Development of a Finite Element Model for W-Beam Guardrails

During the early 1960’s a wide variety of guardrail systems were developed and installed on highways in the US. W-beam guardrails use steel sheets rolled into the W-shape to form a rigid beam that can “catch” the bumpers of typical vehicles. W-beam guardrails have become the most common type of longitudinal roadside barriers used on the roadways in the United States. They have played an important role in improving highway safety when used to redirect vehicles away from roadside hazards such as bridge abutments, light poles, trees, ditches, mounds, severe terrain, or other fixed objects found along the roadside. One significant change resulted from the implementation of the NCHRP Report 350 recommendations for the evaluation of roadside safety features. Report 350 recommended a larger vehicle (the 2000 kg pick-up truck) for testing. This vehicle was considered more representative of the light truck utility vehicles on the road, but it was recognized that the added weight would increase the kinetic energy in crashes with roadside hardware. Full-scale crash tests were conducted on w-beam guardrail systems to examine the performance of the G4(1s) guardrail system under the NCHRP Report 350 guidelines. Full-scale crash testing ultimately determined that a design with steel posts and routed wood blockouts would meet the NCHRP 350 TL 3 criteria. It became apparent in efforts to find an improved design for this guardrail system, that a better means to evaluate design variations was needed. This technical summary describes efforts to develop and demonstrate a viable alternative approach to addressing design improvement needs.