Evaluation of Properties of Constructed Tubular-Steel Cast-in-Place Pilings

Bridge foundations contribute significantly to the serviceability and efficiency of in-service transportation networks. Foundation failure may lead to catastrophic failure of the entire structure, which in turn results in system failure, loss of life, and detours. When the soil within ground surface layers fails to satisfy the bearing capacity requirements, deep foundations such as tubular-steel concrete-filled piles are commonly used in practice. A challenge that often exists with these systems is the uncertainty surrounding in-service capacity as well as condition, which is difficult to determine from the surface. As a consequence, transportation agencies such as the Wisconsin Department of Transportation use conservative approaches, such as neglecting the tubular-steel contribution or bounding the compressive strength of the core concrete, to design these systems. This approach, while effective for safety, can yield overly conservative and costly designs. The main purpose of this investigation was to evaluate the behavior of tubular-steel, concrete-filled, cast-in-place pilings, with a concentration on the compressive strength and composite behavior between concrete core and steel shell. In this regard, a series of experimental studies, including composite and noncomposite compression loading, core samples, push-through, and flexural testing together with a compatible finite element analysis, were conducted on a series of field-cast piles with different geometrical properties. The results indicated that the steel shell made a significant contribution to the axial loading capacity of the cast-in-place piles. Moreover, no evidence of bond loss was observed during the corresponding experimental studies.