EFFECTIVE BENDING STIFFNESS OF HEAVY STEEL-CONCRETE COMPOSITE COLUMNS WITH MULTIPLE ENCASED STEEL PROFILES

Concerning the structural analysis of steel-concrete composite columns, Eurocode 4 foresees only cross-sections with one implemented steel profile and double symmetry. However, an application of composite columns with more than one embedded steel profile can be recognised. The common practice of analysis of such columns uses the simple Euler-Bernoulli beam theory to describe the global behaviour. The performed tests and other available test results in the literature, reveal that the resulting deformations exceed the deformations predicted by the aforementioned analytical model. The presented contribution shows a modified approach to analyse the stiffness of composite columns with multiple encased steel profiles. The novel approach is combining a modified Timoshenko beam theory with embedded Vierendeel truss model for the estimation of the composite member's stiffness. Based on the performed laboratory tests and numerical simulations with the finite element code Abaqus (R), a new method to determine the effective stiffness is proposed. In the result, this modified method leads to the reduced value of the effective stiffness, thus, reduced value of the Euler's critical buckling load.