PSI - Issue 72

Andrii Ivaniuk et al. / Procedia Structural Integrity 72 (2025) 323–329

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et al. (2018), Sobczak-Piastka et al. (2020), Rescavlo et al. (2020), Gomon et al. (2024), Andor and Bellovics (2020)), girders, racks, arches, trusses, and others. Beams can be solid cross-section and glued (Gomon et al. (2022), Nsouami et al. (2022), Sobczak-Piastka et al. (2023)). Such bending elements can work under various operating conditions (Pavluk et al. (2024), Zakic (1974), Homon et al. (2024)). In many cases they can work with and without damage (Zhao et al. (2020), Pavluk et al. (2024)).

Nomenclature L

beam span

b х h

beam cross-section

load

Р h

beam height

tangential stresses normal stresses

xy  x 

displacement

U

In this article, we will be interested in the performance of single-span glued wooden beams with a crack located asymmetrically relative to the mid-span under short-term loading. In particular, it is necessary to experimentally determine the distribution of tangential and normal stresses along the height of beams in different cross-sections, to construct diagrams of relative displacements of the edges of cracks in beams, and to establish the bearing capacity of the beams under study. 2. Methods of experimental research The experimental studies included the testing of single-span wooden beams with a crack located asymmetrically relative to the middle of the span. The span of the beam was L=6000 mm with cross-section b х h=140x600 mmand a crack located along the neutral axis. A total of 3 beams were tested, for each of which the crack length was varied 2l. For the first beam B1-1 crack length 2l=l 1 +l 2 =3300 mm (l 1 =1950 mm, l 2 =1350 mm); for the second B1-2 – 2l=l 1 +l 2 =3700 mm(l 1 =2300 mm, l 2 =14000 mm); for the third B1-3 – 2l=l 1 +l 2 =4200 mm(l 1 =2600 mm, l 2 =1600 mm). For beams the ratio was L/h=10 at 2l/L=0.55 for the first beam B1-1; 2l/L=0.617 – for the second beam B1-2; 2l/L=0.7 – for the third beam B1-3. And the ratio l 1 /l 2 was accordingly 1.444; 1.643; 1.625. All glued wooden beams included in the experimental tests were manufactured in the factory from planed pine boards of the 2nd grade, 40 mm thick, glued together in layers using phenol-resorcinol glue. At the ends, the boards were connected to each other using a toothed glued joint. The moisture content of the beam wood was 10 – 12%. A through crack of length 2l, with its components l 1 and l 2 for each beam, was created using a slot 1 mm thick and 150 mm long from a given vertex to the middle of the span, and the rest of the crack length was created in the form of a rectangular slot 2 mm high. Between the upper and lower edges of the slot, two steel sheets were installed along its length, each 1 mm thick. There was lubricant between the sheet plates. Thus, contact between the crack edges was ensured, and the friction coefficient approached zero. Electrostrain gauges were used to measure relative deformations. The total number of strain gauges was 162 pieces with a 10 mm base and 72 pieces with a 20 mm base. Electrostrain gauges were glued to the side surfaces of the beams. The forces P acting on the beam were created using 5 hydraulic jacks. (Fig.1). Prior to sawing out the cracks, each beam (without a defect) was subjected to a load equal to half of the calculated value. At the same time, the values of deflection and tangential stress in the support cross-section were determined. After that, the beam was unloaded and a crack was created. Repeated loading of the beams with the created crack was performed after 3 days.