Abstract
Multi-storey cross-laminated timber (CLT) buildings are a comparatively recent construction type. Knowledge concerning the performance of CLT buildings regarding the prevention of disproportionate collapse after unforeseeable events (e.g. accidents or acts of terrorism) is not as refined as that for concrete and steel buildings. In particular, alternative load paths (ALPs) after the removal of a wall panel in platform-framed variants have not yet been studied in detail. The goal of this work was therefore to study ALPs in CLT buildings. An eight-storey bay of an existing building was evaluated by conducting a non-linear static pushdown analysis in a finite element analysis on three representative storeys. The analyses accounted for single fastener behaviour, timber crushing, friction, brittle failure and large deformations. The force–deformation behaviours elicited under the pushdown analyses were subsequently inserted in a simplified dynamic model to evaluate the transient response of the entire bay. Four ALPs were identified in this case – shear resistance in the floor panels, arching action of the walls, catenary action in the floor panels and hanging action from the roof. The dynamic analysis did not show a collapse, unless the inter-compartment stiffness was significantly reduced. The resistance mechanisms are described in this paper, which may provide information for improved building design.
Highlights
Cross-laminated timber (CLT) is used in increasing proportions for the bearing structures of multi-storey buildings
3.2 alternative load paths (ALPs) Four different ALPs were identified in the compartment models
& ALP I – a shearing action in the outer floor panels, transferring loads from the pushing wall from above to the supporting stationary walls below. This ALP was limited by transversal shear failure in the floor panels due to the load concentrations beneath the pushing wall
Summary
Cross-laminated timber (CLT) is used in increasing proportions for the bearing structures of multi-storey buildings. CLT is composed of cross-wise laminae of parallel timber boards and is used for wall and floor panels (Brandner, 2013). The tallest timber buildings (both 18 storeys) are Mjøstårnet in Brumunddal, Norway (Abrahamsen, 2017) and Brock Commons Tallwood House in Vancouver, Canada (Fast et al, 2017), and both use CLT panels as floors. The nine-storey Stadthaus in London, UK, is an example of a platformframed CLT building (Wells, 2011). In a multi-storey building with high occupancy, disproportionate collapse resulting from an unforeseeable event such as an accident or act of terrorism needs to be avoided as the consequences would be severe (BSI, 2006). The total probability of a disproportionate collapse, PðCÞ, is usually expressed by (Ellingwood and Dusenberry, 2005)
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