Innovative shot nails fastening for bonded steel plates strengthening concrete structures: A comparative research with conventional chemical anchor

As an alternative to chemical bolt fasteners for bonded steel plate strengthening, shooting nails have the advantages of higher efficiency and lower damage to existing concrete structures. In this paper, through interfacial single-shear tests, a comparative investigation on the shear capacity of different steel-concrete interfaces, including shooting nails, chemical anchors, adhesive & shooting nails, and adhesive & chemical anchors, was first conducted. Further, a comparative study was conducted to evaluate the flexural performance of bonded steel-plate-strengthened concrete slabs using shot nails and chemical anchors, analyzing their flexural load capacity enhancement and failure mechanisms under varying bonded interface lengths. The results of interfacial single-shear tests showed that shooting nails had a comparable shear capacity with chemical fasteners, and multi-nails exhibited better collaborative working than multi-bolts. Flexural test results indicated that when the adhesive length was insufficient, concrete adhesive damage occurred at the interface, the flexural capacity of specimens with nail fasteners was slightly lower, and the load capacity degradation was more obvious. Under a sufficient interface adhesive length, the interface did not fail, and the specimens with nail fasteners and bolt fasteners exhibited comparable bearing and deformation capacity.