The continuous strength method

Saari

Wang

2010

Thin-Walled Structures

Self Cite

182

127

Square and rectangular hollow sections are generally produced either by hot-rolling or coldforming. Cross-sections of nominally similar geometries, but from the two different production routes may vary significantly in terms of their general material properties, geometric imperfections, residual stresses, corner geometry and material response and general structural behaviour and load-carrying capacity. In this paper, an experimental programme comprising tensile coupon tests on flat and corner material, measurements of geometric imperfections and residual stresses, stub column tests and simple and continuous beam tests is described. The results of the tests have been combined with other available test data on square and rectangular hollow sections and analysed. Enhancements in yield and ultimate strengths, beyond those quoted in the respective mill certificates, were observed in the corner regions of the cold-formed sections -these are caused by cold-working of the material during production, and predictive models have been proposed. Initial geometric imperfections were generally low in both the hot-rolled and cold-formed sections, with larger imperfections emerging towards the ends of the cold-formed members -these were attributed largely to the release of through thickness residual stresses, which were themselves quantified. The results of the stub column and simple bending tests were used to assess the current slenderness limits given in Eurocode 3, including the possible dependency on Gardner, L., Saari, N. and Wang, F. (2010) Comparative experimental study of hot-rolled and cold-formed rectangular hollow sections. Thin-Walled Structures. 48(7), 495-507. 2 production route, whilst the results of the continuous beam tests were evaluated with reference to the assumptions typically made in plastic analysis and design. Current slenderness limits, assessed on the basis of bending tests, appear appropriate, though the Class 3 slenderness limit, assessed on the basis of compression tests, seems optimistic. Of the features investigated, strain hardening characteristics of the material were identified as being primarily responsible for the differences in structural behaviour between hot-rolled and coldformed sections.

Section: Discussionmentioning

confidence: 99%

Comparative experimental study of hot-rolled and cold-formed rectangular hollow sections

Saari

Wang

2010

Thin-Walled Structures

Self Cite

182

127

“…2(b), where Esh is the strain hardening modulus. This model considers strain hardening, is included in Annex C of EN 1993-1-5 [14], and has been used throughout the development of the strain-based continuous strength method (CSM), which allows for the beneficial influence of strain hardening on the design of structural metallic elements, including structural carbon steel [6,7,15], aluminium [16,17] and stainless steel [18,19]. However, due to the existence of a yield plateau, this elastic, linear hardening model is less suitable for hot-rolled carbon steels.…”

Section: Existing Stress-strain Modelsmentioning

confidence: 99%

Stress-strain curves for hot-rolled steels

Yun

Journal of Constructional Steel Research

2017

370

190

The use of advanced analytical and numerical modelling in structural engineering has increased rapidly in recent years. A key feature of these models is an accurate description of the material stress-strain behaviour. Development of standardised constitutive equations for the full engineering stress-strain response of hot-rolled carbon steels is the subject of the present paper.The proposed models, which offer different options for the representation of the strain hardening region, feature an elastic response up to the yield point, followed by a yield plateau and strain hardening up to the ultimate tensile stress. The Young's modulus E, the yield stress fy and the ultimate stress fu are generally readily available to the engineer, but other key parameters, including the strains at the onset of strain hardening and at the ultimate stress, are not, and hence require predictive expressions. These expressions have been developed herein and calibrated against material stress-strain data collected from the literature. Unlike the widely used ECCS model, which has a constant length of yield plateau and constant strain hardening slope, the proposed models, reflecting the collected test data, have a yield plateau length and strain hardening characteristics which vary with the ratio of yield to ultimate stress (i.e. with material grade). The proposed models require three basic input parameters (E, fy and fu), are simple to implement in analytical or numerical models, and are shown herein to be more accurate than the widely employed ECCS model. The proposed models are based on and hence representative of modern hot-rolled steels from around the world.

“…These two components have been established for structural carbon steel and stainless steel in previous studies [1][2][3][4][5]. Building on recent proposals [9-12 and 17-18], developments of a base curve, a suitable strain hardening material model and a global plastic analysis approach for aluminium alloy structures are described in the following sections.…”

Section: General Conceptsmentioning

confidence: 99%

“…A series of studies [1][2][3][4][5] have been conducted to develop and improve the CSM in the past decade. Owing to the general similarity of structural behaviour between stainless steel and aluminium alloys, the authors investigated the feasibility of applying the CSM to aluminium alloy structures.…”

Section: Introductionmentioning

confidence: 99%

The continuous strength method for the design of aluminium alloy structural elements

Young²,

2016

Engineering Structures

106

Aluminium alloys are nonlinear metallic materials with rounded stress-strain curves that are not well represented by the simplified elastic-perfectly plastic material model used in most existing design specifications. Departing from current practice, the continuous strength method (CSM) is a recently developed design approach for aluminium alloy structures, which includes the beneficial influence of strain hardening. The CSM is a deformation-based method and employs a base curve to define the continuous relationship between cross-section slenderness and deformation capacity. This paper explains the background and the two key components of the CSM: (1) the base curve, which is extended herein such that the method covers both non-slender and slender sections and (2)