Characterizing Connections in Coated Wood Building Structures for Blast Force Protection

Connections in the design of wood structures often control the ultimate capacity of structures. In this research, the end goal is to replace the Army’s SEA Huts, a plywood-sheathed light-frame residential structure, with a blast-resistant structure. This structure uses coated structural lumber walls that have twice the load resistance and six times the energy absorbing capacity of uncoated walls. However to take advantage of the coated panels, the connections must be strong and ductile enough to allow the panels to reach capacity while maintaining structural integrity. This requires knowledge of the characteristics of the coated structural lumber at typical connections including the stiffness and fastener bearing strength. Through the use of dowel bearing, sheardeformation, and moment-rotation tests, coated structural lumber is compared to the uncoated structural lumber commonly used in residential construction. Dowel bearing is increased approximately 30 percent in coated structural lumber. Shear strength is increased from 30 to 100 percent depending on the type of bolted connection with coated structural lumber. Moment capacity increased 50 percent with the coated structural lumber with both diameters of bolts tested in this study. Three stiffness parameters were derived using bi-linear and tri-linear representations from the data in these tests. These were inputted into a structural mechanics model to predict midspan wall panel deflections during a blast based on linearly elastic assumptions, with the predicted deflections less than the actual deflections from blast testing. Further non-linear based models would be required to determine a more realistic deflection from coated structural lumber