A case study on the shear behavior of pretensioned Spun Precast Concrete (SPC) piles

Pretensioned Spun Precast concrete (SPC) pile has become a very popular solution for deep foundation systems for its easier installation, higher bearing capacity, and overall cost-effectiveness. The pile system also brings both material and construction sustainability to the environment through its cleaner construction process and reduced consumption of construction materials. However, the smaller shear area of SPC piles arising from its hollowness is a big concern particularly when they are subjected to earthquake-induced liquefaction situations. This paper investigates the shear behavior of hollow pre-tensioned SPC piles experimentally. A total of ten full-scale SPC piles comprising high-strength concrete (50 MPa) and high-tensioned (HT) steel strands were manufactured through the centrifugal rotation and steam curing construction pro-cess. The pile segments consist of a variation in two different diameters, numbers of strands, thicknesses, presence of spirals, and spacing. The compressive strength of concrete was deter-mined from the compression tests of extracted core samples from the SPC piles. All pile specimens were tested under a four-point loading up to failure. The load-deformation responses, crack propagations, failure patterns, beam-deformation, and load-strain responses at the pile surface were investigated under different circumstances. The experimental results suggested that the presence of spirals plays a pivotal role in shear capacity and their failure patterns whereas the number of strands does not have a significant role in the shear capacity enhancement. The shear resistance of SPC piles was found in a range of 12-15 % and 8-11 % of their allowable axial capacity with and without the presence of spirals, respectively. The tested ultimate shear resistance is observed to be higher than that of all code-recommended values. This research offers useful information for the SPC pile's shear design that demonstrates its application in deep foundations of the seismic regions.