PSI - Issue 81

Valentin Aleksiievets et al. / Procedia Structural Integrity 81 (2026) 422–429

423

Nomenclature W

moisture; loading;

F

u  F η u

shear deformations; upper load level;

intermediate shear deformations

Δ cyk,i

2. Methods of experimental research The purpose and subject of the research were the operation of dry nail joints of wooden structural elements under the influence of low-cycle loads, the bearing capacity of nail joints depending on the ultimate deformations. For this purpose, 24 samples were manufactured. The 24 dry samples were divided into 8 groups, with three nail joints for each low-cycle load level (Table 1).

Table 1. Nomenclature of prototypes.

Dimensions, mm

Number of samples

Number and diameter of nails, mm

Deformations on the 1st cycle

Connection cipher

a

b

h

1 2 3 4 5 6 7 8

37 37 37 37 37 35 35 35

37 37 37 37 37 35 35 35

260 260 260 260 260 260 260 260

3 3 3 3 3 3 3 3

6/5.0 6/5.0 6/5.0 5/5.0 5/5.0 5/5.0 5/5.0 5/5.0

1.8 1.6 1.4 1.6 1.5 1.2 1.0 0.8

The samples were tested at a moisture content of second-grade pine wood W=12%. For the manufacture of wooden connection elements of all series, pine wood with a width of annual layers of 1-5 mm, without destructive defects and rotting, was selected. To achieve less dispersion of test results, every three twin specimens were made with the same composition of wooden elements, i.e. all left elements were made from the same blank board, the middle ones from the second, and the right ones from the third. Thus, in each individual connection, the elements were made from the same boards. The joints were manufactured for low-cycle load tests. Samples 1-3 were connected with 6 nails with a diameter of 5.0 mm. All other samples were connected by 5 nails with a diameter of 5.0 mm. The nail length in all cases was 150 mm. All elements of the samples with humidity W=12% were made with the same thickness of the extreme and middle elements, which was 35 mm in some samples and 37 mm in others. The height of the samples in all cases was 260 mm. The sample schemes are shown in Fig. 1.

a

b

Fig. 1. The sample schemes: a) for connection ciphers 1-3; b) for connection ciphers 4-8

To measure the deformations of the mutual displacement of the elements of the nail joints of all series, watch-type indicators with a division value of 0.01 mm were used, which were fixed on opposite sides of the joint. The indicators were attached using a