Valorisation action of plastic member capacity of semi-compact steel sections - a more economic design

Learning material (2011)

Enhanced proof strength after cold process of fabrication of non-linear metallic profiles : Comparison of two predictive models for hollow sections

Conference (2010, December)

Sustainable steel constructions – Life-cycle inventory, methods and applications

Conference (2010, July 07)

This document gives an overview of the challenges and issues related to a sustainable use of steel in the construction sector. After an introduction that concerns the challenges associated to the use of ... [more ▼]

This document gives an overview of the challenges and issues related to a sustainable use of steel in the construction sector. After an introduction that concerns the challenges associated to the use of steel as a sustainable material, the principles of a life-cycle analysis are presented. The paper then focuses on the life-cycle inventory data of several products: finished cold-rolled coil, electro-galvanized steel, section rolling and rebar. The data are presented for two (sometimes three) different recycling rates. Indeed, since steel is recycled to more than 85% at the end of its life and recyclable and indefinite number of times, the presented inventory includes allocation for scrap inputs and outputs using the closed material loop recycling methodology developed by the International Iron and Steel Institute (IISI). A description of the method principles is also provided. The influence of the end-of-life credit method will be discussed. Corrosion and subsequently maintenance of steel products will be treated afterwards and a brief comparison of the life-cycle inventory will be provided for electro-galvanized steel and finished steel. [less ▲]

Mechanical behavior of ferritic grade 3Cr12 stainless steel-Part 1: Experimental investigations.

in Thin-Walled Structures (2010), 48(7), 540-552

Ferritic stainless steels are corrosion resistant steels with a low and stable cost. Widely used in automotive applications, structural applications using ferritic stainless steels are only emerging ... [more ▼]

Ferritic stainless steels are corrosion resistant steels with a low and stable cost. Widely used in automotive applications, structural applications using ferritic stainless steels are only emerging mainly because ferritics are partially covered by structural standards due to a shortage of design data. Computer models are more and more used to support the developments of conventional design methods based on expensive full-scale tests or trial and errors methods. And for the modeling of metal forming processes as well as structural behavior of members, it is necessary to afford an accurate knowledge of the mechanical properties. In this paper, the experimental investigations made on the chromium based alloy 3Cr12 (1.4003) in order to characterize its mechanical behavior are presented. During the research, a classical uniaxial experimental equipment and a bi-axial experimental equipment designed by Flores (2005) in the Structures Laboratory of the University of Lige have been used. The collection of tests performed included tensile tests, cyclic shear tests, simple shear tests and successive simple shear and plane-strain tests. The yield locus and the hardening models are presented and identified in a companion paper by the same author. [less ▲]

Life cycle inventory of stainless steel – A review of challenges, methods and applications.

in Sustainable constructions - A life-cycle approach in engineering: International Symposium: Malta, 23-25 July 2010 (2010, July)

Combined distortional and overall flexural-torsional buckling of cold-formed stainless steel sections: Experimental investigations

in Journal of Structural Engineering (2010), 136(4), 354-360

This paper presents a series of 48 full-scale tests on press-braked stainless steel lipped channel section columns subjected to concentric compression. The tests were carried out between fixed ends in the ... [more ▼]

This paper presents a series of 48 full-scale tests on press-braked stainless steel lipped channel section columns subjected to concentric compression. The tests were carried out between fixed ends in the Structures Laboratory of the University of Liège and the test specimens were designed such that distortional buckling developed in the section prior to overall flexural-torsional buckling. The stainless steel alloy was 1.4003 chromium weldable steel, popularly known as 3Cr12. Three different geometries were tested using the same experimental set-up. A critical summary of the standards and methods for calculating the carrying capacity of cold-formed stainless steel compression members is presented in a companion paper by the same authors. [less ▲]

Combined distortional and overall flexural-torsional buckling of cold-formed stainless steel sections: Design

in Journal of Structural Engineering (2010), 136(4), 361-369

This paper provides a critical summary of the European standards and design methods available for calculating the strength of cold-formed stainless steel compression members. The standards considered (so ... [more ▼]

