The influence of the weak axis on the behavior of high strength RC slender columns subjected to biaxial bending

This paper focuses on the behavior of high strength reinforced concrete columns subjected to biaxial bending. Experimental research with 56 high strength columns was carried out to achieve this purpose. The analyzed parameters were: the slenderness, the eccentricity, and the skew angle of the applied load.The coupling of the second order effects in each main direction of bending was analyzed. It has been observed that the behavior of the column was strongly influenced by the flexibility of the weak axis. However, the proposed simplified approaches in ACI-318(05) and EC-2 (2004) do not take it into account.The experimental results have been compared with a numerical simulation and with simplified approaches based on moment magnification factors such as that proposed by ACI-318(05) and by EC-2 (2004). Numerical simulation provided good agreement with displacement-load results and failure loads from the tests. In general, the simplified approaches are conservative in the case of the smaller eccentricities and result unsafe in the case of larger eccentricities.