Bending moment and axial compression interaction of high capacity hybrid fabricated members

Along with proposing any innovative structural element for design purposes it is necessary to understand its behaviour under combined structural actions. This paper includes experimental, numerical and analytical investigations on an innovative type of hybrid fabricated section consisting of high strength tubes and mild steel plates under the effect of axial compression and bending moment interaction. As a special case of interactive condition, pure bending performance of the hybrid fabricated member is examined with focus on the local failure mechanisms and analytical expressions are proposed to predict the moment resisting capacities. Furthermore, compression-bending interaction curves are obtained from plastic analysis of hybrid hollow sections and compared to relevant standard formulations. The compression-bending curves obtained for various ratios of tube cross-section and strength to that of plate show that a linear interaction formula is applicable to predicting the plastic interaction behaviour of sections with high ratios while sections with lower ratios are closely predicted by a bilinear interaction formula. This paper also includes beam-column tests accommodating combined effects of compression, bending and also shear. Employing the developed and validated finite element model, a parametric study is conducted on the effect of section geometry and material on the axial-lateral interaction of beam-columns. Referring to the member interaction results, reaching an optimum interactive performance stands on the design of both geometry and material of plate and tube elements.