Behavior of nailed connections at elevated temperatures

The lateral resistance of plywood-re-wood nailed joints with interlayer gap s was measured at four temperatures of ambient (30 degrees C), 120 degrees C, 200 degrees C, and 265 degrees C in an exploratory test program. As temp erature increased from ambient, strength decreased by 13%, 15%, and 26%, re spectively, and slip modulus decreased by 47%, 61%, and 54%, respectively. The largest incremental percent decreases in strength and slip modulus occu rred at the lowest temperature increment, between ambient and 120 degrees C . Slip modulus was more negatively affected by temperature than strength. F ailure mode IV (two-point nail yield) occurred on nailed joints tested at a mbient, 120 degrees C, and 200 degrees C, but shifted to failure mode IIIs (one-point nail yield in main member) at 265 degrees C. The shin in failure mode occurred because nonuniform temperatures throughout the joint differe ntially changed the embedding strength of the wood members. The yield theor y predicted failure mode IV for nailed joints tested at ambient, but overes timated the strength of the joint by 40%. The results of this research supp ort recent findings reported by Noren (1996).