PSI - Issue 78

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

533

the efficiency and potential benefits of adopting dissipative design strategies. In particular, for MRF, the dissipative structures, both all-timber (T) and all-steel (S), show higher reduction of mass as respect to non-dissipative ones with Δ M - =25-48%. EBFs follow, with Δ M - =21-35%. For D-, X- and V-CBF structural types, in cases of all-timber (TT) and steel frame with timber braces (ST), a lower Δ M - can be noted, with Δ M D =8-31%, Δ M X =16-24% and Δ M V =20 22% respectively. Contrary, the cases of all-steel (SS) and timber frame with steel braces (TS) show a mass increment Δ M + , that in case of D- and X-CBF is due to the upper limit requirement of the dimensionless slenderness of dissipative steel braces (which should be equal to 2), according to section 6.7.3 of Eurocode 8 (EN 1998-1-1, 2005), while in case of V-CBF is due to the shear force acting on the beam, equal to 0.3N pl,Rd , where N pl,Rd is the axial strength of the brace, according to section 6.7.4 of Eurocode 8 (EN 1998-1-1, 2005). 4. Conclusion From the review of hybrid timber-steel framed structural systems based on scientific literature, at first, four typological categories are identified, then the most significant research contributions are critically examined, including experimental investigations, numerical analyses and innovative design approaches for both global structures and connection details. Several hybrid solutions are addressed, also equipped with special devices for seismic protection, such as steel dissipative links, friction connections, advanced self-recentring systems, etc. The reviewed studies demonstrate that combining timber with steel results in efficient structural systems, which exhibit stable hysteretic behaviour, enhanced energy dissipation capacity, controlled damage mechanisms and, in some cases, self-recentring properties that minimize residual deformations after seismic events. The preliminary seismic design of hybrid steel timber framed systems presented allowed for interesting observations. Specifically, the case studies, analysed through linear static analysis, are compared in terms of structural mass, evidencing that dissipative MRFs and EBFs achieve the most significant mass reductions, as well as all-timber (T) and steel frame with timber braces (ST). Contrary, mass increase occurs for all-steel (S) X- and D-CBF and timber frames with steel braces (TS), due the adimensional slenderness requirement of steel braces, while for V-CBF to shear force design of the beam. For the latter types, therefore, dissipative design seems to be not convenient in terms of structural mass. However further to the evaluation of the design impact in terms of structural mass, the seismic performance is going to be evaluated through non-linear static pushover analysis. The suitability of the hybrid framed structures can then be assessed taking into account an integrated parameter. It is also to be noted that this preliminary study involves just simple portal frames, the investigation is in progress towards the analysis of larger structures. Definitely, hybrid timber-steel seismic-resistant structures are promising for future construction, combining sustainability with favourable structural performance. However, further research is recommended, going from numerical and experimental investigations, joint details conception and evaluation, long-term behaviour assessment, towards the development of design guidelines to facilitate the practical implementation of the hybrid systems. Acknowledgements The study is carried out in the context of the research projects DPC – ReLUIS 2024-2026 – WP12 and RETURN. The student Angela Matilde Fusco is acknowledged for the contribution given for the numerical elaborations. References Ascione, F., Esposito, F., Iovane, G., Faiella, D., Faggiano, B., Mele, E., 2024. Sustainable and efficient structural systems for tall buildings: Exploring timber and steel – timber hybrids through a case study. In: Buildings 2024, 14(2), 524. https://doi.org/10.3390/buildings14020524. Asiz, A., Smith, I., 2011. Connection System of Massive Timber Elements Used in Horizontal Slabs of Hybrid Tall Buildings. In: J. Struct. Eng., vol. 137, no. no. 11, 2011. doi: 10.1061/(asce)st.1943-541x.0000363. Bezabeh, M.A., Tesfamariam, S., Stiemer, S.F., 2016. Equivalent Viscous Damping for Steel Moment-Resisting Frames with Cross-Laminated Timber Infill Walls. In: Journal of Structural Engineering, vol. 142, no. 1, Jan. 2016. doi: 10.1061/(asce)st.1943-541x.0001316. Blomgren, H.E., Koppitz, J.P., Valdés, A.D., Ko, E., 2016. The heavy timber buckling-restrained braced frame as a solution for commercial buildings in regions of high seismicity. In: World Conference on Timber Engineering (WCTE2016). Chen, F., Li, Z., Li, M., Shu, Z., 2023. Experimental testing of post-tensioned steel-timber hybrid frames equipped with energy-dissipating braces. In: Engineering Structures 296 (2023) 116960. https://doi.org/10.1016/j.engstruct.2023.116960.