Analysis of a Flexible Bridge Rail System for High-Speed Roadways (0-5210-4)

The T6 tubular W-beam bridge rail has seen widespread use across the state of Texas. However, because it was unable to satisfy Test Level 3 (TL-3) impact performance requirements of NCHRP Report 350, it is no longer eligible for use on high-speed roadways. A new flexible bridge rail system, referred to herein as the T8 rail, has been designed for use on culverts and thin deck structures as a replacement for the T6 rail in high-speed applications. The T8 rail incorporates a tubular thrie beam rail element. Use of a tubular thrie beam provides additional rail height to improve stability for light truck vehicles, reduced clear opening to minimize the potential for vehicle underride, and a standard rail shape for ease of transitioning to approach guardrail. The anchor bolt pattern or ¿footprint¿ for the T8 post is the same as that used for the T6 post. This facilitates upgrade of existing T6 installations. Finite element impact simulations were conducted to evaluate the performance of the new tubular thrie beam bridge rail. The simulations indicated that the T8 rail should be capable of meeting TL-3 impact conditions of NCHRP Report 350. It is recommended that full-scale crash testing be conducted to verify the impact performance of the T8 bridge rail. Details of the recommended T8 bridge rail system are included in the report.