EFFECTS OF BENDING MOMENTS ON THE TENSILE PERFORMANCE OF MULTIPLE-BOLTED TIMBER CONNECTORS .1. A TECHNIQUE TO MODEL SUCH JOINTS

The susceptibility of multiple-bolted timber joints to bending moments is considered in the light of several recent building failures. This study describes an experimental technique to model wood behavior in th e plane perpendicular to the axes of multiple bolts in joint members t hat are subjected to simultaneous bending and tensile loads. Modeled j oints consist of 0.8-mm-thick wood wafers sandwiched between clear pla stic plates, with steel dowels representing bolts passing through them . Combined loads are applied by mounting the arrangement on a servohyd raulic testing machine. Load and displacement data (both axial slip an d bending) were recorded during testing to failure, and failure mechan isms were recorded photographically. Results of tests with two dowel c onfigurations (conventional ''three-in-a-row'' and modified ''triangul ar'') suggest that relatively small bending moment levels can reduce t he tensile performance of joints, and that bolt configuration is an im portant factor affecting this susceptibility. The modeling method may be a useful tool for developing joint designs with reduced susceptibil ity to bending moments and for investigating the effects of variables such as wood quality, growth ring orientation, and moisture content. T he behavior of corresponding whole double-shear joints tested under a similar range of loading regimes and with wood of two grades will be r eported in a companion paper.