Minimum confinement reinforcement for prestressed concrete piles and a rational seismic design framework

The design of prestressed concrete piles in seismic regions is required to include confinement reinforcement in potential plastic hinge regions. However, the existing requirements for quantifying this reinforcement vary significantly, often resulting in unconstructible details. This paper presents a rational approach for designing minimum confinement reinforcement for prestressed concrete piles in seismic regions. By varying key variables, such as the concrete strength, prestressing force, and axial load, the spiral reinforcement quantified according to the proposed approach provides a minimum curvature ductility capacity of about 18, while the resulting ultimate curvature is 28% greater than an estimated target curvature for seismic design. This paper also presents a new axial load limit for prestressed piles, an integrated framework for seismic design of piles and superstructure, the dependency of pile displacement capacity on surrounding soils, and how further reduction to confinement reinforcement could be achieved, especially in medium to soft soils and in moderate to low seismic regions.