Web Exclusive: The Art of Work
January 29, 2009
New York City’s Museum of Arts and Design (formerly the American Craft Museum) has showcased contemporary objects made from clay, glass, wood, metal, fiber and other media for more than 50 years. When the museum outgrew its 53rd Street location in the early 2000s and began looking for a new home, the board of trustees turned to the New York City Economic Development Corporation (NYCEDC), which recommended a vacant 12-story building at 2 Columbus Circle. Situated between Manhattan’s Midtown, Upper West Side and Lincoln Center cultural corridors, the building was the ideal size and layout and would allow the museum to boast one of the city’s most renowned addresses. But before it could lay claim to the space, the museum’s board of governors would first have to win a difficult battle with preservationists.
Historic BoundariesFrom 1874 to 1960, the Columbus Circle property was home to the seven-story Pabst Grand Circle Hotel where more than 100 stage performers joined together in 1913 to form the Actors Equity Association. The hotel was demolished in 1960, and in 1964, a 12-story modernist building designed by Edward Durell Stone was erected. The building opened as the Gallery of Modern Art and housed the art collections of A&P’s founder Huntington Hartford. In 1969, the building was gifted to Farleigh Dickinson University and was operated as the New York Cultural Center. The building was then purchased in 1975 by Gulf and Western Industries and remained vacant until 1980 when Gulf and Western presented the building to the city as a gift. For the next 18 years, the building was occupied by the Department of Cultural Affairs and the Convention and Visitors Bureau. Then, in 1998, the Landmarks Preservation Commission began holding hearings on designating the building as a landmark. Although the NYCEDC named the Museum of Arts and Design as the site’s developer in 2002, it took the museum nearly three years and several lawsuits to overcome the attempted landmark status and obtain a permit to renovate the building.
During this time, the museum’s board of governors, which was chaired by Jerome A. Chazen, began assembling the design team for the project. Allied Works Architecture was named as the team’s design architect; F.J. Sciame Construction Co. was chosen as the construction manager; Robert Silman & Associates was assigned to structural engineering; R.A. Heintges & Associates was named to manage the curtain wall design; and Langan Engineering joined the team to act as project surveyor and site/geotechnical engineer.
The conceptual design for the building’s exterior was to remove the original curtain wall and construct a new façade in front of the remaining structural wall. Under normal building conditions, achieving this objective would not be a problem. However, this building was originally constructed as a zero-setback condition-a review of historic hand-drawn surveys showed the building to extend to the right-of-way (ROW) lines on all four sides. The team realized that the proposed curtain wall might encroach into the adjoining street ROW. Such an encroachment would require a franchise agreement with the city-a license that would allow the use of the ROW encroachment area for specific fees and under certain terms.
Using original building design plans and select field measurements, the design team back-calculated the location of the structural wall in relationship to the property lines. These calculations were then used in conjunction with the thickness of the proposed curtain wall and bracketing system to provide an estimate of the encroachment condition and minimize the franchise fees that would be required. The team settled on a 4-inch franchise requirement, submitted an application and received approval from the city.
Creative ExplorationDuring the preliminary design phase, Langan prepared a detailed CAD-generated site survey supported with digital terrain models (DTM) and a triangulated irregular network. The survey included boundary, topographic, utility and Builders Pavement Plan (BPP) data. (The BPP, which is unique to New York City, includes detailed curbing, walk, pavement elevations and utility data and is used to assist in the overall grading of the city’s public spaces.)
While working on the site survey, Paul Fisher, PLS, project surveyor and manager of Langan’s Laser Scanning Group, was approached by members of the design team with a request to confirm the building’s façade and plumb status in relationship to the site’s property lines. The team also requested clearance distances on a 2-foot by 2-foot grid across each façade of the building. These distances were intended to be used to design the brackets for the curtain wall. The design team detailed concerns relating to the possible building ROW encroachment and the sequence of the proposed construction and asked Fisher to provide a proposal.
