Piles with a variable perimeter over all or part of their length are generically called tapered piles. The benefit of using tapered piles when axial- compressive loads predominate, especially in 'friction' situations involving coarse- grain soils, has been recognized in principle for a long time. However, this benefit does not appear to have been fully exploited in practice, especially in transportation applications. Several recent events have produced a rebirth of interest in tapered piles, at least in U.S. practice. One was the development and commercial introduction of a new type of proprietary tapered steel pipe pile called the Tapertube. It was developed primarily to provide commercial competition to the long-established Monotube pile but it has also demonstrated that it is a structurally robust pile capable of withstanding the stresses of today's high-capacity design requirements. Of relevance to this conference is that Tapertube piles were essentially developed for, and eventually used extensively on, one of the larger transportation-related projects in the New York City metropolitan area in recent years, the major renovation and expansion work at the John F. Kennedy International Airport. This work included both terminal buildings and several kilometres of elevated light-rail structures as well as project-wide design for seismic loading. As a result, a comprehensive pile-load-test program was conducted to verify the performance of Tapertube piles under compressive, uplift and lateral loads.
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