Study On The Ductility Of Reinforced Concrete Flexural Member

Reinforced concrete flexural member are widely used in civil building design, and the plastic design is of special importance in reinforced concrete structures design, especially in high-rise buildings and large industrial plants. In general,the safety of reinforced concrete flexural member depends not only on the bearing capacity of components, but also depends on the plastic deformation performance largely, namely ductility. Ductility in this paper is divided into three parts.(1) The method for calculating the ductility coefficient and plastic hinge rotation capacity of the reinforced concrete flexural members were investigated, and the calculation formulas for determining the depth of compression zone when tension steel yields and concrete strain reached ultimate compressive strain or tension steel strain reached ultimate tensile strain were given; the plastic rotation capacities of members in the range of minimum and maximum reinforcement ratios of longitudinal steel specified in the codes of Chinese, American and Europe were compared; the relationship between the coefficient of plastic moment redistribution and relative depth of compression zone was studied. Research results show that the member hasn't any plastic deformation capacity in the case of maximum reinforcement ratio as specified in Chinese codes, for this corresponded to the balanced failure, and the deformation capacity is less even not the case of maximum reinforcement ratio.(2) 27 reinforced concrete beams were tested. Studies show that increasing the reinforcement ratio will reduce the plastic rotation capacity; increasing section depth will reduce the plastic rotation capacity; the constraint where load apply will increase the plastic rotation capacity.(3) Deformation capacity calculation of reinforced concrete beams considering shear effect were studied. CFT were used in shear tension zone. The results show that plastic deformation considering shear effect is larger than without considering, which is due to the additional tension from inclined cracks induced by shear, leading to steel yield early and increasing plastic hinge length.