by Web Editor | 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/
by Web Editor | 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
by Web Editor | Dec 19, 2016 | News
Videos are now available showing a series of live blast tests on three cross-laminated timber (CLT) structures at Tyndall Air Force Base, conducted by WoodWorks in cooperation with the US Forest Service and Softwood Lumber Board. Post-test observations were exciting. All structures remained intact and matched modeling predictions with acceptable levels of damage under significant explosive loading. The results of this testing will be used to further expand the use of wood solutions for Department of Defense applications and other blast-resistant construction. Watch the videos here: https://bit.ly/2hwVE1g
The CLT structures—each two-story, single-bay structure with anchorage to an existing concrete slab—were constructed in full by Lendlease over a period of eight days. Each structure was constructed using a different grade of CLT (i.e., grade designations V1, E1 and V4 per ANSI/APA PRG-320 provided by DR Johnson, Nordic and SmartLam, respectively) and included window and door openings (with doors provided by American Direct) consistent with an actual building. Self-drilling screws provided by MyTiCon and adhesive anchors provided by Hilti were utilized in concert with angle steel to connect the constituent panels of each structure.
Three shots were performed to demonstrate the effectiveness of CLT over a spectrum of blast loads. The first two shots were designed to stress the CLT structures to within their respective elastic limits. The third shot was designed to push the structures beyond their elastic limits such that post-peak response could be observed. Reflected pressure and peak deflections were recorded and will be used to thoroughly document the response of the structure in time, and support a design methodology for predicting elastic response of CLT under dynamic loads.
Initial observations deriving from these tests are positive. For the first two tests, peak recorded deflections were consistent with pre-test predictions, indicating the efficacy of the design assumptions and supporting design methodologies. Results from the third test 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 three structures. Over the next couple months, WoodWorks will be working with Karagozian & Case, Inc. and the University of Maine to thoroughly post-process and analyze the results of these tests.
From Business Wire: https://www.businesswire.com/news/home/20161215005337/en/WoodWorks-Leads-Blast-Testing-Project-Cross-Laminated-Timber
