Compressive strength of HPS box girder flanges stiffened with open ribs

• Ultimate compressive strengths of stiffened plates were evaluated by nonlinear FEA.
• FEA strengths were compared to those from Eurocode, FHWA, and other predictions.
• New strength predictor equations can cover conventional and high performance steel.
• Most design codes lead to overly conservative design for high performance steel.

This paper presents a set of new strength equations for box girder flanges stiffened with open ribs subjected to uniaxial compression. Tee type and flat-plate type cross-section ribs were considered in the isolated stiffened plate systems that were studied. A total of eighty four hypothetical compression flange panels were modeled with wide ranges of slenderness parameters and then were investigated by nonlinear finite element analysis (FEA). The dimensions of the FEA models were carefully determined to satisfy the major requirements for stiffened flange systems and the longitudinal stiffeners were designed such that stiffener local buckling did not govern the failure of the stiffened flanges. Both conventional and high performance steels (HPS) were investigated in the analysis models by utilizing multi-linear constitutive relationships. Initial imperfections and residual stresses were also considered in the analysis. New design equations to predict the in-plane compressive strengths of the stiffened flanges are proposed based on the FEA results and compared with other design equations specified in Eurocode 3, the Federal Highway Administration (FHWA) design specifications, and the Japanese Road Association (JRA) specifications, and equations previously proposed by other researchers. It has been found that the equations provided in the above design codes underestimate the strengths determined from the HPS models, which may result in an inefficiently conservative strength design.