Challenge

The Merchants Ice and Cold Storage Company Complex includes six buildings that were constructed between 1909 and 1957 and encompasses a five-acre site in San Antonio’s Eastside. An extensive renovation was approved to change the complex into a technology and life science innovation hub. Building #5 was previously used as a warehouse and would be renovated into a two-story Co-Lab facility. Due to the historic nature of the complex, the original interior columns would remain during removal of the building shell and be visible in the new office spaces after renovation. Nine existing interior columns, which were supported by shallow footings would require additional capacity for the new construction. The new column service loads (design working loads) ranged from 67.5 to 79 kips in compression with tension service loads of 12.9 kips. Several factors were considered which lead to a design requirement for removal and replacement of the existing column foundations with a deep foundation system including; a geotechnical investigation showed poor bearing soils below the existing footings used to support the existing columns, the existing column pad concrete had deteriorated with age, and the tension loading could not be handled by the shallow column pads. A temporary support system would be needed for the columns to allow access for construction of the deep foundations below the columns. The temporary support system would limit access for large installation equipment.

Solution

Given the access limitations and other project challenges, helical piles were selected as the most economical solution for deep foundation support at the existing column locations. The nine columns were temporarily supported by spanning the existing concrete slab with structural steel elements welded to the columns prior to removal of the column footings. The Model 288 (2.875-inch OD by 0.276-inch wall) helical pile system with new construction brackets was selected for column pad support. Four helical piles were used at each column pad with maximum individual pile service compression and tension loads of 19.8 kips and 3.3 kips, respectively. An 8”10”-12” helix plate configuration with a minimum termination depth of 19 feet was specified. The minimum termination depth was required to ensure the top helix was below the active soil zone defined in the geotechnical report as 15 feet below existing grade. The helical piles were installed to depths of 19 to 26.5 feet after achieving torque-correlated ultimate capacities of at least 2 times the service load. The 36 helical piles were installed over a period of 5 days.

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Project Summary

General Contractor: Whiting-Turner

Geotechnical Engineer: Raba Kistner, Inc.

Helical Pile Designer: Hayman Engineering

Helical Pile Installer: Baird Foundation Repair

Products Installed: (36) Foundation Supportworks® Model 288 Helical Piles, Service Compression Loads of 19.8 kips or less, Service Tension Loads of 3.3 kips, Installed Depths of 19 to 26.5 feet.