Ductile seismic retrofit of steel deck-truss bridges. II: Design applications

A companion paper has demonstrated how deck-truss bridges can be retrofitted by converting the end cross-frames and lower end panels adjacent to the truss supports into special ductile panels. However, the design of such retrofitted systems must respect constraints on flexibilities to limit global drifts and ductility demands, as well as other constraints germane to the type of ductile device introduced. Proposed, here, are performance based design procedures accompanied by graphical approaches that incorporate all of those constraints affecting seismic response of deck-truss bridges retrofitted using eccentrically braced frames, vertical shear links, or triangular-plate added damping and stiffness device ductile systems. Using the proposed method, ductile panels for a 80-m-span deck-truss example bridge using eccentrically braced frames, vertical shear links, and triangular-plate added damping and stiffness device were designed, detailed, and modeled by computer. From the results of nonlinear inelastic time history analyses of the retrofitted bridge, it is concluded that all three systems designed according to the proposed procedure perform satisfactorily and enhanced seismic performance of the deck-truss bridges.