Issue 31

C.L. dos Santos et alii, Frattura ed Integrità Strutturale, 31 (2015) 23-37; DOI: 10.3221/IGF-ESIS.31.03 26 to stabilize with the laboratory environment. During the tests, the laboratory temperature was kept between 20 ºC and 25 ºC. The specimens used in the single-doweled T-connections were made of maritime pine wood ( Pinus pinaster Ait.), that were manufactured from trees harvested in the region of Viseu (Portugal). Trees with straight stems (absence of reaction wood) and diameters at breast height of approximately 400 mm were selected. Three-meter-long logs were cut from the sample trees between three and six meters above the basal plane. The logs were live-sawn into thick boards that were kiln-dried to a moisture content between 10% and 12%. The specimens were cut from these boards by aligning the parallel-to-grain direction with the length of the specimens and the wood tangential direction with the thickness of the specimens, as depicted in Fig. 3. Wood with knots, resin pockets, or other type of defects was excluded to reduce the usual scatter observed in timber tests. Figure 3 : Procedure for the extraction of specimens from a log of a tree (dimensions in mm). Tab. 1 summarizes the main elastic properties of maritime pine wood, which have been assessed by Xavier et al. [24, 25]. These authors performed their work using wood samples from trees harvested in the same region and with similar dimensions of trees used to extract the wood for this research. Therefore, it is expected that the properties proposed by Xavier et al. [24, 25] are representative of the wood samples used in this investigation. The elastic moduli ( E ) are given for the longitudinal (L), radial (R), and tangential (T) directions. In addition, the Poisson ratios (  ) and the shear moduli ( G ) are presented for the LR, RT, and TL planes. High anisotropic properties are verified for this wood species, which makes connections made of this material more susceptible to cracking due to perpendicular-to-grain tensile stresses. E L = 15.1 GPa  LR = 0.47 G LR = 1283 MPa E R = 1.91 GPa  RT = 0.59 G RT = 264 MPa E T = 1.01 GPa  TL = 0.05 G TL = 1117 MPa Table 1 : Elastic properties of Maritime pine [24, 25]. The load and displacements from four LVDTs were recorded during the experimental tests of the T-connections. Two types of direct displacement measurements were performed, namely, the displacement of a section of the middle wood member, located 60 mm from the loading plate (average displacements of LVDTs 1 and 2), and the displacements of the dowel ends (average displacements of LVDTs 3 and 4), both in relation to the machine base (see Fig. 2). In addition to the previous displacement measurements – (1/2) and (3/4) displacements – the connection slip was computed as the difference between the previous displacements, (1/2)–(3/4). The difference in displacements represents the embedding of the middle member with respect to the dowel. The displacements and connection slip are presented in Fig. 4. The analysis of Fig. 4 shows that the displacements measured at the centre member ((1/2) displacement) are higher than the displacements measured directly on dowel ends ((3/4) displacement). On effect, LVDTs 1 and 2 take into account the total deformation of the centre and lateral wood members; LVDTs 3 and 4 only accounts for the deformation of the lateral members. The analysis of the load-(1/2) displacement results allows the assessment of the global ductility