The question of increasing the reliability and durability of reinforced concrete structures is a priority. One of the ways to increase the strength of concrete is using of dispersed reinforcement. The interest of using of fiber-reinforced concrete in Russia, as well as in Europe, Asia and the USA has increased significantly in recent ten years. The improvement of the physical and mechanical properties of concrete is noted to depend on the reinforcement parameters, such as the volume content of the fiber, the characteristics of the dispersed reinforcement, the structure of the concrete matrix, etc. Authors consider various types of fibers for dispersed concrete reinforcement, specifically polypropylene, polyethylene, nylon, acrylic, polyester, cotton, asbestos, glass, basalt, steel, carbon. Description of the main advantages and disadvantages of each type of fiber is given. Comparative characteristics are presented in terms of density, tensile strength, modulus of elasticity, elongation at fracture of the materials used to manufacture the fiber. The influence of fibers on crack strength of fiber-reinforced concrete under impact loads is studied. Analytical review of existing works found that it is possible to achieve a significant increase of strength of fiber-reinforced concrete in axial compression, tension, tension in bending, shear compared to ordinary heavy concrete.

Relevance. Buckling analysis is important in the design of buildings and structures. It is used in various fields of engineering - mechanical engineering, aircraft and shipbuilding, civil engineering, etc. Until the second half of the twentieth century, mainly analytical methods of buckling were applied in practice. With the appearance of computers, numerical methods, in particular, the finite element analysis, began to prevail. Buckling analysis was implemented in programs of finite element analysis, such as NASTRAN, ANSYS, ABAQUS, ADAMS, DIANA, and others. In view of great responsibility, buckling analysis of structure should be carried out using at least two different programs. However, due to the high cost of software products, not all project organizations are able to have a number of programs. An alternative is to develop programs that can complete buckling analysis using several methods. This would increase the reliability and quality of calculation results. The PRINS computer program has opportunity for buckling analysis using two methods - static and dynamic. The aims of the work - to show the theoretical aspects and practical implementation of the dynamic principle of buckling analysis in buildings and structures using finite element method, as well as to give the algorithm implemented in the PRINS program and the results of verification calculations confirming its reliability. Results. The algorithm presented in this article and implemented in the PRINS computer program allows to determine critical loads using a dynamic buckling criterion. On the basis of numerous verification calculations, it was established that the implemented algorithm was effective for determining critical loads in frame, thin-walled and ribbed plate structures. The use of the PRINS computer program enables to use an alternative method for determining critical loads for a wide class of engineering problems in addition to the classical (static) method.

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