Jacques Rondal

Strength curves for aluminium alloy columns

Abstract The paper describes a column curve formulation capable of producing accurate strengths for extruded aluminium alloys failing by flexural buckling. The formulation uses a simple extension of the Perry curve and is shown to be valid for the full range of alloys used in practice. The material properties are assumed to be expressed in terms of the Ramberg–Osgood parameters ( E 0 , σ 0.2 , n ), typically obtained from a stub column test of the finished product. It is shown that firstly, the formulation is capable of reproducing closely the ECCS a-, b- and c-column curves for aluminium alloys. Secondly, by adopting the ECCS Recommendations of basing the column curve selection on the type of alloy (heat-treated or non-heat-treated), it is shown that better agreement with tests can be obtained by using the column curve formulation proposed in the paper compared with the column curves of the ISO Recommendations and the current pre-standard Eurocode9 for aluminium alloy structures.

Cold formed steel members and structures: General Report

Abstract The aim of this report is to give a review of some recent progresses in the field of cold-formed steel members. Particular emphases are given to progresses in the field of distortional buckling and in recent development of new types of joints.

Residual stresses in cold-rolled profiles

Abstract Structural steel members obtained by cold-forming have become more and more popular in steel construction. They allow for lightening the weight and thus provide appreciable savings over conventional hot-rolled sections. Cold-forming leads to changes in the main structural characteristics of the virgin material. Among them the increase of the yield strength due to strain-hardening and of the ultimate strength due to strain-ageing and the birth of residual stresses which play an important role in the behaviour of the profiles under compression loads. The aim of the paper is to propose a theoretical method for predicting residual stresses due to cold-rolling. The numerical results obtained lead to a better knowledge of the characteristics of the cold-rolling (elastic spring-back, effect of the ratio of the thickness versus the radius of the corner, distribution and size of the residual stresses with respect to the dimensions of the profiles).

Column curves for stainless steel alloys

Abstract The paper describes a column curve formulation capable of producing accurate strength curves for cold-formed stainless steel columns. The formulation uses a non-linear expression for the imperfection parameter but is otherwise identical to the Perry–Robertson equation used in Eurocode3, Parts 1.1, 1.3 and 1.4. It is shown that several column curves are necessary for accurately describing the strength of austenitic and austenitic–ferritic stainless steel alloy columns and two curves are proposed. One of these is close to the curve for cold-formed sections currently used in the draft Eurocode3, Part 1.4. A new column curve is also proposed for ferritic alloys and 12% chromium weldable structural steels.

Stability of built-up beams and columns with thin-walled members

Abstract The aim of this paper is to present experimental results on built-up elements composed of cold-formed C profiles with battened plates or C stitches. The test results are compared with theoretical predictions obtained by means of the classical design method taking into account the Q factor when the profiles are thin-walled, for battened plates, and by means of a new design method for elements using C stitches. A comparison of the results shows that both methods lead to a safe and accurate design.

Beam-column welded stud connections☆

Stud shear connectors have been widely used for many years for providing the composite connection between steel and concrete in composite construction. The present paper is concerned with the feasibility of a similar technique for framing connections between beams and columns by means of threaded connectors. The new kind of connection would be especially suitable for hollow section columns because existing types of connections generally create problems. Several stud sections and diameters have been investigated and tests carried out: tensile and shear tests on welded studs and simple connection specimens and tests on beam to column assemblages. On the basis of the experiental results, a design method is suggested, which is in appearance quite similar to that used for bolted connections.

Influence of flexural residual stresses on the stability of compressed angles

Abstract Structural steel elements that are obtained by cold forming become more and more popular in steel construction. Indeed they are lighter in weight and thus provide appreciable savings compared with the usual hot rolled sections. Because they are obtained by cold forming, two kinds of residual stresses occur: membranar and flexural stresses. The flexural residual stresses are usually larger than the membranar ones. However the ECCS (European Convention for Constructional Steelwork) column buckling curves were established on the basis of longitudinal membranar residual stresses only, in addition to geometrical imperfections. Using a non-linear computer program, the authors investigate the influence of longitudinal flexural residual stresses on the carrying capacity of cold formed angles. This kind of section is now widely used for erecting large transmission towers. Strain hardening due to cold forming is taken into account in the present study. From the numerical results obtained, conclusions are drawn on the suitability of European column buckling curves for cold formed angles.