Adaptation and Development of a MASH TL-1 Low-Height, Glulam Timber Bridge Railing for Use on Transverse Glulam Decks
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ABSTRACT
In a 2009 study for the West Virginia Department of Transportation, the Midwest Roadside Safety Facility developed an AASHTO Manual for Assessing Safety Hardware (MASH) Test Level 1 (TL-1) low-height, glue-laminated (glulam) timber bridge railing for use on a transverse, nail-laminated deck. A series of static component tests and one full-scale vehicle crash test were performed to configure the system and determine the crashworthiness of the bridge railing and deck. More recently, the United States Department of Agriculture – Forest Service (USDA-FS) had expressed interest in utilizing the previously-developed MASH TL-1 low-height, glulam timber bridge railing on a transverse glulam deck system instead of a transverse nail-laminated deck. To cost-effectively adapt and determine the crashworthiness of TL-1 glulam bridge railing system on the alternative timber deck, a series of physical tests were conducted on the bridge railing components installed on a transverse glue-laminated deck and a transverse nail-laminated deck. For each deck type, one static test and one dynamic test was performed on a segment of the bridge railing system supported by two scupper blocks. From the component testing results, the glulam rail and scupper blocks installed on a transverse glulam deck resisted more lateral force, absorbed more energy, and had higher initial linear stiffness as compared to the same rail and scupper blocks installed on a transverse nail-laminated deck. Thus, the low-height, glulam timber bridge railing installed on a transverse, glulam deck will provide equal or greater safety performance as compared to the same bridge rail installed on a transverse, nail-laminated deck. As a result, the low-height, glulam timber bridge rail installed on a transverse glulam deck has also been deemed adequate for use under MASH TL-1 impact conditions.
KEYWORDS
Glue-Laminated Timber, Glulam, Nail-Laminated Timber, Nail-Lam, Bridge Rail, Bridge Deck, Crashworthy, TL-1, Component Testing, Bogie Testing, Static, Dynamic, MASH