Shear Behavior of Ultrahigh-Performance Concrete Pretensioned Bridge Girders

Abstract

Because of their tensile strain-hardening characteristics, ultrahigh-performance concrete (UHPC) materials offer significant advantages in terms of beam shear capacity and postcracking behavior compared to conventional reinforced-concrete beams. These advantages rely on UHPC’s ability to sustain its strain-hardening characteristics at the structural level. This paper reports the results of an experimental investigation on the parameters influencing the structural shear behavior of prestressed UHPC bridge girders. Six pretensioned bulb-tee UHPC bridge girders were tested in shear with the following test variables: the UHPC material properties, the girder height, the web thickness, the number of prestressing strands, and the presence of discrete transverse steel reinforcement in the web. The average relationship between the principal stress and strains in the web was monitored during the tests and compared to behavior obtained from uniaxial tests. The shear behavior and capacities of the tested girders were observed to be largely dependent on the tensile characteristics of UHPC. The results demonstrate UHPC’s capability to sustain its strain-hardening characteristics at the structural scale and highlight the importance of the crack localization strain, corresponding to the end of the tensile hardening behavior, to the global shear performance of UHPC girders.