Corrosion Related Bond Deterioration and Seismic Resistance of Reinforced Concrete Structures

Reinforced concrete structures rely on steel reinforcing, acting in unison with concrete, to produce the essential ductile behaviour required to resist earthquake loading. Corrosion is known to affect bond performance and loss of adequate bond between these two materials introduces increased risk of brittle failure through pull-out of reinforcement. Reinforcing is put through the greatest stress in plastic hinge regions of structures where it is detailed to rupture before pulling out. Such regions are the primary locations for cracking damage, heightening corrosion susceptibility following even minor seismic event. Bridges and wharfs in marine environments are particularly susceptible to deterioration with these key regions coinciding with the highly aggressive `splash zone'. This becomes of particular importance in older, or poorly designed structures which have been designed with laps in plastic hinge zones This paper looks to assess the impacts of bond degradation due to corrosion on seismic behaviour. It follows on from a series of experimental pull-out cyclic testing carried out on corroded steel bars. Testing assessed two parameters; the level of corrosion, ranging from 0% to 25% section loss, along with reduced confinement associated with corrosion of confining steel. From this testing a numerical bond-slip model was developed which included the effects of corrosion and reduced confinement. This paper utilises the developed model in a series of multi-spring models, simulating the reinforcement development and plastic hinge region of bridge piers under various levels of deterioration. Analyses were then performed to determine the seismic susceptibility under degraded bonding conditions. Analysis found that inclusion of the corrosion effects resulted in increased displacement, reduced strength, altered ductility and an overall reduction in seismic performance.