Withdrawal Behavior of the Self-Tapping Screws in Bamboo/Wood-Oriented Strand Board

This study examines how screw diameter, penetration length, and aperture ratio affect self-tapping screw (STS) withdrawal resistance in bamboo/wood-oriented strand board (WOSB/BOSB) to increase bamboo use in construction and furniture. It proposes a widely applicable empirical formula for calculating withdrawal resistance. With its high specific strength, uniformity, and STS withdrawal resistance, BOSB is a promising material for engineering and furniture applications, according to experiments. Screw diameter, penetration length, and aperture ratio significantly influence the STS’s withdrawal behavior. Among these, screw diameter and penetration length are the primary factors affecting screw withdrawal behavior. As the two factors increase, withdrawal resistance increases linearly. However, the relationship between withdrawal resistance and aperture ratio is non-linear, initially increasing and then decreasing as the aperture ratio increases. With an optimal mounting aperture ratio, the STS withdrawal forces in the BOSB face and edge are approximately 3 and 3.5 times greater than in WOSB, respectively. Traditional formulas for withdrawal resistance were refined based on the fitting equation of aperture ratio and withdrawal force, significantly reducing the relative errors of the modified formulas. Notably, the withdrawal resistance results for STSs calculated using the refined equation based on the CCMC 13677-R standard achieve an accuracy of up to 93%.