Improvements to the weak-post W-beam guardrail

Recent full-scale crash tests of the weak-post W-beam guardrail system have resulted in unsatisfactory collision performance as evaluated by the National Cooperative Highway Research Program (NCHRP) Report 350. Since acceptable crash test performance is required in order to use a guardrail on a Federal-Aid Highway in the United States, the poor performance of the weak-post W-beam guardrail is a significant problem to those states that use it. The goal of this project was to improve the impact performance of the weak-post W-beam guardrail system so that it satisfies the requirements of NCHRP Report 350 at test level three

Design of a non-snagging guardrail post

The purpose of this project is to design a non-snagging guardrail post. The procedure will be to first develop a simple finite element (FE) model of a single post, wheel and suspension to explore the snag potential for some existing standard guardrail posts. The next step in the procedure will be to develop appropriate design changes that could prevent wheel snagging and investigate if they do by using a one-post sub-model. An attempt to validate the used material model for wood will also be done by comparison between laboratory tests and finite element simulations

INCREASED SPAN LENGTH FOR THE MGS LONG-SPAN GUARDRAIL SYSTEM

Long-span guardrail systems have been recognized as an effective means of shielding low-fill culverts while minimizing construction efforts and limiting culvert damage and repair. The current MGS long-span design provided the capability to span unsupported lengths up to 25 ft (7.6 m) without the use of nested guardrail. The excellent performance of the MGS long-span system in full-scale crash tests suggested that longer span lengths may be possible with the current design. A detailed analysis of the MGS long-span guardrail system was performed using the finite element software program LS-DYNA®. It was shown that the MGS long-span design had the potential for satisfying MASH TL-3 evaluation criteria at increased span lengths of 31¼ ft (9.5 m) and 37½ ft (11.4 m). Further increasing the span length led to questionable vehicle capture and severe impacts into the culvert wingwall. It was determined that the 31¼-ft (9.5-m) span MGS long-span system would proceed to full-scale crash testing. A critical impact study identified two impact locations that (1) evaluated the structural capacity of the guardrail system and (2) maximized the vehicle’s extent over the culvert and potential for vehicle instabilities. Ultimately, the sponsors decided to perform full-scale crash testing with Universal Steel Breakaway Posts in lieu of Controlled Release Terminal posts to determine their suitability with the MGS long-span guardrail system. Prior full-scale crash testing indicated that the post-to-guardrail bolt connections were sensitive to the MGS long-span design. A simulation study investigated several techniques to improve the modeling of these bolted connections. Advisor: John D. Rei

Design Guidelines for the use of Curbs and Curb/Guardrail Combinations Along High-Speed Roadways

The potential hazard of using curbs on high-speed roadways has been a concern for highway designers for almost half a century. Curbs extend 75-200 mm above the road surface for appreciable distances and are located very near the edge of the traveled way, thus, they constitute a continuous hazard for motorist. Curbs are sometimes used in combination with guardrails or other roadside safety barriers. Full-scale crash testing has demonstrated that inadequate design and placement of these systems can result in vehicles vaulting, underriding or rupturing a strong-post guardrail system though the mechanisms for these failures are not well understood. For these reasons, the use of curbs has generally been discouraged on high-speed roadways. Curbs are often essential, however, because of restricted right-of-way, drainage considerations, access control, delineation and other curb functions. Thus, there is a need for nationally recognized guidelines for the design and use of curbs. The primary purpose of this study was to develop design guidelines for the use of curbs and curb-barrier combinations on roadways with operating speeds greater than 60 km/hr. The research presented herein identifies common types of curbs that can be used safely and effectively on high-speed roadways and also identifies the proper combination and placement of curbs and barriers that will allow the traffic barriers to safely contain and redirect an impacting vehicle. Finite element models of curbs and curb-guardrail systems were developed, and the finite element program, LS-DYNA, was used to investigate the event of a vehicle traversing several curb types. Finite element analysis was also used in the analysis of a vehicle impacting a number of curb-guardrail combinations. The results obtained from these analyses were synthesized with the results of previous studies, which involved full-scale crash testing, computer simulation, and other methods. The combined information was then used to develop a set of guidelines for using curbs and curb-barrier combinations on high-speed roadways

Computerized Simulation using Finite Element Method (FEM) for Guardrail Crashes

The rigid structure of the existing w-beam guardrail design leads to numerous death and injuries. Recently, a new prototype was produced by considering the best design while innovating an additional element to the existing w-shape guardrail to create a safer and more practical device. Yet, the behavior of the prototype when subjected to explicit impaction force with proper environment setting was not properly investigated experimentally. By using Ansys Ls-Dyna software, finite element analysis was conducted by subjecting a higher impaction velocity with proper environment setting on both models: (1) the existing w-beam model, and (2) prototype model. The validity of the produced finite element model was ensured by comparing the maximum impaction force of the existing experimental literature. The model deformation in terms of element displacement and scale of force received by both models was observed. The observation showed that the additional element on the prototype reduced the deformation rate onto the beam span under the impaction force of 26.933 kN

DEVELOPMENT OF STANDARDS FOR PLACEMENT OF STEEL GUARDRAIL POSTS IN ROCK

A steel post W-beam guardrail system was developed for installation in rock-soil foundations. The guardrail system was constructed with a 2.66-mm (12-gauge) thick W-beam rail, 53.34 m in length. The W-beam guardrail was supported by twenty-seven W152x13.4 by 1,346-mm long steel posts, spaced at 1,905 mm on center. The posts were installed in drilled holes in concrete, constructed by drilling three 203-mm diameter holes on 165- mm centers to a depth of 610 mm. The drilled holes were backfilled with compacted ASTM C33 coarse aggregate, size no. 57. One full-scale vehicle crash test, using a 3⁄4-ton pickup truck, was performed on the W-beam guardrail system. The test was conducted and reported in accordance with the requirements specified in the National Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. The safety performance of the W-beam guardrail system with post placed in rock was determined to be acceptable according to the Test Level 3 (TL-3) evaluation criteria specified in NCHRP Report No. 350. Further, guardrail post placement recommendations were also developed for situations where rock is located below the surface. These recommendations were developed through an analysis of bogie testing of posts