Progressive Collapse Behavior of Aging Reinforced Concrete Structures Considering Corrosion Effects

The corrosion of reinforcement is one of the major problems affecting the durability of aging reinforced concrete (RC) structures. In this paper, the results of a study concerning the effects of reinforcement corrosion on the behavior of reinforced concrete structures subjected to the scenario of the loss of a middle column are presented. Four typical RC moment frame structures were selected as case studies. The general corrosion process induced by the penetration of chloride ions was considered for an atmospheric exposure environment that would eventually lead to the loss of reinforcement cross-sectional area, the reduction of reinforcement strength and ductility, and the spalling of concrete cover. A macro-modeling technique, which was validated by the test results and the high-fidelity finite element model, was utilized for pushdown analysis. To account for the dynamic effects associated with sudden column loss, a procedure based on energy equilibrium was employed to generate the dynamic load-displacement curves based on the static pushdown responses. The results established that aging structures with severe corrosion are much more vulnerable to progressive collapse than newly constructed ones. After 50 years of corrosion, the ultimate deformation capacity of structures was reduced by over 40%, and the first peak load capacity and ultimate load capacity of the structures were reduced by a range between 20 and 30%. Finally, linear models that depict the time-dependent changes in the load-carrying and deformation capacities of the structures to resist progressive collapse were developed with the aim of providing a simple way to incorporate corrosion effects in the design process.