This paper provides a critical summary of the European standards and design methods available for calculating the strength of cold-formed stainless steel compression members. The standards considered (so far mainly applied to columns failing by flexural buckling) are applied to the case of lipped channel section columns failing by combined distortional and overall flexural-torsional buckling. As observed during the tests presented in a companion paper, distortional buckling is found to have a considerable effect on the cross-section resistance and is prone to interact with the global flexural-torsional mode. It is investigated how the different formulations account for the two buckling modes and their interaction and how accurate strength predictions they provide. A new Direct Strength Method taking into account these failure modes is then presented and compared to the tests results. [less ▲]

Enhanced proof strength after cold process of fabrication of non-linear metallic profiles – Comparison of two predictive models for hollow sections

in International Symposium on Tubular Structures : ISTS13, Hong Kong, 15-17 December 2010 (2010)

Enhanced mechanical properties after cold process of fabrication of non-linear metallic profiles

in Thin-Walled Structures (2009), 47(12), 1575-1589

It is well known that the cold-forming process is likely to significantly enhance the mechanical properties of the profile by strain hardening leading to increased resistance compared to a resistance ... [more ▼]

It is well known that the cold-forming process is likely to significantly enhance the mechanical properties of the profile by strain hardening leading to increased resistance compared to a resistance assessment based on nominal properties. It is thus necessary to accurately determine the mechanical properties after the cold process of fabrication. In this paper, experimental reference data and formulae calculating the increased proof strength in cold-formed stainless steel profiles are reviewed. A new theory-based formula for the evaluation of the actual mechanical properties of stainless steel structural members using the virgin sheet material properties is then established. This formula is dependent upon the radius of curvature to thickness ratio; it is not restricted to a single alloy but is valid for non-linear metallic materials. Prediction efficiency is evaluated against the collected experimental data and particular attention is paid to the set of experimental data related to hollow sections. The main thrust of the predictive model lies in its axiomatic roots in contrast to the traditional empirical formulae found in the literature. [less ▲]

Mechanical properties, residual stresses and structural behavior of thin-walled stainless steel profiles

Doctoral thesis (2008)

Although it offers a wide variety of interesting properties such as fire resistance or durability, stainless steel has been used in limited amount in structures. It is a known fact that the design rules ... [more ▼]

Although it offers a wide variety of interesting properties such as fire resistance or durability, stainless steel has been used in limited amount in structures. It is a known fact that the design rules don't properly account for the additional benefits of stainless steel properties and are largely based on the specifications for carbon steel. Indeed, a number of similarities exist between stainless steel and ordinary carbon steel but there is sufficient differences to afford a specific treatment in design standards. And since stainless steel is an expensive material, it is important to accurately predict the resistance of structural members. The present research work is dedicated to the study of cold-formed stainless steel profiles. It actually follows the life of a stainless steel construction element and falls on three fundamental topics: the material behavior, the through-thickness residual stress distribution and mechanical enhancement due to the cold-forming process and, last, the strength of concentrically compressed thin-walled columns. Firstly, several constitutive models are characterized such as Teodosiu-Hu's micro-structural based hardening model, capable of predicting the behavior of the studied stainless steel grade submitted to biaxial loading causing plastic strain. This model accounts for the nonlinear hardening behavior, the anisotropy, the Bauschinger effect and more complex behavior such as the observed work-hardening stagnation under reversed deformation at large strains. For this purpose, a collection of tests is carried out including multiaxial tests such as tensile-shear tests and successive simple shear tests and plane-strain tests. Secondly, the effects of the forming process on the mechanical properties are studied. To begin with, on the basis of the constitutive models developed previously, an analytical method that calculates the biaxial residual stress distribution in the walls and in the corners of cold-formed profiles is established. Based on the conclusions drawn from this theoretical analysis, a new formula for the evaluation of the actual mechanical properties is established. This formula is not restricted to a single alloy or type of cross-section. Current design standards are then used to calculate the strength of lipped-channel section columns failing by combined distortional and overall flexural-torsional buckling and the results are compared to tests. Indeed, full-scale tests on cold-formed stainless steel lipped channel section columns were achieved in the Structures Laboratory of the University of Liège. And, once verified against the test results, finite element models were used to generate additional results when necessary. The author then presents a new Direct Strength Method taking into account this phenomenon. Finally, a wide amount of reference results are gathered from the literature, without limiting oneself to any kind of cross-section or stainless steel grade. This database is used to propose an improved formulation for the design of stainless steel thin-walled section columns failing by distortion, local or combination of local and overall buckling in the low slenderness range. [less ▲]