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After directing late-2016 blast tests on three cross laminated timber (CLT) specimens at Tyndall Air Force Base in Panama City, Fla., representatives of the Wood Products Council’s WoodWorks program observed that the structures “remained intact and matched modeling predictions with acceptable levels of damage under significant explosive loading.” The tests were conducted in cooperation with the U.S. Forest Service and Softwood Lumber Board; results stand to expand the use of wood solutions for Department of Defense applications and other blast-resistant construction.

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Blast-resistant structures are cross laminated timber stakeholders’ latest target. PHOTO: Wood Products Council, Washington, D.C.

The two-story, single-bay, slab-anchored test structures were of three ANSI/APA CLT grades, and included window and door openings consistent with an actual building. Three shots were performed to demonstrate the engineered wood’s performance over a spectrum of blast loads. The first two were designed to stress the structures to within their respective elastic limits, the third to push them beyond those 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 CLT elastic response under dynamic loads.

Initial observations deriving from the tests are positive, WoodWorks contends. For the first two tests, peak recorded deflections were consistent with pre-test predictions, indicating design assumption efficacy 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 specimens. WoodWorks staff will analyze test data with Karagozian & Case Inc. and the University of Maine with an eye to publishing Tyndall AFB research findings this year.