DRIVING STRESSES IN FIBERGLASS PRETENSIONED PILES

Four 25 ft long x 10 in. square fiberglass pretensioned piles, two wit h steel spirals and two with fiberglass spirals, were driven through d ense to very dense sands in Tierra Verde, FL, by a 3-kip drop hammer. Two identical steel pretensioned piles were also driven at the same si te to assess the performance of fiberglass pretensioned piles. The pil es were instrumented by strain gages attached to the prestressing stra nds and by reusable strain gages/accelerometers attached to the concre te surface near the pile top. Driving stresses were monitored using a pile dynamic analyzer and by an independent data acquisition system Th e test results showed that the performance of the fiberglass and steel pretensioned piles were very similar, although the confinement provid ed by the fiberglass spirals was inferior compared to steel.