Attaching Steel Bridge Rail Posts Directly to Bridge Decks: Design Procedures,Best Practices,and Case Studies

Abstract

Steel post-and-beam railings which attach directly to bridge decks are beneficial for a variety of reasons, including reduction of dead weight, unrestricted drainage, aesthetics, and rapid installation. However, because of a long-standing convention holding that the use of steel posts without curbs is likely to result in costly deck damage, steel bridge railings are used less frequently than concrete parapets and curbed steel railings. Under NCHRP Project 12-119, this convention was challenged, and an updated methodology for evaluating/designing bridge decks to support steel posts was developed. The method is compatible with both damage-mitigating and damage-permitting design philosophies. Failure of the deck slab is characterized as a trapezoidal yield-line mechanism, which can be adjusted to account for local punching shear damage below the post. To develop the methodology, in this research a physical impact test was performed on an instrumented steel post and bridge deck specimen. A calibrated LS-DYNA model was then developed and used to create a data pool consisting of simulated pushover tests of parametric variations and in-service railing models from which design guidance was extracted. General guidelines and best practices for attaching steel posts to bridge decks, which are consistent with the updated methodology, are presented in this paper alongside general recommendations for selecting appropriate post sizes for a common bridge deck designs.