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A Chance to Connect: Part 2

A Chance to Connect

The UMASS Mass Timber “Integrated Design Building” Project

Part 2

By Rick Reynolds

The new mass timber Integrated Design Building under construction at UMass represents more to the University and the greater community it serves than meets the eye. As the first mass timber structure of its size and scale in the United States, it is hoped that the forward-looking academic building will serve as an exemplar in the region for smart, sustainable architecture, and an inspiration to the local design community to use more carbon-sequestering mass timber.

By relying less on anthropogenic CO2 emissions from the production and use of steel, engineered wood and wood-concrete composite materials offer designers and architects interesting new possibilities, including better strength-to-weight ratio over steel.

Two thousand cubic meters of sustainably harvested wood, a renewable resource, will be used in the construction. With wood’s carbon sequestering properties, the building will act as a carbon sink, offsetting much of the carbon footprint of the remaining concrete and steel components. Academic buildings as carbon sinks can become teachers in their own right, educating the new generations of students essential to the paradigm shift that will need to occur to meet the country’s aggressive carbon-sequestering goals over the coming decades.

Because of the long spans in the cantilevered “commons” section of the building, some steel was needed where a huge steel truss rests on two massive timber columns. And a dynamic, three-dimensional truss, comprised of glulam beams and metal tension rods, supports the roof garden, which will have up to 18 inches of soil for dense planting.

Largely, though, the structural frame is made with engineered wood glulams and CLT (cross-laminated timber) panels, supplied and fabricated by Nordic Structures, which form the beams, columns, structural walls, and composite floor system.

The new floor connection system; a wood-concrete composite system (WCCS), elegantly combines the material properties of wood and concrete, allowing for thinner, longer, stiffer, and more durable spans that control vibration and acoustics, while remaining serviceable. The sandwich, comprised of five layers of cross-laminated timber panels with a concrete topping, is reinforced with 4” HBV connector mesh. Atop the CLT layer sits ¼” of rubber, decoupling everything. Viewed from the floors below, the wood ceilings add warmth to the industrial scale. The Integrated Design Building is the first building in the US to use HBV connector mesh in a wood-concrete-composite system.

Additionally, a new composite-timber/steel-connector-system, using steel dowel/glue peg and perforated steel plate was deployed.

In building the large scale wood structure, there were significant perceptual challenges to overcome. For instance, there are fire code misperceptions regarding timber. Mass timber in many conditions possesses superior fire-inhibiting properties to that of steel.

For example, contrary to common thinking, the type of mass timber used here has an ability to last at least 3 hours in a fire (building codes require only 2 hours). And even after a fire, such timber maintains 75% of its strength (due to the insulating properties of charring). Heavy timber is actually more structurally stable than steel, which can heat to greater temperatures and fail sooner. This advantage, along with the biophilic properties of wood on the occupants’ well being, and the many positive sustainability factors, all make mass timber and innovative timber products very compelling.

On the University side, UMASS Building and Construction Technology professors Peggi Clouston, and Alexander Schreyer, and Chancellor Kumble Subbaswamy have been instrumental in making the project a reality.

Dr. Clouston teaches structural timber design and material mechanics for architects and construction technologists. Her research focuses on the structural behavior of bio-based composite structures, including wood-concrete composite systems (WCCS), local species cross-laminated timbers (CLTs), innovative timber connections, and computational modeling of wood-based composites.

Mr. Schreyer, the Senior Lecturer and Program Director of the Building and Technology program, has a strong background in structural engineering, wood science, and digital design. Along with Dr. Clouston, he, too, shares a special focus on the behavior of wood-based structural systems, innovative connection systems for wooden structures, and wood-concrete composite systems. (Note: the title, “A Chance to Connect” is borrowed from one of Mr. Schreyer’s talks.)

Regarding connection points, the UMASS project is the result of many partners working closely together. These include the architects at Leers Weinzapfel Associates, three engineering firms (Simpson Gumpertz & Heger, Fire Tower Engineered Timber, and Equilibrium Consulting), engineered wood products company and fabricator, Nordic Structures, construction managers Suffolk Construction, union crews from North&South Construction Services, landscape architect, Stephen Stimson Associates, and on-site mass timber consultant and union crew timber installation training handled by Bensonwood.

For its part, Bensonwood trained and collaborated with the North&South union crews in the raising of the building’s mass timber structural components. Bensonwood’s Structural Wood Engineer, Chris Carbone, worked closely with our on-site timberframe specialists, C.J. Brehio and Philip Henry, to ensure the myriad of mass timber elements and connectors came together on time and without fail. According to Brehio:

“Our job was to train the 16-20 union members of the North&South raising crews in how to handle this safely, to use the specialized tools required, to install for proper wind loading, and sequence the order of operations and logistics. To achieve this we devised a system of descriptive drawings: 3D blowups with descriptions so the crew members could see, step-by-step where they were on the job. We needed to be two weeks ahead in managing inventory arriving on 60 tractor trailer loads, while making sure, in real time, that all union crew members and crane operators knew which piece went where, while managing quality control. It was quite a challenge, but a gratifying one.”

Through 21st century building science and collaboration among government, industry, and academic partners, meaningful sustainability within the built environment can be achieved. And nowhere can that paradigm shift be better assured than in our green school environments and the students they inspire.