Buckling resistance of concrete-filled steel circular tube columns composed of high-strength materials

摘要

The paper deals with the problems of the buckling compression of steel-concrete compositerncolumns. The analysis of load-carrying capacity is oriented to the experimental verification and theoreticalrnstudies of the buckling resistance, especially with regards to the usage of high-strength concrete. Within thernframework of this research the following basic steel-concrete columns with different cross-section configurationrnhave been investigated: concrete-filled steel circular tubes with the diameter in the range from 133mmto 168mmrnand thickness from 4mm to 5 mm. The buckling length of investigated columns was 3 m respecting the typicalrnusual length used in building structures, for example. Material of investigated columns has been chosen as follows:rnsteel gradewas either S 235, or S 355; concrete strength classwas in the range from C 20/25 up to C 80/90.Withinrnthe experimental research, steel tubes filled by concrete and steel tubes without concrete subjected to bucklingrncompression force have been tested.A total of 45 test specimens have been verified: so far 27 of them have beenrntested and completely evaluated, another 18 specimens have been tested recently and are evaluated currently.rnBesides influence of high-strength materials (mainly concrete), the theoretical analysis alsowas oriented to actualrnimperfections and their influence on the buckling resistance.Within the experimental investigation, among othersrnthe material tests and their evaluation, as well as the measurement of actual geometrical imperfections, havernbeen performed to verify the theoretical results obtained from theoretical studies.