Design of unconventional slender steel structures by stability analysis

Abstract

The major objective of this thesis is to develop and extend the nonlinear theories and finite element methods to practical analysis and design of slender engineering structures. The studies presented is focused on the effects of geometrically and material nonlinearity of 2- and 3- dimensional structures. A detailed geometrically nonlinear formulation of doubly symmetric and tapered members, based on the co-rotational formulation and the principles of potential energy, has been presented. Few work has been conducted on the advanced analysis of trusses consisting of members of angle section. Based on the special load characteristics and response of angles of equal legs, the effects of load eccentricity and finite stiffness at connections are allowed for. The secant and tangent stiffness matrices for a new elasto-plastic beam-column element are presented on the basis of the refined elasto-plastic section moment-curvature relations. Spread-of-plasticity effects are considered by searching the section curvature loaded beyond the first yielded curvature. An integrated second-order analysis method, which uses the one-dimensional beam-column elements to model beam or column members and shear-wall or core members in high-rise wall-frame structures, is proposed. The developed method is coded in a computer program which is then used to solve a number of examples to illustrate its accuracy and efficiency. The proposed computer method provides a new and accurate tool for advanced analysis of unconventional steel structures, which is believed to be of contribution to the profession of Structural Engineering.