PSI - Issue 44

Elisabetta Maria Ruggeri et al. / Procedia Structural Integrity 44 (2023) 464–471 E. Ruggeri, G. D’Arenzo, D. Li Cavoli, R. Cottonaro, M. Fossetti/Structural Integrity Procedia 00 (2022) 000–000

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1. Introduction and background Cross-Laminated timber (CLT) buildings are realized with prefabricated CLT panels used for both vertical walls and horizontal floors, which are mutually connected through metal fasteners and mechanical anchors. Due to the relatively high in-plane stiffness of CLT panels, the lateral behavior of a CLT shear wall depends to a large extent on the properties of the mechanical connections, which provide the necessary ductility and energy dissipation during seismic events (Izzi et al. 2018). Typically, it is assumed that the Lateral Load Resisting System (LLRS) of CLT structures is entrusted to the shear walls, which work simultaneously, as an in parallel system, undertaking both global base shear force and global overturning moment. Such shear walls are typically anchored at their base with hold downs and angle brackets, which, according to most of the calculation models available in literature, provide the resistance against the lateral loads. Typically, CLT buildings can be realized according to two different construction techniques. Platform construction, where the vertical continuity of the walls is interrupted at each story by the floors and balloon construction, where the vertical continuity of the walls is not interrupted by the floors at each story, but they are connected on the internal side of the vertical walls by means of connections. Among the different platform construction techniques, CLT buildings can be realized in two different configurations: “shear type”, in which perpendicular walls are not connected, and “box type”, in which perpendicular walls are mutually connected. Although it is common to assume the lateral response of a CLT building being governed by the shear walls and their base connections, in a “box type” construction typology, there are other connections at the wall corner of the structure, see Figure 1, which join together the perpendicular walls and contribute to the lateral performance of the CLT shear walls.

Fig. 1. Example of CLT building under later loads with perpendicular walls.

Interaction between perpendicular walls involve variations of the lateral stiffness and the lateral capacity of CLT shear walls and contribute to the so-called box-behavior of the building. The perpendicular walls and the wall-to-wall connections play an important role in the three-dimensional behavior of the structure. However, knowledge about the effects of perpendicular walls on lateral performances of CLT buildings is limited. The effect of the perpendicular walls on the lateral behavior of CLT buildings was found in different analytical and numerical studies such as Shahnewaz et al (Shahnewaz, Popovski, and Tannert 2020), Hummel and Seim (Hummel and Seim 2019), Tamagnone et al. (Tamagnone, Rinaldin, and Fragiacomo 2017) and Ruggeri et al. (Ruggeri et al. 2021). The effects of perpendicular walls was found in several experimental campaigns on full-size Light Frame Timber (LFT) (Van De Lindt et al. 2010; Tomasi et al. 2015) and CLT (Popovski and Gavric 2015) platform buildings. As already mentioned earlier, current analysis methods for lateral design of CLT buildings do not take into account the effects of the perpendicular walls and the wall-to-wall connections. This is also the case of analysis methods used for seismic design, in which the application of capacity design principles may lead to overdesigned connections between perpendicular walls, which entails larger interaction effects. Although neglecting the interaction effects between perpendicular walls simplifies the seismic design procedure, from the other side, disregards a relevant structural interaction which was found in several studies to be significative for the lateral performance of CLT buildings. This paper presents an experimental study aimed at investigating the lateral behavior of CLT shear walls connected to perpendicular walls by means of typical screwed wall-to-wall connections. The main objective of this study is to quantify the increase of lateral stiffness and the lateral capacity of CLT shear walls due to the interactions between perpendicular walls.