Impact analysis of a vertical flared back bridge rail-to-guardrail transition structure using simulation

Abstract

Bridge rail-to-guardrail transitions are designed to shield unprotected ends of bridge rails, which are fixed-obstacle hazards. These structures should provide an effective transition between longitudinal barriers with different lateral stiffness and contain and redirect impacting vehicles without any contact with the rigid sections of the system. Recently, a full-scale crash test was performed on a vertical flared back concrete bridge rail-to-guardrail transition design to evaluate its compliance with the NCHRP Report 350 test level 3 requirements. Due to vehicle rollover the design failed to meet the requirements. To gain an insight about the crash test details, a finite element simulation study was performed. Accuracy of the simulation was verified using qualitative and quantitative comparisons. Based on in-depth examination of crash test and simulation recordings, W-beam height of 685 mm was determined to be the main cause for vehicle rollover. In the light of this finding, the current transition model was modified to have 810 mm top rail height. Subsequent simulation results predict that the improved model performs much better in containing and redirecting the impacting vehicle in a stable manner. No wheel snagging was observed due to increased rail height. The overall performance of the transition design was so good that consideration is given to testing it to next level of testing, test level 4. Therefore, a follow up finite element simulation study is recommended.