56 Leonard Street

56 Leonard is an iconic landmark located in the Tribeca area of New York. This residential building consists of 145 luxury condominiums. It is an 821 feet tall, 57-story skyscraper often described as ‘houses stacked in the sky’. It is the tallest structure in Tribeca in Manhattan, New York City.

56 Leonard Street Project Overview:

Each floor in this building is designed to give the impression of being a singular, virtually independent structure. As every floor in this tower designed differently, and rotated from the floors above and below, the design made it a challenging detailing project. Its scheme of stacked and shifting volumes meant that no two consecutive floors are the same. Because the columns don’t align from level to level, the building was designed with concept of ‘walking columns’. The building has complex one- or two-story structural walls that transfer loads between floors.

56 Leonard Street Highlights & Challenges:

• The complexity to this project posed several challenges given that the layout and sizes of the various structural concrete components were not typical and varied within each floor and from floor to floor. Due to this the detailers had to detail each element separately on every floor. 
  

Slabs:

• Due to numerous slab depressions, elevation changes, and slab steps, each layer of rebar (top, bottom and additional) in both directions had to be detailed on separate sheets. Additionally, there were several openings on each floor which made the detailing task challenging, to which our knowledgeable team was able to handle skillfully.
• The DBM Vircon team worked closely with the engineer and architect to detail the floor as close to a regular mat slab as possible while meeting design requirements and not exceeding the stock material lengths available.

Columns:

• The use of Transitional Columns in many locations required these columns to be detailed with a high level of accuracy and to be presented very clearly.
• The columns needed special attention due to their constantly changing shapes and locations. Many were ‘walking columns’, which shifted locations at each floor but still needed some continuity of the rebar.

Beams:

• Due to complex design at the column and beam intersections, the reinforcing arrangements varied by each location.
• There were many openings in the beams to allow for other trades, which was a major challenge for the rebar detailer.
• Each beam was detailed clearly on a separate sheet giving in-depth information about all bars and ties. Details were provided in sections, elevation, and plan views to provide clear instructions for the ironworkers.  The informative representations on the detailed drawings were very helpful for the placement of the rebar on the jobsite, which was appreciated by the customer.

Miscellaneous:

• Per the customer’s request, DBM Vircon’s detailers quickly adapted to follow the ‘Intelligent Bar Marking’ system. This method is used extensively in the New York construction market, and requires bar marks to have a description within the name.
• In order to avoid confusion for placing the variety of rebar lengths and sizes on the jobsite; special legends & icons were used to differentiate the reinforcing in different areas.
• Bar supports and accessories were detailed on separate sheets for ease of placement of rebar on the jobsite.
• The shear wall reinforcing was detailed in such a way as to permit cages of reinforcing steel to be pre-built and then hoisted into place, thus providing the contractor with tremendous time savings.
• Multiple revisions had to be made to the drawings as a result of design changes and construction convenience, as the complexity of construction was often not realized until the work was underway. Despite numerous contract design and field changes, the DBM Vircon team was able to stay ahead of the construction process by dedicating adequate and knowledgeable resources that worked throughout the approval and revision phases of this project. All revision work was properly tracked and support documentation was provided to our customers in a timely manner.
• DBM Vircon utilized aSa CAD Detailing software to detail all the reinforcement on this project. The use of several advanced features of this software allowed for expedited rebar detailing, along with creating bar bending schedules, and lists for standard and special bar shapes. The program also facilitated the creation of bar lists showing bar quantities and lengths and complete details for the shop fabrication.

Project Awards:

This project received the following awards:

• 2017 Engineering Excellence National Recognition Award by ACEC
• 2017 Best Projects Winner in the Residential/Hospitality Category by ENR New York