Ключевые слова: reinforced concrete

The high-tech and effective method of strengthening reinforced concrete structures with CFRP materials with preliminary modification of the cross-section shape

https://doi.org/10.58224/2618-7183-2024-7-6-7
Аннотация
It is known that the effectiveness of reinforcement with CFRP composite materials of reinforced concrete structures of round or oval sections is significantly higher than rectangular or square ones due to the uneven distribution of internal limiting pressure in the latter. This study is devoted to the study of the effectiveness of a new method of strengthenet based on a preliminary change in the shape of reinforced concrete and concrete columns of square section. The sharp corners of the columns create a concentrating internal limiting stress in the CFRP composite cage, while the amplification system collapses prematurely, and the amplification efficiency is greatly reduced. To comprehensively solve this problem, the authors have manufactured, strengthened and tested a number of reinforced concrete columns with different variants of CFRP composite reinforcement. For the purity of the experiment, reference racks were also made, not reinforced, and reinforced with CFRP composite clips without rounding. All prototypes were made of the same materials, as well as strengthened and tested using the same techniques. The paper describes the features of traditional and modern methods of composite strengthenet of reinforced concrete columns, analyzes the main disadvantages of existing strengthenet methods and, based on this, presents a new strengthenet method that allows more efficient use of composite materials in the transverse direction. The new strengthenet method is described in detail, the main schemes and procedure for performing strengthenet work are presented. The final stage of the work is the main results of an experimental study, where the characteristics of reference samples were compared with similar structures strengthened in the transverse direction with CFRP composite materials. The experimental results show that the proposed amplification method is highly effective. For the best effect, it is proposed that the material used for rounding has higher strength and less deformability compared to concrete columns.
PDF

Cauchy problem for modeling of unsteady mass transfer processes in an unbounded plate by the integral laplace transform method

https://doi.org/10.58224/2618-7183-2024-7-5-4
Аннотация
The article outlines the formulation and solution of the problem of physical and mathematical modeling of non-stationary processes of mass transfer of chemical components of the structure of reinforced concrete enclosing structures under the influence of factors (chemical, biological) of the operating environment. The theory of operational calculus (integral transformations) is used as a mathematical apparatus for jointly solving Cauchy and Laplace problems. To solve the problem and study the processes considered in the article, a dimensionless plate with a dimensionless concentration of aggressive components on its surface was chosen as an idealized model of the enclosing structure. Carbon dioxide, dissolved in the liquid and penetrating with it into the material of the structure through pores and microcracks, was chosen as an aggressive component acting on the enclosing structure. The final solutions of the considered boundary value problems are presented for the case of constant values of the kinetic coefficients of external and internal mass transfer. The results presented in this work can be used in the development of software for predicting the strength characteristics of enclosing structures operating in aggressive environments. Thanks to the obtained solutions to the problems of non-stationary mass transfer processes, using the example of the consequences of carbon dioxide corrosion, it is possible to consider the time period of the life cycle of buildings and structures, the timing of repair work with greater accuracy.
PDF