PSI - Issue 81

Bohdan Karavan et al. / Procedia Structural Integrity 81 (2026) 396–400

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The test arches were loaded in stages, each stage amounting to 5 – 10% of the destructive load (5 – 10 kN), which was determined in advance by theoretical calculations. After each stage of loading, a “holding period” of 7– 15 minutes was observed, necessary to stabilize the deformations, during which readings from all measuring instruments were recorded in the research log, a visual inspection of the external surfaces was carried out, the processes of crack formation and development were recorded, and the width of the cracks was measured (Dovbenko et al. (2024), Drobyshynets et al. (2024), Dvorkin et al. (2021), Korniychuck et al. (2024)). 3. Results and discussion 3.1. Arch A1 At a load of Fu = 105 kN, the deflection of the arch belt was f = 7 mm, which is less than the maximum permissible value fu = 1/150 l = 13.3 mm (Fig. 3). The increase in deflections at load steps of 5 kN: at F = 10 kN was Δ f = 0.14 mm, in the range F = 15...70 kN was on average Δ f = 0.25 mm, in the range F = 75...90 kN was on average Δ f = 0.5 mm, at F = 98 kN and F = 105 kN was Δ f = 0.7 mm. The dependence of the arch belt deflection on loads up to F = 70 kN is linear. Further, with an increase in load, the increase in deflections at the steps increases significantly, which is associated with an increase in plastic deformations of concrete, the formation and development of cracks and, in general, a decrease in the stiffness of the belt (Fig. 3). The arch expansion measured on the support using a ring dynamometer: at a load of F = 20 kN was H = 10.84 kN, at F = 50 kN was H = 29.19 kN, F = 80 kN was H = 45.7 kN, at Fu = 105 kN was H = 60 kN (Fig. 3). As can be seen from the graph, the expansion forces in the arch are proportional to the load. With the accepted load diagram, the expansion forces are equal to: at F = 10 kN was H = 0.5 F ; in the range F = 15...40 kN was on average H = 1.85 F ; in the range F = 45...105 kN was on average H = 1.74 F . a b

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Fig. 3. Dependencies: a) deflection of the belt under load in arch A1; b) effort of thrust from load in arch A1.

Arch A1 collapsed under a load of Fu = 105 kN along a through main inclined crack with simultaneous destruction of compressed concrete in the upper zone of the belt under a concentrated force (Fig. 4).

Fig. 4. The nature of the destruction of arch A1 and the main crack in its belt.