Deflection‐based assessment of residual prestress in simply‐supported bridges accounting for creep variability

Abstract Several test methods have been proposed in the literature for measuring the level of residual prestress, most of them involving either semi‐ or fully destructive techniques for local measurements which could be highly sensitive to boundary conditions and execution details. This preliminary study presents an analytical approach to estimating residual prestress in simply‐supported prestressed concrete (PC) bridge girders through deflection measurements and elastic beam theory including linear viscoelasticity. Two alternative formulations are proposed: a fib Model Code‐based approach requiring comprehensive information on the bridge and accounting for creep uncertainty, and an extended approach applicable when the initial prestressing force is unknown. Both approaches estimate the residual prestressing force through a back‐analysis procedure matching theoretical long‐term deflections with on‐site measurements. Validation against an existing roadway bridge showed that the estimated residual prestressing force differed by less than 5% from values obtained through direct measurements. Sensitivity analyses indicated limited influence of concrete compressive strength and satisfactory robustness with respect to creep variability. Furthermore, the methodology shows potential for structural health monitoring applications, as long‐term camber measurements may provide indications of additional prestress losses associated with tendon deterioration or damage. The proposed approach offers a practical and scalable tool for the large‐scale assessment of PC bridge infrastructure.