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

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.