Issue 39

A. Lokaj et alii, Frattura ed Integrità Strutturale, 39 (2017) 56-61; DOI: 10.3221/IGF-ESIS.39.07 57 pinpointing of the round timber bolted joints load carrying capacity near-unfeasible due to the insufficient support in the current standards. To compare the behaviour of this type of connections, a series of laboratory static tests in different inclinations of the loading force to the grain has been made. The reference tests of squared timber joints were also carried out [3]. Mechanical behaviour of the round and the squared timber bolted joints were tested in the laboratory of the Faculty of Civil Engineering in Ostrava. Samples type Value Tension orientation at an angle to the grain 0° 60° 90° ̅ݔ SD CV ̅ݔ SD CV ̅ݔ SD CV Round timber Number of samples 12 12 12 Density (kg  m -3 ) 412.6 42.1 10.2 405.9 26.4 6.5 414.9 46.2 11.1 Moisture (%) 11.6 1.1 9.4 11.3 1.0 8,9 11.4 1.1 9.6 Squared timber Number of samples 9 10 12 Density (kg  m -3 ) 426.8 13.77 3.2 443.6 14.6 3.3 454.4 50.1 11.0 Moisture (%) 11.2 0.6 5.3 12.2 0.5 4.1 11.6 0.5 4.3 Table 1 : Characteristics of tested wood ( x is the arithmetical average; SD is the standard deviation; CV is the coefficient of variation). The special steel element for testing was prepared (Fig. 1). In order for the load direction to be perpendicular (or at an angle 60°) to the grain, the samples were subjected to a simple tensile test with the loading force being increased gradually. The test parameters were invariable for all samples. Each round timber sample subjected to a simple tension test had the same test parameters. The tension force on samples loaded parallel to the grain was increased gradually. The selected rate of displacement of the press jaws was optimal. Each specimen failure occurred in time boundary of 300 ± 120 sec. It corresponds to the current European standard. Figure 1 : Steel product for testing in tension perpendicular to the grain and sample in press machine. M ATERIAL AND TEST METHOD s spruce wood is the most common type of timber, it was used as samples for testing. A few non-destructive tests were carried out before the onset of the static tests in the press, [4, 5]. Dimensions of the test samples were adjusted to the equipment possibilities of the laboratory at the Faculty of Civil Engineering. Thus, the specimen A