Static behavior of small-rib-height perfobond connectors embedded in UHPC: Experimental and analytical studies

Abstract

Combining ultra-high-performance concrete (UHPC) and perfobond strip connectors (PBLs) to strengthen deteriorated steel columns has become a competitive repair method, but the large rib height (exceeding 100 mm) of PBLs limits their application. This paper proposed small-rib-height perfobond strip connectors (SRHPBLs) and investigated the shear performance of SRHPBLs embedded in UHPC under static loading. Results show that most of the SRHPBLs in UHPC exhibited similar failure modes. However, steel strip rupture was observed when the rib thickness was below 5 mm or the reinforcement diameter exceeded 18 mm. Moreover, the superposition of load-slip curves from specimens with UHPC dowels and transverse reinforcement exhibited behaviour similar to that from the specimen combining UHPC dowels and transverse reinforcement simultaneously. Furthermore, for the specimens without transverse reinforcement, the ultimate shear strength and initial shear stiffness increased by 40.10% and 154.87% respectively, as the rib height increased to 85 mm. But the ultimate shear strength and initial shear stiffness of the specimens without concrete dowels just increased by 12.28% and 69.51% respectively. In contrast, increasing the rib height led to a poor ultimate slip capacity and ultimate transverse uplift. Appropriate hole diameter (25 mm), rib thickness (10 mm), and reinforcement diameter (18 mm) should be considered to ensure favourable strength, stiffness, and ductility. Raising the cover thickness or considering interfacial bonding effectively enhanced the shear capacity and stiffness but limited interfacial slip/uplift development. Compared with existing models, more accurate theoretical models were proposed to predict the ultimate shear capacity of SRHPBLs embedded in UHPC.