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

摘要

Recently published and popular national design codes 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 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-Δ and P-δ 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. The eccentric connection and different end conditions in angle members can be simulated automatically in analysis model in the proposed method so that the design process can be much simplified.;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 second-order elastic and inelastic 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.