|主題||Shear Analysis of Reinforced Concrete Beams by Fictitious Crack Model Using Orthogonal Rod Elements|
|筆頭著者||Nasra Zareen（Graduate School of Nagoya University）|
|連名者1||Junichiro Niwa（Nagoya University）|
The performance of shear analysis for reinforced concrete members is an important area of structural engineering research. Shear failure of concrete structures can be sudden, without warning, and can lead to catastrophic results. To capture the effects of shear has followed generally an empirically-based approach as considered in codes.
This paper will present the research work performed by the authors into the application of fracture mechanics, in conjunction with finite element analysis, to shear behavior and will illustrate the size effects and its consequences in shear design. Numerous experimental and analytical studies have indicated that the traditional approach utilizing ACI, whereby a constant value of shear capacity, Vc, is computed for any size member, may not be keeping with the actual behavior exhibited. Many studies have shown that the shear capacity of reinforced concrete beams without stirrups is significantly influenced by the effect of member size. Recognizing this size effect, the JSCE in Japan and CEB in Europe incorporated this effect in shear design equations and obtained reasonable predictions. Therefore, the shear strength obtained from the JSCE and CEB will be used for comparisons and to verify the numerical results from the finite element analysis.
In this paper the application of fracture mechanics in the form of fictitious crack model to the shear problem is executed, In this model orthogonal rod elements are provided to predict the shear behavior and formation of cracks. Here some improvements in the model have been considered.
Shear analysis can be improved using orthogonal rod elements to prevent the slip along the crack path. From this study, it was concluded that the shear behavior of reinforced concrete beam without reinforcement is much affected by the inclination and location of the diagonal crack. It is observed that by increasing the value of inclination angle of crack, shear strength starts decreasing and gives the minimum value of shear capacity. So we fixed the angle for the diagonal crack at this minimum value. Similarly the nominal shear strength is also affected by the location of crack. We obtained the minimum value of the shear strength at the distance, d from the support, so we fixed this value for our analysis.
The shear capacity predicted by the finite element analysis shows good agreements with tIle JSCE and CEB shear equations. All three showed that the shear strength of reinforced concrete beams is significantly affected by the beam size.