Zum Verbundverhalten ausbetonierter Hohlprofilstützen mit massivem Stahlkern unter erhöhten Temperaturen

Investigations on the composite behaviour of concrete-filled tubular columns with massive steel core at high temperatures. This paper deals with experimental investigations concerning the composite behaviour of concrete-filled tubular columns with embedded massive steel core. As the inner profile provides the main load-bearing capacity, the load introduction and transfer is of particular interest for the structural detailing of such columns. It is desirable to transfer part of the load via composite action between steel and concrete instead of applying mechanical shear connectors. Due to a lack of experimental data, currently, no specific design regulations regarding the shear strength are available – neither for room temperature nor fire design. The presented investigations provide a basis for design recommendations on reliable shear stresses. Three series of push-out tests at room temperature and high temperatures are analysed in terms of ultimate shear strength, bond strength and shear strength-displacement-curve shape. The test parameters involve the steel core diameter and concrete cover. On the one hand, the test data reveal higher bond strength at room temperature conditions than observed for other composite column types. On the other hand, a distinctive reduction in both ultimate shear and bond strength for high temperatures was observed. Thereby, the thermal elongation has a mayor influence on the resulting composite behaviour. These effects need to be considered in the design for fire situations.