Title:
Friction Losses in Full-Scale Post-Tension Girders: Experimental Study (Prepublished)
Author(s):
Mostafa Osman Serry, Mohamed Salah El Din Darwish, and Ezzeldin Yazeed Sayed-Ahmed
Publication:
Structural Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
friction losses; post-tension; prestressed concrete; regression analysis
DOI:
10.14359/51750685
Date:
4/23/2026
Abstract:
Prestressed concrete enables slender, economical, and durable structures, with post-tensioned (PT) precast girders widely used in bridge construction. Accurate design requires precise prediction of prestress losses, among which friction losses, arising from duct curvature, wobble, and anchorage slip, are most significant. Existing codes employ simplified exponential models, yet notable discrepancies persist between predicted and actual field values. This study presents full-scale experimental testing on PT precast girders used in Egypt’s Light Railway Transit (LRT) Project. Prestressing forces were measured using strain gauges to evaluate friction losses along tendon profiles. Results revealed that measured losses consistently exceeded code-based predictions, highlighting the influence of stress level and nonlinear variation along the tendon; factors often ignored by current provisions. Regression analysis yielded refined exponential models with improved accuracy and strong agreement with observations. The proposed refinements enhance predictive reliability and provide a foundation for updating design codes toward safer, more realistic PT concrete structures.