Hybrid grouted steel connections using adhesively bonded granules in the steel grout interface: Development and validation of an innovative joining technique

This study introduces an innovative hybrid grouted connection method which utilizes organic adhesive with embedded granulates as a bonding agent to connect high strength grout mortar uniformly to smooth steel surfaces. This approach eliminates the need for welding additional shear keys, which are currently used for local form fit. The primary objective is to investigate the general usability of this method, particularly for demanding applications in steel construction. The manufacturing procedure on small-scale specimens is shown by using epoxy-based adhesive tape and paste –like two component epoxies. With help of such small-scale hybrid test specimens, different combinations of grout, adhesive and granulates were tested to qualify the combinations with the highest load-bearing capacity. It could be shown that even when connected to smooth steel surfaces, high loads with a slight scattering could be transferred with help of the adhesive-granulate promoter. Because these types of connections are widely exposed to harsh environmental conditions, further investigations concerning the temperature stability and durability were implemented. Temperature variations within the typical range of offshore structures, namely T = −20 °C as minimum and T = 60 °C as maximum temperature are considered and set into relation to the test results performed at ambient temperature. Temperature variations have a notable effect on load-bearing capacities, with lower temperatures showing a beneficial influence. The results demonstrate the operational capability of the hybrid connections, even at higher temperatures the expected reduction of the load capacity was very modest. Durability has been proven by specimen exposure to artificial seawater and climatic cycling tests produce varying effects. Some samples exhibit an increased load-bearing capacity, indicating further crosslinking of the adhesive, while others show no significant reduction of load-bearing capacity. As fracture patters could verify, both adhesive systems effectively protect against corrosion, as no infiltration of corrosion into the steel-adhesive interface were observed. In conclusion, the hybrid grout connection method, presented in this research offers several advantages over conventional grouting techniques. The ability for high load transfer, temperature stability and durability underline its potential as a reliable alternative for joining steel components in various applications.