Commercial Foundations Case Studies: Schenectady Community College Elston Hall Portico - Helical Piers
Challenge
Schenectady Community College Elston Hall recently underwent extensive renovations to its entrance portico; i.e., the grand entrance with roof structure supported by columns. The original six-story brick building was constructed in 1925 and served for many years as the Hotel Van Curler. The building is listed with the U.S. National Register of Historic Places. The Schenectady Community College acquired the building in 1968 and renamed the building after their longtime chairman, Charles Elston. The main entrance portico is adorned with six Corinth columns supporting the roof structure. The base construction of the portico includes brick and poured concrete foundation walls with a limestone veneer. The limestone veneer would be carefully removed for reuse on the renovated portico.
The building and portico are constructed over deep alluvial soils deposited by the waters of the former Erie Canal. A soils investigation identified variable, but adequate-strength soils within the upper portion of the profile, becoming weaker with depth. The project was designed with ten hydraulically-driven push piers to support existing and new loads on the portico foundation walls and three new construction helical piers to support the new end wall foundation for the code-compliant stairs. Pier depths were to be no greater than 75 feet to prevent influence of the deep, weaker native soils.
Solution
Ten Model 288 (2.875-inch O.D. by 0.165-inch wall) push piers were installed along the perimeter of the existing portico foundation walls to depths ranging from 21 to 75 feet (average of 42 feet). The piers were installed to ultimate capacities of at least 36 kips to provide a factor of safety of at least 2.
Three Model 288 (2.875-inch O.D. by 0.276-inch wall) helical piers with 10"-12" double-helix lead sections were installed to support the new foundation wall. The helical piers were installed to depths ranging from 18 to 36 feet (average of 30 feet) and to torque-rated ultimate capacities of 40 kips (FOS = 2). The helical piers were immediately cast into concrete grade beams upon completion. The push and helical piers were installed in two days.
Project Summary
Architects: Griffith Dardanelli Architects
Structural Engineer: Klepper, Hahn and Hyatt
General Contractor: Mid-State Industries
Certified Pile Installer: Foundation Supportworks Northeast
Products Installed: (10) Foundation Supportworks™ Model 288 Push Piers, Installed to depths of 21-75 feet, 18 kip Design Working Load; (3) Foundation Supportworks™ Model 288 Helical Piers, Installed to Depths of 18 to 36 feet, 20 kip Design Working Load.
