Flexural behaviour and connection efficiency of cross-laminated timber–glulam composite floor systems

Abstract

Driven by the growing demand for sustainable and high-performance construction, mass timber products are increasingly recognised for their potential in modern structural engineering. Recently, cross-laminated timber (CLT)–glulam composites are emerging as a promising solution for efficient and environmentally friendly long-span floor systems. However, the structural behaviour of CLT-glulam composites–particularly the performance of their shear connectionsremains insufficiently understood, often resulting in overly conservative designs. This study presents a comprehensive experimental investigation into the flexural behaviour of CLT–glulam composite floor assemblies through full-scale four-point bending tests. A range of connection systems were examined, including inclined and vertical self-tapping screws, perforated steel plates, and adhesive connections–representing both mechanical and hybrid connection systems. Detailed analyses of failure modes, load-deflection, and load-slip were conducted, alongside evaluations of strain distribution and composite efficiency. The results show that all assemblies exhibited brittle failure, characterised by a combination of tensile rupture, shear failure along the lamina, and delamination. The adhesive connections achieved full composite actions, though with sudden failure without prior sign. Assembly with 45° inclined self-tapping screws exhibited the highest load-bearing capacity and the second-highest stiffness. The addition of perforated steel plates or a concrete topping had limited influence on load capacity under bending but significantly enhanced initial stiffness. Notably, shear lag effects were observed across all specimens, indicating the need for further quantitative investigation.