مقاله انگلیسی قالب بندی سطح و نمایان شدن ترک های نرمال
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Abstract
The article is devoted to the study of the main regularities of the normal cracks level formation in reinforced concrete elements and structures. A critical analysis of the latest publications related to the theme of these studies has been carried out. The main characteristics of prototypes, the conditions for their manufacture and storage are given. Based on the experimental studies results, it has been established that in the real design of bending reinforced concrete elements, when calculating their crack resistance, one can restrict oneself to only two levels of normal cracking. A statistical comparison of the calculation results using the author’s and other methods with experimental data confirmed the effectiveness of those calculation methods in which the crack formation step is directly related to the basic laws and parameters of reinforcement to concrete adhesion.
1. Introduction
In general, it is known that the processes of cracks formation and development, including normal ones, significantly affect the operational properties of reinforced concrete elements and structures. Therefore, it is quite obvious that the issues of their crack resistance will always remain one of the main issues in the reinforced concrete deformation theory. And with the introduction of deformation methods for calculating reinforced concrete elements and structures into modern design practice, they acquire even greater weight and relevance. Indeed, using deformation models, it becomes possible to more accurately reproduce the real stress-strain state of reinforced concrete elements and structures in their deformation process.
At the same time, the results of experimental studies indicate that the cracks formation and development in reinforced concrete elements is multilevel and leads to a gradual disruption of the reinforcement with tensioned concrete interaction. Under such circumstances, it would be advisable to build a general methodology for calculating the normal cracks formation and opening on the basis of the reinforcement to concrete adhesion defining laws direct involvement. Otherwise, the calculation of the normal cracks opening width according to the Thomas (1936) hypothesis will continue to remain predominantly declarative. This is due to the fact that it is extremely difficult to perform this calculation from the standpoint of the concrete and reinforcement mutual displacements sequential accumulation. Since the actual dependence of the reinforcement and concrete mutual displacements is very complex and cannot be described by a single function, its direct integration in most cases is practically impossible. However, the calculation of the normal cracks opening width can be significantly simplified if the cracks step and their opening width are directly related to the reinforcement to concrete adhesion forces and take into account that the cracking process is multilevel. Therefore, the possibility and expediency of such an approach to the calculation of the main parameters of reinforced concrete elements and structures crack resistance requires special studies.