Structural performance of a dual-purpose connection for two-way spanning CLT-concrete composite floors

Point-supported two-way spanning cross-laminated timber (CLT)-concrete composite (CLTCC) floors offer a high-performance solution for mass-timber structures but are technically limited by the inherent orthotropy of CLT and the difficulty of ensuring structural continuity across panel edges. In this study, a dual-purpose connection system utilizing steel T-bars and laminated veneer lumber (LVL) splines to simultaneously provide interfacial shear transfer and inter-panel rotational stiffness ( C ϕ ) is proposed and validated. With numerical sensitivity analyses, it was shown that interfacial shear stiffness in both major ( C ux ) and minor ( C uy ) strength directions, alongside C ϕ , is essential for effective two-way action. The analysis established that C ϕ = 50,000 kNm/rad/m allows the floor to reach an idealized rigid benchmark. Push-out tests characterized the T-bar’s bi-directional shear performance, revealing high major-axis stiffness (40.4 kN/mm) via steel flange bearing and ductile minor-axis performance (24.2 kN/mm), confirming the system’s two-way action. Full-scale bending tests on hybrid T-bar and LVL spline joints yielded a mean C ϕ of 2549 kNm/rad/m, corresponding to 86% composite efficiency relative to the rigid benchmark. When integrated into the composite CLTCC system, the connection system achieved a composite efficiency of 75% in minor span with minimal interfacial slip. These findings demonstrate that the proposed force-couple mechanism effectively bridges the minor-axis weakness, transforming independent CLT panels into a unified, high-performance two-way spanning CLTCC floor system.