Experimental Behavior of Laminated Veneer Lumber with Round Holes, with and without Reinforcement

Laminated veneer lumber (LVL) is an engineered wood product that is commonly used for joists in wooden buildings. Holes in joists are often necessary to allow piping systems to pass through. Introducing a hole into an LVL joist remarkably changes the distribution of stresses in the vicinity of the hole. Tensile stresses occur perpendicular to the grain, and the capacity of the joist can be decreased accordingly. This study presents the experimental results of LVL joists with holes and reinforcement methods around the holes. The results showed that cutting a large enough hole contributed substantially to the strength reduction of LVL joists. Holes with a diameter-to-joist depth ratio of 0.4, 0.5, and 0.6 reduced the load-capacity 50.1%, 59.6%, and 68.8%, respectively. Glued plywood and glued-in threaded rods were both effective methods for reinforcing LVL joists with holes having a diameter-to-joist depth ratio of less than 0.5. The reinforcement effect of nailed plywood was relatively poor, increasing the load-capacity less than 30%. The reinforcement effect of all of the methods depended on the effective joint with the LVL. The thickness of the plywood, the number of nails, and the withdraw strength were also important factors.