Experimental study on direct-shear behaviour of narrow joints in socket connections for precast pier-to-pile footing systems

The application of precast concrete segmental piers in modern construction, being economic and environmental, is an inevitable global trend. With the ease of construction and high performance, socket connections have a broad prospect for substructures, which can connect precast piers to footings with preformed sockets through narrow joints grouted by high-performance cement-based materials. However, these joints are different in directshear behaviour than those in precast concrete segmental beams. In this study, the direct-shear behaviour of narrow joints in socket connections for precast pier-to-pile footing systems is investigated through experimental analysis. The joint specimens were designed as full-scale local models for push-out tests. The results reveal that improving the tensile strength of the grouting material by applying steel-fiber reinforced concrete or selfcompacting concrete, decreasing the width of the joints and increasing the number of shear keys are all beneficial to improve the direct-shear performance, while the use of corrugated steel pipes as a stay-in-place formwork without additional reinforcements in footings reduces this characteristic.