Determination of mechanical properties of hollow steel beams created using smart screw, sheet metal, and box profile

This study experimentally investigates the mechanical performance of fasteners obtained by joining steel sheet metal and box profiles using the self-tapping screw method. In the first stage, 2 mm and 3 mm thick specimens (with 2 and 4 screws) prepared from ST37 grade steel were subjected to tensile tests. Data obtained from load-displacement curves showed that increasing the number of screws significantly improved connection performance. Four-screw connections achieved approximately twice the peak load capacity, a wider plastic deformation range, and a more ductile failure behavior compared to two-screw configurations. This result demonstrates that energy absorption and residual carrying capacity increase significantly with increased load transfer paths. Increasing the sheet thickness increased initial stiffness and capacity, but limited ductility. In this context, 3 mm sheet metal was suitable for static systems requiring high stiffness, while 2 mm sheet metal exhibited a safer and more ductile behavior under impact and cyclic loading. In the second stage, the effect of loading direction was evaluated. Specimens loaded in the screw direction exhibited stiffer behavior with initial stiffnesses of approximately 6.0–6.5 kN/mm. Conversely, specimens loaded in the box section direction achieved approximately 11% higher peak loads and 57% greater peak displacements, resulting in approximately 75% increases in ductility and energy absorption capacity. While high stiffness was achieved with screw-directed loading, premature bearing crushing and thread stripping were observed. Loading in the box section direction, however, resulted in a more stimulating and safer ductile behavior due to the distribution of the load to the profile walls. A 3 mm – 4 screw configuration offers the most suitable solutions for static systems and a 2 mm – 4 screw configuration for dynamic and cyclic loads. With these features, smart screw connections provide a safe, economical, and sustainable design alternative for light gauge steel structures.