Development of a 3D-RBSM numerical model for corrosion-induced deterioration in prestressed concrete (PC) beams

This study develops a three-dimensional Rigid Body Spring Model (3D-RBSM) to simulate the deterioration and failure of prestressed concrete (PC) beams subjected to tendon corrosion. The model incorporates corrosion-induced concrete cracking, tendon cross-sectional area reduction, rupture-strain degradation, and tendon–concrete interaction through beam and link elements. The cracking-related reduction in apparent bond resistance is first assessed using a two-end pull-out model with a deformed reinforcing bar. Comparative analyses with and without reinforcement cross-sectional area reduction showed that corrosion-induced cracking and confinement loss reduced the calculated bond strength by 52.70% and 60.82% at corrosion degrees of 10% and 15%, respectively, while area reduction produced additional decreases of 2.86 and 3.73 %age points. The model was subsequently assessed against pretensioned PC beam tests under monotonic four-point bending. The numerical results captured the overall reduction in load-carrying and deformation capacities and the transition from flexural failure to premature tendon rupture with increasing corrosion degree. For corrosion degrees up to 10.4%, the maximum absolute relative errors in ultimate load and ultimate displacement were 13.78% and 28.53%, respectively. For the 13.8% specimen, these errors increased to 76.24% and 195.60%, indicating reduced quantitative accuracy under severe corrosion and highly brittle tendon rupture. Rupture-strain degradation was also necessary to represent premature tendon rupture and the associated reduction in deformation capacity. Within the investigated conditions, the model provides a framework for examining the deterioration mechanisms of small-scale pretensioned PC beams subjected to accelerated average distributed corrosion within a 300 mm constant-moment region and monotonic four-point bending.