Mechanism-based numerical investigation of temperature- and corrosion-related local distresses in a long-span PC box-girder bridge: A case study

Long-span prestressed concrete (PC) continuous rigid-frame bridges may develop persistent local distress under long-term traffic loading and environmental exposure. Temperature- and corrosion-related mechanisms can contribute to recurrent local deterioration. This paper presents a case-based failure analysis of two representative distress modes observed in a 28-year-old in-service long-span PC continuous rigid-frame bridge: longitudinal cracking at the flange-web chamfers and corrosion-induced concrete spalling at the flange edges. Using field inspection data, long-term monitoring and load-test records, available material information, and nonlinear finite element analysis, three complementary mechanism-specific models were developed with the concrete damaged plasticity (CDP) constitutive model. The models examine the roles of long-term deformation, temperature gradients, corrosion-induced expansion, and steel-concrete thermal mismatch. The numerical damage patterns show spatial consistency with the observed distress. Model 1 shows that a positive temperature gradient extends the high-tensile-stress zone along the chamfer when applied to the deformation-induced stress state. Model 2 reproduces progressive cover damage under idealized corrosion expansion, while Model 3 produces a connected interfacial high-damage path in the 37.5 K unconfined thermal-mismatch case. Together, the field evidence and numerical results support a plausible deterioration pathway linking chamfer cracking, environmental ingress, and flange-edge spalling, providing a basis for targeted durability assessment and maintenance.