High-Capacity Driven-Pile Foundation for 33-Story High-Rise in Milwaukee, Wisconsin, USA-Paper

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The project involved a 33-story mixed-use tower with two basement parking levels on a constrained Milwaukee site with highly variable soils. Driven, closed-end 16-inch steel pipe piles were selected over drilled alternatives because they were locally available and offered lower installation risk. The piles were concrete-filled after driving.<br /><br />A pre-production program tested ten piles using dynamic monitoring, long-term restrikes, and an instrumented static load test. The testing assessed drivability, pile capacity, load transfer, toe relaxation, and time-dependent soil set-up. The static test established a compression capacity of 1,346 kips. Restrike results showed substantial shaft-capacity gains from set-up, even after short pauses in driving, while no significant toe relaxation was observed.<br /><br />Engineers developed a conservative, depth-dependent set-up profile and combined it with end-of-drive capacity estimates to establish production criteria. This allowed required driving resistance to decrease at greater embedment depths, where greater set-up was expected. The criteria supported both 500- and 600-kip allowable-load piles; the selected maximum allowable compression load was 600 kips, based on a safety factor of 2.0. Separate criteria also addressed tension resistance and varying pile-cap elevations.<br /><br />During production, monitoring and inspection identified damaged piles and piles with limited penetration. Test results enabled engineers to assign realistic reduced capacities to these piles and reassess the capacity of other piles in affected groups. This reduced the number of replacement piles required by 50 percent, saving time and cost. Overall, coordinated testing and design produced an efficient foundation solution while accommodating subsurface variability and practical installation limits.

Keywords

mixed-use tower

steel pipe piles

driven piles

dynamic monitoring

static load test

pile capacity

soil set-up

toe relaxation

production criteria

foundation design