Optimizing the Design of Driven Pile Foundations with Instrumented Static Load Tests

Two large bridges over the Great Miami River in Dayton, Ohio, were constructed. The foundations for these bridges consist of driven piles, and as part of a value engineering change proposal (VECP) the foundation design was optimized for the least cost given the constraints of the site conditions and pile drivability. Over 40 different possible combinations of pile diameter, pile wall thickness, pile capacity, and pile hammer were considered during design, including open ended piles. Cost factors included material costs for steel and concrete including length surcharges over 15.2 m (50 ft), crew and equipment time and costs to unload and drive the piles, and time and material costs for splices. Foundation costs were compared on cost/ton basis. The selected pile design was a 406 mm (16-inch) pipe pile with an ultimate capacity of 2890 kN (650 kips), which exceeded the state DOT’s recommended maximum pile capacity of 1600 kN (360 kips) for this size pile. During construction, two instrumented static load tests and many dynamic load tests (with signal matching analyses) were performed to evaluate the selected foundation design. The results were used to develop a construction pile driving criteria that accounted for pile setup and checked for pile tip relaxation. The results of the static load tests indicated that one pile had an ultimate capacity of at least 2980 kN (670 kips) and the second pile had a capacity in excess of 4900 kN (1100 kips).