Reinforced Concrete Flexural Members To Change The Calculation Of Crack Width

At present, the general calculation theory of crack width is just for the short-term, and long-term crack width of reinforced concrete members is only roughly approximated by multiplying the expansion coefficients. In this way, calculation accuracy cannot be guaranteed. This paper focuses on the prediction of the time-dependent crack width of bended concrete members.First of all, the theories and methods for calculating crack width in codes of domestic and aboard have been summarized,then an analytical model for short-term crack width has been established based on mechanical model,and the formulae of short-term crack width along with the neutral axis distribution functions have been derived.Secondly, based on Age-adjusted Effective Modulus Method(AEMM) and the internal force equilibrium and the compatibility of deformation in section, a Simple Cubic Equation with the variables of compression zone height has been derived. By solving stress and strain of intermediate cross-section between cracks, stress distribution function of reinforcement, curvature formula as well as the neutral axis distribution function are derived.Thirdly, based on the mechanism of the concrete stress relaxation, AEMM is applied to time-dependent shear of concrete due to creep and shrinkage. The strain equation in tension zone of the concrete has been established at the same time, and the strain in tension zone of the concrete is obtained. The formulae for calculating the long-term crack width is also derived by considering the effect of creep of concrete in compression zone,tiem-dependent flexural neutral axis position and stress relaxation in tension zones of concrete, etc. Relevant parameters have been revised by introducing experimental result. It can be used for calculating crack width of flexural reinforced concrete members.Finally, time-dependent crack width of reinforced concrete flexural members has been used to calculate the tested specimens fulfilled by the Nanjing Institute of Technology (Now Southeastern University). C omparison between experiment results and theoretical values shows that the presented method holds appreciable accuracy, The established approach in this paper can easily consider the effect of shrinkage and creep and the arrangement of the reinforcement to long-term crack width which bears wider applicability than the formula provide in the existing codes.