Comparative analysis of dynamic response behavior between welded stud and demountable bolt connectors in steel-UHPC composites

This study explores the dynamic response behavior of steel-UHPC composite through an impact test focusing on the behavior of shear connectors under impact loads. Using drop hammer impact tests, the study evaluates the dynamic responses and failure mechanisms of welded studs and demountable bolted connectors. The experiments are conducted on various specimen groups, each differentiated by connector type and subjected to different mass and height of impact to simulate varied impact scenarios. Test results indicate that under impact loading, the failure for all specimens, except those using high-strength studs (which experienced weld failure), is shear failure of the connectors. This is consistent with the failure observed in static push-out tests. Compared to welded studs, demountable bolts exhibit higher ultimate slip and better ductility. The study quantified the energy distribution and transformation relationship between stud and UHPC, and the mapping relationship between their failure modes under impact loads. Notably, the study shows that demountable bolted connectors with nut embedded in UHPC can provide superior performance by limiting the extent of local damage and preserving the integrity of the interface between steel and UHPC. The results contribute valuable insights into the dynamic design and optimization of composite elements, offering guidelines for enhancing structural resilience against dynamic loads, and contributing to safer engineering applications.