Expanding the Use of Elastomeric Bearings for Higher Demand Applications

Book excerpt: Elastomeric bearings have been widely used in short-span bridge systems as they provide a reliable and cost-effective means of accommodating translations compared to the pot bearing alternatives. However, in higher demand applications pot and disk bearings are commonly used to accommodate significant forces and rotations and complex bridge movements from both thermal loads and daily truck traffic. Although elastomeric bearings have been designed for and utilized in twin steel trapezoidal box girder systems in Texas, classifying as higher demand applications, the lack of experimental and numerical research on such bearings, as well as some occasions of poor performance, dictate the need of further investigating their design requirements and performance. The research presented in this dissertation is part of a broader research project including material-level studies, field monitoring of bridge bearings, large-scale experimental testing, and finite element simulations. This dissertation focuses on the large-scale experimental testing and investigates the effect of several parameters on the compression and shear stiffness of elastomeric bearings. Specifically, bearing tests demonstrated the poor prediction ability current AASHTO axial stiffness prediction equations as well as a shear stiffness dependence on the level of axial load and, in some cases, on the shearing direction of the bearing. However, it was shown that both AASHTO Method A and B produce safe elastomeric bearing designs. The finite element studies demonstrated that shim misalignment and cover friction can cause a reduction in the axial stiffness of an elastomeric bearing. In addition, an extensive finite element parametric study was performed to show variations in elastomeric bearings shear stiffness with different axial loads and shearing directions with a wide range of aspect ratios and height to width ratios.