Abstract:
Hackensack University Medical Center (HUMC) in New Jersey, USA is the state's largest inpatient and outpatient service provider and the crown jewel of the Hackensack Meridian Health (HMH) Group. With the ever-growing volume of patients HUMC serves, a new 9-story, over-500,000 sq ft (46,451.52 sq. m) addition was needed to expand hospital capacity. To maximize the amount of building floor space on an already crowded, cramped, and heavily-sloped hospital campus, the new addition was set to span the width of 2nd Street, some 25-ft (7.62-m) above street grade to allow for through-traffic after project completion. Due to the nature of the structure, with long spans between columns and heavy floor loads, the foundation system would be required to support large loads, both axially and laterally, with some foundation elements being within 3 ft (0.91-m) of the active hospital.As with any large structure in a crowded, urban environment, the success of the project relied upon an economical foundation, tailor-made to take advantage of the geotechnical conditions present, while also understanding the site constraints for the methods of construction. With much of the site not limited by headroom restrictions and the presence of shale bedrock near ground surface, drilled shafts were used to support the large column loads from the building's superstructure. In the few areas with restricted headroom, micropiles were the preferred method of foundation support. The geotechnical contractor retained for the work, with its team of engineers, re-designed the shafts and micropiles, as well as an adjacent support of excavation system, to take advantage of smaller equipment and the contractor's range of drill tooling, limiting the amount of time spent switching out equipment for different tasks. The re-design resulted in both a financial savings and a reduced schedule.This presentation looks to highlight the design and constructability constraints of the project described above.