Investigating the Response of Bolted Wood Connections Subjected to Bast Loads

Title: Investigating the Response of Bolted Wood Connections Subjected to Bast Loads
Authors: McGrath, Andrew
Date: 2020-04-28
Abstract: With recent improvement in wood manufacturing technologies, taller and larger wooden structures are being constructed, thereby increasing the risk for potential damage due to a blast threat against such structures. Recent studies on the effects of high strain rate in wood have been undertaken, however the vast majority of these studies have focussed on structural elements with idealized boundary conditions. Some studies included realistic connections as the boundary conditions, but little progress has been made to date in order to quantify the behaviour of connections in isolation. The current study aims to investigate the response of steel-wood-steel bolted connections when subjected to blast loads. This includes determining the dynamic increase in resistance and stiffness for stocky and slender bolts in both the parallel and perpendicular to grain directions. The study also explores analytical solutions to predict the joint behaviour and discusses the validity of current blast design provisions. Bolted wood connections were investigated under both static and simulated blast loading using the University of Ottawa’s shock tube. The study found a dynamic increase in resistance and stiffness when the failure mode was dominated by wood crushing in both the parallel and perpendicular to grain directions. No increase in resistance or stiffness was observed when bolt yielding dominated the failure. A loss of ductility was observed under dynamic loading for the parallel to the grain connections designed to fail in wood crushing. It was found that the use of self-tapping screw reinforcement was an effective method of preventing premature splitting failures and enhancing the performance of a connection. The results showed that connections which engaged the fastener in bending exhibited more favourable behaviour than connections which engaged only in wood crushing. A two degree-of-freedom model was capable of modelling the connections even when the support frame system had some flexibility. The validated model was used to investigate cases where the connection could contribute to the energy dissipation. It was found that the performance of the assembly improved when the connections were considered. Recommended future work includes an investigation of brittle failure modes in bolted connections, exploring connections with more deformation capacities, and expanding the experimental component of the study to include full-scale structural assemblies with wood elements and boundary connections. Limited design recommendations have been proposed in the current study, however testing at the assembly level could shed more light on such an important topic.
CollectionThèses, 2011 - // Theses, 2011 -