Experimental study on multi-bolt shear connectors of prefabricated steel-concrete composite beams

Abstract

Prefabricated steel-concrete composite beams, which consist of steel beams, prefabricated reinforced concrete (RC) slabs, as well as shear connectors, are getting widely used in engineering structures. As a kind of post-installed shear connector, shear performance of the bolt connector has been broadly investigated in recent years, because their application is conductive to improve the construction and retrofitting efficiency of the composite beams. In this paper, ten push-out specimens of bolt shear connectors were fabricated and tested, and the effect of the layout form of multi-bolt connectors, the row spacing of bolts, as well as the strengthening measure of RC slabs on the shear performance of multi-bolt connectors was investigated. Experimental results showed that different numbers of bolts fractured due to shear force during the tests and crushing of concrete around the preformed holes near the inside slab surfaces was observed. Comparing with the push-out specimen possessing single-row bolts, the maximum drop of the average ultimate shear resistance per bolt for the specimens with two and three rows of bolt shear connectors reached 11.4% and 13.3% respectively. The shear force versus relative slip curves of bolt connectors present three-stage changing characteristics and the maximum slip at the ultiamte load was about 1.28 times the diameter of M16 bolt. A calculation method of ultimate shear resistance applicable for the M16 bolt shear connector considering multiple bolts effect was proposed, and the calculation values of shear resistance agreed well with the experimental results. Furthermore, a simplified shear force - slip model of M16 bolt shear connectors was developed. It is anticipated that the proposed calculation models can be applied to assess the shear behaviors of M16 bolt shear connectors, including shear stiffness and ultimate shear resistance.