PSI - Issue 81

Mykola Pidgurskyi et al. / Procedia Structural Integrity 81 (2026) 439–446

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pitched systems are double-pitched and arched beams.

Fig. 1. Manufacturing method for perforated steel I-beams.

Another approach involves modifying the boundary conditions of the beam, specifically by rigidly connecting it to the columns. Rigid end fixity significantly reduces midspan deflections due to a lower bending moment at midspan. While such modelling assumptions are straightforward to implement, achieving rigid connections in practice is often limited by insufficient space for detailing or inadequate capacity of the joint components. To address this issue, special stiffening elements in the form of haunches may be introduced. These plate elements, fabricated from steel of the same thickness as the beam components, are typically installed in the eaves and apex joints (Fig. 2).

Fig. 2. Perforated steel beam with haunches in the eaves and apex joints.

The most complex method of improving the performance of perforated beams involves modifying the shape, size or configuration of the perforation openings. Adjusting these parameters can significantly enhance the strength and stiffness of the member; however, each case requires substantial analytical effort and individual optimization (Pidgurskyi et al., 2021). 2. Review of Previous Studies and Problem Statement A review of existing studies on perforated steel beams shows a consistent trend: both deflections and flange stresses in perforated I-beams decrease compared with their solid-web counterparts. However, due to the discontinuity introduced into the web by the perforation, the normal and shear stresses become non-uniformly distributed over the beam depth, creating pronounced stress concentration zones (Fig. 3). The stresses arising around the openings are localized, and their magnitudes may exceed the maximum flange stresses of the original solid-web beam by several times (Chung et al., 2001). To reduce stresses in the vicinity of the perforation openings, several structural approaches are employed, including welding the opening closed, strengthening them with stiffening rings, or modifying the overall beam geometry: for example, adopting a double-pitched or arched configuration (Zaher et al., 2018). Welding the openings closed provides the most substantial stress reduction at the strengthened locations; however, it is generally impractical, as it significantly increases the beam weight, requires considerable fabrication effort, and negates the benefits of perforation when applied to multiple openings (Psyrras et al., 2025; Romaniuk et al., 2024). Using a circular stiffening ring is a more efficient solution, since such rings can be fabricated from standard tubular sections, and their weight contribution is negligible relative to the beam mass when only a limited number of openings require reinforcement (Al-Thabhawee et al., 2018; Abbas & Al-Thabhawee, 2022; Zeytinci et al., 2021). Additionally, the installation of structural elements such as haunches reduces stresses around near-support openings by increasing the beam depth and, consequently, the cross-sectional area. Therefore, to address the aforementioned issues, this study investigates the stress-strain state of perforated beams – specifically, the distribution of stresses around circular openings in horizontal, double-pitched and arched beams, both with and without haunches, and including reinforcement of selected openings with stiffening rings.