Tensile behaviour of four LVL-truss end connections for timber spatial structures

Abstract

This study analyzes four types of steel-to-timber connections for potential use in spatial truss structures with high-performance, small-section Laminated Veneer Lumber (LVL) elements. The experiments were comprised of 42 monotonic pull-pull tests, including 30 tests on dowel-type connections and 12 tests on screwed connections. Dowel-type connections were subdivided into dowel-nut connections and bolted connections featuring either one inner or two outer steel plates. None of the dowel-type connections met code requirements on minimum lateral-edge distance. For some configuration, also loaded-end distance was non-conforming. Screwed connections used a threaded insert parallel to the longitudinal element axis, accommodating a metric threaded rod. Even in this case, the connection was non-conforming due to violation of code requirements on edge distance and inclination angle with respect to veneer planes. Bolted connections showed high load-carrying capacities, but at the cost of a significant steel usage. The screwed connection, while reducing steel usage, exhibited high stiffness but relatively small load-carrying capacity. This last one, however, was shown to be improved by the application of transverse confinement. The dowel-nut connection proved to be particularly effective, combining good mechanical performance with a low aesthetic impact. These results provide valuable insights into the design of safe and efficient connections for LVL spatial structures, contributing to the growth of knowledge on sustainable engineering applications.