SAISC projects an open layout for future retail flexibility, and floor vibrations for occupant comfort were taken into consideration in the design of the structure. In accordance with AISC Design Guide 11: Vibrations of Steel- Framed Structural Systems Due to Human Activity, these vibrations were limited to a maximum of 1.5 % gravity acceleration at 2 % damping.( You can read more about the new edition of Design Guide 11 in“ Living( Comfortably) with Vibration” on page 58.)
The primary W14 × 193 and W14 × 283 moment frame columns are set back 14 ft from the east façade, and round 10-in. hollow structural sections( HSS) were used along the east façade to minimize their visual impact. The floor framing consists of typical W18 × 35 beams spanning to 30-in. and 36-in. girders, and floor slabs are 3.5-in. lightweight concrete on 3-in. metal deck. The structure is designed to support a 60-ft billboard above the roof as well as a full-span LED display anchored to the north façade, a nod to the Times Square lighting requirements.
Planted plaza
Another design challenge was accommodating the change in grade at the perimeter of the site. The elevation of the northern section of the renovated plaza is 3 ft higher than the ground floor elevation of the Cubes. Structural engineer GMS designed a series of“ bent” transfer girders to maximize the retail ceiling heights below. The plaza renovation also demanded careful attention to the design and installation of tree pits so as not to encroach on floor-toceiling heights below. The bottom of the 9-in. pit slab is flush with the bottom flange of neighboring W36 and supported by L3 angles welded to either side of HSS9 × 5 × ½, which spans in between existing W36 beams at 3 ft, 6-in. on center. This provided adequate support for the weight of the soil and trees, which required a design load of 600 psf.
Approximately 30 ft of the southern portion of the prior plaza was demolished and rebuilt at a lower elevation to match the level of the sidewalk at 41st Street. This generated a more inviting space, similar to the pedestrian approach from the north. Planters, stairs and ramps separate the lower southern portions and raised northern portions of the plaza.
Augmented atrium Across the plaza from the Cubes, the existing 1095 Avenue of the Americas is a 40-story steel-framed office building, constructed in 1972, with four moment frames in the north-south direction. The westernmost frame( plaza-side façade) needed to be modified to accommodate the relocation and vertical enlargement of the building’ s main lobby into a 33-ft-high, two-story atrium. The second floor slab was removed at four north-south bays( 25
BELOW( clockwise): Westward view of plaza. Setbacks. Northwest view of plaza. The mechanical penthouse.
MdeAS Architects MdeAS Architects
MdeAS Architects
MdeAS Architects
Steel Construction Vol. 40 No. 6 2016 17