PSI - Issue 59

Volodymyr Romaniuk et al. / Procedia Structural Integrity 59 (2024) 479–486 Volodymyr Romanіuk et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Keywords: perforated element, stress-strain state, stress, load-bearing capacity, deformability.

1. Introduction An important factor influencing the efficiency of modern construction is the consumption of materials for supporting and enclosing structures. Therefore, the development of new structural forms or the improvement of existing ones are currently quite relevant tasks. One constructive approach that facilitates an increase in the load bearing capacity of elements while maintaining constant steel consumption is the utilization of perforation in structural elements. This approach is frequently used in flat load-bearing structures of the coating. When developing new forms or improving existing ones, it is not only desirable but, in certain cases, necessary to conduct experimental verification of their load-bearing capacity. The calculation of perforated elements is addressed in the current domestic (DBN V.2.6 – 198: 2014, 2014) and foreign (Eurocode 3, 2005) standards governing the design of steel structures. These standards provide formulas for computing stresses in characteristic and most critical cross-sections along the length of single-span hinged or supported beams. Specifically, calculations are performed at the support, in the middle of the beam's length, and at points where concentrated forces are applied, leading to the occurrence of local stresses. Deformation calculations are conducted using the method of initial parameters, necessarily considering the increase in rigidity of the cross sections of the elements resulting from their development in height by perforation. Currently, researchers from different countries (Chung et al., 2003; Tsavdaridis and D’Mello, 2011 a,b; Samadhan et al., 2015) have performed many experimental studies of perforated elements, as well as structures based on them. Unfortunately, the comprehensive dissemination of these study results is lacking in literary sources. Sometimes, these findings not only exhibit contradictions among themselves but also deviate from the theoretical premises set forth by the respective authors. Moreover, experimental studies were mainly carried out on models in the form of hinged single-span beams that were subjected to bending under the action of an external load in order to establish the degree of accuracy of various calculation methods. The complete methods and features of conducting experimental research are given in monographs (Romanіuk and Supruniuk, 2013, 2017). The study of full-scale construction samples in modern practice is rare due to the relatively high complexity of compliance with the calculation and experimental schemes. Moreover, experiments involving combined systems that incorporate perforated elements are notably scarce in open literary sources, with only a few individual cases available for reference. Therefore, the objective was to conduct comprehensive experimental studies on the stress-strain state of a full scale sample of a steel arch structure, designed by the authors. These studies were executed in accordance with realistically conceivable scenarios of symmetric and asymmetric loads applied to the top chord of the arch in the form of concentrated forces uniformly distributed along its length. The distinctive feature of the research design for the arch lies in its capability to facilitate experimental studies for both the variant without prestressing and with Aligned with the study's objectives, a pre-stressed steel perforated rafter arch was conceptualized, fabricated, and subjected to testing in the research laboratory of the Department of Industrial, Civil Construction and Engineering Structures of the National University of Water and Environmental Engineering (NUWM) (Fig. 1). The experimental arch construction was designed according to the utility model patent. The triangular arch consists of two half-arches (1), made of perforated (developed in height) I-beams. These half-arches are rigidly affixed with the help of flanges and bolts made of steel of ordinary strength at the ridge node A. Ties (2) are attached to the semi-arches at the level of the supporting hinges, with support B being hinged immovable and support C being hinged movable. A spacer (3) is connected to the semi-arches at the hinge joints D, one of which is equipped with a mechanism for tensioning the spacer (4). Suspensions (5) support the tie during the transportation and installation of the arch in the designated position. prestressing, which involves creating initial stresses in the arch spacer. 2. Design of the arch and methodology of experimental research