Shear performance of small-rib-height perfobond strip connector groups embedded in UHPC: Experimental investigations and design recommendations

Employing ultra-high-performance concrete (UHPC) with perfobond strip connector (PBL) groups for strengthening steel columns has emerged as a promising solution for the rehabilitation of steel structures. To reduce the cross-sectional area of strengthened members, PBL groups with small rib heights are adopted in thin UHPC layers. However, there are few studies focusing on the shear behaviours of small-rib-height PBL (SRHPBL) groups embedded in UHPC. Therefore, 20 push-out tests were conducted with the variables of SRHPBLs arrangements. The experimental results demonstrated the grouped effect of SRHPBLs embedded in UHPC: (1) the overall shear capacity of twin-rib SRHPBL groups were about 1.67 times higher than that of their single-rib counterparts; (2) the overall shear capacity of SRHPBL groups decreased as the rib spacing of SRHPBLs increased; (3) the overall shear capacity of both the single- and twin-rib SRHPBL groups increased with the row numbers of SRHPBLs, whereas the average shear capacity of an individual SRHPBL increased gradually as the row numbers of SRHPBLs decreased; and (4) the row spacing of SRHPBLs slightly affected the shear performance of single- and twin-rib SRHPBL groups. Finally, theoretical models were developed to predict the shear capacity of SRHPBL groups encased in UHPC.