AISC (2010), Eurocode 3 (2005) and CoPHK (2005) recommend the use of second-order analysis and design method as an advanced tool in place of the first-order analysis and design method such that the unreliable estimation of effective length and determination of buckling reduction factors can be eliminated. The use of this simple and accurate advanced design tool for typical steel structures has been proposed by many researchers. However, research with aim for practical application of the method for steel-concrete composite structures receives relatively few discussions and verifications against test and code results. The aim of this thesis is to propose and develop a practical advanced design method for light-weight and composite structures. The light-weight structures such as the transmission towers and tower cranes which collapse quite commonly in different parts of the world. The collapse of these structures is mainly due to the structural instability rather than material yielding. Therefore, the inclusion and consideration of the nonlinear effects such as P-{439} and P-{463} moments, member initial imperfection and global structural imperfection in analysis are important so as to reflect the actual structural behaviors. However, the way to consider these effects in design by estimation of effective length in the first-order analysis and design method is not only inconvenient, but also inaccurate and unreliable. Incorrect estimation of the effective length may lead to under-design of the structures which may eventually cause the collapse of the structures.
Convenience and reliability in design of steel structures, especially for angle members are another attraction for second-order analysis and design method. The monosymmetric or asymmetric section property and eccentric connection in angle members further complicates its design process, and many design codes provide different complex equations to consider these effects which can be simulated automatically in analysis model in the proposed method so that the design process can be much simplified. Steel members have been popularly used in different structural forms. Due to the increase of building height and structural span, the use of steel-concrete composite members becomes more popular because of its advantages over bare steel and reinforced concrete members. Most nonlinear finite element packages are complicated and unsuitable for practical design because of the requirement of huge computational time. Therefore, an efficient and accurate analysis and design method, which includes the nonlinear effects and fulfills code requirement, is proposed for steel-concrete composite members with verification examples to confirm its validity for practical applications. Consideration of material nonlinearity in study of inelastic behavior of composite members is obviously important and the second-order inelastic analysis is proposed in the final part of the thesis to include both the geometric and material nonlinearities in analysis. Refined plastic hinge method in conjunction with initial and full yield surfaces is used to trace material yield for guaranteeing both efficiency and accuracy. In this thesis, extensive numerical examples are provided for verification.

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