No. 120. The bases of the structural behaviour of steel-concrete construction - Technical report (170 pages, ISBN 978-2-88394-202-8, January 2026).
Title: The bases of the structural behaviour of steel-concrete construction
Technical report
Year: 2026
Pages: 170
Format approx. DIN A4 (210x297 mm)
ISBN: 978-2-88394-202-8
DOI: doi.org/10.35789/fib.BULL.0120
Abstract:
The bases of the structural behaviour of steel–concrete construction is a Bulletin developed by fib Commission 2 – Analysis and Design, and more specifically by Task Group 2.6 – Composite Steel–Concrete Construction. The document is fully consistent with the mission of Commission 2, which recognises analysis and design as the core tasks of structural engineering and promotes the development of physically based, coherent, and design-oriented models for structural assessment and dimensioning.
In recent years, and with due respect given to the responsible use of resources, the role of structural analysis has grown significantly. In other words, this growth was driven by the need for refined models capable of realistically describing stress–strain states under serviceability and ultimate limit conditions, as well as under long-term effects, fatigue, fire, and extreme actions. At the same time, and with a desire to minimize our environmental footprint, the refined design of new structures—comprising conception, dimensioning, and detailing—remains fundamental to engineering practice. fib Commission 2 supports a unified approach to all of the aforementioned activities, whereby the same mechanical principles underpin both advanced analytical models and simplified methods suitable for practical application. Steel–concrete composite construction, involving materials with markedly different mechanical and time-dependent behaviours, provides a particularly meaningful field in which to pursue this objective.
Although steel–concrete composite solutions are well known and widely used worldwide, their development has followed different traditions depending on whether the design culture has been primarily rooted in reinforced concrete or in steel structures. Consequently, similar mechanical phenomena may be treated differently in design practice and in code provisions, despite sharing common physical foundations. This Bulletin is aimed at bridging this gap by revisiting the fundamental aspects of steel–concrete composite construction from an integrated perspective, consistent with the fib principles of homogenisation and integrity of structural concepts across materials.
The Bulletin proposes rational and mechanics-based models aimed at supporting engineers’ understanding of structural behaviour and improving the quality of design decisions. It addresses the sectional behaviour of composite members under complete and partial interaction, the modelling of shear connections, instability and buckling of composite columns, time-dependent effects of concrete, and the analysis of statically determinate and indeterminate composite systems. Fatigue phenomena and structural behaviour under fire conditions are also examined. Particular attention is given throughout to material nonlinearity, construction stages, load history, imperfections, and second-order effects, in line with the analytical and design philosophy promoted by fib Commission 2.
The activity of fib Commission 2 is explicitly oriented towards supporting the development and continuous improvement of the fib Model Code, and this Bulletin contributes to that objective by consolidating research outcomes and established knowledge into a coherent and mechanically consistent framework. By presenting concepts and models that are applicable to both new and existing structures, and that are compatible with uniform safety formats, the Bulletin provides a technical basis that can inform future fib Model Code provisions and their interpretation in practice.
Oguzhan Bayrak
Chair of fib Commission 2 : Analysis & design
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