PSI - Issue 78

Giacomo Iovane et al. / Procedia Structural Integrity 78 (2026) 528–535

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energy has made timber a central element for sustainable construction strategies. Nowadays, timber is no longer confined to traditional applications, in fact it is widely used for the realization of modern tall as well as large span timber buildings (Ascione et al., 2024). Furthermore, timber is often combined with other structural materials such as steel and concrete, giving rise to innovative high performance hybrid construction systems. These solutions allow for the development of structures that exploit the potential and advantages of the materials while simultaneously reducing the overall environmental impact (ECCS, 2024). Within this framework, hybrid steel-timber structural systems show intelligent and more efficient use of the materials to improve the global and local behaviors with respect to all-timber and all-steel structures. By efficiently combining the complementary properties of both materials, such as the timber environmental benefits, lightness and fire resistance and steel mechanical strength, stiffness and ductility, these systems offer a balanced and efficient structural solution. This paper provides an exploration of the potential applications of hybrid steel-timber framed structural types. Specifically, four main typological categories are identified from a review of the current state of the art in the scientific literature. Subsequently, a preliminary seismic design of selected hybrid steel-timber framed structures is presented, assessing the pros and cons of the proposed solutions in terms of structural mass. 2. Identification of the typological categories for hybrid framed structural systems from literature From the analysis of the state of the art, four types of steel-timber composite and hybrid structural systems can be distinguished: Type 1 . Steel frame with timber shear panels; Type 2 . Steel-timber hybrid and composite floor diaphragms; Type 3 . Steel-timber hybrid framed systems; Type 4 . Timber Buckling-Restrained Brace (T-BRB). Among Type 1, it is possible to identify the following most common system configurations: (1.1) steel edge frame with mass timber panel ; (1.2) steel edge frame with light-weight timber wall ; (1.3) cold-formed steel frame with timber based panel . The Type 1.1 hybrid system consists of steel edge moment resisting (MR) frames coupled with CLT panels. This solution improves overall stiffness and strength compared to traditional all-steel frames, especially as far as the number of stories and spans increase (Dickof, 2013). In these hybrid systems, energy dissipation mainly occurs for plastic deformation of the connections between CLT panels and steel frame, which are hold-down and angle brackets, purposely designed, thus limiting damage to both the structural members of the steel frame and the timber panel (Setti et al., 2025; Gao and Song, 2025). As an alternative to dissipative steel connections, different types of mechanical fastening systems and epoxy adhesives are proposed to optimize the frame-panel interaction, avoiding localized damage to the timber panel (Loss et al., 2016), while the dissipative function is entrusted to advanced seismic protection technologies, such as friction dampers, Self-Centering Rocking Wall (SC-RW; Hashemi et al., 2016) and Equivalent Viscous Damping (EVD; Bezabeh et al., 2016). Type 1.2 hybrid system consists of steel edge MR frames combined with light-weight timber shear walls, typically composed of Oriented Strand Board (OSB) panels and Spruce-Pine-Fir (SPF) post and beams of small sizes. In these systems, the timber shear walls contribute significantly to resist lateral loads at small deformations while the steel frame works at large deformations, providing additional strength and stiffness after the timber components damage (He et al., 2014). Instead of traditional hold-down and angle bracket connections, friction dampers placed at the interface between the frame and the timber wall have proven to improve both seismic energy dissipation and post-earthquake repairability (Li et al., 2021). Also self-centering solutions are developed, combining post-tensioned steel frames with timber panels and friction devices to control the seismic response and minimize damage (Cui et al., 2020; Dong et al., 2021). Type 1.3 hybrid system features Cold- Type 1 Type 2 Type 3 Type 4 1.1 1.2 1.3 2.1 2.2 3.1 3.2 3.3 Fig. 1. Types of hybrid and composite structural systems.