Search

The aim of this study is to explain from a fundamental perspective, how distributing the material thickness of a metal plate in different ways can be used to control the shape of the elastic buckling mode. The Evolutionary Structural Optimisation (ESO) method is modified to control the buckled shape of plates simply supported on three sides with the remaining longitudinal edge free. The bucking objectives are considered both from a fundamental perspective, and for the application of kinetic façade design, that is, façade panels that undergo shape changes to facilitate ventilation or shading control. A series of buckling experiments of optimised aluminium plates validates the optimised designs. It is shown that in order to achieve a maximum opening in a buckled plate, the buckled shape should be controlled in such a manner as to create a relatively flat zone of maximum transverse displacement over much of the displaced free edge, a shape that differs from the fundamental mode of a uniform thickness plate. Notably, such a shape may be achieved via optimisation with objectives that relate either to the shape itself, or to the objective of maximising the opening. The design methods and experiments demonstrate that redistribution of plate material can efficiently control the buckling characteristics of metal plates for desired functions, and provide significant performance enhancements over uniform thickness plates. • Buckling shape of metal plates is controlled via material distribution of the plate thickness. • ESO method is used to optimise the plate material distribution. • Experiments validate the optimised plates. • Optimised plates have substantially larger buckled openings than uniform thickness plates. • Optimised plates are suitable for kinetic façade applications. [ABSTRACT FROM AUTHOR]

Abstract: There is a large body of literature on the experimental behaviour of steel plates under a variety of loading and edge support conditions. Typically the longitudinal plates edges were either laterally restrained (stiffened) or laterally unrestrained (unstiffened). There are no such plate experiments reported in the literature of plates with a longitudinal edge stiffened with an edge-stiffener (partially stiffened). This paper presents 30 plate tests of plates simply supported on three sides, with the remaining (longitudinal) edge stiffened with an edge-stiffener. The edge-stiffener was increased in size from zero (unstiffened plate) to a size sufficient to create a stiffened edge (stiffened plate). Edge-stiffeners of an intermediate size resulted in partially stiffened plates. The behaviour of partially stiffened plates is fully documented with the aid of a 3D photogrammetry system, and the adequate size of edge-stiffeners required in order to create a stiffened plate edge are discussed. Edge-stiffener types investigated are simple lips, simple inclined lips and complex lips. Design procedures for partially stiffened elements previously inferred from numerical studies are shown to accurately and reliably determine the plate strengths, and further validate the procedure for use as a general strength approach in current international cold-formed steel specifications. [Copyright &y& Elsevier]

Abstract: Recent investigations of square hollow section (SHS) metal tubes with externally bonded carbon fibres have shown significant increases in the axial capacity and mean crushing load, compared with the metal SHS. The composite metal–fibre tubes employed carbon fibre reinforced polymer (CFRP) matrix layouts of two and four layers of carbon fibres. In this paper the same sized two and four layer CFRP SHS were manufactured independent of the metal SHS, and the axial capacity and crushing behaviour were determined experimentally. Four different tube sizes were tested, resulting in tube width to thickness ratios between 32 and 144. A photogrammetry system was employed to accurately determine the buckling and post-buckling behaviour. It is shown that the capacity and mean crush load of the composite metal–CFRP SHS exceed the sum of those for the individual metal SHS and CFRP SHS, by up to 1.8 times. This composite action results from the bond between the metal and the carbon fibres, and the mechanics with respect to buckling, capacity and crushing is discussed. The strength of metal, composite metal–CFRP and CFRP tube walls are determined using the effective width approach, and are shown to compare well with the experimental results. [Copyright &y& Elsevier]

The current slenderness limits are significantly different in international design codes for cold-formed Circular Hollow Sections (CHS) under pure bending. This paper aims to use the Finite Element (FE) method to understand the behaviour of cold-formed CHS under pure bending and to propose new design rules. The model is calibrated by comparing its predicted load-deflection curves with previously published experimental data. In total, 21 specimens were modelled with diameter-to-thickness ratios ranging from 13 to 122. The current slenderness limits in the present international steel specifications were examined using the FE model and their suitability for cold-formed CHS is discussed. The effect of section slenderness on rotation capacity has been examined where the predicted variation of rotation capacity against section slenderness has been compared to the experimental results. A new equation for the amount of initial geometrical imperfection as a function of section slenderness has been developed and proposed for design purposes. The ovalisation deformation ratio and the critical strain at local buckling were determined and compared for compact, non-compact and slender sections. The progressive bending deformations of CHS at 10 critical steps have been presented and compared for the three cross sectional types, in particular at the maximum moment and bending rotation. In general, a good agreement has been obtained between the predicted strengths and ductilities using the current FE models and those of the experimental data of cold-formed CHS. • Using finite element method to determine the slenderness limit of cold-formed steel tubes and compared to the previous experimental results. • The effect of geometrical imperfections on the deformation cold-formed CHS has been examined. • The rotation capacity has been presented for CHS. • The ovalisation of compact, non-compact and slender section has been analysed. • The buckling mechanism has been analysed by using strain analysis, the critical strain at maximum moment has been determined and compared to the theoretical results. [ABSTRACT FROM AUTHOR]