Abstract: The proposed Blennerhassett Island Bridge crosses the Ohio River and historical Blennerhassett Island connecting Wood County, West Virginia to Washington County, Ohio. The hybrid steel girders for the Ohio approach spans have span length of 52.1 m, 54.7 m and 42.6 m. One of the limitations presented in the AASHTO (1998) LRFD Bridge Design Specifications, with 2003 interims, is that when considering shear design for hybrid sections, there is no allowance for tension field action. The shear design of girders using these specifications required in excess of 120 transverse stiffeners per girder. The use of the tension field action for designing hybrid girders, which is allowed in the AASHTO (2004) LRFD Bridge Design Specifications, reduced the number of transverse stiffeners required to 36 per girder. This reduction in stiffeners reduced the cost by approximately 10% for each girder. The stresses in the web and the transverse stiffeners for the two designs are presented. Because there is a significant difference in the transverse stiffener requirements under each design, we were prompted to take a closer look at the tension field action anticipated. The tension field action involves the effects of out-of-plane forces on the transverse stiffeners due to the shear post-buckling response of the web panels. Therefore, a three-dimensional finite element model was used considering material and geometric non-linearity. The analysis demonstrated that the anticipated tension field did form as assumed in the design.
Keywords: Shear resistance, Post buckling, Hybrid steel girders, Tension field action, Transverse stiffeners
