The durability and fatigue performance of bridge components are critical factors in their long-term viability. This study investigates the experimental results of fatigue tests on injected Steel Reinforced Resin (iSRR) connectors, a promising connection technology for Glass Fibre Polymer (GFRP) composite decks in bridge construction. This research expands on previous work by examining the impact of environmental exposure on the cyclic performance of iSRR connectors. A total of twelve iSRR connectors were subjected to fatigue testing. Two connectors were exposed to outdoor conditions for one year, two connectors were fully submerged in water, and four connectors served as reference specimens without aging. The experiments aimed to evaluate the fatigue resistance and performance degradation of the connectors under varying environmental conditions. Additionally, the cyclic loading was conducted with varying R-ratios to understand the influence of load ratio on the fatigue life of the connectors. The specimens were loaded until failure, and a detailed analysis of the failure modes was conducted to determine the impact of environmental exposure and the load ratio on the failure characteristics of the connectors. The findings provide insights into the effects of environmental exposure on the fatigue performance of iSRR connectors and contribute to the development of more durable and reliable connection technologies for GFRP composite decks.

The durability of bridge connections is critical for the long-term performance of bridge systems with GFRP composite decks. This study investigates the shear fatigue behaviour of injected Steel Reinforced Resin (iSRR) connectors embedded in FRP composite decks, through a series of fatigue tests performed under different load ratios and exposure conditions. Twenty-four connectors are examined: twelve unaged reference specimens, eight specimens tested under varying R ratios, two connectors with deck parts submerged in water and two subjected to outdoor aging, both for a duration of one year. The results show that, despite the composite nature of the connector, the load ratio and mean load level have minimal influence on fatigue life. Instead, fatigue performance in the high-cycle regime is governed primarily by the applied load range. A unified F-N curve including all R ratios was developed, demonstrating the consistency of this trend and enabling fatigue-life prediction across different loading conditions. Environmental exposure led to measurable stiffness degradation but did not significantly alter fatigue life. These findings highlight the robustness of the iSRR connector and support its application in durable GFRP-steel hybrid bridge systems.

The integration of Glass Fibre-Polymer composite (a.k.a. GFRP) deck panels in bridge infrastructure is hindered by lacking a robust connection technology. A promising bolted connection, utilising injected steel reinforced resin (iSRR) material, has demonstrated lower creep deformation and sustained significantly more shear load cycles than conventional bolts. Nonetheless, the production and testing conditions in all prior experimental campaigns followed idealized lab set-ups. This study bridges the gap between laboratory conditions and the challenges arising during connector's fabrication under representative conditions, coupled with cyclic load testing at room and elevated temperatures. The iSRR connectors design is modified and tested in actual composite sandwich web core panels, revealing excellent fatigue performance. The statistical analysis yielded F-N curves for shear performance of the connectors that can be used in the design. The slopes of the F-N curves of − 6.6 and − 5.8 were found at room and elevated temperatures, respectively. Finally, with post-cyclic static tests displaying significant connectors’ residual stiffness, resistance, and ductility, the research provides a step forward in enabling the integration of glass fibre composite deck in infrastructure.

Resins are essential structural materials predominantly used in load-bearing connections such as adhesively bonded joints and resin-injected bolted connections. In an effort to improve the latter, a new injection material, Steel Reinforced Resin (SRR), has been developed, consisting of spherical steel particles embedded in a resin. SRR's applicability has been explored in injection bolts used in composite steel-to-concrete floor systems and as an injection material in Fibre Reinforced Polymer (FRP) sandwich web-core panels of highway bridges. While the short-term and creep performance of SRR has been researched, its fatigue behaviour remains unexplored. From joint-level cyclic experiments with SRR, it was observed that joint endurance is dominated by SRR's fatigue performance. There is currently no research on the influence of temperature on SRR's mechanical properties and moisture uptake. This paper fills this gap, by investigating the static and fatigue performance of epoxy, unsaturated polyester polyurethane hybrid (UPE + PU), and vinyl ester based SRRs under ambient and elevated temperatures. Water absorption assessments were conducted on the three resins with and without steel particles to evaluate their durability and corrosion resistance. The results show that temperature significantly impacts tensile stiffness, tensile splitting strength, and fatigue life. Epoxy based SRR endured 20 times more tensile splitting stress cycles to failure compared to the UPE + PU resin based SRR at the same stress range. However, after 200 days of water exposure at maximum temperature, the epoxy resin (with and without steel shot) exhibited a weight increase of 4.0% and 0.50% respectively, suggesting that despite its superior fatigue performance, it may not be suitable for SRR applications in high moisture environments. In contrast, UPE + PU resin and its corresponding SRR displayed substantially lower water absorption.

Due to the low weight and excellent durability of composite materials, Fibre Reinforced Polymer (FRP) decks mounted on steel superstructures are becoming increasingly common in engineering practice. Bolted joints are generally used to facilitate connections between an FRP deck and steel girders in road bridges. The connections are subjected to both high magnitude static forces as well as fatigue loading due to overpassing vehicles. With ever increasing traffic on both road and railway bridges, fatigue performance is of critical concern. Bolted FRP joints have been extensively researched in the past under static loading, but less is known about the fatigue and creep behaviour of such joints. Furthermore, little research exists on non-pultruded FRP profiles connected using bolted connections. Therefore, the objective of this research is to investigate connectors’ feasibility by means of static, fatigue and creep experiments on four different types of bolted joints comprising mechanical connectors and injection techniques. The study focuses on application in vacuum infused GFRP panels with integrated webs made of multi-directional laminates) connected to steel bridge superstructures. In addition, experimental results are used to validate Finite Element Analyses (FEA). Based on the obtained results, the novel injected steel-reinforced resin (iSRR) connector shows promising potential in hybrid steel-FRP bridges where good fatigue endurance of the connection, are required.

In response to the sustainability requirements set in the EU Commission´s “Green Deal” towards reduction of the greenhouse gas emissions, it is estimated that the structural design for deconstruction is going to contribute considerably to the sustainable development of the built environment. The demountability of multi-material structural systems basically depends on the shear connectors used in the structural system. This paper focuses on a type of demountable injected shear connector with an injected steel-reinforced resin (iSRR) which consists of spherical steel particles embedded in a resin. Its application to steel-to-concrete and steel-to-Fiber Reinforced Polymer (FRP) decks is presented along with its benefits. In parallel, an overview of the experimental and numerical research on the evaluation of the mechanical properties of the demountable bolted connectors with iSRR is discussed. Last, detailed finite element (FE) models and a parametric study are performed to quantify the confinement level of the SRR material influenced by the oversized hole diameter.