Increased span length for the MGS long-span guardrail system.

PDFTech ReportTRP-03-310-14TPF-5(193) Supplement #56GuardrailsCulvertsFinite element methodHighway safetyDesignImpact testsSimulationUnited StatesMidwest States Regional Pooled Fund ProgramWeiland, Nicholas A.Reid, John D.Faller, Ronald K.Bielenberg, Robert W.Lechtenberg, Karla A.Midwest Roadside Safety FacilityUnited States. Federal Highway AdministrationUS Transportation CollectionLong-span guardrail systems have been recognized as an effective means of shielding low-fill culverts whileminimizing construction efforts and limiting culvert damage and repair. The current MGS long-span design provided thecapability to span unsupported lengths up to 25 ft (7.6 m) without the use of nested guardrail. The excellent performance ofthe MGS long-span system in full-scale crash tests suggested that longer span lengths may be possible with the currentdesign.A detailed analysis of the MGS long-span guardrail system was performed using the finite element softwareprogram LS-DYNA\uc2\uae. It was shown that the MGS long-span design had the potential for satisfying MASH TL-3 evaluationcriteria at increased span lengths of 31\uc2\ubc ft (9.5 m) and 37\uc2\ubd ft (11.4 m). Further increasing the span length led toquestionable vehicle capture and severe impacts into the culvert wingwall. It was determined that the 31\uc2\ubc-ft (9.5-m) spanMGS long-span system would proceed to full-scale crash testing. A critical impact study identified two impact locationsthat (1) evaluated the structural capacity of the guardrail system and (2) maximized the vehicle\ue2\u20ac\u2122s extent over the culvert andpotential for vehicle instabilities. Ultimately, the sponsors decided to perform full-scale crash testing with Universal SteelBreakaway Posts in lieu of Controlled Release Terminal posts to determine their suitability with the MGS long-spanguardrail system.Prior full-scale crash testing indicated that the post-to-guardrail bolt connections were sensitive to the MGS longspandesign. A simulation study investigated several techniques to improve the modeling of these bolted connections