Особливості розрахунку на витривалість баштових споруд при дії вітрових навантажень

This article describes the effect of the phenomenon of vortex shedding under the action of frontal wind on tower structures of solid crosssection.The phenomenon of vortex shedding occurs at wind speeds higher than certain critical ones, which on the Beaufort scale correspond to weak and moderate winds with a very large number of cycles, which requires the calculation of structures forendurance. An additional feature of this aspect is that the phenomenon of vortex shedding is quite unknown in broad engineering practice in Ukraine and for the first time a reference to the need to calculate structures for vortex excitation appeared with the introduction of Amendment 2 to DBN V.1.2-2:2006 "Loads and influences. Design standards" only in 2020. This article provides an analysis of existing calculation methods and the state of the provisions of national standards for thecalculation of tower structures for complex wind effects. In particular, the problems of calculating structures for dynamic action when calculating for frontal wind are indicated. The critical speeds for real tower structures and the approximate number of vibration cycles per year occurring during normal operation were also estimated. It was found that thenumber of cyclic self-oscillations from vortex shedding with a stress asymmetry coefficient ρ=-1 is from 2 to 15 million per year, which indicates the need to limit the stresses in structures and their details to the values of the endurance limit. Thearticle provides calculations of the values of the endurance limits for different groups of structures, analyzes the feasibility of using high-strength steel grades. An analysis of the reduction in the number of cycles when stresses exceed the endurance limit is also performed and it is proven that insignificant excesses of stresses within 3..5% can significantly reduce the endurance of structures by several times.This conclusion is especially relevant when calculating lattice-type space-frame structures that have an external enclosing shell that creates a wind effect in the structure similar to a solid-wall structure. Such features are relevant primarily for largescale monumental structures.