Fatigue Performance of Orthotropic Steel Decks with FRP Angles: Field Measurement and Numerical Analysis

Abstract

Rib-to-deck joints in orthotropic steel decks (OSDs) are among the most fatigue-prone details of steel bridges. To improve the fatigue performance of existing bridges with OSDs, a strengthening method using externally bonded fiber-reinforced polymer (FRP) angles was proposed and experimentally studied. This study also presents a field investigation of strengthened OSDs with FRP angles. First, on-site strengthening procedures with glass FRP (GFRP) angles were proposed and demonstrated on a long-span suspension bridge. Two-day field strain monitoring indicated that daily equivalent stress ranges (ESR) decreased significantly after strengthening. The strengthening mechanism was further studied through numerical analysis, in which the effective notch stress method and submodel technique were adopted to investigate stress fields of the welded details. The results showed that among the dimensions under investigation, thicker, wider, and longer GFRP angles generally result in better fatigue performance by providing higher additional local stiffness to rib-to-deck joints. Calculation of stress intensity factors at crack tips resulted in similar conclusions to the effective notch stress analysis, and the strengthening effect was found to be more remarkable for deeper cracks.