Building on History
The Beacon mixed-use development features a six-story overbuild of the Brown Brothers Harriman Co. building, as well as an adjacent 14-story addition. The 110,000 square foot building will feature 98 apartments, and tenant amenities such as a fitness center, roof deck, catering kitchen and game room.
When approached to do the overbuild of the existing early 1900s building, the challenge was meeting code for lateral loads. Based on what could be viewed at the time, the columns, foundations and soil conditions were robust and tightly spaced (16’ o.c.). It was decided to engage the adjacent 28’ parcel and tie in a horizontal expansion that had sufficient capacity to support the lateral loads for the addition and the existing building. Heavy lateral loads boosted the steel tonnage for the addition to almost 20 psf.
The existing building had built up riveted steel columns. After the tenant left the top floor, it was determined that the existing columns were significantly reduced in size at the top floor. The existing columns were then boxed in with steel plates to create tube columns to support the load. Additionally, due to the stepped existing column sizes, all existing splices were reinforced.
Last but not least, during construction it was determined that the existing columns at the basement perimeter were embedded within the brick foundation wall. The porous material and water soaked soil rotted out 50% of the existing columns. The columns were immediately shored and reinforced one by one and encased in concrete down to the existing foundations.
Detailing of the connections between the existing and new columns was critical. Careful field dimensions limited any offset. The connecting details allowed for additional tolerances in the field taking any eccentric moments into the upper columns and into supporting girders.
The project was extremely challenging and rewarding, resulting in newly found real estate at a highly visible and valuable city corner.View the Gallery Print PDF
Structural Systems Used
Concrete Encased Steel (Existing Building)
Structural Steel with Concrete on Metal Deck (Overbuild)