Ana M. Girão Coelho

A ductility model for steel connections

A model for the evaluation of the ductility of steel connections loaded in bending is presented in this paper. In the context of the component method, whereby a joint is modelled as an assembly of springs (components) and rigid links, using an elastic post-buckling analogy to the bi-linear elastic‐plastic behaviour of each component, a general analytical model is proposed that yields the maximum rotation of the connection. Despite the complexity of the various connection types, the proposed model is able to provide analytical solutions for the moment‐rotation response of a steel connection by using appropriate transformation criteria for assemblies of components in series and in parallel. The model is applied to typical beamto-column connections, showing good agreement with numerical results.

Equivalent post-buckling models for the flexural behaviour of steel connections

Abstract Analytical solutions for the evaluation of the behaviour of steel connections are presented which are able to reproduce their full non-linear behaviour. Because usual models for the analysis of steel connections consist of translational springs and rigid links whereby the springs exhibit a non-linear force–deformation response, usually taken as a bi-linear approximation, they require an incremental non-linear analysis. Using a substitute elastic post-buckling model where each bi-linear spring is replaced by two equivalent elastic springs in the context of a post-buckling stability analysis using an energy formulation, closed-form solutions are obtained for a connection loaded in bending. Application to a beam-to-column welded connection using the component (spring) characterisation of code regulations yields the same results in terms of moment resistance and initial stiffness, being additionally able to trace the full unstiffening response.

Guidance for the Design of Spliced Columns

Steel columns in sway and nonsway frames that are spliced along their length generally have a lower strength capacity in compression. This load capacity can be further reduced owing to the inevitable presence of small geometrical imperfections in the form of the out-of-straightness of the column and column segment misalignment. The current work examines the buckling behavior of a framed spliced column with initial imperfections and the possibility of a nonuniform cross section. A geometrically nonlinear model accounting for imperfect elastic buckling behavior is formulated using the differential equations of equilibrium. This is followed by a study of the imperfection sensitivity to the linearly evaluated critical load. A discussion on the variation of the load-carrying capacity with the level of imperfections on a practical spliced column is also presented. The findings suggest that a spliced column can be considered equivalent to a prismatic Euler column, with an appropriate effective length, for design purposes. In this context, some implications for design are deduced from the presented analysis.