The predicting ultimate of joint withdrawal resistance constructed of plywood with regression models application according to diameter and penetrating depth

The goal of this study was present regression models for predicting resistance of joints made with screw and plywood members. Joint members were out of hardwood plywood that were 19 mm in thickness. Two types of screws including coarse and fine thread drywall screw with 3. 5، 4 and 5mm in diameter and sheet metal screw with 4 and 5mm were used. Results have shown that withdrawal resistance of screw was increased by increasing of screws، diameter and penetrating depth. Joints fabricated with coarse thread drywall screws were higher than those of fine thread drywall screws. Finally، average joint withdrawal resistance of screwed could be predicted by means of the expressions Wc = 2. 127× D1. 072 × P0. 520 for coarse thread drywall screws and Wf =1. 377× D1. 156 × P0. 581 for fine thread drywall screws by taking account the diameter and penetrating depth. The difference of the observed and predicted data showed that developed models have a good correlation with actual experimental measurements.