Seismic Retrofit of End-Sway Frames of Steel Deck-Truss Bridges with a Supplemental Tendon System: Experimental and Analyical Investigation
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Among the various types of steel bridges, deck-truss bridges are particularly vulnerable to seismically induced inertia forces. Under earthquake excitation, high transverse inertia forces that accumulate along the deck are transferred to the end sway frames and bearing supports. One of the major issues in developing efficient seismic retrofit strategies is to identify the continuous load path traveled by the seismically induced lateral inertial forces from the deck level through lateral load resisting system to the bearings and eventually to the substructure. Hence, this study investigates an alternative seismic retrofit approach that can be employed in main sway frames of steel deck-truss bridges. The proposed approach provides various possible modified bracing configurations that include supplemental damping systems. The effectiveness of the retrofit configurations is demonstrated experimentally and analytical on a one-third scale model of an existing steel end-sway frame structure tested on a shaking table. The tested configurations include pairs of tendon elements in two directions in the plane of sway-frames with/without supplemental system. The supplemental system consisted of mechanical fuse-bars and/or elastomeric spring dampers (ESD). Experimental results are present in comparison with the analytical results using an enhanced version of nonlinear time history analysis program Drain-2DX.