New technique for self-centering shear keys in highway bridges. (1st January 2022)

• Record Type: Journal Article
• Authors: Wilches, José; Leon, Roberto; Santa María, Hernán; Fernández, Claudio; Restrepo, José I.
• Is Part Of: Engineering structures. Volume 250(2022)
• Publication Date: 2022-01-01
• Subjects: Bridges -- Reinforced concrete -- Self-centering geometry -- Shear keys -- Soil class -- Time-history response analysis -- Residual displacements; Structural engineering -- Periodicals; Structural analysis (Engineering) -- Periodicals; Construction, Technique de la -- Périodiques; Génie parasismique -- Périodiques; Pression du vent -- Périodiques; Earthquake engineering; Structural engineering; Wind-pressure; Periodicals; 624.105
• DOI: 10.1016/j.engstruct.2021.113395
• Languages: English
• ISSNs: 0141-0296

Abstract

Highlights: A new self-centering shear key geometry is proposed that eliminates residual displacements of the superstructure, using only the structure's own weight, geometry and conventional bearing pads to generate the required restoring force. The proposed solution is simply a change in the kinematics of the bridge allowing superstructure's self-centering. The new self-centering technique is used to analyze a typical Chilean bridge using a set of records classified by soil types, considering the three translational components of the ground motion components. The results indicate that the technique is feasible, but care needs to be taken in accounting for an increase in forces in the substructure. The proposed shear key concept does not need additional devices such seismic isolators or energy dissipation elements. With a simple change of the geometry, the elimination of the residual displacements ensures the superstructure's self-centering behavior. Abstract: Shear keys are elements in bridges designed to prevent or limit transverse unseating, rotation, and/or collapse of the superstructure responding to strong-intensity earthquake input ground motion, as well as to absorb breaking and various self equilibrating forces. During the 2010 Maule earthquake, Chile's highway infrastructure was seriously impacted. Shear key failures were endemic and did not function as intended. As a result, some bridges experienced partial or complete collapse. Even when the shear keys appeared to have worked, the superstructure exhibited large offsets, which required expensive repairs. An expensive retrofit of undamaged bridges was also carried out as a result of the inadequate response of the bridge infrastructure. This paper addresses the behavioral issues of bridges designed incorporating conventional shear keys and proposes an innovative self-centering concept that eliminates residual displacements in the superstructure. The self-centering shear key concept, as it will be termed here, makes use of the bridge self-weight as a restoring force to ensure self-centering. This concept proposal takes advantage of the kinematics of the bridge. The self-centering shear key concept was validated for a typical Chilean bridge via an extensive study that made use of nonlinear time history analyses. The results indicate that the increase in seismic demand on the substructure is small enough to maintain the bridge base structure in the elastic range while eliminating any residual displacements in the superstructure.