Axial load limit considerations for 14 in. square prestressed concrete piles

Abstract

The 2018 International Building Code and American Concrete Institute Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) have adopted axial load limits that prohibit the use of some 14 in. (350 mm) square prestressed concrete piles in areas of moderate to high seismicity. This paper presents the results of a study that examined the development of these axial load limits, their appropriateness as an attempt to ensure reliable seismic performance, and the expected seismic performance of commonly used 14 in. (350 mm) square prestressed concrete piles when the axial load limit is increased to levels commonly used in seismic design practice. Results of the study suggest that the axial load limits established by previous researchers are overly conservative and do not ensure reliable seismic performance. This paper recommends that reduced nominal moment strength be used in lieu of axial load limits for consistency with codified approaches already used in the United States and to help ensure reliable seismic performance when appropriate.