by the projected bolt area, LD. Section Strength Bolted Connection Lag Screw Withdrawal. When the design load is less than the bolt-bearing capacity of the side plates, the spacing may be reduced below that required to develop their maximum capacity. For bolts bearing parallel to the grain, the distance from the edge of a timber to the center of a bolt should be at least 1.5 times the bolt diameter. The American Wood Council offers a Connection Calculator that determines connector capacity. In fact, a 1/4 UNF thread is roughly 14% stronger than a UNC thread, even if the screws are the same size. If you have a single screw with that level of shear strength, it will also have minimum distance specifications for the material in which it is used. where . Mechanical connections in wood structures. The material contained herein has been developed by researchers based on their research findings. Screw plug strength Find the maximum allowable load P when a MSW30 screw plug is subjected to impact load. Any decrease in these spacing's and margins will decrease the load in about the same ratio. wood structural rating, its humidity content, species, storage history as well as mechanical strength and type of fastener (screw, bolt, lag bolt, prefabricated fasteners and kits) and the mode of their failure( shear, bending moment, pull out, etc..) and alos the function of the connection, there are load factors for seismic loads or shear loads, etc. If a tensile strength is specified, but a shear strength is not, the shear strength can be approximated as 2/3rds the tensile strength. Some screws have great shearing strength while having terrible tensile strength, and vice versa. The theoretical approach is based on work done in Europe (Johansen 1949) and is referred to as the European Yield Model (EYM). For bolts bearing perpendicular to the grain, the margin between the edge toward which the bolt pressure is acting and the center of the bolt or bolts nearest this edge should be at least four times the bolt diameter. Google use cookies for serving our ads and handling visitor statistics. Equations below indicate how to make adjustments if the tapped metal (nut) strength is lower than the screw/bolt. If the screw is too thin, it may pull out of the wood. When a joint is in tension, the bolt nearest the end of a timber should be at a distance from the end of at least seven times the bolt diameter for softwoods and five times for hardwoods. Proportional limit loads for joints with bolt holes the same diameter as the bolt will be slightly higher than for joints with a 1.6-mm (1/16-in.)