Keywords: Seismic performance. Bidirectional-resistant ductile end diaphragms. Unbonded braces. Retrofitting. Steel bridges. Skewed bridges. Hysteretic models. Irregular structures. Hysteretic energy dissipation. Inelastic behaviors.
Abstract: This research aims to extend the known ductile end diaphragm concept to make it applicable for bidirectional earthquake excitation, using unbonded braces as the ductile fuses. Irregular (i.e. skewed) bridge superstructures are also covered to determine if the ductile diaphragm concept could be used in skewed bridges. Two retrofit schemes are investigated in detail to search the best geometrical layout (to maximize the dissipated hysteretic energy) of the ductile diaphragms with unbonded brace end diaphragms. Closed form solutions are sought for practical design purposes. Behavioral characteristics of the proposed retrofit schemes are quantified with an emphasis on hysteretic energy dissipation. Results from many numerical examples show that the bidirectional loading, the loading ration, and the skew angle have pronounced effect on the end diaphragm’s inelastic behavior.