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.

Due to the low weight and excellent durability of composite materials, Fibre Reinforced Polymer (FRP) decks mounted on steel superstructures are becoming all the more 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 validated by Finite Element Analyses (FEA). Based on the obtained results, the novel injected steel-reinforced resin (iSRR) connector developed at TU Delft shows promising potential in hybrid steel-FRP bridges where good fatigue endurance of the connection and local loads in FRP panel, are required.

As many bridges are reaching the end of their service life, researchers are searching for new solutions to extend the lifespan of those bridges. Fibre reinforce polymers (FRP) could be possible a solution for bridges with deck problems. Lightweight FRP decks can be installed quickly via bolted connectors on steel substructure. In general, shear force in the connector is not taken into account during the design of FRP decks because slip behaviour and interaction with steel substructure is unknown. This research connects to research at TU Delft on non-slip shear connectors for FRP decks. Aim of this paper is to quantify shear forces in bolted connectors due to traffic and temperature loads. The direction of webs, fibres in panel facings and the expansion coefficient of resin has been investigated to determine the influence of the FRP deck on the shear force in the connectors. To investigate the results of traffic loading and temperature loading on real bridges, a database of bridges in the Netherlands has been used. Results from the analyses offer an indication of the influence of the laminates on the shear force in the connectors and show shear force ranges that can occur in existing bridges.

Due to constantly increasing traffic loads and ageing infrastructure, innovative materials for implementation in renovation and new bridge construction projects are gaining attention. One such innovation is hybrid structures consisting of Glass Fibre-Reinforced Polymer (GFRP) composite decks connected to a steel girder(s) superstructure. By combining the stiffness provided by steel members with the superior fatigue endurance and strength to weight ratio of FRP, the properties of both materials can be efficiently exploited. The main restriction to the implementation of hybrid steel-FRP structures lies in the lack of knowledge and efficient technical solutions for the connection between the two materials. Adhesively bonded and grouted connections have been identified as possible connection systems, whereas limited research has been performed on bolted connections. To address this research gap, this paper discusses an experimental investigation into the performance of two types of slip-resistant bolted connectors, namely conventional resin injected bolts and a novel connector system developed at TU Delft comprising of a bolted connector injected with steel reinforced resin (iSRR). Connectors’ performance is evaluated by means of long-term (sustained and cyclic) and short-term experiments with shear load. A single-lap shear joint configuration is used to compare performance of the two connector types. A vacuum infused GFRP multi-directional laminated plate, 20 mm thick, is connected to steel plates by means of M20 bolts. Results indicate comparable stiffness, resistance and ductility of the two connector types in short-term experiments. Superior fatigue performance of iSRR connector is found with 100 times more fully reversed load cycles that are needed to reach the same failure criterion as the conventional injected bolts.

As traffic loads are ever increasing and bridge infrastructure is ageing, existing materials and connection methods used in renovation and new construction projects are reaching their limits. New materials, such as Fibre-Reinforced Polymer (FRP) in the form of hollow decks can be a competitive solution due to good resistance to fatigue and corrosion. By combining the stiffness provided by steel main and secondary girders with lightweight FRP decks, the properties of both materials can be efficiently utilised. However, the main restriction to the implementation of hybrid steel-FRP structures lies in a lack of knowledge regarding the level of interaction as well as efficient and durable connection solutions of FRP decks and steel girders. Adhesively bonded and grouted connections have been identified as possible connection systems, whereas limited research has been performed on bolted connections. This paper focuses on blind-bolted shear connectors. Connector performance is evaluated experimentally by means of short-term (static) experiments to determine shear resistance and long-term experiments with sustained (creep) and cyclic (fatigue) loading. A vacuum infused GFRP multi-directional laminated plate, 20 mm thick, is connected to steel plates by means of M20 blind-bolts. Static resistance, fatigue and creep behaviour of blind-bolted connectors, as a bearing type, are compared to results of a parallel experimental campaign conducted on slip-resistant injected connectors. A comparable static resistance and ductility is found. However, fatigue endurance is much lower compared to slip-resistant connectors. Therefore, due to low fatigue endurance, low initial stiffness and initial slip, the use of blind-bolted connectors is limited to applications where hybrid interaction and fatigue endurance is not required.