Adhesive bonded tubular cast steel - steel joints in framework structures

Today hollow and tubular sections are used as structural members in buildings and bridges as well as in crane and wind energy plant constructions. To develop design guidelines for welded hollow section nodes under static and fatigue loads numerous research projects have been carried out in the past decades. Since fatigue cracks usually initiate from the weld root, higher safety factors are required during the design process such as a classification in low FAT classes.
In the research project presented an adhesively bonded joint for steel tubes and cast steel components is developed and investigated. In a first step constraints as well as mechanical and thermal stresses in the field of steel constructions were analyzed and requirements for the bonded connections were derived. It was found that production and manufacturing tolerances are a central issue, as thick film bonding and precise manufacturing processes are required.
Surface analytics and adhesion tests showed sufficient bond strength to corundum blasted cast steel surfaces. On the basis of bulk and lap shear test, two adhesive fulfilling the previously defined requirements have been identified and characterized. ... mehrFor the manufacturing of the test specimens using the injection method, a semi-automated joining device has been developed and tested. This device combines the processes joining, fixing and injection of adhesive. Filling experiments showed a filling free of air bubbles in the gap of the joint.
To investigate the durability of the adhesive bonded joint quasi-static load tests were performed on the bonded tube samples under various external influences. Fatigue tests on bonded tube joints showed the load bearing capacity of the adhesively bonded joint for dynamic loading. Furthermore, the adhesives were tested with regard to their resistance to creep loading. The load carrying capacities of bonded tube specimens with variation of tube cross section, adhesives layer thickness, overlap length and with defined imperfections were determined in experimental investigations. To optimize the geometry of the adhesively bonded joint numerical studies were performed to demonstrate the significant reduction of stress peaks resulting from the enlargement of the thickness at the ends of the adhesive layer.
Finally, the knowledge gained in this research project was applied to manufacturing and testing of full scale components. The results of this full scale tests demonstrate, that based on results of this research project adhesively bonded joints between cast steel and steel tubes can be manufactured reliable and with reproducible load bearing capacity.