Sustainable/LEED

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 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.  

The Wharf Parcel 8

Situated on the edge of the Potomac River, the Wharf Parcel 8 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. 

Benjamin Banneker High School

SK&A provided structural engineering services for a new 200,000 sf, four-story, innovative high school facility that aims to inspire academic and civic excellence within the student body of 800 students.  A new learning commons area is centrally positioned within the facility’s four-story atrium and will host interactive and collaborative activities.  The new school is constructed on the Shaw Elementary School site, which was demolished and replaced by the new structure.  The site also incorporates public recreational facilities, including a skate park, dog park, and basketball courts.

The project features indoor and outdoor classroom spaces, rooftop terraces, an outdoor plaza, a new outdoor athletic field, and a new gymnasium, which cantilevers over the floor below.  Long span roof trusses cross the length of the two-story gymnasium’s perimeter.  The columns and braced frames offset vertically from the perimeter frame through to the recessed cafeteria floor below.  The building is aiming for LEED BD+C Schools - Gold certification with a goal to be Net Zero Energy ready.

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.

Midtown Center/Fannie Mae HQ

SK&A provided structural engineering services for a new headquarters building for the Federal National Mortgage Association (FNMA), commonly known as Fannie Mae.  The new 875,000 sf Midtown Center office complex is comprised of two 14-story towers, East and West.  The structure features 45,000 sf of retail space, multiple three-story atria, three levels of below-grade parking, as well as a fitness center, rooftop terrace, and private alley.  The project also includes a 15,000 sf public courtyard surrounded by the buildings on three sides and is activated by ground floor retail.

A unique and distinct design feature within the complex are its three interconnecting “tunnel” bridges which span more than 110 feet across the site’s courtyard, connecting the east and west towers at levels 9 through 14.  The bridges feature interior walkways (inside of the bridges) and exterior walkways (on top of the bridges, open to the air).  The bridges were typically designed as “king-post” trusses utilizing heavy W36 section for top chord, eight-inch square tube steel section for bottom chord, and two (2) three-inch diameter high-strength tension rods by “Macalloy” as diagonal members connecting to an eight-inch square tube section vertical steel post, at the center of the bridge.

The three-story, below-grade parking deck uses conventionally reinforced concrete flat slab construction.  The courtyard slab and private alley above the top garage level is designed for landscape and fire truck loads.  The office level structural framing consists of eight-inch, post-tensioned concrete slab with eight-inch-thick drop panels over columns.  This efficient framing system allowed sufficient plenum space for the installation of MEP systems within the ceiling as well as the curtainwall anchors.  The project will pursue LEED Gold certification.  

View photos from a 2017 Site Visit.

Ron Brown College Preparatory High School

SK&A provided structural engineering services for the renovation of an existing school building into a modernized facility for a new all-male high school, particularly for young men of color.  Originally constructed in 1966, the building was shuttered due to decreased enrollment in 2013.  The project is located in northeast DC on a site adjacent to a community center/library.  The project was implemented over two phases. 

Phase 1 included the modernization of the building’s main entrance, which is centrally located and connects the structure via two wings—an academic wing and a multi-purpose wing.  Additional modifications included: a new main office and administrative suite; a new, expanded library/media center; a cafeteria/multi-purpose room, music room, lab spaces and classrooms.  Phase 2 of the project entailed renovations on the second and third floors, including the gymnasium and auditorium. 

Structural work included introduction of new rooftop mechanical equipment and screen enclosures, new entrance vestibules and lobby, removal of a portion of the second floor to create the two-story media center, and extensive crawl space repairs to address significant deterioration.

Murch Elementary School

SK&A provided structural engineering services for the modernization and expansion of the historic two-story Murch Elementary School building, originally built in 1929.  The renovated building and new addition is approximately 100,000 sf and serves a student body of 700 students.

The school’s renovations include updated classrooms, “pull-out” instruction spaces, a full-size gymnasium with stage, media center with “maker space,” laptop laboratory and small group instruction spaces, an administrative/welcome center, an art and kiln room, cafeteria, and a parking garage.  The building is expected to achieve LEED for Schools Gold certification.  

The project’s superstructure primarily consists of structural steel framing in combination with a limited area of cast-in-place concrete construction. Structural steel framing within the project includes composite steel, open web joists, and long-span roof construction.  The project’s concrete construction is limited to the floor framing above the garage and plaza.  The existing buildings were analyzed to support new mechanical equipment and provide large openings in the existing bearing walls at the connection between the old and new building.
 

Bancroft Elementary School Modernization

The old Bancroft campus consisted of five adjoining buildings totaling 94,000 sf.  Originally constructed in 1923, numerous modifications were made to the base structure: three buildings were added in 1932, 1961 and 1973, along with an addition constructed in 1938.  Due to the site’s topography, the buildings adjoined at various misaligned levels.  

Integrating ideas from a completed feasibility study (which SK&A also contributed to), the modernization of the campus included the demolition of two of the existing buildings as well as the previous expansion.  A new unifying building addition was constructed, knitting together the remaining historic structures with the new facility and providing a simplified circulation pattern within the reconnected campus.  

The completed project features multiple courtyards; a new multi-purpose “Curiosity Center” media area; and new outdoor playing fields.  The project’s superstructure primarily consists of structural steel framing in combination with a limited area of cast-in-place concrete construction.  Structural steel framing includes composite steel, open web joists and long-span roof construction.  Concrete construction is limited to the floor framing above the garage and plaza.

The existing buildings to remain were analyzed to support new mechanical equipment and provide large openings in the existing bearing walls at the connection between the old and new building. The modernized school will serve over 550 students and is LEED for Schools Gold certified.  
 

DC Water Headquarters

SK&A provided structural engineering services for the design of DC Water’s new headquarters. The stylistic, modern facility is located on 2.75 acres, adjacent to the waterfront mixed-use development, The Yards, and the Washington National’s baseball stadium.  

The new building is a six-story, 150,000 gsf steel-frame structure with a fluid form. The building footprint was carefully shaped to develop a unique, site-specific solar response and consists of full-height curtainwall on the south, east, and west sides to take advantage of the scenic views, and gradually shifts to punched windows on the less scenic north side of the building.  The structure consists of a framed concrete slab-at-grade with six levels (five office levels and an accessible roof terrace) of composite steel construction.

The exterior facades feature a glass and aluminum curtain wall system on the south facade, and a “variegated green rainscreen panel system” on the north and west facades.  The building was constructed around and above the existing “O” Street Pumping Station, which maintained full operations throughout construction.  Foundations for the structure consists of below grade transfer elements and deep foundations.  As part of the landscape design, an exterior boardwalk and metal grating structure was implemented over existing tidal gates.

New mechanical equipment support and an enclosure were added on top of the existing pump station building.  New openings in the exterior walls at the ground floor  of the pump station facility provide a visual connection to the pump room from the new lobby.

Additional project features include an entry court, interactive exhibit space, and a boardwalk along the south facade.  The mechanical systems uses the pump station wastewater for heat recovery and rainwater from the rooftop will be collected in a cistern to use for toilet flushing.

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