DETERMINATION OF DEFLECTIONS OF BEAMS WITH RHOMBIC PERFORATION OF THE WEB

Subject: due to a wide spread in construction practice of castellated beams with the rhomb-shaped perforation of the web, influence of parameters of such openings on beam’s deflections was investigated. Currently, in the Design Codes, both domestic and international, and also in Eurocode 3, the recommendations on determination of deflections of such beams are absent although they contain regulatory requirements. Research objectives: elaboration of analytical relationship, convenient for engineering calculations, for estimation of deflections of castellated beams with rhombic perforation of the web. Materials and methods: derivation of the deflection formula was carried out using one of the efficient methods for calculating deformations of perforated I-beams, based on the use of the theory of compound bars. Several numerical coefficients included in the expression for the stiffness coefficient of the elastic layer, formed by web-posts, were refined by means of finite element calculations. As a criterion for reliability of the analytical expression for deflections, the results of the finite element analysis of the beam, obtained with the ANSYS software complex, are used. Results: results of the study constitute the analytical relation for engineering calculations of deflections of castellated beams with the rhombic perforation of the web. The applicability of the proposed dependence to the calculation of deflections for beams with different shapes of rhombic perforation is verified by varying both the height of the openings and the width of the web-posts. In all cases, only the angle of inclination of the hexagonal sides, taken equal to 60°, remains fixed. An example of analysis of a perforated beam according to the method considered is given. For beams made by wasteless technology, when the width of the web-posts is equal to the horizontal side of the opening, for a rhomb-shaped perforation with a constant relative height of the openings, the total cut-out area remains practically unchanged for any width of the web-posts. A consequence of this is the weak influence of the relative width of the web-posts on deflections of beams with a fixed height of the openings. Conclusions: obtained engineering relationship will certainly be of practical interest to designers and can be recommended for including into the Design Codes of the Russian Federation.