Increasing the Displacement Ductility Factor of Spun Pile Using Concrete Infill

Displacement ductility is one of the parameters used to measure the seismic performance of a structure. This study experimentally determines the increase in displacement ductility of the spun pile with 400 mm of outer diameter and 100 mm of wall thickness using concrete infill cast inside the hollow of the pile. The spun pile and concrete infill's concrete compressive strength was 54.4 MPa and 33.0 MPa, respectively. Loading was conducted with constant axial and reversed lateral flexural loads. A total of six samples were tested with different axial loads of 392 kN (0.08fc'Ag) for S-DB-1, S-DB-2, S-DB-5, and 784 kN (0.16fc'Ag) for S-DB-3, S-DB-4, S-DB-6 with the reverse flexure load applied in the middle span of the pile. The results showed spun piles with concrete infill could resist the flexural load combined with axial loads until the displacement ductility 5.8 for P0 = 0.08fc'Ag, and 3.7 for P0 = 0.16fc'Ag, respectively. Compared with the ordinary spun piles, which had a hollow section, the presence of concrete infill due to the presence of the concrete infill the displacement ductility increased by 18% when loaded with 0.08f'cAg and 42% at 0.16f'cAg of axial loads. In conclusion, according to seismic codes, displacement ductility evaluation showed that tested piles for plastic concept design applications are appropriate for moderate seismic risks category state under axial loads of 0.08fc'Ag. The increasing of the axial load becomes 0.16fc'Ag decreasing the displacement ductility to become less than 4, applicable for low seismic risks category state