Experimental investigation on prestressed concrete beams with localized strand damage: Tilt-based deflection mapping and damage indicators

This study investigates the structural response of prestressed concrete beams with localized strand damage under both serviceability and ultimate loading conditions. Seven simply supported beams, with a clear span of L = 7.0 m, were cast as scaled bridge girders representing different damage scenarios. Inspection windows were created at L /2, L /3, and L /4 to simulate corrosion-induced defects by selectively severing prestressing strands in a controlled manner, thereby reducing the effective prestressing steel area. The beams were tested under combined dead load and increasing midspan live load, applied through loading-unloading cycles from service levels up to failure. A dense network of MEMS tiltmeters was used to measure spanwise rotations, which were converted into deflection profiles using a straightforward slope-integration procedure that preserved support compatibility and was cross-validated against independent laser targets and LVDTs. Based on the reconstructed deflected shapes under incremental quasi-static cycles at serviceability load levels, two complementary sets of damage indicators were defined. The first set, DI₁ (loading), includes the absolute peak deflection during the load plateau (DI 1- u ) and its position (DI 1- x ). The second set, DI₂ (residual), includes the peak residual deflection after unloading (DI 2- u ) and its location (DI 2- x ). The u components reflect damage severity, while the x components provide damage localization. These indicators consistently identified the damaged regions and scaled with the number and position of severed strands, in agreement with force–displacement responses, moment–curvature relationships from sectional analysis and observed failure modes. The results demonstrate that rapid static testing combining tilt-based deflection mapping and local crack-opening measurements provides a practical and reliable approach for detecting, ranking, and localizing tendon damage in prestressed concrete girders.