Jean-Pierre Jaspart

Benchmarks for finite element modelling of bolted steel connections

Abstract This paper presents part of the results of a study devoted to the analysis of bolted steel connections by means of finite elements. In detail, the paper introduces elementary tee stub connections which are endowed with different plastic failure mechanisms and can be adopted as benchmarks in the validation process of finite element software packages. Moreover, the simulations of these benchmarks performed by means of bricks as well as contact elements allow the properties and results of these elements to be commented upon. Finally, the comparison between computed and measured values permits the effectiveness and degree of accuracy of the proposed finite element models to be mirrored.

Basic issues in the finite element simulation of extended end plate connections

Abstract Numerical simulations of steel bolted connections performed with finite element models depend heavily upon constitutive relationships, step size, number of integration points, kinematic descriptions, element types and discretizations. The aforementioned items combined with complex non-linear phenomena which are commonly observed in connections render the finite element technique not attractive for this class of problems. In this paper these issues are scrutinized and both a legitimate methodology suitable to the analysis of extended end plate moment resisting connections and proper three-dimensional finite element models are established. These models are provided first for non-preloaded and preloaded bolted tee stubs which are proposed as benchmarks. Next, both a solid model and an assemblage of three-dimensional beam finite elements, viz. the spin , are proposed to model the bolt behaviour either in a rigorous or simplified fashion, respectively. Lastly, a three-dimensional non-linear finite element model suitable for the analysis of isolated extended end plate connections is proposed and validated.

Calibration of a finite element model for isolated bolted end-plate steel connections

Abstract This paper presents parts of results of a study devoted to the analysis of bolted steel connections by means of finite elements. Initially, the paper deals with the calibration of finite elements of the code ABAQUS on test data as well as on simulations of elementary tee stub connections engendered with the LAGAMINE software package. These connections were proposed as benchmarks in a previous companion paper and simulated to the ultimate limit state. Next, an assemblage of three-dimensional beam finite elements is proposed to model the bolt behaviour in a simplified fashion. Lastly, a three-dimensional finite element model is set with the ABAQUS code in order to simulate the stiffness and strength behaviour of isolated extended end-plate steel connections. The comparison between computed and measured values in each phase highlights the effectiveness and degree of accuracy of the proposed finite element models.

General report: session on connections

Abstract As a result of a world-wide intensive research activity, a new design concept for structural moment resistant joints has been suggested and implemented in design codes. In the present paper, its background is first briefly described and the main contributions to its development are presented. As a matter of fact, because of the high number of past and ongoing researches, reports and papers devoted to this topic, an exhaustive list of all these works could not be established in a limited number of pages. The possibilities of extension of the new design concepts, which have been first developed for steel beam-to-column joints under static loading, are particularly pointed out. This aspect appears quite important as in the near future it should provide designers with a unified design approach for structural joints whatever their loading, their configurations and the nature of their constitutive material(s).

The stiffness model of revised Annex J of Eurocode 3

Publisher Summary A major technical improvement in the revised Annex J of Eurocode 3 is the new model for the determination of the rotational response of joints. The objective of this chapter is to provide backgrounds to this model. In general, the moment rotation characteristic (M-Φ curve) of joints is non-linear. Although Annex J can be used to determine a simplified linear, bi-linear or multi-linear M-Φ curve, this chapter focuses on its on its potential to predict a full non-linear curve. This is to enable a direct comparison between model and test results. The test results are taken from the databank SERICON. This databank forms a collection of M-Φ data from different laboratories all over Europe. The databank contains results for different types of joints and for different joint configurations.

Combined Distortional and Overall Flexural-Torsional Buckling of Cold-Formed Stainless Steel Sections: Experimental Investigations

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 Liege 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 setup. 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 writers.

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

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 test results.

Economy studies of steel building frames with semi-rigid joints

The traditional design of steel structures assumes for global frame analysis either rigid or pinned joints. Consequently the design of the joints must satisfy these initial assumptions in terms of joint behaviour. This may lead to uneconomical solutions for the joint detailing or for the choice of member sections. Modern standards for steel design like Eurocode 3 allow to take into account the actual joint behaviour, i.e. semi-rigid and/or partial-strength. Because of this they enable new concepts and strategies for economical design of steel structures. This paper discusses opportunities for optimum solutions as well as the impact of the joint classification on economy. It presents existing and new comparative studies on the economy of steel building frames which are designed according to the traditional and the new concept respectively.

New interaction formulae for beam-columns in Eurocode 3: The French–Belgian approach

Abstract This paper presents one of the two new proposals for beam-column interaction formulae, which will be made available in the forthcoming EN version of Eurocode 3. It is based on second-order in-plane elasticity, and has been derived in order to exhibit an understandable physical background, as well as accuracy and consistency with the other resistance and stability formulae of the code. The formulae ensure all the required continuities: between the cross-section classes, from plasticity to elasticity when slenderness and axial force are increasing, and continuity between all the individual stability member checks and cross-section verifications. The paper shows how the basic format may be extended to cover a wider range of cases, i.e. spatial elastic–plastic behaviour with possible lateral–torsional buckling. Through an extensive comparison with the results of FEM numerical simulations of about 15 000 beam-columns, the proposal is found to be safe and accurate.

Improvement of the interaction formulae for beam columns in Eurocode 3

Abstract This paper presents a new proposal for beam-column interaction formulae initially based on second-order in-plane elastic theory, as an alternative to those proposed in the Eurocode 3 pre-standard [1] . It has been derived according to the following requirements: theoretical background, clear physical meaning, consistency with the other related formulae of Eurocode 3 and accuracy. Besides that, the suggested formulae cover all required continuities: between the cross-section classes, from plasticity to elasticity as slenderness and axial force increase, and continuity between all the individual stability member checks and cross-section verifications. Further to the presentation of the formulae and their background, the good agreement of the proposal is shown through an extensive comparison with more than 15,000 results of finite element numerical simulations.