A proposal for beam-column interaction formulae

Peer reviewe

Improvement of the interaction formulae for beam columns in Eurocode 3

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. (C) 2002 Civil-Comp Ltd. and Elsevier Science Ltd. All rights reserved

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

peer reviewedThis 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. (C) 2003 Elsevier Ltd. All rights reserved

Experimental and theoretical analysis of shear bolted connections for tubular structures

In this paper, numerical and experimental investigations devoted to the evaluation of the bearing resistance of tubular members, with gusset plates and through-all long bolts, are presented. Unlike lap shear joints, the analysed connection shows a limited confinement of the bearing area associated with the use of long bolts and the presence of a gap in the member, which can lead to a reduction of the bearing resistance. In order to investigate the behaviour of shear connections composed by thin or thick SHS (Square Hollow Section) profiles and long bolts, experimental tests on 24 specimens and FE simulations have been conducted. Both experimental and FE results have confirmed the influence of local instability of the hole in bearing on the resistance of thin profiles and the poor accuracy of the available standards for this specific joint typology. In particular, the performed comparisons have shown that, for thin profiles, EC3 model is likely to overestimate the resistance, while for higher thickness of the SHS conservative predictions are obtained. The paper presents the conducted experimental and numerical investigations highlighting, at the end, the need for a proper formulation able to account for the local instability effect on the bearing resistance

Seismic pre-qualification tests of EC8-compliant external extended stiffened end-plate beam-to-column joints

An experimental and numerical campaign was carried out to validate the design procedure and prequalify extended stiffened end-plate (ESEP) joints for ductile seismic resistant moment-resisting frames in the framework of Eurocodes. In fact, the tested ESEP joints have been designed with the aim of guaranteeing ductile and dissipative seismic response in accordance with the principles of the hierarchy of resistances to enforce plastic deformations in ductile components of the joints. Two alternative types of dissipation mechanisms are promoted, namely either (i) plastic deformations solely in the connected beam using full strength joints or (ii) plastic deformations in both the beam and the connection using equal strength joints. The adopted design criteria and technological details are described and discussed. The results of experimental tests confirmed the expected yielding mechanisms of the joints, which satisfied the acceptance criteria for both North American and European prequalification. Finite element simulations of ESEP joints have been validated against the experimental results and have been used to investigate the local response of the joints, thus highlighting the influence of both geometrical and mechanical parameters

Preliminary study on beam-to-column joints under impact loading

Background: Recent catastrophic events have pointed out the need to ensure the integrity of structures under “exceptional” events. Since many years, the University of Liège is involved in different activities and projects related to the robustness assessment of structures. The robustness of a structure is the ability of the system to remain globally stable after events not directly accounted for in the design, like impact, fire or consequences of a human error, which should lead to a reasonable damage when compared to the original cause. Objective: The presented preliminary work reports the experimental campaign of different European projects (FREEDAM and ROBUSTIMPACT) carried out or currently ongoing, with the aim of understanding the behaviour of different joint typologies under impact loading protocol. Method: The experimental programmes have mainly regarded static and impact tests on steel joints by the means of a dropping mass using DIC (Digital Image Correlation) for the data acquisition. Conclusions: In the present paper, an overview on the design criteria adopted in the design of the experimental campaign, for the FREEDAM project, is given, and some earliest results are discussed

On the robustness of earthquake-resistant moment-resistant frames: Influence of innovative beam-to-column joints

Background: The deformation capacity of beam-to-column connections strongly influences the robustness of earthquake-resistant Moment Resistant Frames (MRFs) when subjected to a loss-of column scenario. As a consequence, with the aim of foresee the structural response up to the failure, an accurate modelling of the ultimate behaviour of the joints is needed. Objective: In this paper, the influence of the connections on the behaviour of MRFs under a loss-of-column scenario has been analysed considering an accurate modelling of the joints. Method: In addition, in order to achieve this goal, different beam-to-column joints designed for seismic actions and tested at the Salerno University, have been modelled and introduced in a case-study structure, whose response has been evaluated by means of push-down analyses. In particular, the connections analysed and modelled are of three different types: a dog-bone connection, a partial strength Double Split Tee (DST) joint and a partial strength connection with friction dampers. Results/Conclusion: The results of pushdown analyses performed by means of SAP2000 computer software have been examined with the aim to determine the Residual Reserve Strength Ratio (RRSR) index that, combined with the energy balance method proposed by Izzudin et al. (2008), allow to assess the structural ro-bustness