Structural behaviour of Gerber half-joints subjected to steel corrosion

The Gerber half-joints assessment is today a topical problem since they are widespread in the infrastructure heritage of different countries. These structural elements are often affected by chloride corrosion phenomena due to their positioning under the deck joint. The paper presents some of the results of a wide research survey, developed at the Laboratory of the University of Rome Tor Vergata, aimed at evaluating their behavior when subjected to corrosion decay, up to failure, through experimental tests and analytical models. The experimental behavior of the specimens, designed with different criteria, and subjected to different degree of accelerated corrosion, is discussed. An accurate design phase of the specimens was followed, based on typical Strut and Tie models, to obtain peculiar and different failure mechanisms, involving both brittle and “ductile” crises. Particular care was devoted to the corrosion process, suitably calibrated for providing different degradation scenarios. The obtained results are analyzed and discussed in terms of load-displacement curves and cracking pattern, underlying the influence of corrosion on the failure mechanism. The experimental outcomes show that both design details and reinforcement corrosion could compromise the strength and ductility requirements of the elements and need to be accounted for in analytical and numerical structural assessment of existing corroded Gerber half-joints.