| 種別 | paper |
| 主題 | Fundamental Study on the Application of Fracture Mechanics to the Crack Propagation Analysis of Thermal Stress Fields of Concrete |
| 副題 | |
| 筆頭著者 | Denzil Lokuliyana （Nagoya University） |
| 連名者1 | Tada-aki Tanabe （Nagoya University） |
| 連名者2 | |
| 連名者3 | |
| 連名者4 | |
| 連名者5 | |
| キーワード | |
| 巻 | 11 |
| 号 | 2 |
| 先頭ページ | 661 |
| 末尾ページ | 666 |
| 年度 | 1989 |
| 要旨 | INTRODUCTION In the case of mass concrete structures,there happen to be generated major cracks during even construction,and sometimes at much later age of concrete ( i.e. 10 years and 20 years after the completion of construction ).These cracks are mainly due to thermal heat which is produced by hydration of fresh concrete. In the design of these type of structures thermal cracking is taken into account in predicting both the ultimate load capacity and behavior in service conditions since width,spacing and length of cracks have major influence on structural performance. Most of the exsisting design codes are based on tensile strength approach and not on fracture mechanics. But it is understood that the structures should be designed according to fracture mechanics when fracture is considered. However,fracture obviously cannot form if the tensile strength (peak stress) is not reached. So the strength criterion is a necessary condition of fracture,but not a sufficient one. For the fracture to form,the maximum principal stress must also reduce to zero and for this to happen the energy characterizing the complete stress-strain curve must be supplied. Thus the strength criterion indicates only whether the fracture can initiates,while the energy criterion indicates whether the fracture can actually form or propagate- In this study cracking is modeled in continuous or smeared manner,and fracture is treated as a propagation of smeared crack band through concrete. With this fundamental idea,the crack propagation analysis is done and its applications to real structures were discussed. CONCLUSION The crack propagation in mass concrete structures was analyzed using the energy criterion of fracture and smeared crack band concept. It is known that the dissipated energy by the cracking can be calculated in two ways as follows. a.Considering the total energy difference of the structure before and after the crack advanced. b.Taking the summation of the strain energy released by cracking and the work done by the traction on the cracked surface when it is released to zero. The first method of calculating energy however,can not be applied to a structure with initial stresses due to hydration heat of cement. Hence the detailed derivation of formula for the second method is performed. With these preparations,a simply supported plain concrete beam was analyzed and the path obtained was reasonable. The two-dimensional analysis done for thermal crack propagation in a mass concrete structure has given reasonable results. A further extension can be done to analyze massive concrete structures three-dimensionally. |
| PDFファイル名 | 011-01-2111.pdf |