Fatigue behavior of steel reinforced resin connectors for fibre-polymer composite bridge decks

Abstract

The need to renovate many European road bridges due to end-of-life conditions, fatigue, corrosion, and increasing traffic loads drives the demand for innovative solutions. The Dutch Ministry of Infrastructure and Water Management, RWS, estimates that 50 bridges in the Netherlands will require renovation annually over the next three decades. Lightweight, fatigue-resistant fiber-polymer composite panels have emerged as a promising solution for deck replacement in steel bridges. However, the adoption of this technology is hindered by the lack of a reliable connection method. This research, conducted at Delft University of Technology in collaboration with RWS, develops and evaluates the novel injected Steel Reinforced Resin (iSRR) connector to enable the use of glass fibre-polymer composite decks, often termed as GFRP. Initial tests demonstrate that the iSRR connector offers superior static, fatigue, and creep performance compared to existing \gls{gfrp}-steel connection technologies. The main objective of this PhD project is to understand the fatigue behavior of iSRR connectors and provide prediction methods for their performance that can be used for efficient design in engineering practice. The research pursues two specific goals: (1) characterizing the fatigue behavior of iSRR connectors under realistic GFRP panel configurations and load conditions, and (2) evaluating the effects of environmental conditions, such as moisture and temperature, on connector performance. The research involves extensive fatigue testing at both material and connector levels, together with finite element analysis. A specialized test set-up is developed in the Stevin 2 laboratory to apply cyclic shear loads, replicating realistic boundary conditions and load transfer. Temperature and moisture tests are also conducted to assess the impact of environmental conditions on the connectors. At the material level, coupon experiments are carried out to evaluate the SRR properties, and detailed finite element models are developed to better understand the mechanical behavior and failure mechanisms of SRR material and iSRR connectors. This dissertation identifies the fatigue mechanisms that lead to degradation in iSRR connectors for GFRP decks on steel girders. It establishes a fatigue detail that characterizes iSRR connectors, enabling the design of reliable connections between GFRP decks and steel girders. Furthermore, it provides a methodology to describe the fatigue degradation of iSRR connectors using a phenomenological model that builds upon existing Continuum Damage Mechanics (CDM) principles. The findings of this research fill a significant knowledge gap in understanding the behavior of iSRR connectors, offering a practical and sustainable solution for the upcoming bridge renovations in engineering practice. This project bridges theoretical understanding and practical application, aiming to enhance the performance and longevity of GFRP-steel bridge systems under growing traffic and environmental challenges.