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

In recent years, ground transportation infrastructure has been exposed to an increasingly large number of natural hazards, such as earthquakes, tsunamis, and hurricanes. During the 2010 Chile Earthquake, a number of girder bridges lost spans or rotated with transverse offset, causing out-of-plane rupture of concrete girders and flexural damage to lateral restrainers. Storm surges associated with Hurricane Katrina in 2005 floated and displaced some bridge superstructures when end diaphragms and girders trapped air under water, dropping the bridge spans into water.<br/>The goal of this multi-phase proposal is to prevent the above failures 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 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 support, the key provides controllable lateral and vertical friction forces during natural hazards and regulate corresponding displacements over time.<br/>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 system subjected to ground accelerations. These objectives will be achieved through experimental and computational research in laboratory.

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