Aerodynamic Enhancement of Guardrails to Reduce the Drag Force on Long-span Bridge Decks

Abstract In this study, the use of simple attachments to existing guardrail members was investigated to evaluate their potential for reducing the overall drag force on long-span bridge decks. Wind tunnel testing and computational fluid dynamics (CFD) analysis were conducted to reveal the drag force reduction effect with the placement of attachments onto the rear sides of guardrails. A series of case studies of single-rail members and three-layer guardrails was performed to determine the optimal shape. A steel twin-box suspension bridge with a main span of 1545 m was selected as a prototype bridge deck, and the evaluation indicated an overall drag reduction ratio of 11.1% when an optimal attachment was applied. CFD analysis was also conducted to clarify the mechanisms responsible for the drag reduction achieved by the modified guardrails and to address Reynolds number effects. This study demonstrates the importance of optimizing the aerodynamic shape of guardrails and achieving drag force reduction by adding attachments to the rear sides of the guardrails without compromising the crash performance.