Seismic Performance of Column-to-Drilled-Shaft Connections in Reinforced Concrete Bridges

Drilled shaft foundations are often used to support reinforced concrete bridge columns founded in soft soils or locations where a small footprint is desired. Increasingly, the being built with diameter larger than that of column, allow tolerance column placement and facilitate plastic hinge formation rather shaft. The column–shaft connection, which involves noncontact splice between bars, key component this structural system. However, there limited research on behavior these connections under seismic loads. In order understand force-transfer mechanism loading, one quasi-static cyclic experimental test was conducted subassembly. Measured results were compared those from three previous experiments performed at University Washington others California San Diego. study found amount transverse reinforcement connection region critical determining failure mode connection. specimens relatively low amounts reinforcement, including specimen tested during Washington, failed through prying mode; developed large vertical cracks confined core annular transition region, eventually fractured drift ratios. Therefore, methodologies for detailing evaluated, new analysis procedure using strut-and-tie model proposed. It consistent measured observed performances applicable shafts supporting either precast cast-in-place columns. allows engineers (a) more accurately predict (b) prevent an undesirable below-ground region. Lastly, set design equations based findings existing models proposed use practice.