Performance of SMART Shear Keys in Concrete Bridges under Tsunami Loading: An Experimental Study

Bridges have recently been exposed to an increasing number of natural hazards such as earthquakes and tsunamis. These extreme events have resulted in transverse offsets, overturning moments, and even dropping-off of superstructures due to their weak connection to substructures. These outcomes are potentially prevented or mitigated by developing and deploying sliding, modular, adaptive, replaceable, and two-dimensional (SMART) shear keys as fuse elements between superstructures and substructures. The novelty of SMART shear keys is to enable an adaptive control of both the force and displacement of bridges under different types of loads. In this study, the performance of SMART shear keys under tsunami loading was investigated through a 1/5-scale six-girder concrete bridge model. Four levels of tsunami-like solitary waves 0.27, 0.42, 0.57, and 0.72 m in height were generated in the large wave flume at Oregon State University and applied on the reinforced concrete bridge. To evaluate the performance of the shear keys, the dynamic responses of the bridge model were measured from accelerometers, load cells, and displacement sensors. The shear keys were prestressed to 0, 100, and 200 MPa to represent flexible, medium, and fixed superstructure-substructure connections, respectively. The test results indicated that the residual displacements of the SMART shear keys were less than 1 mm in the vertical direction and zero in the horizontal direction. The energy dissipated by the SMART shear keys was up to 32.5% of the input energy that the bridge received from the tsunami loading. The natural frequency and energy dissipation of the bridge were respectively modified up to 18% and 14.2% by changing the prestress level of the SMART shear keys from 0 to 200 MPa.