SUMMARYIn this study the employment of buckling-restrained braces (BRBs) as energy dissipation dampers is attempted for seismic performance upgrading of steel arch bridges and the e ectiveness of BRBs to protect structures against strong earthquakes is numerically studied. With buckling restrained, BRB members can provide stable energy dissipation capacity and thus damage of the whole structure under major earthquakes can be mitigated. Cyclic behaviour of such members is addressed with a numerical simulation model, and a strength design method for BRBs is proposed. BRBs are then placed at certain locations on the example steel arch bridge to replace some normal members with two schemes, and the e ect of the two installation schemes of BRBs for seismic upgrading is investigated by non-linear time-history analyses under various ground motions representing major earthquake events. Compared with the seismic behaviour of the original structure without BRBs, satisfactory seismic performance is seen in the upgraded models, which clariÿes the e ectiveness of the proposed upgrading method and it can serve as an e cient solution for earthquake-resistant new designs and retroÿt of existing steel arch bridges.
SUMMARYIn this study the inelastic behavior of steel arch bridges subjected to strong ground motions from major earthquakes is investigated by dynamic analyses of a typical steel arch bridge using a three-dimensional (3D) analytical model, since checking seismic performance against severe earthquakes is not usually performed when designing such kinds of bridge. The bridge considered is an upper-deck steel arch bridge having a reinforced concrete (RC) deck, steel I-section girders and steel arch ribs. The input ground motions are accelerograms which are modiÿed ground motions based on the records from the 1995 Hyogoken-Nanbu earthquake. Both the longitudinal and transverse dynamic characteristics of the bridge are studied by investigation of time-history responses of the main parameters. It is found that seismic responses are small when subjected to the longitudinal excitation, but signiÿcantly large under the transverse ground motion due to plasticization formed in some segments such as arch rib ends and side pier bases where axial force levels are very high. Finally, a seismic performance evaluation method based on the response strain index is proposed for such steel bridge structures.
SUMMARYThe performance-based philosophy has been accepted as a more reasonable design concept for engineering structures. For this purpose, capacity evaluation and demand prediction procedures for civil engineering structures under earthquake excitations are of great signiÿcance. This work presents a displacement-based seismic performance veriÿcation procedure including capacity and seismic demand predictions for steel arch bridges and investigates its applicability. Pushover analyses is employed as a basis in this method to investigate the structure's behaviors. A failure criterion for steel members accounting for the e ect of local buckling is involved and an equivalent single-degree-of-freedom (ES-DOF) system with a simpliÿed bilinear hysteretic model formulated using pushover analyses results is introduced to estimate the displacement capacity and maximum demand of steel arch bridges under major earthquakes. To check the accuracy of the proposed method, seismic capacities and demands from multi-degree-of-freedom (MDOF) time-history analyses with Level-II design earthquake record inputs modeling major earthquakes are used as benchmarks for comparison. By a case study, it is clariÿed that the proposed prediction procedure can give accurate estimations of displacement capacities and demands of the steel arch bridge in the transverse direction, while insu cient for the longitudinal direction, which conÿrms the conclusion drawn in other structure types about the applicability of pushover analyses.
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