The diaphragmatic behaviour of floors represents one important requirement for earthquake resistant buildings since diaphragms connect the lateral load resisting systems at each floor level and transfer the seismic forces to them as a function of their in-plane stiffness. This paper presents an innovative hybrid timber-steel solution for floor diaphragms developed by coupling cross-laminated timber panels with cold-formed custom-shaped steel beams. The floor consists of prefabricated repeatable units which are fastened on-site using pre-loaded bolts and self-tapping screws, thus ensuring a fast and efficient installation. An experimentally validated numerical model is used to evaluate the influence of the; i) in-plane floor stiffness; ii) aspect ratio and shape of the building plan; and iii) relative stiffness and disposition of the shear walls, on the load distribution to the shear walls. The load transfer into walls and lateral deformation of the construction system primarily depend on the adopted layouts of shear walls, and for most cases an in-plane stiffness of floors two times larger than that of walls is recommended.
Cross-laminated timber (CLT) is a new panelized mass timber product that is suitable for building tall wood buildings (higher than eight stories) because of its structural robustness and superior fire resistance as compared with traditional light-framed wood systems. A number of tall CLT buildings have been constructed around the world in the past decade, and taller projects are being planned. The energy efficiency of this emerging building type was evaluated numerically in this comparative study with the use of a building energy simulation program. A 10-story multiunit residential building model constructed using CLT was simulated and compared with a light-frame metal construction model with the same floor plan. A sensitivity analysis was also conducted to study the impact of different weather profiles, building types, and internal load conditions on building energy consumption performance. It was concluded that CLT generally provides significant improvement on heating energy efficiency as a heavy and air-tight envelope, but its energy performance efficiency can be affected by weather, building size, internal loading, and HVAC control.