A NOVEL, STRAIN LIMITED, UNI- & BIAXIAL DESIGN METHOD FOR CONCRETE ENCASED STEEL COMPOSITE COLUMNS WITH NORMAL AND HIGH STRENGTH STEEL AND CONCRETE

In this study, a novel design method for concrete encased steel sections hav- ing normal and high strength concrete and steel is presented. The proposed method develops around strain limitation principle as opposed to plastic section assumption. It extends current Eurocode 4’s simplified method’s material strength limitations to C90/105 for concrete and S550 for steel, proposes a new equation for equivalent second order flexural stiffness to calculate internal bending moments considering an initial bow imperfection value of L/400. Proposed design method enables to conservatively convert a fully plastic interaction diagram to a strain limited one depending on mate- rial resistances on the column. Finally, an analytical equation is presented to develop biaxial interaction surfaces from interaction curves about principal axes. The proposed equation allows for accurate resistance calculation under biaxial bending and economic design solutions.