Old Town North, Alexandria, VA
Holbert Apple Associates provided the structural engineering design, including construction administration services, for this new 8-story cast-in-place concrete structure that is located just north of Old Town Alexandria, Va.
The project site has a triangular footprint, with the hypotenuse located along Mount Vernon Trail. Two levels of below grade parking and the 1st Floor occupy the majority of the site. The 1st Floor consists of a mild-reinforced concrete two-way slab, with a framed exterior “Arts Walk” terrace that separates the 3-story mixed-use building at the southwest corner of the site from the 8-story residential tower located along the Mount Vernon Trail. Six transfer girders were designed to support columns that were relocated above the 1st Floor in order to accommodate the drive aisle for the below-grade garage levels. The typical floors and Main Roof were designed as two-way post-tensioned concrete slabs. Large green roof terraces were incorporated to accommodate the required façade setbacks at the 5th Floor along 3rd Street and North Royal Street. The Main Roof was designed as a transfer slab to support the top story columns that did not align with columns below as well as to serve as a rooftop terrace with amenity space and various green roof areas. Approximately 20 sloping columns and 14 rotated columns were incorporated throughout the building to meet the architectural program requirements. The building is supported on traditional spread foundations and the lateral system consists of reinforced concrete shear walls at the central elevator shaft and egress stairs.
A structural steel framed pedestrian bridge was designed to span over the “Arts Walk” in order to connect the 2nd Floor of the 3-story mixed-use building to the main 8-story residential tower. Special connections and expansion joints were designed and detailed to allow for differential movement between the two buildings connected by the pedestrian bridge. The façade consists of a mixture of storefront glazing, brick, and a Quest window wall system (integrated windows and metal panels).