Mechanical behaviors and effects of reinforced concrete members under different loadings

Based on the element of beam with hinges in OpenSees, the linear elastic shear restoring force model, defined on the level of section, was adopted. The zero length section element with bond-slip material was introduced to simulate the bond-slip at the end of element. Meanwhile, the geometric nonlinearity caused by P-D effect which is additional overturning moment resulted from the vertical load was taken into consideration. The Mohle-Kunnath constitutive model which is able to accurately simulate the low-cycle fatigue damage and cracking phenomenon of steel was used to analyse the mechanical properties of components under different loading histories. The mechanical properties of components were studied under monotonic loading, asymmetric cyclic loading and symmetric cyclic loading. Under different cycle number, the mechanical properties of components with symmetric and asymmetric loading and the characteristics of steel strain varied with displacement loading history were further analysed. The results indicate that under cyclic loading conditions, stiffness degradation and strength degradation phenomena on colums of reinforced concrete frame are obvious. The damage of components gradually exacerbates with the decrease of shear span ratio and the increase of shaft pressure ratio, while the damage is more clear with the increase of cycle number. The strain of reinforced materials varies significantly with the increase of cycle number. The stiffness degradation and strength degradation become more obvious with the increase of axial compression ratio and the decrease of shear span ratio, and the strain of steel also increases to some extent.