FPL Researcher Featured in Engineering News-Record

A rendering of the 25-story Ascent building currently under construction in Milwaukee, Wisconsin. Photo credit: Korb + Associates
Laura Hasburgh
Building and Fire Sciences
Materials Research Engineer

Engineering News-Record recently featured Forest Products Laboratory’s (FPL) materials research engineer, Laura Hasburgh and her expert consultation on the Ascent construction project in Milwaukee. At 25 stories, the Ascent building is making history as the soon-to-be tallest timber building in the world. And because of its unprecedented height and exposed mass timber interior, Hasburgh was contacted to lend her fire testing expertise.

The top eighteen floors of the Ascent will be framed in mass timber and the interior architectural design features exposed glued-laminated timber (glulam) framing and cross-laminated timber (CLT) slabs to showcase the natural beauty of the wood. But with these design and material choices, the Ascent’s fire safety planning needed to be carefully considered.

A rendering of the Ascent’s interior design, exposing the natural beauty of wood to the interior. Photo credit: Korb + Associates

Hasburgh got involved with the Ascent fire resistance rating tests when she was contacted by a consultant on the building project. “They wanted to know if FPL had previously run three-hour fire tests. And if not, whether FPL could run them on some glulam columns. The fire test results would help inform the engineering analysis of exposed mass timber in the Ascent building,” explained Hasburgh.

Hasburgh’s three-hour burn tests proved that oversized yet unprotected glulam columns do not lose structural integrity because outer layer charring protects internal layers. Photo credit: FPL

The required fire tests were different than FPL’s previous standard tests on glulam because the burn time was an hour longer and the specimens were not protected by a noncombustible membrane.

But why are these tests so important? Especially to mass timber buildings?

Hasburgh explained, “The fire resistance of a structural building member consists of its ability to survive a specified fire, in both exposure and duration, without loss of its loadbearing function. For exposed mass timber, the ability to endure a fire includes the development of a char layer that protects the unburned wood and slows down the pyrolysis.”

FPL researchers discovered that the glulam columns performed better during the three-hour fire test than what they expected. Their columns qualified for a three-hour fire resistance rating, and Hasburgh’s research helped get the Ascent project off the ground.

Read the full-length Engineering News-Record article here: Milwaukee’s 25-Story Ascent Stacks Up as Tall Timber Role Model | 2020-12-16 | Engineering News-Record (enr.com)

To find out more about the amazing advancements our scientists are making, visit the Forest Products Laboratory at https://www.fpl.fs.fed.us/