Two novel techniques to study multiple bolted wood connection behavior

Abstract

Two novel techniques, instrumented shear bolts and digital image correlation, were evaluated for studying multiple-bolted wood connection behavior. The instrumented shear bolts output an electronic signal proportional to the shear forces transmitted through the bolt in a double-shear connection during loading. The digital image correlation method combines digital image analysis and image correlation to calculate surface displacements from a set of digitized video images of an object under an applied load.

Double-shear connections constructed of clear, straight-grained yellow-poplar were tested in compression parallel to grain. Five different bolt patterns were used to analyze the effect of number of bolts in a vertical row and number of bolts in a horizontal column on load transfer among the bolts.

Both techniques were utilized simultaneously during testing of specimens. The shear bolts were found to effectively determine the load distribution among bolts in a multiple-bolted wood connection by providing detailed quantitative data concerning which bolt was the major load carrier throughout the entire test and exactly if and when the load was transmitted between the bolts. The digital image correlation method was found to effectively describe the creation of the surface displacement fields, both parallel and perpendicular to load, below each bolt during loading.

The results obtained from this research may be useful to facilitate the understanding of multiple-bolted wood connection behavior and for developing simplified design equations for multi-fastener joints in the future.