Calculation Of Crack Width Of Flexural Reinforced Concrete Members Under Short-term Loadings

Cracks occur inevitably in flexural reinforced concrete members which are use commonly engineering structures. The crack width of the reinforced concrete member must be controlled since the cracks affect the durability of concrete structures. Today, there is still no consistent aspects on mechanism of cracks, calculation of crack width and influence factors of crack. This paper focuses on the calculation of short-term crack width of flexural reinforced concrete members.First of all, the mechanism of cracks and calculation of crack width in codes around the world are summarized, and the approaches to calculate the bond stress and the uneven coefficient of tensile reinforcement strain are also summarized and analyzed.Secondly, the relationship among reinforcement stress, concrete stress and bond stress based on the equilibrium condition of the sections between the cracks is established by introducing the relationship between the bond and slip suggested by the CEB-FIP MC1990, and then a crack model in flexural members in which plane cross-section assumption is not applied for any sections between cracks is established. An analytical solution of reinforcement stress and bond stress in tensile zone in any sections between cracks is deduced in the view of the fact that bond slip relation changes with the change of bond stress (associated with the applied loads), then the formulae to calculate short-term crack width, bond stress and uneven coefficient of tensile reinforcement strain are obtained.Thirdly, a comparison between the presented formulae and the provided formulae suggested by codes and researchers on calculation of crack width, bond stress and uneven coefficient of tensile reinforcement strain is fulfilled, and the discussion on the construction character and influence factors in above formulae is finished.Finally, a comparison between the theoretical values between those obtained based the presented formulae in this paper and those obtained based on the formulae provided in codes is achieved, also the experimental results are compared with values, showing that the theoretical values based on presented formulae in this paper bear specific accuracy. A new approach to calculate short-term crack in Flexural reinforced concrete members under short-term loadings is provided.