Collection 14
Project Location
– Washington, DC
Awards
2021 Craftsman Award
Project Type
– Mixed Use/ Multi-Family Residential;
– Parking;
– Retail;
– Office;
– Renovations/ Adaptive Re-use;
– Repair/ Restoration
Services
– New Construction;
– Renovation;
– Construction Administration;
— Specialty Structures;
– Condition Surveys and Reports;
– Feasibility Studies;
– Repair and Restoration
The Project
A new 7-story, 240,000 SF mixed-use multi-family building. The development has 233 apartment units with penthouse amenities, rooftop terraces, green roof and structured bio-retention, ground level retail and office space, and below-grade parking. The structure is comprised of post-tensioned concrete slabs at the elevated levels, reinforced cast-in-place concrete construction below grade with a continuous mat foundation.
The Challenge
To preserve the historic character of the neighborhood, the project aimed to preserve three significant street-facing masonry façades as well as to retain an entire 2-story historic “garage” building in the center of the site. The four existing structures on grade needed to be shored in place and suspended in mid-air while excavating for the below grade parking garage. Further, to achieve the architectural vision, the new structure needed to wrap around and then bridge over the historic garage building. Adding to the complex site challenges, the adjacent WMATA subway tunnels impacted the foundation design.
The Solution
Creative temporary shoring and bracing systems, including micro piles, bracket piles, continuous and segmental concrete underpinning, needle beam shoring and vertical truss bracing, were orchestrated to stabilize and suspend the historic structures during the excavation and construction of the new below-grade parking garage. Special connections permanently attached the historic components to the new superstructure, while large stage-stressed transfer girders allowed the new tower to clear span two stories over the historic garage building.
