INVESTIGATIONTHE STRESS-STRAIN STATE OFTHE BENT ELEMENTS TAKING INTO ACCOUNT TECHNOLOGICAL DEFECTSWITHPOLARIZATION-OPTICAL METHOD

Abstract

The elements of reinforced concrete (prefabricated and monolithic) are actively used in modern construction of buildings and structures that is why the reducing of the costs of their production and the reducing of their cost is of great national economic significance. For the rational reinforced concrete constructions and their structures design it is necessary to improve calculation method, that entails more detailed study of concrete properties and reinforced concrete constructions’ work under load. Thus, one of the concrete’s features that has been identified recently, is its damage by technological cracks. The character of distribution pattern stresses, deformations and displacements in the bent elements taking into account the technological defects with polarization-optical (photoelasticity) method is reviewed in the article. The possibility of the residual strain evaluation in the limpid models by means of the given method is demonstrated. According to the experiment one can approve that over loaded or loaded areas of the test sample are identified by the polarizationoptical method. An experimental study of the stress-strain state near the vicinity of the crack tip in the limpid models with the technological crack is carried out on the basis of the polarization-optical method. It has been established that the presence of technological cracks in structures largely determines the work of materials, their deformation, cracking and fracture. The stress field near the vicinity of the crack tip is represented by an asymptotic M.Uilyams’es expansion. The samples’ models of epoxy resin were transferred to the concrete samples with the purpose of experimental and theoretical grounding of the impact of technological defects on the bearing capacity of reinforced concrete structures, their work, deformability, the formation character and the cracks development in them. It is experimentally proved that all the cracks in the prototypes were developed by the technological defect that makes it possible to forecast their development. The depth of the technological crack was measured in the concrete samples by means of the nondestructive testing method. It was found that the methods of non-destructive testing without changing the quality, parameters and characteristics of the product, allow to detect the hidden defects, or reveal such features that entail the potentially products’ unreliability by the indirect secondary features. The graphics of the crack depth dependence under the action of small cycled load were built on the basis of experimental data.