Experimental investigation on connection performance of fully-grouted sleeve connectors with various grouting defects

Abstract

Grouted sleeve connector is one of the most widely used connections in precast concrete structures. However, various defects may be introduced in the grouted sleeve connectors due to construction errors, which could significantly weaken their practical performance. In this study, 42 connectors were manufactured and tested under uniaxial tensile loading, where multiple grouting defects were considered (i.e. end defect, middle defect, anchor length defect, uniform defect, grouting density defect, thickness defect, horizontal defect, eccentric defect and grouting strength defect). First, the defect fabrication is examined by using the cone-beam computed tomography (CT) inspection system. Based on the tensile testing results, three failure modes including tensile fracture of reinforcing bar, anchor failure of the top reinforcing bar and anchor failure of the bottom reinforcing bar, could be observed. Besides, the decrease of the total effective anchor lengths of the bottom reinforcing bars could significantly lead to deterioration of the anchor properties and change the failure mode from fracture failure to anchor failure. For the specimens with end defect, when the defect length was longer than 42 mm, the connection performance deteriorated and the failure mode shifted from the tensile fracture of reinforcing bar to the anchor failure of reinforcing bar. Meanwhile, there was a significant correlation between the ultimate displacement and the failure mode, that is, the ultimate displacement of the anchorage failure specimens was generally less than that of the tensile fracture failure specimens. For connectors with the same total effective anchor lengths, discrete defects resulted in lower bearing capacity than concentrate defects, and when defects were farther away from the sleeve end, the bearing capacity is lower. That is, the lowest ultimate anchor strength was found in specimens with uniform defect, followed by specimens with middle defect and specimens with end defect. The presented work could be used for defect prevention and evaluation of grouted sleeve connectors.