ABSTRACT
ABSTRACT Torsion stiffness of steel tubes connected to concrete remains an issue. Three preliminary experiments, including strip and stud connectors demonstrate the failure mechanisms. A high degree of robustness for torsion exists for strip connectors. From the first loading a composite action of steel and concrete exists. The successive failures are due to exceeding compression of the surrounding concrete, followed by high of pressure in the contact area between both materials and final failure due to yielding of the steel strips as reinforcement of the composite cross-section. For stud connectors failure occurred prematurely due to concrete splitting at the contact area of the stud shaft. This is avoided by normal reinforcement. This type of connection does not show any robustness, since after first modification of the strength mechanism, no further increase of the torsion moment was possible. Another result indicated that strip connectors have but 20% of the stiffness of studs.
