SMART Shear Keys for Multi-Hazards Mitigation of Diaphragm-Free Girder Bridges – Phase II

The goal of this multi-phase project is to prevent the out-of-plane rupture of concrete girders and flexural damage to lateral restrainers under earthquake loads and floated-and-displaced bridge superstructures under hurricane events by exploring and developing a novel concept of diaphragm-free girder bridges with Sliding, Modular, Adaptive, Replaceable, and Two-dimensional (SMART) shear keys. Each key is composed of three precast concrete modules arranged in an L-shape that are horizontally and vertically post-tensioned with replaceable unbonded steel bars to form two wedged sliding surfaces. When installed next to a girder and anchored into its capbeam support, the key provides controllable horizontal and vertical friction forces during natural hazards and regulates corresponding displacements over time. The first phase aims to: (1) characterize novel SMART shear keys under cyclic loads, (2) develop a friction-gap model of the shear keys for inclusion in computational modeling and simulation of bridges, and (3) understand and evaluate the effect of SMART keys on the seismic behavior of a small-scale bridge bent subjected to ground accelerations. The objectives of this research are: (1) to understand the system behavior and responses of a simplified highway bridge, particularly the torsional effect of spatially-distributed SMART shear keys under strong multi-component earthquakes, and (2) to develop a strategy and algorithm for optimal placement of SMART shear keys, and to understand and develop a similitude law of SMART shear keys for the prediction of their behavior and responses through small-scale model tests.

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