**3. Experimental Tests**

### *3.1. Static Schemes and Investigations Procedure*

For the purposes of experimental testing, technical scale beam models were made from pine wood (Pinus sylvestris L.) of 360 cm in length and with a cross-section measuring 12 cm × 18 cm. Testing involved four series, each with three models. Series A included continuous beams as references, whereas series E, F, and G included beams with stop-splayed scarf joints in the horizontal plane. The series with joints differed from one another in terms of the methods uses to strengthen the joint, i.e.:


With respect to the geometry of the joints, these were based on data obtained for real structures and on data from the literature. The schematics and views of the various models used for testing are presented in Figures 9–11.

**Figure 9.** Schemes of the experimental testing models: (**a**) series E—with 2 drawbolts (double-sided tooth plate connectors type C10 + M10 screws), (**b**) series F—with wood inserts (and additional steel clamps), (**c**) series G—with steel clamps.

**Figure 10.** Axiometric schematics of joints used in the experimental models: (**a**) series E—with 2 drawbolts (double-sided tooth plate connectors type C10 + M10 screws), (**b**) series F—with wood inserts (and additional steel clamps), (**c**) series G—with steel clamps.

**Figure 11.** View of an example beam in each series: (**a**) series E—with 2 drawbolts (double-sided tooth plate connectors type C10 + M10 screws), (**b**) series F—with wood inserts (and additional steel clamps), (**c**) series G—with steel clamps.

In order to determine the load-bearing and the load-deflection plot, the beam was subjected to four-point bending tests, in accordance with the standard procedure described in [36]. A schematic of the experimental testing is provided in Figure 12 (drawing based on data from [36]).

**Figure 12.** Scheme of the four-point bending test in accordance with standard procedure.

The experimental testing was carried out at the Building Construction Laboratory of the Faculty of Civil Engineering of the Wroclaw University of Science and Technology. An electronically-controlled linear hydraulic jack, the Instron 500 (Instron®, Norwood, MA, USA), was used. The results were registered using the MGC plus measurement system made by the Hottinger Baldwin Messtechnik (HBK GmbH, Darmstadt, Germany). The measurement equipment used in the experimental testing was calibrated to at least class 1 accuracy.

The beams were freely supported at both ends. The span between the axes of the supports was 3.24 m. The supports included a fork support, which ensured that there was no loss in flexural static (lateral buckling). The beams were loaded symmetrically with a loading force applied at two points, thanks to which pure bending was obtained in the central part of the element. The speed of application of the loading was 5 mm/min. A schematic and view of the testing stand is presented in Figures 13 and 14. Registration of the strains observed in the materials was carried out by means of a series of RL 300/50 strain gauge.

**Figure 13.** Scheme of the experimental testing site showing locations of the strain gauges.

**Figure 14.** View of experimental stand for testing with an example beam.

Additionally, during the course of the testing, the wood moisture was determined using a resistance hygrometer (FMW moisture meter) to take measurements in several locations on each tested beam. The moisture content of the elements was kept close to the required standard of 12% [36,37].
