Reserve of strength in reinforced concrete frames : analysis of arching action

Compressive membrane (arching) action increases both the capacity and stiffness of longitudinally-restrained reinforced concrete elements; however, contribution of arching action in the loading capacity of reinforced concrete beams within framed structures has not been investigated. In this study, the formulation of a non-linear 1D finite element model is briefly explained and then verified against available experimental data. The developed formulation and analytical tool are employed to undertake a parametric study and effects of compressive strength of concrete, longitudinal reinforcing ratio, stiffness of end supports and number of spans on the ultimate capacity of beams within different types of reinforced concrete assemblages is investigated. For the analysed 2D sub-assemblies, the capacity of the beams calculated from plastic hinge analysis (according to AS3600-2009) is more than 15% below the capacity obtained from non-linear 1D finite element model and this is partially attributed to enhancing effect of arching action which cannot be captured by the model adopted in Australian standard AS3600-2009.