Design for Seismic Resilient Cross Laminated Timber (CLT) Structures: A Review of Research, Novel Connections, Challenges and Opportunities

As a sustainable alternative to steel and concrete, cross laminated timber (CLT) shear wall systems are getting increasingly popular in mid-rise and high-rise construction, and that imposes new challenges on their seismic performance. The conventional connections used in this system, such as steel hold-downs and angle brackets, are, however, susceptible to brittle failures, thus being inappropriate for use in structures in seismic regions. A series of innovative connections have therefore been proposed in recent years for achieving better seismic behaviours in CLT structures, characterised by an adequate capacity, significantly improved ductility and dissipative capacity, as well as more controllable ductile failure modes. This paper first reviews the recent studies of CLT shear wall systems and conventional connections. Connection systems and shear wall reinforcement methods that have been recently proposed for seismic resilient CLT structures are then introduced, with their design strategies being summarised accordingly. The connections are then discussed comprehensively in terms of structural performance, manufacturability and constructability, employing similar criteria that have previously been proposed for steel modular connections. It is found that much improved ductility along with more predictable, ductile, timber damage-free deformation modes are achieved in most of the new connections. Some new connectors are designed with additional functionalities for optimised seismic performance or for easing the construction process, which, however, lead to complex designs that may add difficulties to the mass production. Therefore, comprehensive considerations are needed in connection design, and the discussion of this paper aims to assist in the future development of connection systems for seismic resilient multi-storey CLT buildings.