Mixed-Use

SK&A provided structural engineering services for this 11-story, 325-unit, multifamily residential apartment building. Located on a former part of the Navy Yard, the project included approximately 20,000 sf of retail space as well as two courtyards, a rooftop pool, and a small green roof.  The building sits atop a three-level, 110,000 sf below-grade structured parking garage for 250 cars and has a landscaped plaza on the garage roof slab at grade level.

At the northern end of the building, two existing sewer lines cross the site. Located just below the B1 level, the first of the two sewer lines is a 6-foot diameter, 100-year old masonry sewer that crosses the entirety of the east-west footprint.  The sewer had to remain active during construction and the ability to access this line in the future was mandated by the utility. Drilled shaft foundations were used to support the building on either side of the line, circumventing the sewer and maintaining the required clear distances.  A structured slab-on-grade was used above the line, spanning to the adjacent drilled shafts while imposing no additional loads on the sewer from occupancy use.  Additionally, this slab was designed to allow for a 10-foot section to be removed for future maintenance of the line while the larger area of slab continued to provide support for the primary building structure.

The CSX East development located in the Capitol Riverfront neighborhood of Southeast, Washington DC, consists of two residential buildings (Illume) and one hotel building (AC Hotel Capitol Hill).  The development includes pedestrian bridges that connect all three buildings, with the most striking bridge connecting the AC Hotel Capitol Hill’s 11th floor to the existing ORE 82 Eye apartment building.  Standing over 100 ft. above the ground level, the bridge facilitates guests’ access to the amenities offered by the two buildings, without imposing any additional loads on the existing building.

The biggest challenge in the development of the design of the bridge was to ensure no additional loads were imposed on the existing ORE 82 Eye apartment building.  To achieve that, the bridge had to cantilever ~20 ft. off the new building, and safely transfer the loads to it.  Eight attachment points were located on the structure where the bridge’s structural framing can attach to.  The bridge and its roof, made of wide flange beams and tube column sections, connect to the 11th and 12th (roof) levels, respectively.  Under the bridge, a set of steel tube braces are provided to transfer loads to the 10th and 9th floors to reduce the true cantilever.  

Situated along Washington DC’s Southwest Waterfront, the Wharf Parcels 6&7 also known as 670 Maine and 680 Maine, consist of two 11-story, Class “A” office buildings (480,000 sf), which are part of the phase two development at the Wharf DC.  The office buildings consist of concrete framing with a post-tensioned concrete slab over a two-level underground garage extending under multiple towers.  

The hybrid foundation system is comprised of multiple foundation solutions, spanning over the Washington Metropolitan Area Transit Authority’s (WMATA) green line metro tunnel.  The transfer mat over the tunnel with rigid anchor and drilled displacement piles create an innovative solution to control the settlement.  Also, vibration isolation was included to eliminate any vibration and noise for the tenants. 

To create a maximum unobstructed interior space within the buildings, columns were spaced up to 42 feet and 15 feet cantilevered slabs all around the perimeter of floor plates guaranteed open and continuous views through the sophisticated curtainwall and glazing system.  An innovative shallow 81 feet concrete post-tensioned bridge connecting the two buildings with an oculus in the middle created a dramatic view while the interior open space with the bridge was used as the continuation of the office space.  

Press House Warehouse is a new mixed-use complex located in Northeast, Washington, DC and surrounded by several urban amenity-rich neighborhoods such as Union Market, NOMA, and Shaw.  The 462,511 sf building features the historic retrofit and renovation of the existing building at 301 N Street, NE, a warehouse designed in 1931 for the National Capital Press.  The historic press building is a three-story building consisting of two levels of conventionally reinforced, two-way concrete slabs, with the roof comprising of a series of steel monitor trusses spanning between girders supported on built-up steel columns.  

The repurposed building is also used for office and ground level retail, while rental units were added between two new high-rise structures over two levels of below-grade parking.  Hickok Cole Architects currently occupy office space at the 2nd and 3rd floors of the newly renovated historic building.  SK&A served as the engineer of record for their office fit-out, which included cutting an additional large opening for an interconnecting stair.   

The new Chemonics International headquarters is housed in an 11-story, Class “A” office building at The Yards mixed-use development.  Located at the corner of New Jersey Avenue and N Street, SE, the building includes 315,000 sf of office space and ground floor retail, amenities and lobbies, plus two levels of below-grade parking totaling 78,000 sf (167 parking spaces).  The Chemonics tenant space includes a monumental stair between levels one and two and the build-up plinth below the stair consists of metal stud support walls and a plywood subfloor.  

The building massing consists of two overlapping curved bars placed over a “full-site” base with retail and amenity spaces.  The façade’s curvilinear design allows for unobstructed views down New Jersey Avenue and N Street.  The building also features several roof terraces, located on levels three, ten and the main roof/penthouse level.  

