Keywords: stainless steel structures, bolted joints, finite element analysis, plastic analysis, non-linear analysis.

Changes of attitudes associated with the building construction industry and a global transition for a sustainable reduction in environmental impacts arising from developments has been causing an increase in the use of stainless steel. Despite this fact the current stainless steel design code, Eurocode 3, part 1.4, 2003 [1] is still largely based on analogies with the carbon steel structural behaviour. An important step to increase the understanding and the use of the stainless steel in structural systems was the development, and subsequent publication of specific design codes, such as the Eurocodes. However, considering that these codes represented a first attempt to produce specific stainless steel structural design rules, the idea of using similar rules to the ones adopted for carbon steel, enabled engineers to perform a smooth transition for the stainless steel design.

The net section rupture represents one of the ultimate limit states usually verified for structural elements subject to tension normal stress. The present paper presents a finite element numerical model, developed using the ANSYS [2] program, which aims to evaluate the tension capacity of stainless steel bolted structural elements. The numerical results obtained were calibrated and compared to previously performed experiments in terms of load versus deformation curves, stress distributions and failure modes.

A fully nonlinear analysis was performed using the numerical model developed. The material non-linearity was considered using a Von Mises yield criterion associated with a multi-linear stress-strain relationship and an isotropic hardening response. The geometrical non-linearity was introduced in the model by using an updated Lagrangean formulation. This procedure represents the full structural assessment of the bolted joints analysed, and may be summarized using several outputs, namely the stress distribution (that detects, among other data, first yield), or the force-displacement curve for any node within the connection.

Comparing experimental and numerical results in terms of load versus strain curves and deformed shape, a good agreement may be verified. The experimental ultimate load was equal to 463 kN and the numerical ultimate load was equal to 448.2 kN representing a ratio P_num/P_exp of 0.97. However, when these values are compared with Eurocode 3 results, the ultimate limit state related to the net section failure leads to an unsafe design prediction since this resistance, according to the Eurocode 3 recommendations is equal to 592.4 kN. When the stainless steel is used in structural engineering, the design criteria based on deformation limits needs to be proposed such as the criteria adopted in the steel structural tubular joints arising from the large strain observed in these structures.

Future steps in this investigation will consider the development of more tests with cover plate joints subjected to tension to enlarge the experimental dataset enabling its use in further numerical simulations. With these results in hand, the authors will envisage the production of some modifications to the rules of the stainless steel design code with the aim of producing more economical and safer solutions.

1

Eurocode 3, ENV 1993-1-4, 2003, "Design of steel structures - Part 1.4: General rules - Supplementary rules for stainless steel", CEN - European Committee for Standardisation, 1996.

2

Ansys, Inc., "Theory Reference", (version 11.0), 2008.

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