Fisher met with the other survey project managers to determine the best methods and equipment for obtaining the required data. The survey team decided that laser scanning combined with an unconventional use of CAD options would provide the level of detail requested by the design team. However, while Langan had routinely used laser scanning to collect façade/planimetric data and had produced CAD models and paper prints of those data, the firm had never had been asked to provide detailed clearance distances. “Langan had produced similar elevation surveys in the past to check for deformation in building walls and encroachments,” Fisher says, “but those point data were collected on a very large grid using Trimble reflectorless total stations. With the laser scans, Langan would have to address the amount of data produced and how to decimate the data to make it usable in CAD and [useful] to the client.”
To further complicate the project, the building would be wrapped in scaffolding during the field work. “We knew we had a difficult task to complete,” Fisher says.
Scans and ModelsUsing the horizontal and vertical controls that had been established during the site survey, the three-person crew began obtaining multiple scans of the building using a Trimble GS200 3D scanner. The first set of scans captured data with the marble panels still on the building. If the crew was unable to obtain enough data with the scaffolding and netting installed, these data would allow the team to back-calculate to the concrete structure using some general thickness measurements of the marble. However, Fisher notes, “our hope was this data would only be for backup and we would not have to use this data for the final calculations.”
A second set of scans was completed with the scaffolding in place and with the marble panels removed. To observe the building façade, the scan sessions had to be completed not only from grade level but also from various vantage points adjoining the site. “The crew needed to perform multiple scans of the same area to enable the scanner to obtain data on the building face that was obscured by the scaffolding,” says Crew Chief Tim Hydrusko. “We were able to use a fourth-floor office, which had an overlooking window, as well as the roof of a seventh-floor apartment and a 15-story building. The large number of scan sessions required the setting of over 60 building-mounted scan targets, which by far is the the greatest number of targets that we ever had to set.”
After the scan data were collected, technicians began the registration process using Trimble’s RealWorks Survey software. The massive amount of targets made the registration process far more complex than most of the firm’s previous scan projects, and a lot of time was spent registering the clouds together. Once registration was complete, the firm began the tedious process of removing all of the scaffolding from the cloud. “We had to be sure all of the point data we would be using to create our offset plans was real wall data and not scaffolding or other construction components,” Fisher says.
Technicians spent a lot of time working on the model to remove anchor plates and other fixtures used to hang the scaffolding. Chris Tarzia, senior scanning technician, was tasked with this critical portion of the project. “Removing the scaffolding from the point cloud proved to be the toughest part of the project,” Tarzia says. “Every object along the building face had to be removed, from the wooden planks down to the bolts holding the scaffolding into the building. It was the toughest ‘noise-removal’ task from a scan project I have ever completed to date, but in the end the process worked perfectly.”
Once the cloud was reduced to only the concrete structure, technicians decimated the point data to make it usable. After some experimentation, the team reduced the point cloud to a 1/2-foot grid, which made the data “light” enough to work with in a standard CAD program. The point data were then exported as an ASCII file into Trimble Terramodel, a stand-alone CAD/survey/modeling program, which is one of several CAD platforms Langan employs for modeling.
Each elevation was prepared in a separate file that included the franchise line adjacent to the building face and the point data. Each face and franchise line was rotated to either due north or due east. Elevations were assigned to the franchise line to produce a 3D plane that ran parallel with the vertical wall of the building. These data were then exported as an ASCII file and imported into a new CAD file. Changing the coordinate values so that the z value was entered as a northing provided a scaled elevation of the building that served as a DTM surface and allowed a horizontal plane to be created from the franchise line.
The final step was to create an isopach model from the two surfaces using standard surface modeling options within the Trimble Terramodel design and surveying software. A dense grid was then overlaid on the isopach data, and offset values to the franchise line were extracted. The deliverables to the design team were a CAD file in the original dense-grid format as well as paper prints created with a 2-foot grid to make the data legible and to coincide with the curtain wall grid. The curtain wall designer was then able to overlay its bracketing plan onto the wall offset drawing and determine the exact size of the bracket required to place the curtain wall on the franchise line.