Nonlinear Sectional Analysis Of RC Beams With The Effect Of Shear

The effect of shear on the nonlinear sectional analysis is often ignored when the shear span ratio is large, it is believed to be appropriate as it brings little error. But if the shear span ratio is relatively small, the effect of shear can not be ignored in this way, hence a modeling method that can take both flexure and shear into account is strongly desirable. In this paper, the modified compression field theory (MCFT) is implemented to carry out the nonlinear sectional analysis of RC beams. An effective analysis method is adopted as a result. This method can be used to analyze accurately the complete load-deformation response of RC beams loaded in combined shear, moment, and axial load. Based on the theory above, the program on nonlinear sectional analysis of RC beams is developed by FORTRAN in this paper. Then it was used to simulate the curve of RC beams with shear and compared with experimental results. By comparing the analytical curves with the measured ones of simple-span beams under monolithic loading and the skeletons of the measured hysteretic curves of beams under cyclic loading, it is found that the analytical and the measured curves agrees well and thereby reliability of the program is verified. At the same time,the program is also extended to analyze RC column sections. By comparing the analytical curves with the measured ones of columns loaded with pure moment for low axial compression ratio and the skeletons of the measured hysteretic curves of columns under cyclic loading for high axial compression ratio, it is found that analytical and measured curves do not agree so well for high axial compression ratio as for low axial compression ratio. It seems that the main reason is that in MCFT, the stress-strain relationship of concrete in compression does not contain the enhancement of strength and ductility due to the stirrups. Therefore, in this paper, several concrete compression models have been compared, and finally the Mander model is adopted and the soften effect of stress and strain is considered. In this way, the analytical curves and the measured curves of columns agree well for columns with high axial compression ratio.In addition, the program is also used to analyze the curves, M-V interactive curves and curves of beams with different shear span ratio. By comparing the analytical curves for different shear span ratio, it is found that the effect of shear on the nonlinear of RC beam can be ignored if shear span ratio is larger then 6, on the other hand, if shear span ratio is not larger then 6, the effect of shear is significant and it must be considered.