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

"The goal of this multi-phase proposal 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/tsunami 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 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 regulate corresponding displacements over time. The Phases I and II of this project were mainly focused on: 1) characterizing and modeling novel SMART shear keys under cyclic loads, 2) understanding and evaluating the effect of SMART keys on the seismic behavior of a small-scale bridge bent and a simplified highway bridge subjected to ground accelerations, 3) developing a strategy and algorithm for optimal placement of SMART shear keys, and 4) understanding and developing a similitude law of SMART shear keys for the prediction of their behavior and responses through small-scale model tests. The Phase III of this project is mainly to understand and model the tsunami behavior of bridge superstructures with SMART keys. Specifically, it will conduct small-scale model tests under broken and unbroken waves and develop the drag, lift, and moment coefficients as a function of friction force."

"Once successfully developed, the design and performance data of shear keys will be disseminated through professional meetings (e.g., TRB annual meetings), national/international conferences, and archival journals. Towards the end of this project, the small-scale model design, test and analysis will be conducted to determine the relation of various forces as a function of friction force. "

The expected outcomes of this study include a bridge superstructure model with SMART shear keys, and the determination of drag, lift and moment coefficients as the friction force changes. These outcomes will benefit the seismic bridge engineering by providing an innovative solution against tsunami tide wave effects.

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