Strengthening of Steel Through-Girder Bridges Using UHPC and Post-Tensioning

Abstract

This paper presents a series of strengthening concepts for steel through-girder bridges using ultrahigh-performance concrete (UHPC) and external post-tensioning (PT). Five concepts were investigated either by large-scale proof-of-concept experimental testing or numerical analysis. The goal of the research was to determine the characteristic behavior of the UHPC–steel composite system and provide guidance to designers regarding calculating the elastic and ultimate flexural behaviors of the strengthening concepts. Experimental work included laboratory testing of a single half-scale girder specimen designed using an actual in-service railway bridge as a reference. The half-scale girder specimen was subjected to elastic and ultimate loading. The numerical analysis included the development of a moment–curvature-based flexural capacity model and a limited parametric study. The findings suggest that the strengthening concepts are viable in some circumstances but have some drawbacks such as a need to implement a large UHPC cap with PT to observe increased system capacity. Finally, a brief set of design considerations is provided.