Abstract This paper presents axial loading tests of steel‐only and concrete‐filled stud specimens, comprising either single profiles or built‐up (toe‐to‐toe) sections based on Clipped 100×50×15 profiles. The focus is on local buckling; therefore, only stub columns (300 mm long) are investigated. Since the objective is to study the behaviour of battened columns in future research, either no intermediate fasteners are used between the paired profiles, or they are very small and intended solely for construction purposes. The behaviour of the stubs is analysed, revealing several notable particularities, along with a comparison of performance across the different tested configurations. Finally, existing design approaches are preliminarily evaluated.

Abstract Advancements in metal Additive Manufacturing (AM) have enabled the production of lightweight and functional metallic parts. In particular, Wire and Arc Additive Manufacturing (WAAM) processes have gained prominence due to their efficiency and high deposition rates. However, the WAAM process generates residual stresses (RS), wherein the tensile RS may improve the mechanical performance and load‐bearing capacity of the substrate by essentially prestressing specific parts (i.e., the flange tips) of steel sections against applied compressive loading. Therefore, it is crucial to design a WAAM stiffener so that the structure benefits not only from the imposed geometry but also from the induced RS. While previous research has identified heat source and material type as influencing factors on RS, there is little consideration of critical parameters such as position of deposition zone (stiffener), layer count (deposition height), and base plate thickness. This paper provides insight into the impact of such design parameters on the resulting RS from WAAM deposition of a stiffener on a base plate through validated finite element (FE) modelling. The base plate is simulated for both clamped and unclamped conditions. The results demonstrate that adding WAAM stiffeners on the webs of I‐sections generates tensile RS in their vicinity, with peak values reaching the material's yield strength. Moreover, increasing the base plate or stiffener thickness reduces the RS relative to the mid‐thickness of each base plate. While the location of the stiffener does not significantly affect the magnitude of the peak RS, it causes a shift in the residual stress pattern and distribution. The results presented in this paper can be used to infer appropriate WAAM design parameters to achieve favorable RS patterns, enhancing the quality of manufactured parts for new production or the repair and reinforcement of existing infrastructure.

Abstract On February 2, 2024, a landslide of several hundred cubic meters caused several massive rocks (50 to 100 m 3 ) to fall down the slope of Vevey valley region in Switzerland. The rockslide hit and damaged part of the structure of the A9 Lausanne‐Saint‐Maurice national road/bridge before settling at the bottom of the slope near the bridge foundation. Luckily, the rockslide did not cause any casualties, nor did it affect any homes. Noting that the structure “Pont de Veveyse” consisting of 2 parallel and identical composite steel and prestressed concrete bridges that was put into service in 1969 ensures the passage of approximately 61000 vehicles/ day. In the bridge region, the geological conditions are very complicated and are characterized by an extended sliding zone that experiences slippage of a few cm per year. Since in this region, erosion and thus, slope as well as rockslides occur naturally and often, the following study was performed to determine the behavior of the bridge under different rockslide impacts. Following the accident, field investigations were conducted to gather information and identify the trajectory of the rockslides and bridge damage. Then, based on the principle of linear impulse and momentum as well as the conservation of linear impulse and momentum, the velocity of rockslides as well as the average impulse forces were calculated. The obtained results were used in the numerical simulations performed using the nonlinear software Abaqus to investigate the bridge behavior and responses caused by the impact of the massive rockslide. The effects of impact load, its direction and location on the behavior of the bridge were examined. The obtained results showed that the simulated damage mechanisms agree with field observations. Moreover, bridge stability is affected by the rockslide impacts. The obtained results can be considered a mean to assess the stability of the bridge and perform as guidelines for authorities to mitigate future hazard rockslides impact strategies for the A9 bridge.

Abstract A novel concrete‐filled steel tubular (CFST) column with inner semi‐circular stiffeners is proposed in this study. The semi‐circular stiffeners are developed based on the confinement mechanism in square CFST columns and aim to strengthen the confinement effect on concrete in the whole cross‐section area, therefore improving the overall structural performance of the composite column. The section is also flexible to use different grades of concrete in the core and cell regions. Experimental investigations on axial compressive behaviour of the semi‐circle stiffened concrete‐filled steel tubular (SCS‐CFST) columns as well as the hollow section columns were carried out. High strength steel Q690 and two concrete grades C40 and C90 were adopted for the test specimens. Various parameters including steel tube thickness, cross‐section slenderness, combination of different concrete grades as well as semicircular stiffener size were investigated. The test results showed that the stiffened hollow sections achieved significantly higher compressive strength with delayed local buckling failure compared to the unstiffened counterparts. SCS‐CFST columns presented significantly enhanced compressive strength and ductility compared to the corresponding unstiffened CFST columns. The applicability of existing design equations was evaluated for the novel SCS‐CFST columns. A new design approach considering the confinement effect in different regions was proposed and exhibited good predictions.