Situated on “The Hill,” Fairfax County’s highest elevation, and in walking distance to the Greensboro Metro station on the Silver Line of the Washington area’s subway system, The Boro is a new, mixed-use, transit-oriented, urban-style community within Tysons, VA.  Totaling 4.25 million square feet on 18.1 acres, the development integrates a mix of residential, office, retail, and entertainment buildings along with 4.23 acres of community green spaces.   

SK&A provided structural engineering services for a two-level upscale, luxury movie theater, and a new 20-story class “A” office tower.  The Showplace Icon theater (94,800 sf) includes 14 state-of-the-art screens and upscale dining options.  The Boro Tower (345,000 sf) includes ground level retail (8,260 sf) and five levels of below grade parking for 1,200 spaces.  The building also features a glass curtain wall and up to 10-foot ceiling heights.    

Situated on the edge of the Potomac River, the Wharf Parcel 8 also known as the Tides Apartments and Pendry Hotel, pushed the boundary of sloped buildings.  With 13 stories of hotel on the west side and 13 stories of residential units on the east side, the U-shaped building creates unobstructed views of the Potomac River for both functions.  This was imperative to the architectural design of the building. 

Located directly over the underground METRO green line tunnels, the new foundations needed to adhere to the strict requirements of the Washington Metropolitan Area Transit Authority for building overtop of an existing operational tunnel.  A hybrid system of a mat foundation and spread footings were used to help reduce the surcharge on the tunnel below as well as create an economically efficient design for the foundations.  Noise and vibration from the tunnel below were also a concern.  An isolation pad under the mat foundation, spread footings, and columns were used to mitigate any noise and vibration from the tunnel below that would propagate through the first several floors of the building. 

Situated directly across from the new Washington Nationals Stadium, West Half Street is a 13-story residential building featuring a modern, high-end, canti-levered design with gradually alternating and descending outdoor terraces.  The building includes 465 apartments in studio, one- and two-bedroom layouts, 61,000 sf of retail on two floors, and multiple amenities such as a rooftop pool, penthouse lounge areas/clubrooms, and a central courtyard.  The aboveground structure sits atop a three-story underground garage with 329 parking spaces.  

The building was designed to be the crown jewel of the surrounding development area providing residents with unobstructed views of the baseball stadium and surrounding Navy Yard waterfront neighborhood.  SK&A worked with the architect to design a building that continuously rotated and twisted which allowed for these views.  To support the large cantilevers from the building face, Y-branch columns with tie-beams were utilized.  Strategically placed concrete shear walls resist the building’s natural tendency to twist and rotate under its own self-weight.  The Y-branch columns were also designed to support the ends of the ever-increasing cantilevers.

The completed design culminated into a graceful, functional, and exceptional residential structure that adds to the diverse architectural fabric of the Navy Yard waterfront neighborhood.  The building’s new residents will enjoy prime views of game-day action with personalized experiences of the surrounding ballpark atmosphere.   

Part of a 3.3 million sf mixed-use development situated along Washington DC’s Southwest Waterfront, The Wharf Parcel 3A also known as 800 Maine, is an 11-story, 233,000 sf Class “A” office building.  The office building is constructed atop a shared two-level underground garage occupying the entire project site.  The superstructure and underground garage are concrete-frame with conventionally reinforced floor slabs, reinforced concrete columns (typically 30-ft. apart), concrete shear walls, and select post-tensioned concrete components.

The building is also located in a section of the site where WMATA’s Yellow Line metro tunnel and air intake shaft conflict with the western side of the building’s columns and foundations.  To bridge over the existing WMATA structures, a solution was executed using underground concrete transfer girders over the tunnel and a two-story elevated steel truss between levels 2 to 4, which spans 90 feet. 

The SK&A team’s structural ingenuity and close collaboration with the owner, architect, and design builder ultimately delivered a visually appealing and structurally sound building, with WMATA’s structures intact and operational during construction.

Located in Hanover, MD on the Baltimore-Washington Corridor, the Arundel Town Center is a component of the Arundel Preserve, a 268 acre, smart-growth mixed-use community within the larger 1,100 acre Arundel Mills development. Developed in multiple phases, the project includes a hotel, residential and retail structures.

The hotel phase of this project involved the construction of a seven-story above-grade, 150-room hotel building that included retail space at the ground floor level.  The building’s substructure and superstructure consist of cast-in-place concrete footings and walls with conventionally reinforced slabs and post-tensioned slabs in the tower.

The residential phase of the project involved the construction of a multi-family residential structure consisting of five to six levels, as well as three stories of retail space with an attached five level parking garage. The project also includes a clubhouse with a swimming pool in the courtyard.  The building’s substructure and superstructure consist of cast-in-place concrete footings and walls with Hambro system floor joist slabs and the precast concrete parking structure.

The parking garage phase of this project involved the construction of a seven-level above-grade cast-in-place concrete parking structure, consisting of footings, columns and walls with post-tensioned reinforced slabs.

SK&A provided structrual design services as well as testing and inspection services including concrete, masonry, and structural steel construction, EIFS observations, field testing, and visual weld inspections.