*2.2. Methods*

The main research program was to test 28 wall masonry panels. The specimens were made under laboratory conditions. The preparation of the panels, their curing, testing, and processing of the test results were carried out in accordance with the EN 1052-1 standard [49]. The angle of the bed joint changed: θ = 0◦, 22.5◦, 45◦, 67.5◦, 90◦ (Figures <sup>4</sup> and 5). The samples had standard dimensions of 50 × <sup>50</sup> × 12 cm3, except for those with bed joints parallel to the load direction (<sup>θ</sup> = 90◦) of dimensions <sup>27</sup> × <sup>75</sup> × 12 cm3. The dimensions of the panels were selected in accordance with the RILEM guidelines used in the other discussed works in the field of this research [35,50].

**Figure 4.** Description of θ angle measurements of tested samples.

**Figure 5.** Load application diagram for compressed wall samples at different angles of bed joints (**a**) θ = 0◦, (**b**) θ = 22.5◦, (**c**) θ = 45◦, (**d**) θ = 67.5◦, (**e**) θ = 90◦.

Five specimens were prepared for each joint angle, except the θ = 0◦, where eight specimens were used.

The samples were built on the flat surface of the compressive strength test stand plate on a thin sand bed. Until the test, the elements were stored at a temperature of 20 ◦C and an air humidity <65%. The tests were carried out 28 days from the date of preparation of the samples.

The models were loaded with a hydraulic actuator (Pneumat P3000, Minsk, Belarus) with a steadily increasing rate on the stand of own production, with the use of a 1250 kN hydraulic press. The samples were loaded with an increase in force equal to 12 kN per minute up to the value at which their collapse occurred. The force was measured with a dynamometer (Pneumat M, Minsk, Belarus). Dial gauges were installed on both surfaces of each sample to measure horizontal and vertical displacements (Figure 6).

**Figure 6.** Compressive strength test with dial indicator installation, hs—height of the sample, ls—length of the sample (**a**) θ = 45◦, (**b**) θ = 90◦.

Young's modulus and Poisson's ratio were determined in terms of the elastic work of the samples, in accordance with the requirements of the standard [49].

During the experimental tests, the destruction processes were also recorded with high-resolution cameras.

#### **3. Results and Discussion**

*3.1. Results of Compressive Strength Tests*

The main results obtained during the compressive strength tests are presented in Table 2.



There are visible changes in the average strength of the masonry with a change in the load angle in relation to the bed joints. The highest compressive strength of 15.1 MPa was obtained for samples loaded in the direction perpendicular to the bed joints (θ = 0◦). The lowest results (3.6 MPa) were obtained for the angle θ = 67.5◦. The strength of the element was 4.2 times lower than the strength of the model with force acting in the direction perpendicular to the bed joints. Figure 7 presents the changes in the wall strength in relation to the reference model (θ = 0◦).

As the results obtained show, minimal compressive strength should be expected for the load acting on the samples with the angle of the bed joints θ = 57.5◦. Its value is limited to 21% of the compressive strength for the load acting parallel to the bed joints (θ = 0◦). For the samples with angle θ = 90◦, the compressive strength was limited to 75% of the strength of samples with θ = 0◦.
