670 and 680 Maine, The Wharf Parcels 6 & 7

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

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.   

Chemonics Headquarters, The Yards West Parcel G

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.  

The Boro

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.    

Eight Tower Bridge Roof Replacement

The Eight Tower Bridge office building features an existing ethylene propylene diene terpolymer roof membrane and roof assemblies, which were scheduled to be replaced due to the failure of the existing roof membrane and accessory materials. The desired basis-of-design for the roof replacement consisted of a torch-applied modified bitumen roof membrane over rigid insulation and roof board materials. The roof replacement project also included in installation of façade access tie-back anchors.

SK&A provided engineering and building enclosure consulting services for the office building roof and prepared permittable project specifications, plans, and details for the roof replacement program. The specifications included general conditions, technical requirements for the work, material requirements, roof assembly technical specifications, and bid forms.

Throughout the roof replacement project, SK&A provided construction administration services and quality assurance/quality control inspections to ensure that the work conformed to the project specifications and manufacturer’s requirements. SK&A worked closely with the roof manufacturer to address field inconsistencies as well as third-party electronic leak detection testing.

DCX Office Building, The Wharf Parcel 10

Situated on the waterfront, this five-story office building provides breathtaking views of the Potomac River.  Cantilevering out over 35 feet, Parcel 10 also known as the DCX Office Building, has been compared to a floating jewel box extending to the Potomac River.  Even more striking, the structural profile at the ends of the cantilevered floors is only eight inches thick.

The challenge to the team was simple: create a light, floating five-story office building with 35-foot cantilevers.  SK&A worked closely with the architect early on for studies that would be acceptable to the architectural program.  While numerous concepts with steel and concrete were done, at the end it was determined that a two-way post-tensioned high strength concrete (7,000 psi) slab with drop panels provided both the thin structural profile and long cantilevers, which the architect envisioned.  To achieve a thin profile at the ends of the perimeter, the drop panels were tapered in thickness.  A 5’-0” perimeter of a “no drop panel zone” was created to allow the thin profile at the exterior of the building, while also allowing the glass façade to extend up from floor to floor without the use of spandrel glass.  

555 12th Street, NW, 11th Floor Renovation

The 555 12th Street, NW office building was constructed in the early 1990s and occupies the full city block between 11th and 12th Streets, NW and E and F Streets, NW.  Currently known as “District Center,” the building is constructed of reinforced concrete with post-tensioned floor slabs and features a full-height atrium at its center.  The almost 200,000 square feet of commercial office space in District Center has undergone many renovations to suit new tenants.  The latest renovation at the 11th floor was more involved than most tenant-related projects.  

SK&A was tasked with increasing the floor plate by 2,300 square feet by filling in a portion of a double-height space between the 10th and 12th floor.  In order to limit the structural depth and maximize the possible spans, SK&A proposed a system of Vierendeel trusses spanning between existing building columns.  The trusses featured HSS chord and web members and stand a total of 10’-6 ¾” tall.  There are two trusses (Labeled T2) that span 35’-6” from a building column to the shear wall at an elevator core.  A third truss (Labeled T1) spans the 45’-0” between the other two.  

1600 Market Street Roof and Skylight Replacement

Located prominently in Philadelphia’s Center City, the landmark and historic 1600 Market Street building consists of 39-stories and 105,000 sf of contiguous office space.  SK&A’s Repair and Restoration Division performed a comprehensive property condition assessment of the building including a detailed survey and evaluation of the building’s roof assemblies and skylights.  The survey also included review of the original architectural and structural drawings as well as historical maintenance reports for the building.

Each roof area was then visually inspected in order to evaluate the condition of the two-ply modified bitumen membrane and to observe the condition of the flashings, terminations, and overall quality of the roofing construction.  An evaluation of the existing roof tie-back anchors and Davit bases was also performed.  Destructive roof cuts were made to document the condition of the insulation materials, verify the as-built configuration of the roof assembly, and test select materials for asbestos.  The building roof, which was original to the building, was recommended for complete removal and replacement with a two-ply SBS modified bitumen system and reinforced PMMA liquid flashings.  

APTA Headquarters

SK&A provided structural engineering services for the American Physical Therapy Association’s (APTA) new headquarters building located in Alexandria’s Potomac Yard neighborhood.  The seven-story, 85,000 sf building features and atrium with floating stairwell, meeting space, roof terrace, fitness center, café, and a public plaza.  The building is expected to achieve LEED Silver certification with sustainable design features, which incorporate spaces that save energy and water, generate less waste, and support human health.

The ground floor and below grade parking levels are conventionally reinforced concrete with drop panels supported by concrete columns.  A landscaped public plaza at on the ground floor is located over the garage.  It includes planters up to 4’-6” deep and has been designed to support firetruck loading.  Above grade, the slabs are post-tensioned concrete with 44-foot maximum spans.  The roof terrace at the 7th floor includes planters and paved public gathering spaces.    

800 Maine, The Wharf Parcel 3A

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.