Image Correlation Analysis of Multiple-Bolt Wood Connections

John W. Stelmokas, Audrey G. Zink, Joseph R. Loferski


Displacement beneath the bolts in multiple-bolted wood connections was studied using digital image correlation. This 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-popular 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 displacement distribution among bolts. It was discovered that for multi-bolt patterns in a vertical row, parallel to load displacements below the outer bolts, are higher than those below the center bolt(s) but not equal in magnitude as previously assumed and the surface displacements perpendicular to the load beneath the bolts split along the centerline of the bolts. Variation in material properties, rigid body motion, eccentric loading and/or wood failure beneath a bolt are detectable with digital image correlation and may influence the results if not carefully considered in experimental design.


Multiple-bolted wood connections;digital image correlation;displacement analysis;mechanical connections;double shear joints

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