WoodWorks Leads Successful Blast Testing Of CLT Structures

by | Nov 8, 2017 | News

WoodWorks, in cooperation with the USDA Forest Service Forest Products Lab and Softwood Lumber Board, conducted a second series of blast tests on three existing two-story, single-bay cross-laminated timber (CLT) structures at Tyndall Air Force Base—the same structures involved in a series of initial blast tests performed in 2016. While a full analysis will be published early next year, on-site observations are decidedly positive. All structures remained intact under significant explosive loading well beyond their design capacity.

“Last year, we tested the structures under their own self-weight,” said Bill Parsons, VP of Operations for WoodWorks. “Those tests were successful and, this year, we built on that effort by testing whether the design methods established as a result of those initial tests needed to be adjusted when the buildings carried typical gravity loads and included different connection configurations, increased panel thickness, and alternate mass timber wall systems.”

Four tests were performed covering a spectrum of blast loads. For tests one and two, the size of the blast load and configuration of the structures were the same as prior testing, except the structures had axially-loaded front panels. The loads applied were intended to simulate conditions associated with a 5-story residential or office building. For tests three and four, different variables were altered on each of the buildings. One building used 5-ply CLT front wall panels, the second used off-the-shelf prefabricated angle brackets, and the third included nail-laminated timber (NLT) front panels. Reflected pressure, peak deflections, and panel acceleration were recorded at front and side faces in order to compare results to previous testing.

As with the tests performed in 2016, peak recorded deflections were consistent with pre-test predictions indicating the effectiveness of design assumptions and methodology in predicting elastic response of CLT to dynamic loads. The second test also indicated a controlled response in which localized panel rupture was observed but connection integrity and load carrying ability were not compromised for any of the loaded structures. Of particular note, all three structures remained standing following the fourth and largest blast, intended to take the structures well beyond their design intent. While panel rupture was expected and observed on all front and side wall panels, the buildings maintained enough residual capacity to remain intact and safe to enter.

From The Construction Specifier: https://www.constructionspecifier.com/woodworks-leads-successful-blast-testing-loaded-mass-timber-structures/

U.S. Forest Service: Build Better, Stronger, Faster With CLT

by | Apr 5, 2017 | News

The U.S. Forest Service is working to build markets for innovative forest products. One of these products, cross-laminated timber, also known as CLT, offers an opportunity for raising tall buildings with wood, opening up a completely new market for wood products.

And there’s tremendous opportunity to increase the market share for wood-based construction. Because of its high strength, CLT is an advantageous alternative to traditional building materials such as concrete, masonry, and steel. Because CLT panels resist compression, they are well-suited for building multistory structures, especially mid-rise buildings. Made from layers of dried lumber boards, stacked in alternating direction at 90-degree angles, glued and pressed to form solid panels, CLT has exceptional strength and stability and can be used as walls, roofs, and floors.

Additionally, CLT is highly resilient to fire, earthquakes, and even explosions. In fact in a recent series of live blast tests, CLT passed with flying colors. An examination of the results showed that the CLT structures suffered less degradation than expected and might outlast concrete and steel.

In terms of fire, CLT is like using a large log to start a campfire—it doesn’t ignite easily. And when it does burn, a char layer forms on the outside, protecting the inside and allowing the wood panel to maintain its structural integrity during fire scenarios.

Researchers have conducted extensive seismic testing on CLT and found that the panels perform exceptionally well in multi-story applications. When a seven-story CLT building was tested on the world’s largest shake table in Japan, it survived 14 consecutive earthquake simulations with almost no damage.

From the USDA: https://www.usda.gov/media/blog/2017/04/04/build-better-stronger-faster-clt