Posts tagged with "Glulam":
Climate-change denial appears to be on the verge of becoming official U.S. policy. But all hope for reducing our carbon footprint is not lost. Case in point is the pending Timber Innovation Act, one of the rare eco-friendly pieces of legislation that enjoys bipartisan support. The bill (H.R. 1380, S. 538) seeks to establish a market for so-called mass timber buildings more than 85 feet tall that are built from panelized wood construction products such as cross-laminated timber (CLT) and glued-laminated timber (glulam).
“Building with wood benefits both rural economies and the environment,” U.S. Senator Debbie Stabenow (D-Michigan) said when she announced the legislation in early March. “This bill will help expand markets for wood products coming out of forests in Michigan and all across the country. At the same time, using wood for construction reduces pollution and incentivizes private landowners to keep their land forested, rather than selling it to developers.”
Architects who study the new wood construction materials say mass timber has economic, ecological, seismic, and aesthetic advantages over steel and concrete. “Photosynthesis, the process of growing a tree, absorbs C02,” explained New Haven architect Alan Organschi, adding, “Until it burns or decomposes, that carbon will stay in the wood like a bank investment.”
The concrete and steel industries are adamantly opposed to the Timber Innovation Act. More than 160 stakeholders from the construction, labor, and building materials sectors jointly signed a letter to the U.S. Senate opposing a version of the bill introduced last year. The letter questioned the fire and structural safety of mass timber and stated the bill would create an “imbalance in the marketplace by allowing the federal government to choose winners and losers.”
However, the bill’s supporters say the new wood technology promises to significantly reduce carbon loads in the building industry, which is currently responsible for close to half of the U.S.’s greenhouse gas emissions. A typical mid-rise concrete and steel building, because it relies on pollution-generating resource-extraction industries, is responsible for emitting 3,210 tons of CO2 in its construction and lifetime, according to Timber City, an initiative undertaken by Organschi’s firm, Gray Organschi Architecture, that is supported by the Hines Research Fund for Advanced Sustainability at Yale University. In contrast, because trees are a renewable resource that sequesters CO2, a typical mass timber mid-rise building built from wood harvested from sustainably managed forest is responsible for capturing 4,720 tons of CO2.
Innovations in mass timber technology also resolve fireproofing and seismic issues that, until recently, were a major disincentive to using wood in large urban buildings, according to Yugon Kim, founding partner of the architecture firm IKD, who curated the exhibit Timber City at the National Building Museum in Washington last fall. “U.S. cities in the 1800s used to be made of wood, but then because of urban fires that started to change,” he said. “Now, because of products like CLT, we will be able to use wood in the centers of our cities the way we did in the past.”
Tall wood building construction is most advanced in Europe, especially in Austria, which boasts the world’s largest mass timber industry. An example of a commercially viable mass timber development that garnered worldwide attention is the nine-story Murray Grove designed by Waugh Thistleton Architects, which was built in London in 2009. It consists of wood load-bearing walls, wood elevator cores, and wood floor slabs. In addition to paying off for the environment, Murray Grove took only 49 weeks to build, whereas an equivalent-size concrete structure would typically have taken 72 weeks to build.
The mass timber industry is still in its infancy in the U.S. There are only several wood companies that make mass timber products, and local building codes generally disallow tall wood structures. The Timber Innovation Act seeks to change that situation by funding competitive research on mass timber technology at institutions of higher learning and by making funds available for a tall wood building competition and a wood innovation program for retrofitting sawmills in areas where there is high unemployment.
The pending legislation expands upon a federal program that established an earlier U.S. Tall Wood Building Prize Competition, which in 2015 awarded $3 million to support the construction of two such structures. One was Framework, a 12-story mixed-use building in Portland, Oregon, designed by LEVER Architecture, which is due to break ground this summer. The other was 475 West 18th Street, designed by SHoP Architects, an upscale residential building project near the High Line that was shelved in early March, reportedly in response to a market downturn for high-end properties.
Getting government sponsored research funding was critical to defraying added expenses associated with the extensive testing and research necessary to secure local building department approvals for building wood structures more than six stories, according to Thomas Robinson, founding principal of LEVER Architecture. “Whenever you are doing something for the first time it is more complicated,” he said, noting that a critical aspect of his project was demonstrating that exposed CLT and glulam can achieve a two-hour fire-resistant rating.
Given the increasing environmental concerns over the widespread use of steel and concrete, mass timber promises to be a more palatable alternative. “What the Timber Innovation Act does is make this an even playing field,” Organschi said. “We have these vast forest reserves which are not being utilized.… By using mass configurations of timber, we will get more carbon sequestration.”
