Drilled Shaft Socket Connections for Precast Column in Seismic Regions
Tran, Hung Viet
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Conventional cast-in-place method in bridge construction requires long on-site construction time and substantial labor in the field, which can result in high construction costs and traffic delays. Using precast bridge elements is one solution. However, achieving good connections between precast elements is challenging, particularly in seismically hazardous areas, like the Pacific Northwest, in which the largest forces are developed at the beam-to-column or column-to-footing connections. Therefore, the connections need to be strong enough to resist seismic excitation and easy to construct with high quality. This study adapts the column-to-foundation socket concept to connections between a precast column and cast-in-place drilled shaft. In this connection, the column is precast with a roughened outer surface at the bottom of the column, where it will be embedded in the drilled shaft. Two specimens were fabricated and tested at the University of Washington. The only difference between the two specimens was the amount of spiral reinforcement in the column-to-shaft transition region, which was reduced by half in the second specimen. The goal was to promote failure in the shaft transition region in the second specimen, in order to develop an understanding of the load transfer mechanism there. The response and mode of failure of each specimen was the same as had been anticipated during design. It shows that the new design provides agencies a good method for accelerating bridge construction.
- Civil engineering