LATERAL LOAD RESISTANCE OF CROSS-LAMINATED TIMBER SHEAR WALLS Thomas Reynolds Ph.D. C.Eng 1 Robert Foster Ph.D. 2 Julie Bregulla Ph.D. C.Eng 3 Wen-Shao Chang Ph.D. 4 Richard Harris C.Eng 5 Michael Ramage Ph.D. C.Eng 6 This is the author’s accepted version, accepted for publication in the ASCE Journal of Structural Engineering. ABSTRACT Cross-laminated timber shear wall systems are used as a lateral load resisting system in multi- story timber buildings. Walls at each level typically bear directly on the floor panels below and are connected by nailed steel brackets. Design guidance for lateral load resistance of such systems is not well established and design approaches vary among practitioners. Two cross-laminated two-story timber shear wall systems are tested under vertical and lateral load, along with pull- out tests on individual steel connectors. Comprehensive kinematic behavior is obtained from a combination of discrete transducers and continuous field displacements along the base of the walls, obtained by digital image correlation, giving a measure of the length of wall in contact with the floor below. Existing design approaches are evaluated. A new offset-yield criterion based on acceptable permanent deformations is proposed. A lower bound plastic distribution of stresses, reflecting yielding of all connectors in tension and cross-grain crushing of the floor panel, is found to most accurately reflect the observed behavior. BACKGROUND Cross-laminated timber (CLT) is a panelised glued-laminated mass timber structural product, comprising sawn timber sections, laid-up in layers, with each layer at right angles to the adjacent layer. CLT floor and wall elements have consequently been used to form the principal vertical and lateral load resisting systems of multi-story buildings around the world. A number of benefits have been attributed to CLT in mid-rise construction including: low dust, low noise, light cranage, high tolerances, reduced onsite waste, reduced construction times, low number of person-hours on site and negative embodied carbon (if carbon sequestration of forests is taken into account) (Waugh et al. 2009; FII and BSLC 2014). 1 Chancellor’s Fellow, School of Engineering, University of Edinburgh, Edinburgh EH9 3JL, UK Email: t.reynolds@ed.ac.uk 2 Senior Lecturer, School of Civil Engineering, The University of Queensland, Brisbane St Lucia, QLD 4072, Australia 3 Director, Building Technology Group, BRE, Bucknalls Lane, Watford WD25 9XX 4 Lecturer, BRE Centre for Innovative Construction Materials, University of Bath, Claverton Down, Bath BA2 7AY 5 Honorary Professor, BRE Centre for Innovative Construction Materials, University of Bath, Claverton Down, Bath BA2 7AY 6 Senior Lecturer, University of Cambridge, Department of Architecture, 1 Scroope Terrace, Cambridge CB2 1PX 1 Author’s accepted version J Struct Eng