Lessons from time-dependent deflection in record span prestressed concrete bridges.

Abstract

Globally, over 60% of record-span segmentally constructed prestressed concrete (PC) bridges exhibit excessive deflection, severe cracking, and underestimated prestressing losses. Decades of practice in continuous girder and rigid-frame PC bridge design have limited the maximum span capacity to about 350 m, mainly due to unreliable design methodologies and software constraints. This study proposes a multi-field time-dependent numerical framework integrating concrete cracking, nonlinear creep, shrinkage, reinforcement behavior, and prestressing tendon relaxation (including threaded bars). Implemented in Abaqus/Standard through user-defined subroutines, the framework enables high-fidelity 3D simulations and is validated on three record-span PC bridges. Results show that nonlinear creep and cracking significantly aggravate deflection, a phenomenon poorly documented in prior studies. The analysis further reveals that downward-curved cantilever tendons are necessary to counter the unreliable prestressing effectiveness of threaded bars. An in-depth evaluation of these bridges highlights that achieving a reasonable finished stress state is essential for controlling long-term deflection. The findings provide valuable insights for improving the design and durability of segmentally constructed PC bridges.