This paper summarises the experimental and numerical investigation conducted on the main connection of a novel steel-timber hybrid system called FFTT. The component behaviour of the hybrid system was investigated using quasi-static monotonic and reversed cyclic tests. Different steel profiles (wide flange I-sections and hollow rectangular sections) and embedment approaches for the steel profiles (partial and full embedment) were tested. The results demonstrated that when using an appropriate connection layout, the desired strong-column weak-beam failure mechanism was initiated and excessive wood crushing was avoided. A numerical model was developed that reasonably reflected the real component behaviour and can subsequently be used for numerical sensitivity studies and parameter optimization. The research presented herein serves as a precursor for providing design guidance for the FFTT system as an option for tall wood-hybrid buildings in seismic regions.
In recent years, hybrid systems have grown in popularity as potential solution for mid-rise construction. There is also an increased interest in using timber for such systems. The lack of established design guidance, however, has tabled the practical implementation of timber-based hybrid structures. The aim of this thesis is to address the existing knowledge gap regarding the detailed connection design of hybrid systems through combined experimental and numerical investigations on a novel timber-steel system called “FFTT”. The FFTT system relies on wall panels of mass timber such as Cross-Laminated-Timber (CLT) for gravity and lateral load resistance and embedded steel beam sections to provide ductility under seismic loading. A vital step towards practical implementation of the FFTT system is to obtain the proof that the connections facilitate the desired ‘strong column – weak beam’ failure mechanism.
The numerical work applied the software ANSYS; a parametric study based on the results of previous tests was conducted to obtain a suitable connection configuration for improved structural performance. The experimental work, carried out at FPInnovations, consisted of quasi-static monotonic and reversed cyclic tests on two different connection configurations: fully and partially embedded ASTM wide flange sections in combination with 7 ply CLT panels. The combination of partial embedment length and full embedment depth, even when using the smallest wide flange section, did not facilitate the desired behavior. The connection performance was significantly improved when reducing the embedment depth (to avoid creating stress peaks on a weak cross layer) and increasing the embedment length (larger center to center distance between bearing plates). The used small size steel beam, however, is not practical for a real structure; therefore, further studies with larger beams and a modified geometry are recommended before the FFTT system can be applied in practice.
Recent developments in novel engineered mass timber products and connection systems have created the possibility to design and construct tall timber-based buildings. This research presents the experiments conducted on the steel-wood connection as main energy dissipating part of a novel steel–timber hybrid system labelled Finding the Forest Through the Trees (FFTT). The performance was investigated using quasi-static monotonic and reversed cyclic tests. The influence of different steel beam profiles (wide flange I-sections and hollow rectangular sections), and the embedment approaches (partial and full embedment) was investigated. The test results demonstrated that appropriate connection layouts can lead to the desired failure mechanism while avoiding excessive crushing of the mass timber panels. The research can serve as a precursos for developing design guidelines for the FFTT systems as an option for tall wood-hybrid building systems in seismic regions.