Investigation of Dynamic Properties of Timber-Steel Hybrid Buildings Utilizing Ambient Vibration Testing and Finite Element Modelling
Abstract
Vibration serviceability can govern the design of lightweight tall mass timber and hybrid buildings, yet finite element (FE) modal predictions remain uncertain because they incompletely represent the mass and stiffness contributions of non-structural elements, composite floor action, and connection stiffness. This study characterizes the dynamic properties of four Canadian hybrid mass timber–steel buildings of 5 to 12 storeys using ambient vibration testing and detailed FE modelling. In operational modal analysis, natural frequencies from Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification agreed within 3%, whereas damping ratios differed by up to 170% between algorithms. The measured damping ratios decreased with increasing frequency, and regression envelopes fitted to these data provide a practical reference range for design. Staged construction testing of one building showed that non-structural elements contribute both mass and stiffness: after fit-out, lower-order mode frequencies decreased by up to 9%, whereas higher-order mode frequencies increased by up to 19%. FE sensitivity analyses showed that connection flexibility had negligible influence under low-amplitude operational vibrations, that including non-structural mass without the associated stiffness underestimated frequencies by up to 57%, and that neglecting shear interaction between cross-laminated timber floor panels and their toppings, even in floating systems without mechanical connectors, produced discrepancies up to 80%. A rigid-diaphragm model with full superimposed dead loads provided acceptable frequency estimates for preliminary design, although it neglects the orthotropic stiffness of the floors and can therefore alter the predicted mode sequence.
Reference
Samira Mohammadyzadeh; Jianhui Zhou; Md Shahnewaz; Robert Jackson; Fei Tong. (2026). Investigation of Dynamic Properties of Timber-Steel Hybrid Buildings Utilizing Ambient Vibration Testing and Finite Element Modelling. Elsevier BV. https://doi.org/10.2139/ssrn.7576805
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