دانلود رایگان مقاله انگلیسی یک مدل انتشار ترک بهبود یافته برای بتن ساده تحت بار خستگی - نشریه الزویر

ABSTRACT

Fatigue crack growth phenomenon in concrete is complex in nature and is characterised by various parameters. Important crack growth characterizing parameters must be considered in the analysis for accurate crack propagation and fatigue life prediction. In the present work, an analytical formulation has been developed to predict the propagation of crack in plain concrete members subjected to repetitive nature of loading. Dimensional analysis approach for fatigue crack growth problems has been adopted in conjunction with the theory of intermediate asymptotic for the development of the proposed model. The model has been derived considering the effect of critical energy dissipation in fatigue called fatigue fracture energy which can capture the observed size effect in concrete fatigue. Other important crack growth characterizing parameters considered in the present formulation are, change in energy release rate, maximum energy release rate, initial crack length, tensile strength, and ratio of maximum aggregate size to characteristic size of the structure. Further, the influence of fracture process zone has been incorporated in the proposed formulation through the loading parameter. The developed closed form expression has been calibrated with the available experimental results. The applicability of the mathematical model has been verified using the existing experimental results following both deterministic and statistical approach. The dependence of various governing parameters on fatigue life has been demonstrated through sensitivity study.

9. Conclusions

In this study, a mathematical model has been derived for the prediction of crack growth under the action of fatigue loading. This has been calibrated and validated with the available experimental results in the literature to demonstrate its applicability in plain concrete members. The analytical formulation considers important parameters namely, critical energy dissipation in fatigue called fatigue fracture energy ( ) UC and the ratio of maximum aggregate size to structural size along with the other conventional crack growth characterizing parameters. According to Le et al. [15] and Kirane and Bazant [17], the parameter critical energy dissipation defined for cyclic loading governs the fatigue crack propagation behaviour and different from critical energy dissipation for the monotonic case Gf . Critical energy in fatigue has been evaluated for geometrically similar beams of different sizes and is incorporated in the proposed model in non-dimensional form. Further, both deterministic and statistical analysis have been followed to verify the performance of the developed model. The results of crack propagation predicted by the model have been compared with the existing experimental results and are observed to be in good agreement. The influence of each parameter incorporated in the developed model namely, the structural size, fatigue fracture energy, crack length, change in energy release rate, maximum size of the aggregate and tensile strength on fatigue life has been studied through sensitivity analysis. Structural size is found to be the most sensitive parameter to the fatigue life of concrete structures followed by the energy release rate corresponding to maximum load.