Design and Construction of Driven Pre-Stressed Concrete Piles to Support Large Transmission Structures-PPT Presentation

PPT Presentation

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The project replaced century-old transmission towers at the Port of Long Beach, California, to raise power and telecommunications lines for larger cargo ships. The work involved four 160-foot tubular steel poles and two lattice steel towers, including structures up to 388 feet tall.<br /><br />Site conditions posed significant challenges. The area was once tidal mudflat, later reclaimed with dredged material, and experienced severe subsidence from oil extraction. The site is also seismically active, with deep, variable soil layers, liquefiable materials, contamination, corrosion risks, underground utilities, and overhead construction constraints.<br /><br />The foundations used 24-inch octagonal prestressed concrete piles beneath seven-foot-thick concrete caps. Design embedment depths were 90 feet for the pole foundations and 105 feet for the lattice-tower foundation, based on loading and subsurface conditions. Because precast piles are difficult to splice or shorten, the team addressed constructability early and coordinated closely with the pile manufacturer.<br /><br />A non-production testing program used pile driving analyzer (PDA) measurements and CAPWAP analyses to assess drivability and capacity. Test piles encountered denser soil at depth and, in many cases, refusal near the design embedment. Measured capacities varied by structure type, and the results informed production-driving settings, predrill limits, cut-off lengths, retesting schedules, and termination criteria.<br /><br />The project’s key lessons were that close collaboration between designers and contractors is essential, and that field modifications to prestressed concrete piles can be managed successfully when planned in advance.

Keywords

Port of Long Beach

transmission towers

prestressed concrete piles

pile foundation

seismic conditions

subsidence

pile driving analyzer

CAPWAP

lattice steel towers

constructability