| 種別 | paper |
| 主題 | Nonlinear Finite Element Analysis for Shear Behavior of Reinforced Concrete Beams Based on Fracture Mechanics |
| 副題 | |
| 筆頭著者 | Nasra ZAREEN（Department of Civil Engineering, Nagoya University） |
| 連名者1 | Junichiro NIWA（Department of Civil Engineering, Nagoya University） |
| 連名者2 | |
| 連名者3 | |
| 連名者4 | |
| 連名者5 | |
| キーワード | |
| 巻 | 15 |
| 号 | 2 |
| 先頭ページ | 1273 |
| 末尾ページ | 1278 |
| 年度 | 1993 |
| 要旨 | INTRODUCTION The phenomenon of shear behavior of reinforced concrete members has been stud-ied by many researchers over the years, but because of its complexity, there is still no universal theoretical solution which can accurately predict this behavior. The shear ca-pacity and the behavior of members are affected by numerous factors, such as size, crack pattern, ratio of shear span to effective depth,the compressive strength of concrete,etc.Sheal failures generally are sudden and catastrophic,therefore,there is a strong incentive to predict shear behavior more accurately than is possible now.There have been numerous experimental and analytical studies over the years that have indicated that the traditional approach utilizing ACI whereby a constant value of sheal value capacity,Vc,is computed for any size member,may not be keeping with the actual behavior exhibited.Shear equations considering the size effect are proposed for design by the JSCE,and CEB,respectively.Recently the application of fracture mechanics to the shear problem has shown great promise.In all of these alternative approaches,the idea is to analytically capture the behavior and failure of members under shearing forces and then to provide the designer with a simplified approach that can be readily used in the design office.The objectives of this study are to numerically investigate the behavior of rein-forced concrete beam without shear reinforcement.The shear capacity of geometrically similar reinforced concrete beam is calculated.The cracking of concrete is the major topic addressed.This study utilizes finite element analysis together with the fictitious crack modeling of identified diagonal tension crack.Firstly the application of fracture mechanics in the form of fictitious crack model to the shear problem is executed,and then the results predicted in this analysis are compared with those predicted through JSCE and CEB equations.The Fictitious Crack Model with nonlinear rod elements is used to predict the formation of cracks.In this model,the location and orientation of a diagonal crack are predefined,and the crack zones are presented by crack planes,whose material properties are associated with Mode I fracture energy.Accordingly,the shear model to be investigated consists of linear elastic finite element models with nonlinear rod elements joining one side to the other across the crack plane. CONCLUSION From this study we conclude that the behavior of reinforced concrete beam without shear reinforcement is much affected by the inclination and the location of the diagonal crack,ck where the crack intersects the bottom of the beam.It can be observed that the nominal shear strength is decreased as we increased in the inclination.Similarly the nominal shear strength is also affected by the location of crack.We observed that as the location is going away from the support,the value of nominal shear strength is decreased.It can be observed that there is indeed a size effect that can be analytically shown to exist when investigated using a finite element technique.Shear capacity predicted by the finite element method shows good agreement with the JSCE and CEB shear equations.All three showed that the behavior of reinforced concrete beam is generally affected by the beam size.The behavior ranges from ductile to brittle if the beam size increases, in the same time the nominal shear strength decreases.The stress distribution for the rod elements showed that the peak resistance does not mean the fracture of all rod elements,because at the peak resistance,all rod elements did not reach the tensile strength of concrete.The neutral axis of the crack plane at peak was nearly at the mid height of the beam but it moved towards the compression zone as the response of the beam entered in the softening region. |
| PDFファイル名 | 015-01-2215.pdf |