Architects

161 Peachtree Center

Previously constructed as a seven-story cast in place parking garage, the new vertical expansion of 161 Peachtree Center in Atlanta, GA included two new parking levels and 18 floors of residential units.  Originally designed in 2001 for a future 12-story office building, the new developer acquired the current building with the intent of revising the future office tower into a residential building.  The main issue is an existing office structural frame layout was not conducive to a modern residential building.  

Tower only columns were introduced to reduce the span and minimize the slab thickness to eight inches max.  This allowed for shorter floor to floor heights and reduced the weight and height of the structure.  Since tower only columns could not extend below to foundations due to the existing parking garage drive aisle and parking layout, large 8’-0” deep bonded post-tensioned transfer girders were introduced at the interstitial 14th floor.  Similarly to the tower only columns, the tower only shear walls could not extend below into the existing parking garage.  The shear walls had to stop at the 14th floor transfer level, which created a vertical irregularity within the lateral system.  Nine-foot-tall bonded post-tensioned transfer girders were used to transfer the shear wall gravity and lateral loads to the surrounding columns and diaphragm.  

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. 

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.  

Ingleside at Rock Creek

SK&A provided structural engineering services for the addition of new buildings and the renovation of an existing facility at the 14-acre Ingleside Retirement Community Campus in Washington, DC.  Located adjacent to Rock Creek Park at 3050 Military Road, NW, the non-profit retirement community’s current site was originally established in 1960.  The new changes to the site consist of:  

  • A new independent living facility (120,000 sf) with 90 units, a new assisted living facility (50,000 sf) with 15 residences, and structured parking (60,000 gsf).  The two residential buildings will connect to each other as well as existing buildings at the site.
  • A new skilled nursing and memory support facility (100,000 gsf), plus structured parking below (44,000 gsf).
  • A new independent living commons, renovation of the existing commons, as well as overall sitework (15,000 gsf).  The new commons or “Center for Healthy Living” will contain multiple amenity spaces, including a salon/day spa, classrooms and art studios, cafe, yoga and aerobics studio, technology center, meditation room, and fitness center.  

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.

The Silva, 1630 Columbia Road, NW

SK&A provided structural engineering services for the Silva, a new 10-story, residential building in the Adams Morgan neighborhood of northwest DC.  The building features 172 luxury apartment units and amenities such as a rooftop pool, café/lounge, courtyard with fire pits, fitness center, and pet spa.  Below grade are two levels for parking along with bike storage and electric vehicle charging stations.  The building also provides an internal connection to the existing Scottish Rite Temple building. 

The Silva is a multi-story concrete frame structure.  The slabs are post-tensioned at upper levels and conventionally reinforced slabs at ground and underground floors.  Lateral resisting system consists of concrete shear walls in combination with moment frames.

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.    

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