Office

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.  

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.

The Watergate EIG Tenant Fit-Out

The Watergate EIG Tenant Fit-Out project involved fitting out levels 11 and 12 of the Watergate office building located at 600 New Hampshire Avenue, NW for EIG Global Energy Partners.  Structurally, SK&A was specifically tasked with creating three new openings in the existing 12th floor post-tensioned slab as well as designing two new inter-connecting stairs.  

The stairs were called the “Patricia” and “Ricardo” internally by the design team, named after the Nixon couple associated with the infamous Watergate scandal.  The Patricia is a single center stringer stair that is wider at the bottom and top than it is in the middle and finished with terrazzo treads.  The Ricardo was the more unique and challenging of the two stairs, using a ½” curved steel plate for the stringer on each side.

Architecturally, the team had very specific aesthetic expressions for each staircase, as can be seen by the specific naming of each, and SK&A met the challenge to ensure that the architectural vision was fully realized.

 

Constitution Square

Located at First and M Streets, NE, in the vibrant NoMa neighborhood, Constitution Square is a 3.1 million-square-foot, multi-phased, urban mixed-use complex featuring multiple office, residential, hotel, and retail buildings. SK&A was selected to provide structural engineering services for the Class “A”office buildings, Three Constitution Square (OB3) and Four Constitution Square (OB4), as well as Residential Building Two (RB2), a 13-story apartment building.  SK&A also provided special inspection services for construction of a 12-story office building (OB3) over a two-level parking garage.  The construction of the building is a conventionally reinforced slab in the substructure and post-tensioned reinforced slabs in the superstructure levels above. 

Special inspection services were also provided for construction of a 13-story residential building (RB2) over a three-level below grade parking garage.  The substructure of the building (mat foundation, foundation walls, slabs, and columns) consists of conventionally reinforced concrete and the superstructure consists of post-tensioned reinforced concrete slabs above grade.

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.

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.

The Watergate Complex Plaza Repairs

The Watergate Complex in Washington, DC includes a hotel, office building, condominiums, and retail.  SK&A’s Repair & Restoration Division provided repairs to the office building’s B-2 level retail plaza area and B-3 level parking garage directly beneath the plaza.  The B-2 level retail plaza area is leased by Penzance and the B-3 level below is owned by Watergate East, Inc. and consists of residential parking, tenant storage rooms, various hallways, and mechanical rooms.

The original waterproofing on the structural slab located below the exterior plaza topping slab is a continuous coal tar fluid-applied waterproofing system, which at the time of the repair was approximately 43 years in age.  Over the years, the original waterproofing has been exposed in isolated areas throughout the plaza, and removed and replaced with either sheet membranes or hot fluid-applied rubberized asphalt systems.

In 2012, SK&A provided construction documents and specifications related to the concrete repairs and waterproofing design for the B-2 level retail plaza and B-3 level garage.  The work was performed from December 2012 to May of 2013 and consisted of the removal and replacement of the exposed aggregate topping slab located throughout the B-2 level plaza within the retail mall area.  Once the topping was removed, the existing waterproofing was removed and replaced and concrete repairs were also performed to the underlying waffle slab.  An existing two to four inch thick decorative concrete topping was replaced in the center of the plaza with a new black, gray, and white alternating colored Miracote coating.  New waterproofing details were provided at drains and along the plaza perimeter in order to provide tie-ins and terminations, as well as to aide in drainage of the plaza.  The repairs involved daily coordination between the contractor and management in order to complete the work and maintain daily access to each individual retail store impacted by the work.  

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