Timber-timber composite (TTC) beams subjected to hogging moment

Abstract

This study aims to investigate the structural behaviour of timber-timber composite (TTC) systems subject to hogging moment. A total of thirty-one TTC and six bare timber beam-to-column subassemblies (including fourteen replicates) were fabricated and tested to failure under hogging moment. The TTC beams were fabricated by connecting a cross laminated timber (CLT) slab to the top edge of a pair of laminated veneer lumber (LVL) or glued laminated timber (GLT) beams/joists. The effect of the CLT slab thickness, width, and orientation (i.e., loaded lengthwise or crosswise), column penetration in the CLT slab, bending moment to shear force ratio (span length), degree of shear interaction between the slabs and beams (controlled by the size of the shear connectors), and type of beams (LVL or GLT) on the structural performance of the TTC subassemblies were investigated experimentally. In addition, an analytical model was adopted for composite Timoshenko beams and modified to predict the stiffness and load carrying capacity of the TTC beams under hogging moment. The width of the CLT slab and column penetration in the slab (resulting in the reduction of the slab area of up to 20%) had minor (less than 9%) influence on the stiffness and peak load. However, the CLT slab thickness (in the range of 60–100 mm) had a major (up to 48%) influence on the peak load and stiffness of the TTC beam subject to hogging moment. The size of shear connectors (degree of shear connection provided by 8–12 mm screws) and orientation of the CLT slab had a moderate (max. 18–23%) influence on the load carrying capacity and stiffness of the samples.