Abstract Welded box columns made of high‐strength steels are characterized by high buckling resistance and low dead weight. The residual stresses introduced by the welding process are of particular importance. In the area of the weld seams, the cooling process creates residual tensile stresses that are in equilibrium with the compression stresses distributed over the cross‐section of the column. In Europe, the buckling resistance of box columns with welded cross‐sections made of high‐strength steels is insufficiently covered by the rules of EN 1993‐1‐1 and EN 1993‐1‐12. The application for columns made of high‐strength steels in the medium slenderness range is quite conservative. As part of the AiF‐FOSTA research project P1588, residual stress distributions of welded box sections were determined for steel grades S460 to S960. The buckling resistance was investigated experimentally and by structural‐mechanical calculations. The results lead to a re‐evaluation of the buckling curve assignment of compression members with welded box sections and to standardized residual stress distributions.

Abstract Hybrid steel construction, combining the production efficiency of traditional manufacturing methods with the geometric freedom and scope for optimisation enabled by additive manufacturing, has shown great potential for use in structural applications. Wire‐based 3D printing methods, including wire arc additive manufacturing (WAAM), are considered to be the most suitable for the scale and demands of construction. Anticipated benefits include reduced material usage, heightened structural efficiency, enhanced automation and reduction in environmental impact. Specific applications include the utilization of additive manufacturing for the production of detailed components, such as connections, nodes and stiffeners (that also lend themselves to topology optimization) and for the strengthening of both new and existing structural members. The hybrid steel construction concept, early successful examples of its application and an outlook for future developments are presented in this paper.

Abstract Companies performing international structural design work are confronted with varying requirements imposed by different standards and methodologies. This paper presents a brief comparison of stability analysis procedures for steel structures using the Eurocode 2022 and the American Institute of Steel Construction Specification for Structural Steel Buildings (ANSI/AISC 360‐22) standards. Several structural types will be investigated, ranging from those with clearly defined effective lengths to others with more ambiguous effective lengths requiring stability analysis techniques involving explicit modeling of system imperfections and member (bow) imperfections. Geometric and material nonlinear imperfection analysis (GMNIA) will be used for comparison. Through these case studies, we illustrate the practical implications of each method, highlighting key differences. Ultimately, this study aims to enhance understanding of stability analysis and inform international best practice in structural design, contributing to safer and more efficient engineering solutions.

Abstract The impact of earthquakes on building structures is well‐known, leading to a growing focus on seismic‐resistant design. Among various energy dissipation devices, the Crescent Shaped Brace (CSB) stands out for its ability to meet stiffness, strength, ductility and ultimate capacity requirements due to its unique geometric configuration. This study presents an optimized version of the corner CSB device, transitioning from a fully dense to a lattice‐based configuration, a transformation made possible by Wire Arc Additive Manufacturing (WAAM) technology, among the Additive Manufacturing (AM) processes. WAAM enables the fabrication of complex geometries unattainable with conventional methods, allowing the realization of a lightweight, structurally efficient lattice corner CSB. The CSB is based on diamond lattice unit cells, leading to two configurations: diamond‐frame and diamond‐truss, the latter incorporating additional vertical struts for an axial‐force‐dominated behavior, improving load‐bearing capacity. An experimental campaign validated the WAAM fabrication of high‐quality struts and nodes, ensuring structural reliability.

Abstract In the context of structural optimisation, high‐strength steels represent the highest strength‐to‐weight ratio of the existing steels, thereby contributing to the optimisation of steel structures by reaching the same level of resistance with a reduced material quantity and resulting in lighter buildings requiring less extensive and costly foundations. New production technologies are already available for the manufacture of hot‐rolled steel sections with a yield strength up to 500 MPa in Europe and 80 ksi (550 MPa) in the United States, which comply with the product norms for civil engineering applications. The selection of the right steel at the right place may result in further investments by manufacturers in the future to develop the optimal material solution for each application. Nevertheless, the use of mild steels is still often preferred for hot‐rolled sections due to a lack of information regarding the existing high‐performance products and the advantages they offer, as well as a scarcity of availability due to the current low demand. Furthermore, using a higher steel grade is often associated with an increase in the unitary cost of steel, accompanied by an increased carbon factor, a reduced weldability and ductility as well as an increased risk of local and global buckling instabilities. This paper demonstrates the considerable weight, cost and carbon savings that can be attained through the selection of an appropriate steel grade for multi‐storey building columns and propose reference slenderness ratios to facilitate the selection of the steel grade.

Abstract Laser metal deposition (DED‐LB), or wire laser beam directed energy deposition (DED‐LB), is a metal 3D printing technique with growing appeal in civil engineering due to its efficiency and cost‐effectiveness in producing large‐scale components. However, limited data on the mechanical and geometric properties of DED‐LB steels hinder broader adoption. This study presents a comprehensive experimental investigation of ER 308LSi stainless steel DED‐LB plates. Laser scanning, tensile testing and microstructural characterisation were conducted on 2 mm and 8 mm thick coupons, with varying surface finishes and orientations. The results showed minimal geometric irregularity and comparable mechanical properties between as‐built and machined specimens. Thinner coupons exhibited reduced strengths and greater anisotropy, attributed to coarser grains and a strong crystallographic texture. An or‐thotropic constitutive model, adapted from WAAM stainless steel, was successfully applied to describe the material's anisotropic behaviour in both the elastic and inelastic regimes. The findings highlight the potential for using DED‐LB in construction, offering a viable alternative for fabricating large‐scale metal components of complex geometries.