On top of Boston's Big Dig

The first permanent structure on top of Boston's Big Dig showcases direct to fabrication digital modeling.

A lot of jokes are made at the expense of -- and at the expenses of -- Boston's Big Dig and the efforts to make the former swath of highway an active urban greenway. It hasn't all come together yet, but the potential is easier to see in the summer months when the Rose Fitzgerald Kennedy Greenway is filled with people walking and taking advantage of the public greenspace. Celebrating its one year anniversary, the Greenway's first completed permanent structure is an appropriately innovative, optimistic gateway to the city's waterfront.

Intended to raise awareness of the chain of islands only 20 minutes from the city, the Boston Harbor Islands Pavilion is made of two canopies, two kiosks, and a large scale map imprinted into its pavement. The components may seem simple but the design and construction of the swooping concrete roofs involved a huge collaboration between a team of architects, interactive designers and researchers from IDEO, and engineers from SGH (Simpson Gumpertz & Heger.) The pavilion's sensitive position sitting on what is essentially the roof of the I-93 tunnel required further coordination and approval from various government and bureaucratic agencies including the Federal Highway Administration, the Masachusetts Executive Office of Energy and Environmental Affairs, the always involved Boston Redevelopment Authority, and the U.S. Congress. The resulting pavilion which provides shelter, rainwater control (the spout shaped end of the lower canopy pours rainwater into a basin and irrigation system), information, art, and commerce (visitors can buy tickets at one of the kiosks) is well worth the effort.

On a pleasant August afternoon, Paul Kassabian, the project manager for SGH conducted an on-site discussion of the structural design of the pavilion and the spread of direct to fabrication digital modeling.

Besides the sensitive site, which is only separated from the tunnel roof by four feet of space in some spots, the pavilion design presented lots of challenges. Most difficult were the double-curved concrete roofs, which required the right concrete mix (not so thin that it would run off the formwork, not so thick that it couldn't be worked around and under rebar) and the right formwork.

After several tests and trials with conventional formwork like plywood and foam, the SGH team decided to go with digitally milled wood. The digital fabrication process would ensure that each piece of formwork would be monitored and cut in a controlled environment. Since the shapes were based on a parametric model and then cut by robots, human error is removed. When the formwork was measured against the steel supporting members, the steel's extremely low degree of tolerance was visible next to the exact precision of the wood milled by robots.

Contractors and unions shouldn't be too upset at the digital fabrication revolution, yet. Kassabian pointed out that even with all the advanced technology, each piece of rebar had to be bent and adjusted by human hand.

Simpson Gumpertz & Heger have worked with innovative architecture firms like Steven Holl , Herzog & de Meuron, and Howeler + Yoon on projects large and small. The value of working on art installations and small projects like the Harbor Islands Pavilion, Kassabian points out, is that testing materials and methods at a small scale involves less risk. They help engineers and designers develop better tools and design approaches and figure out if and how they can be applied at a larger scale.

The big takeaway from the talk is that while labor costs in construction are increasing, the quality of work is not. Disruptive technologies like digital fabrication are helping the construction industry become better and faster, even in the middle of bureaucratic nightmares like the most expensive American highway removal project.

Already honored with a 2011 Honor Award for Design Excellence from the Boston Society of Architects and the 2011 Grand Honor Award from the Associated General Contractors of New England, the Harbor Islands Pavilion also won a Silver Award from the 2012 ACEC/MA Engineering Excellence Awards. See more construction photos of the pavilion in the photo gallery .

Related in SmartPlanet: Salvaging Boston's Big Dig scraps

Images: courtesy and copyright SGH

This post was originally published on Smartplanet.com