An abstracted version of a street tree, a canopy of tessellated irregular polygons balances atop slim steel posts.When Public: Architecture + Communication visited the site of the transit shelters the University of British Columbia had asked them to design, they found that something was missing. The main point of entry to the campus, University Boulevard is lined with trees—except where the bus shelters would go. “There was this language of gaps that we noticed,” said Public’s Christopher Sklar. The shelters themselves, they decided, should fill in the tree line. The designers were left with a question, articulated by Sklar: “How does it be a quiet piece but also something interesting and unusual that relates to its surroundings?” Beginning with the image of a tree’s branch structure, Public placed a wood canopy defined by a repeating pattern atop slim steel posts. As for the pattern itself, the designers considered a range of options, from Moorish patterns to simple geometric shapes. The trouble with a geometric pattern, said Sklar, is that it is “often a static thing. We looked at triangles; they’re just triangles. Add a side, it’s just a square.” But if you add one more side, you have a pentagon. And that is where things get interesting. The tessellation of irregular pentagons is surprisingly complicated, on both a mathematical and an aesthetic level. “The thing that we liked about the repeating pentagon is that it creates something that is repetitive, but it’s also something that’s fluid and dynamic,” said Sklar. “It doesn’t feel like it’s repeating when you’re actually in it. It’s kind of a flowing structure above you.” Public alternated between Rhino and Grasshopper, finding that it was easier to perfect a line drawing and plug it into Grasshopper than to allow Grasshopper to generate the tessellation. “I think it’s one of these things where it’s a new technology, people want to see what it can do, think it can help you generate forms,” said Sklar. “But it’s taking away the last thing we have left to us. We’re designers, we want to shape the thing.” The team built a full-scale model of two of the canopy’s cells to get a sense of their size, hoisting the cardboard shapes onto the ceiling pipes in their Vancouver studio. Structurlam fabricated the Glulam canopy on a Hundegger CNC machine. The steel supports were manually welded at Bosmon Steelworks. The shelter’s concrete benches were also fabricated by hand, at Szolyd. This was a surprise for Sklar, who had delivered a Rhino model of the bench design to the fabricators. But Szolyd said the design, which incorporates a series of fine edges as built-in skate-stops, would require as much work to prep the CNC machine as it would to build a mold manually—so they hired a carpenter to do just that. “Sometimes you do to all this work to make a digital model, and they’re like, ‘no, we’re just going to build it by hand,’” said Sklar. The shelters were assembled by Dan Georzen at Dancin Timber Works. Besides the wood canopy itself, the most dynamic component of the transit shelter is its surround, built of bronze-tinted glass from Columbia Glazing Systems. The tint serves three purposes. First, it cuts down on UV exposure. Second, it will give the canopy a warm cast even as the wood weathers. Finally, it creates a subtle reveal for passers-by. “When you’re approaching the shelter you see it in front of you, you can’t see through the bronze-tinted thing,” said Sklar. “Then when you get under it, it reveals itself to you. As you approach, it reflects its surroundings from all sides; then you get underneath and: ‘oh wow, look at that.’”
StructureCraft fabricates an orchid-shaped roof that supports vegetation and Living Building Challenge principles.After serving patrons at one of Vancouver’s oldest botanical gardens for nearly 100 years, the VanDusen Gardens Visitors Centre had fallen dangerously into disrepair. Perkins+Will Canada conceived of a new, orchid-shaped center that meets CaGBC’s LEED Platinum ratings, and is the country’s first structure to target the International Living Building Challenge with features like geothermal boreholes, a 75-square meter photovoltaic array, and a timber roof that supports vegetation. To help fabricate the wooden structure to Perkins + Will Canada’s vision, the team contracted StructureCraft, a Vancouver-based design-build studio specializing in timber craftsmanship and structural solutions. Initial designs for the 19,000-square-foot building were delivered to StructureCraft as Rhino files. The uniquely shaped rooftop, which mimics an outline of the indigenous British Columbia orchid, had to be economically fabricated in a way that took net carbon effects into account. Within Rhino plugins—mainly Grasshopper—and with the help of strucutral engineers Fast + Epp, the StructureCraft team sliced the shape of the building into 71 long, curved panels of repeatable geometries. “Each curve is unique, so there’s a different radii for each beam,” said Lucas Epp, a structural engineer who worked on the project. “We optimized the global geometry of the roof so the radii of all the beams were in our fabrication tolerances but still achieved the architect’s desired aesthetic.” Also within Rhino, the team integrated all of the building’s services into each of the panels. Since much of the piping and wiring for other trades like insulation, sprinklers, and electric utilize flexible formats and conduits, modularizing the panels significantly reduced site time from months, to weeks. And to protect the wooden structures, moisture barriers and closed-cell thermal insulation were applied throughout. The parametric model was then imported to Solids modeling software to develop a bespoke fastening system. StructureCraft used jig and table sawing methods to mill panels of Glulam, chosen for its flexibility and strength. Timber battens were affixed as cladding in sizes that were thin enough to naturally accommodate the curves of each panel. Solid timber support columns, carved on StructureCraft’s in-house lathe, taper at both ends to Perkins + Will Canada’s design specifications. Business development engineer Brian Woudstra, who worked on the project, attributed the accuracy of fabrication and the speed of installation to the expansive capabilities of parametric modeling. “We could model every joist, Glulam panel, and ceiling batten to help with conflict detection and feasibility,” he said. “We always prefabricate our projects in our shop, so it’s like a kit of assemblies that all clicks into place.”