Project Type: Evaluation
The Vital Structure:
Tower Main Entrance Canopy Foundation Design,
Boston, MA
Issue
Vital Structures was hired to perform a new foundation design to support a pre-engineered aluminum canopy located at the front entrance to the building. Previously, the front entrance was protected by a lightweight, fabric awning, which was reportedly damaged by a delivery truck, and was removed for the placement of vertical access during the concrete balcony restoration project at the facility. As a replacement for the previous awning, JT&T hired Duo-Gard Industries of Canton, MI, to design and manufacture a new, 18’-0” long by 8’-0” wide by 9’-5” tall aluminum framed canopy, with polycarbonate glazing. As Duo-Gard’s design was limited to the canopy structure, Vital Structures was retained to perform the foundation design.
Diagnosis
Due to the high wind forces experienced at the front of the 30-story building, a suitable foundation was required to provide resistance to uplift and overturning. Based on a limited exploratory test pit and soil borings performed by a licensed geotechnical engineer, the existing soil located at the front of the building was determined to be poorly suited to support a foundation, as sub-standard backfill material was apparently used following original construction of the building.
Solution
Our design included four (4) new 3’-0” wide by 1’-4” thick concrete strip footings, placed below minimum frost depth, and tied together in a grid pattern with additional 2’-0” wide footings. Each strip footing supports two (2), 1’-6” square reinforced concrete piers – eight (8) total piers, which extended to the top of the concrete slab on grade, to receive each canopy post. New footings and slab-on-grade were placed on compacted structural fill.
Result
The new foundation system allowed the new front entrance canopy to be erected prior to the winter season. As such, the residents of the facility are protected from wind and inclement weather when and entering and exiting the building.