American Physical Society, Ridge, N.Y.

Owner: American Physical Society, Ridge, N.Y.

Owner’s Rep: LePatner & Associates, New York

Architect: Marvel Architects, New York

*Structural Engineer: Gilsanz Murray Steficek, New York

General Contractor: T.G. Nickel & Associates, Ronkonkoma, N.Y.

Fabricator: STS Steel, Schenectady, N.Y. (AISC member / AISC certified fabricator)

Detailer: STS Steel, Schenectady, N.Y. (AISC member / AISC certified fabricator)

*Firm that entered the project in the IDEAS² contest

In late 2014, the American Physical Society (APS) renovated its existing 30,000-sfeditorial headquarters and added an additional 18,500 square feet above it. This facility employs 150 people and is located in Ridge, NY. APS is a non-profit scientific organization founded in 1899 to “advance and diffuse the knowledge of physics.”  The Long Island Pine Barrens Preservation Act prohibited expanding the building’s footprint hence the addition had to occur above the existing structure. To meet the project’s $6 million construction budget the operation of the facility could not be interrupted while the work was performed, eliminating the leasing of temporary space and the employee relocation. The entire construction, including columns, floor and roof framing, was achieved with the building occupied and in operation. The structural engineering involvement started in 2009 during dismal economic times. To minimize cost the steel was purchased and fabricated in advance and stored off-site in a controlled environment before it was required for erection. This strategy proved to be cost-effective even after including the storage cost.

The existing structure – footings, columns, roof framing and lateral system – did not have the capacity to support the second story additional loads above. The design allowed the new steel to be installed without disrupting the building’s ongoing use. The long-span design with a column grid up to 38’ x 62’ results in spacious, column-free, and architecturally flexible interiors with minimal penetrations through the existing ground floor.

The majority of the perimeter columns were located outside the walls of the existing building, forming an exoskeleton, and in its existing courtyard. The W12 columns of the new frame are situated 5 feet to 9 feet outside the perimeter of the existing structure eliminating any interference with the existing foundation and allowed most of the foundation work to be done outside the building. Only six columns penetrate the interior of the old building. These columns and footings were installed one at a time with limited impact to the occupied building.

The new second floor is elevated 4 feet over the existing roof, providing a 4-ft interstitial space that serves both the existing building below and new structure above. The mechanical services could be then distributed efficiently from the rooftop equipment on top of the single-story building. The existing roof served as the working platform or the erection of the second-floor framing.

The thermal analysis of the exoskeleton accounts for the differential expansion and contraction created by the temperature differences between the interior and the exterior of the building. All members that penetrate the building envelope are insulated for the first 8 feet as they enter the building. A series of skewed W8x24 members brace the exterior beam-column connections not only to resist lateral loads, but also to dissipate the increased stresses caused by the temperature differentials.

The long-span design took into account the deflection, vibration and construction of the steel members. The 57-ft-long W24 filler beams span N-S between W30 and W36 E-W girders which in turn, frame into columns at the interior. At the north side, the girders are offset from the columns, serve as spandrels beams and are located within the building envelope. These spandrels frame into 62-ft-long W30 beams at the N-S column line that extend through the envelope and connect to the exoskeleton columns.

The building’s lateral system consists of eight braced frames, which utilize diagonal HSS8x8 braces that frame at three locations around the perimeter of the exoskeleton, two locations within the existing single-story section of the structure and three visually exposed locations at the new double-height interior atrium. The existing one story building was laterally upgraded by tying it to the new two-story structure so that the building behaves as one.

Floor slabs consist of 2½-in. normal-weight concrete on 3-in. metal deck. To moderate deflection that occurs in long-span frames, the concrete was placed from the center of the diaphragm outward. The design called for slip joints at the top of all interior partition walls so that deflection under snow loads or other live loads would not impose load and cause interior partitions to buckle.