PSI - Issue 78

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

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an alternative to traditional steel connections. Experimental tests on multi-story 3D specimen have demonstrated stable hysteretic behavior with self-centering capabilities, both under quasi-static and dynamic conditions, maintaining structural integrity with minimal damage, typically limited to the connections at the base of the columns (Jamil et al., 2015). Type 3.2 hybrid system consists of timber frames integrated with dissipative steel members and joints. A common solution involves the use of steel friction braces or Additional Damping And Stiffness (ADAS) devices, which provide significant increases in lateral resistance, stiffness and energy dissipation capacity compared to conventional timber frames. Post-tensioning techniques combined with steel devices further enhance seismic response by concentrating dissipation in replaceable steel elements while limiting damage to timber members (Miller et al., 2021; Chen et al., 2023). Dissipative steel links can also be applied at beam ends, column bases or brace connections in various structural types, including Moment-Resisting Frames (MRF), Concentric (CBF) and Eccentric (EBF) Braced Frames. Numerical and experimental analyses have confirmed the effectiveness of these dissipative solutions, also showing significant mass reductions compared to non-dissipative frames (Iovane et al., 2023a, 2023b; Mekonnen et al., 2025). Different beam-to-column joint configurations of this system are tested to optimize the energy dissipation mechanism, such as either a continuous column and a steel dog-bone or I-section link at the beams end, connected to the column, or a column interrupted by a steel box connected to the end beam steel dog-bone link, demonstrating good dissipation capacity, but with some localized brittle failures in the timber-steel connections (Krauss et al., 2025). Type 3.3 hybrid system combines timber and steel frames. In this configuration, gravity loads are often supported by timber beams and columns while lateral forces are supported by steel frames coupled with Steel Plate Shear Walls (SPSW) and CLT floors (Li et al., 2023). Comparisons of all-timber, all-steel and steel-timber hybrid solutions have shown that hybrid solutions can maintain seismic performance equivalent to all-steel systems while reducing embodied carbon emissions, contemporary they are more expensive than all-timber structures, although they offer a favorable balance between environmental impact and structural efficiency (Hsu et al., 2025).

Type 3.1

Type 3.2

Type 3.3

Jamil et al., 2015 Miller et al., 2021 Chen et al., 2023 Mekonnen et al., 2025

Iovane et al., 2023b

Hsu et al., 2025

Fig. 4. Type 3 steel-timber hybrid framed systems.

Finally, Type 4 hybrid system is Timber Buckling-Restrained-Brace (T-BRB), applicable to both steel and timber structures. T-BRB consists of a steel core, which can be made of profiles of various shapes or bars and is responsible for axial energy dissipation, enclosed in a timber shell, generally made of radiata pine or Douglas fir, which provides restraint against buckling. This configurat ion improves the system’s strength and stiffness while also allowing for the integration of advanced seismic control mechanisms (Blomgren et al., 2016). Large-scale tests have shown that the mechanical performance of T-BRBs is sensitive to the timber shell characteristics, which influence both the response to fatigue loads and buckling resistance (Murphy et al., 2021). The use of adhesives in combination with mechanical fasteners has limited influence on failure modes, while increasing sizes or strength grade of the steel core generally it leads to a reduction in ductility (Kia and Valipour, 2021; Luo et al., 2022). More recently, hybrid solutions integrating T-BRBs into post-tensioned timber frames with re-centering capabilities are proposed. In these systems, beams and columns are equipped with tensioned cables to restore the initial position after the seism, while T-BRBs provide energy dissipation. Experimental and numerical results have confirmed the system high ductility, achieving seismic performance without brittle failures in timber elements (Williamson et al., 2025). 3. Preliminary seismic design of hybrid framed systems The case studies is a single storey structure 3m high, with a rectangular plan layout, having one bay, 6m long, in the y transverse direction, and three bays, 6m long, in the longitudinal x-direction, for a total length of 18m (Iovane