Hot New Video! Full-Scale CLT Fire Testing Yields Impressive Results

Trust us, you’re going to want to see this.

Forest Products Laboratory researchers conducted fire testing on a two-story cross-laminated timber (CLT) structure. Watch the short video below to see these one-bedroom apartments go up in flames, and to find out how CLT performed in the heat of the moment.

You can read more specifics about the tests in this previous LabNotes blog post, or if you’re really into the details and data, check out the full FPL general technical report.

Step by Step: Developing Design Standards for Hardwood Stairways

More than 1,500 wood samples are currently being evaluated at the Forest Products Laboratory (FPL) as part of an experiment that is helping researchers gain insight into the structural capabilities of various domestic hardwoods.

Hybrid hardwood, glass, and steel staircase in a commercial building.

In collaboration with Mississippi State University and Stairbuilders and Manufacturers Association, engineers at the Lab are developing structural design standards for use in residential stairway and guard construction.

The project aims to survey the strength and stiffness of species such as red oak, white oak, Southern Pine, hard maple, and yellow poplar from nearly all regions of the United States.  Engineers and builders typically use these species solely for aesthetic purposes, but researchers believe testing their strength will lead to greater economic value and opportunity in the domestic wood construction industry. Ultimately, this will also contribute to a thriving job market, and allow forests and stewardship to thrive on both private and public lands.

Laminated hardwood curved staircase that incorporates a large variety of species for architectural effect.

Though the project began in 2017, engineers are still busy testing the species’ mechanical properties against current ASTM standards.  Final testing and result analysis will conclude in 2020. To learn more about this study, read the full Research in Progress report.

Blog post by Francesca Yracheta

Creative Learning: Forensic Botany Class Goes from Science to Sculpture

In the University of Wisconsin-Madison (UW) Department of Botany’s Forensic Botany class, Forest Products Laboratory (FPL) research botanist Alex Wiedenhoeft gives his students full creative license when it comes to their final projects.

“They could even do an interpretive dance.” said Wiedenhoeft, “Although they’d have to interpret it for me, since I’m a botanist.”

Undergraduate student Jennifer Baccam appreciated the freedom of the assignment and chose an interesting medium to demonstrate what she had learned in Wiedenhoeft’s class: sculpture.

Jennifer Baccam’s sculpture of FPL’s Arthur Koehler.

Baccam is majoring in plant biology and when she heard about Wiedenhoeft’s forensic botany class, her curiosity was piqued.

“I love botany and have done lots of field work,” said Baccam. “This class seemed like an interesting way to meet the requirement of taking a laboratory class.”

In giving thought to her final project, Baccam wanted to know how forensic botany came about. When she began to research the topic, Baccam discovered it all began with a scientist named Arthur Koehler from none other than the Forest Products Laboratory.

Koehler was the chief wood technologist at FPL in 1932 when Charles Lindbergh’s infant son was kidnapped and a wooden ladder was nearly the only evidence at the scene of the crime. Koehler was asked to participate in the investigation and eventually testified in the trial. Based partly on Koehler’s testimony, Bruno Hauptmann was convicted of the crime, and subsequently executed.

At the time, no one had heard of an expert witness in wood. In fact, one of Hauptmann’s lawyers stated the following in objection to a question posed to Koehler: “We say that there is no such animal known among men as an expert on wood; that it is not a science that has been recognized by the courts; that it is not in a class with handwriting experts or with ballistic experts. But this is no science, this is merely a man who has had a lot of experience in examining trees, who knows the barks on trees and a few things like that.”

Koehler of course balked at this statement, and it was stricken from the record as the court deemed Koehler was indeed “qualified as an expert upon the subject matter.”

As Baccam read Koehler’s testimony, she found it plenty apparent that he was confident in his skills and abilities as a wood expert, and he stood behind what he had learned in examining the ladder as evidence.

Forensic Botany student Jennifer Baccam.

“Koehler came across as a larger-than-life personality,” said Baccam. This observation is apparent in her sculpture, in which Koehler’s bust is looming over the other aspects of the case that are represented, including the ladder itself.

Baccam’s curiosity about forensic botany continues to lead her down a new path, as she is set to begin working in FPL’s Center for Wood Anatomy Research with Wiedenhoeft soon, and will complete her senior thesis at FPL beginning in the fall.

“I’m lucky to have Alex as my mentor,” says Baccam. “Since the beginning of the Forensic Botany course he has helped me further realize that research is truly my passion. My perspective of my future is much less uncertain now.”

To learn more about Wiedenheoft’s forensic botany course, which he co-teaches with UW Professor Sara Hotchkiss, see this feature story from UW-Madison.

Borate and Adhesives: Can They Work in Harmony?

Scientists at the Forest Products Laboratory (FPL) are continually honing their expertise on all things cross-laminated timber (CLT) and this time, they’re digging deeper to learn how preservatives can protect and enhance this handy material.

Borate, an environmentally friendly preservative, has been proven effective in shielding decay and termite damage, while also protecting CLT’s aesthetic appearance, making it a suitable treatment for interior residential applications. But researchers from the Lab’s Durability and Wood Protection Research unit and Michigan State University are wondering how far borate can go if a sticky situation comes into play.

The project, which began in January 2018, aims to discover how well borate can protect CLT against termites, fungal decay and fire when it teams up with adhesives.

Fire test samples. Top, Class I fire-retardant coating; bottom, borate-treated spruce.

Researchers are currently studying how borate will change the surface properties of CLT.  They plan to compare how adhesive formulations interact with CLT that is treated with borate with that which is left untreated.  The wood will be analyzed using various spectroscopy methods. After measuring the adhesive properties of both polyurethane and phenolic glues, researchers will construct small-scale samples of CLT from borate-treated wood and a range of adhesive formulations.  The strength of these formulations will be tested when they are applied to a selection of treated and untreated CLT.

A borate spray solution will also be developed and applied to various CLT samples, where it will then be observed under conditions like fire, termites, and fungal decay. By the conclusion of the project in 2020, researchers hope to further understand how preservative-treated CLT performs under stress, especially when exposed adhesive is involved.

To learn more about this study and how borate and adhesives coexist, read the full Research in Progress report.

New Videos of Blast Tests Available

New video footage has been released of blast testing performed on cross laminated timber (CLT) structures, and it’s quite a sight to see.

The Forest Products Laboratory, in cooperation with WoodWorks and the Softwood Lumber Board, led a second round of live blast testing in 2017 at Tyndall Air Force Base in Panama City, Florida.

The charges in the videos were large enough to potentially cause lethal injury, and the structures survived. The objective of these studies was to demonstrate the capability of CLT structures to resist airblast loads, thereby allowing the military to incorporate mass timber materials like CLT into their construction projects.

You can read more about the study here, and see all the blast test videos on the WoodWorks YouTube channel.