No abstract

The corrosion development of the reinforcement and shear stud connectors in the cracked steel–concrete composite beams under the salt-fog wet–dry cycles is presented in this investigation. Seven identical composite beams with load-induced concrete cracks were exposed to an aggressive chloride environment. The reinforcement and shear connectors were retrieved after specimens underwent a specified number of wet–dry cycles to obtain the corrosion pattern and the cross-section loss at different exposure times and their evolutions. The crack map, the corrosion pattern and the cross-section loss were measured and presented. Based on the experimental results, the influence of crack characteristics, including crack widths, orientations and positions on the corrosion rate and distribution, were accessed. Moreover, the effects of the connecting weldments on the corrosion initiations and patterns were analyzed. It was shown that the corrosion rate would increase with the number of wet–dry cycles. The characteristics of load-induced cracks could have different influences on the steel grids and shear stud connectors. The corrosion tended to initiate from the connecting weldments, due to the potential difference with the parent steel and the aggressive exposure environment, leading to a preferential weldment attack.

This paper presents an innovative solution for steel-concrete composite beams under hogging moment. Compared to normal composite beams, additional concrete was cast inside the steel box girder of these innovative composite beams, aimed to increase the resistance to hogging moment. Bending tests were performed on three series of beams including four innovative composite beams and five normal composite beams. The load-displacement curves, load-crack width curves and ultimate strengths of test specimens were recorded. It was shown that concrete inside the steel box girder effectively enhanced the stiffness and ultimate strength of composite beams under hogging moment. The crack widths of concrete slab were reduced. In addition, the resistance to local buckling of the steel box girder was also remarkably enhanced due to the concrete inside. Design equations for determining the ultimate bending strength of the proposed solution were proposed, with particular emphasis for transverse sections under hogging moments. The results of those equations in terms of ultimate bending capacity complied well with the observed experimental results.

Experimental investigation was conducted on corroded composite push-out specimens to study the behavior of shear studs subjected to fatigue loading. A total of eight standard EC4 push-out specimens were tested. The expected corrosion rate of test specimens ranged from 0 to 50%. The main purpose of these tests was to determine the fatigue life and the reduction effect caused by the corrosion on the fatigue life. The effect of corrosion on the fatigue crack, load-slip curves, and failure modes was also studied. In addition, the test results were compared with current Eurocode design predictions, which is only for specimen without corrosion. It is shown that the current Eurocode design predictions are quite conservative for the test specimens in this study. Design equations were also proposed for fatigue life of corroded composite push-out specimens.

The behavior of corroded steel-concrete composite beams under hogging moment was studied by experimental investigation and theoretical analysis. A total of eight specimens, six of which had corroded shear studs, were tested. The corrosion rate of studs ranged from 0 to approximately 50%. The constant-current accelerated corrosion method was adopted to accelerate the corrosion process. The loading test results indicated that the bending capacity of the corroded beams decreased slightly with increasing corrosion ratio of the studs. The corroded beams also exhibited an obvious decrease in bending rigid stiffness and increase in the slip between the steel beam and the concrete slab. An analytical model was developed to study the steel-concrete composite beams with corroded studs under hogging moment. It is shown that the analytical model is able to predict the test results with reasonable accuracy.