PSI - Issue 81

Mykola Pidgurskyi et al. / Procedia Structural Integrity 81 (2026) 539–546

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Due to advances in metalworking and computer-aided design, other large-span welded structures have become available on the market, namely, frames with tapered I-sections along their length. Such structures can easily span up to 30 m. Since these frames are fabricated from individual steel plates, their manufacturing labor intensity is not significantly lower compared to metal trusses, and the solid cross-section does not allow optimal material utilization, leading to additional material costs. Today, alternatives to solid I-beams include lightweight beams, namely: corrugated web beams, cellular beams, bi-steel beams, and perforated web beams. Steel perforated beams are usually produced by cutting a parent hot-rolled I-beam and subsequently welding parts onto the protruding sections of the web. Consequently, the manufacturing labor intensity of such structures is the lowest compared to other lightweight beams, making them a more optimal choice in this context. These beams combine sufficient load-bearing capacity (Pidgurskyi et al., 2021; Panedpojaman and Thepchatri, 2013) with reduced mass and significantly lower fabrication complexity. In large-span buildings, the roof slope may be structural (5-10°) to ensure efficient water drainage, or functional, to maintain the proper thermal and humidity regime, improve lighting and ventilation characteristics, or optimize the angle for solar panel installation. For such structures, double-pitched roofs are typically used, which provide the most effective drainage of rainwater and enhance the stiffness characteristics of the beam due to the development of horizontal thrust at the supports. Arched beams are considered more efficient in terms of internal force distribution, as they do not have local stress concentrations, unlike double pitched beams. A structural feature of double-pitched and arched configurations is the presence of horizontal forces (thrust) at the supports, which are provided by rigid connections to the columns. Significant bending moments occur at the support (eaves) joints, which reverse in sign along the span. As a result of this force distribution, the bending moments in the beam are lower compared to a horizontal simply supported beam, leading to more efficient material usage. This enables a reduction in the geometric dimensions of the beam’s cross -section while providing the structure with greater architectural expressiveness. In the study by Romaniuk et al. (2024), a double-pitched beam with hexagonal perforation was investigated. The beam had an inclination of approximately 26.5°, and a tie was used to provide horizontal thrust. Such configurations satisfy the requirements of the first and second load-bearing states but increase both fabrication and design complexity. For structural purposes, trapezoidal perforated beams can also be fabricated using a single cut (Al-Thabhawee and Al Kannoon, 2022; Maulana et al., 2018; Osmani et al., 2025). These beams have minimal structural slope and improved characteristics compared to solid beams, but this method does not allow the production of beams with greater slopes. Arched perforated beams demonstrate high strength and stiffness (Zaher et al., 2018), but further investigations of their stress strain state within frame structures with minimal slope and the use of haunches are required. An additional reduction in the weight of the beam (along with the use of perforated beams) can be achieved by providing a rigid connection between the beam and the columns. In this case, bending moments arise at the support sections, which reduce the bending moment in the span (Fig. 1). As a result, the bending moment distribution becomes more uniform, and the material is utilized more efficiently. The beam deflection is also reduced. According to the EN 1993-1-8:2005, Eurocode 3, 2005 joints are classified according to their stiffness and strength. With respect to the stiffness, joints are classified as rigid, semi-rigid, or nominally pinned. The stiffness of a joint may be determined on the basis of experimental data, previous satisfactory service performance, or calculation results based on test data (EN 1993-1 8:2005, Eurocode 3, 2005; Chan et al., 2005). According to Nilov et al. (2010) a reduction in beam weight can be achieved provided that the flexural stiffness per unit length of the column approaches the effective stiffness of the beam. If the flexural stiffness per unit length of the beam significantly exceeds that of the columns, the unloading effect is lost, since rigid frame joints simultaneously increase bending moments in the columns. Therefore, frame systems of this type are most efficient for structures with relatively small column heights. Therefore, to improve the clarity of the results, ensure their correct comparison, and reduce the number of influencing factors, rigid fixity with horizontal restraint was applied at both ends of the beam in the numerical model. Fig. 1 shows the distribution of internal forces in horizontal (a), double-pitched (b), and arched (c) beams.

Fig. 1. Distribution of internal forces in: a) horizontal beam; b) double-pitched beam; c) arched beam.