ВИБІР РАЦІОНАЛЬНИХ ПЕРЕРІЗІВ СКЛАДЕНИХ ДВОТАВРОВИХ БАЛОК З УРАХУВАННЯМ КОНСТРУКТИВНИХ І ТЕХНОЛОГІЧНИХ ОБМЕЖЕНЬ

Abstract

The classic method of configuring a compound I-beam for bending moment resistance is based on determining the optimal beam height that corresponds to the minimum steel consumption. The disadvantage of this approach is that it does not take into account the real dimensions of sheet metal, as well as design and technological restrictions on the ratio of the flanges and the web dimensions. The purpose of the article is to develop a method for determining the rational cross-section of a welded I-beam of modular height, taking into account a complex of architectural, design and technological requirements and limitations, as well as standard dimensions of sheet metal. The choice of rational cross-sections was carried out by enumerating all possible layout options for the welded I-beams of a given height, the parameters of which correspond to the specified requirements. As a selection criterion, an efficiency indicator was used, which allows to identify I-beams with the maximum possible elastic section modulus with a minimum cross-sectional area. It has been found that I-beams of the same height have similar cross-
section efficiency indicators. Changing the height of the I-beam can significantly change the cross-section efficiency. A shortened assortment of welded I-beams has been formed, the height of which is a multiple of 100 mm, the values of the elastic section modulus form a geometric progression with a denominator of about 1.05, and the efficiency indicator of the cross-section are the highest for the accepted elastic section modulus. Cross-sections from the developed assortment correspond to standard dimensions of sheet metal, conditions of local stability of the web and compressed flange, other structural and technological requirements and provide the possibility to select cross-sections of beams with safety margins within 5%.