Monitoring the mechanical performance of self-drilling, self-tapping fasteners after installation using impact-type tooling in Modern Methods of Construction (MMC)

The rapid adoption of Modern Methods of Construction (MMC) in the United Kingdom has introduced new challenges in ensuring structural rigidity, particular in light-gauge steel structures. This study investigates the impact of fastener installation methods on the mechanical performance of connections in MMC applications, addressing a critical knowledge gap in the industry.

The research focused on comparing the performance of self-drilling, self-tapping fasteners installed using traditional electric screwdrivers and increasingly popular impact-type screwdrivers. Two standardised test series based on EAD 330046-01-0602 were conducted to determine the characteristic lap-shearing resistance and characteristic withdrawal resistance of fastener connections.

Test specimens were prepared using stainless-steel fasteners (EN 1.4301) and cold-rolled mild structural steel (S350GD+Z) in various thicknesses, representing common MMC configurations. A total of 500 tests were performed using a calibrated universal testing machine, with rigorous quality control measures implemented throughout the experimental process.

Results revealed significant reductions in fastener performance when impact screwdrivers were used for installation. Withdrawal resistance decreased by 34.71% to 59.71%, while lap-shearing resistance reduced by 47.85% to 70.65% compared to traditional installation methods. Statistical analysis confirmed the significance of these findings, with all tests falling within ± 3.0 standard deviations in Z-score analysis.

These results have profound implications for the structural integrity of MMC units. Connections designed based on traditional installation assumptions may be significantly under strength when impact screwdrivers are used, potentially leading to premature structural failures. The research highlights the need for updated design guidelines, stricter quality control in MMC fabrication, and potential revisions to building codes and standards.

The research also establishes a foundation for future studies, including investigations into the long-term effects of installation methods on fastener performance, coating integrity and overall structural health. The findings underscore the importance of proper installation techniques in ensuring the safety and reliability of MMC structures.

This research contributes valuable insights to the field of fastener technology in MMC and calls for immediate action from industry stakeholders to address the identified issues. The results provide a basis for updating fastener selection and installation guidelines for MMC applications, ultimately enhancing the structural performance longevity of light-gauge steel structures in innovative construction techniques.