Tales from the Test Floor: Air Cannon Makes a Perfect Shot

Researchers at the Forest Products Laboratory (FPL) are back to work using the debris launcher in the Engineering Mechanics and Remote Sensing Laboratory.

The debris launcher is an air cannon that fires two-by-fours at 100 mph to replicate what could happen in a house or any wood structure during a tornado. The equipment has been used frequently over the past several years, most recently to test the viability of tornado safe rooms constructed of wood.

This time, researchers are using the cannon for a new purpose: shooting the lumber ‘missiles’ at sections of cross laminated timber to test the engineered material’s performance withstanding projectiles in high-wind events, and there was a surprise ending to the test.

The missile was fired at the test wall, and it bounced off the wall…right back into the cannon! Take that, cannon!Missle  after testSeems like a one-in-a-million shot. But wood, er, would you believe it happened twice?! Goes to show that even after more than a century of research at FPL, good ol’ wood still has a few tricks up its bark, er, sleeve.


Tales from the Test Floor: Glulam Arches


Researchers here at the Forest Products Laboratory (FPL) wrapped up testing a set of glued laminated (glulam) arches with a bang by breaking the last arch in a series of three. The arches measure 30-feet tall by 30-feet wide. Only ten arches have been tested worldwide.

This experimental work is evaluating the seismic design parameters of glulam arches by simulating the forces of an earthquake and measuring how the arches perform under such stress. The collected data will be analyzed and results published in the near future to serve as a reference for architects and engineers looking to design buildings using glulam arches.

The test took place on the strong floor in FPL’s Engineering Mechanics and Remote Sensing Laboratory (EMRSL). Here, researchers conduct physical and mechanical tests on a wide range of materials, building systems, and structures – from houses to bridges. Results inform the development of building codes and structural design standards.


Re-evaluating Evaluation : New Materials, New Methods

In today’s world of energy-efficient building requirements, structural insulated panels (SIPs) remain an attractive option. Modern SIPs combine the strength of wood with the energy-saving attributes of cutting-edge foam plastic insulation, to create a cost-effective solution for construction professionals. These sandwiched panels stand ready to meet the building codes of tomorrow, but many fear that the lack of adequate, systematic testing of these new materials may hinder their popularity and stifle their widespread implementation.

The Forest Products Laboratory (FPL), APA – The Engineered Wood Association, and the Structural Insulated Panel Association are on a mission to change this. Because of their unique construction, researchers believe SIP walls must be tested differently than more common light-frame walls. Unlike traditional walls, SIP walls are required to bear weight on their cap and sill plates, so that vertical loads from the story above are effectively transferred down to the foundation.

Creep test setup for a structural insulated panel.

A structural insulated panel undergoing performance testing at FPL.

This “restrained” method of evaluation yields the most accurate data for SIP performance.

Until recently however, SIP walls have been evaluated in the same way as their conventional light-frame counterparts, using an “unrestrained” configuration. Researchers fear that these tests may not realistically reflect the lateral load-bearing ability of the SIPs.


A diagram illustrating how the 24 full-size SIPs will be tested.

Between May 2015 and August 2016, 24 full-size SIP walls will undergo a carefully monitored regime of restrained, lateral load performance tests, which represent the most common configurations used by industry professionals. Researchers will consider a wide range of variables — from the obvious, such as wall thickness and type — to the minute, such as nail size and nail spacing. The final report will be prepared by December 2016.

Results of this project will not only increase the accuracy SIP performance data, it may help guide further evaluations of similar building materials in the future. Most importantly, it will provide construction and design professionals with the data they need to make informed choices when considering these new building materials, so that they can keep tomorrow’s buildings efficient and safe.

For more information, please see this Research in Progress.


WholeTrees Lifts Roundwood to New Heights: Commercial Installation Complete in Madison

WholeTrees LLC, a long-time partner of the Forest Products Laboratory (FPL), has completed the installation of structural columns and trusses made from- you guessed it- whole trees, in a Festival Foods grocery store currently under construction in Madison, Wisconsin.

New grocery store features WholeTrees technology. Photo credit: Heartland Images Photography

The new grocery store features WholeTrees technology. Photo credit: Heartland Images Photography

For the project, which broke ground last fall, WholeTrees worked closely with Tri-North, Gebhardt Development, and the City of Madison to re-purpose ash trees for use as structural columns in the store. The trees had previously been removed due to emerald ash borer disease .

WholeTrees also provided 88 structural trusses made with local red pine. The WholeTrees Wing Truss spans 30′ to 60′ with design loads of over 350 pounds per linear foot, and over 10 pounds of carbon stored per square foot.

Similar trusses were recently tested at FPL as the latest in a collaborative effort to demonstrate the technical feasibility of using tree stems in their original form as structural building components.

WholeTrees’ website features a great slideshow following the trees from harvest to installation that’s worth a look.

For more information on the project, see this feature story from Isthmus on WholeTrees’ involvement in the Festival Foods development.

Creep Performance of Structural Insulated Panels (SIPs)

Few places in the United States can understand cold like the Midwestern United States. In Wisconsin, where January’s low temperatures average around 13 degrees Fahrenheit and snowfall is typically measured in feet, a well insulated home can spell the difference between enjoying the winter and enduring the winter. At the Forest Products Laboratory (FPL) in Madison, Wisconsin, helping to evaluate effective yet structurally sound insulation methods for wooden construction is a small but important part of the laboratory’s vast repertoire.

Modern construction efforts have incorporated more and more structural insulated panels (SIPs) into designs—and with good reason. SIPs are a panel-shaped building material that consist of two wood-based composite boards with an insulating layer of foam plastic in between them. The end result is extremely strong, energy efficient and cost effective.

Creep test setup for a structural insulated panel.

Creep test setup for a structural insulated panel.

Although SIPS have been used in floor and roof applications for years, little is known about their long-term structural integrity. Recognizing this gap, researchers at FPL set to work investigating the “creep performance” of these systems, or the tendency of the panel to deform when subjected to a sustained load. The rate of creep deformation is a function of material, time, temperature, moisture, and applied load—and the right combination could spell structural failure.

The project, in cooperation with The Engineered Wood Association (APA) and the Structural Insulated Panel Association (SIPA), began in 2013 when 12-inch-wide panels were brought to FPL to be subjected to 90 days of shear and bending tests. The SIPs performed very well, and all of the 24-foot-long sections survived without any bending failure. In addition, after a recovery period, researchers retested the panels to determine the residual strength of each panel. Again, the SIPs remained strong, unfazed by the 90-day test.

Based off the positive results from the first test, the team launched into the next phase of the project. The second phase kicked off in 2014, and was much more comprehensive than 2013’s efforts. This round of tests involved as many as 28 specimens per test configuration, several different configurations, and lasted into spring of this year. Although the research is completed, the final report has yet to be released—but when it is, building professionals will have a new body of knowledge that will allow them to incorporate SIPS into designs with added peace of mind.

When the days get darker and the snow begins to pile up, SIPS have always been trusted to keep the cold air out. Now, consumers will be able to rest assured that bending, shearing and other deformation won’t be creeping in at night either.