Beam-to-column joints are one of the most common types of joints in metal structures. In the design of load-bearing aluminium structures, welding, as a joining method, is often avoided because of localised degradation of mechanical properties in the heat-affected zone (HAZ). However, recent experimental studies on the extent and strength of the HAZ show a significant difference compared to very conservative design rules when modern welding techniques are used. Therefore, the numerical study conducted in this paper addresses the influence of HAZ on the mechanical behaviour of the welded aluminium beam-to-column joint. Parametric numerical analyses were performed varying the aluminium alloys, the reduced mechanical properties of the HAZ, and different definitions of the HAZ extent. The obtained results show that the highest stress concentration occurs at the connection between the top beam flange and the column flange, resulting in plastic softening in this region. Different joint capacities were observed by varying the mechanical properties of the HAZ. A detailed overview of numerical models as well as the obtained moment–rotation curves show that the behaviour of some models is not as conservative as assumed in the design standards considered.

It is known that steel–concrete composite systems are very efficient. However, such steel–concrete composite systems can be optimised using cold-formed steel elements and innovative shear connections. In other words, by considering demountability and reusability, the negative impact of the built environment on the whole ecosystem can ultimately be reduced. This paper, therefore, presents a numerical study of an innovative solution for a composite floor system consisting of built-up cold-formed sections and concrete slabs. Through parametric numerical analysis, parameters such as the diameter and quality of bolts, the concrete class, the type of concrete slab, and the steel quality of sections and bolts were varied. The numerical analysis results show that the system with a solid concrete slab had a higher shear resistance and ductility than the system with a concrete slab made with profiled sheeting and showed different failure modes. The presented results form the basis for push-out tests for the proposed shear connection types.

Composite systems made by combining cold-formed steel (CFS) and concrete can produce excellent properties compared to traditional solutions. One such innovative solution is the subject of this paper which consists of built-up CFS with corrugated web, connected by spot-welds and concrete slab with innovative type of shear connection. This paper presents numerical investigation of two types of shear connections suitable for the proposed composite solution. One type of shear connection is completed using bolts which provide a direct shear connection between the flange of CFS girder and the concrete slab. The second type of shear connection was completed using composite dowel rib connector. The results of FE simulations indicate that solution with bolts ensures higher stiffness of the shear connection, but in turn reduces its ductility.

Cold-formed steel composite floors are lightweight systems whose application increased in the last few decades. According to the design guidelines, the frequency of floor systems should be more than 4 Hz while in the case of light steel floors, the natural frequency of the system should be in the high frequency range above 8 Hz. The main focus of this paper is to investigate the vibration performance of an innovative lightweight composite floor system called LWT-FLOOR. The LWT-FLOOR system is composed of spot-welded built-up cold-formed steel elements that are connected to a lightweight concrete slab. Based on laboratory tests material properties of all components of the system are obtained and the finite element model of cold-formed steel concrete composite floor is created to investigate its vibration behaviour. Numerical analyses were conducted in Abaqus/CAE, where after mesh density verification, the influence of the degree of shear connection, spot weld density, concrete type and class, steel channels cross-section thickness and the arrangement and diameter of the shear connector were analysed. The results show that the flexural rigidity of the system and vibration characteristics can be improved by changing those parameters, especially by changing steel channel cross-section characteristics and support conditions from nominally pinned to nominally rigid.

Steel and composite shear wall systems are used for vertical stabilisation of buildings and have been widely investigated in recent decades. Such systems provide excellent shear strength and ductility while allowing material savings due to optimal material usage and an increase in construction speed. A double-skin cold-formed steel shear wall filled with concrete is an innovative composite shear wall that is composed of cold-formed corrugated steel sheets and intermediate fasteners filled with concrete which is in turn bounded by a steel frame. Steel sheets are connected onto a concrete core with the help of intermediate fasteners behaving as shear connectors forming a sandwich Steel–Concrete–Steel panel. Compared to reinforced concrete shear walls, this type of wall has enhanced strength and ductility due to steel confinement while allowing for a reduction in construction time. The numerical simulation of double-skin cold-formed steel shear walls filled with concrete has been studied in this paper. The numerical parametric simulations are conducted in ABAQUS/CAE, where the influence of steel sheet thicknesses, concrete strength and the arrangement and diameter of the shear connectors were analysed. The wall shear capacities for all parameters were compared and the results provide suggestions for future investigations.

The Innovative Lightweight Cold-Formed Steel–Concrete Composite Floor System (LWT-FLOOR) addresses key challenges faced by the construction industry related to the efficiency, adaptability, and life-cycle usability of structural elements. Within this context, the present study investigated the behaviour of demountable bolted shear connections in a composite system combining built-up cold-formed steel (CFS) girders and concrete slabs. An experimental programme comprising 18 push-out tests was conducted on two composite configurations: built-up back-to-back CFS sections and built-up sections incorporating a corrugated web. The influence of key parameters, including the bolt diameter, CFS thickness, steel grade, and connector spacing, was evaluated. The results show that increasing the bolt diameter enhanced the shear resistance and initial stiffness while reducing ductility, whereas reducing the CFS thickness led to a moderate decrease in resistance accompanied by a pronounced increase in ductility. The incorporation of a corrugated web increased the ultimate shear resistance by approximately 30–40%. The existing analytical models from current standards were found to be inadequate; however, the introduction of a spacing-dependent correction factor into the prEN 1994-1-1 model significantly improved the prediction accuracy, reducing the coefficient of variation from 16% to 4.36%. The findings provide a quantitative basis for improving the design of demountable shear connections in lightweight composite CFS-concrete systems.