Crash-Tested Bridge Railings and Transitions for Wood Bridges - Phase IIB Report on Glulam Bridge Post and AGT Development
REPORT NUMBER
TRP-03-494-25
AUTHORS
Aaron Lechtenberger, Ronald Faller, Tewodros Yosef, Joshua Steelman, Cody Stolle, Bob Bielenberg, Scott Rosenbaugh, James Wacker
PUBLICATION DATE
2025-07-28
ABSTRACT
Limited research exists to develop bridge railing systems for high-service-level roadways that meet current vehicular impact safety standards. This study continued a multi-phase project aimed at developing, crash testing, and assessing a MASH Test Level 4 (TL-4)- compliant glued-laminated (glulam) timber bridge railing system with a curb, as well as a MASH TL-3 approach guardrail transition (AGT) system. A comprehensive literature review identified critical deck configurations and parameters, including deck thickness, cantilevered overhang dimensions, and panel geometry. Additionally, soil-interaction dynamics for AGT posts were examined through prior bogie impact testing. Cost-effective design strategies were proposed to minimize the exposure of timber deck elements to prolonged water accumulation beneath the asphalt wearing surface. The AGT system design was based on an earlier crash-tested configuration. Dynamic impact testing of single, double, and triple AGT posts embedded in soil was conducted, yielding valuable insights into their impact behavior and performance. Data from these tests informed the calibration of BARRIER VII models, enabling the development of an optimized AGT system. Prototyping and iterative designing facilitated the creation of a reliable connection between the bridge railing and AGT systems. A critical impact point (CIP) investigation further identified locations most prone to failure under MASH TL-3 impact conditions for a final AGT system recommendation. The study culminated in the design of four dynamic component tests to evaluate critical timber deck configurations and connections. Test no. TRTD-1, involving a 7,186-lb bogie impacting a surrogate post on a 5⅛-in. thick transverse Douglas Fir-Larch glulam deck, revealed premature tensile splitting of the deck due to insufficient restraint. This issue was addressed by introducing timber bolts through the scupper to enhance deck performance.
KEYWORDS
Glue-Laminated Timber, Glulam, Bridge Rail, Bridge Deck, Crashworthy, TL-4, Bogie Testing, Dynamic, MASH, BARRIER VII