Issue 31

C.L. dos Santos et alii, Frattura ed Integrità Strutturale, 31 (2015) 23-37; DOI: 10.3221/IGF-ESIS.31.03 25 between the centres of the supports (span) was 426 mm. The load transfer between wood members was assured by means of a steel dowel, which is representative of the most common joining technique in wooden structures. Wood members were cut aligned with the wood grain orientations, as illustrated in Fig. 1. The thickness direction was chosen to correspond to the tangential direction of the wood. All tests were performed with a steel dowel with a nominal diameter, d = 14 mm. The nominal thickness of each wood member was 30 mm. Figure 1 : Geometry and dimensions (in mm) of the single-doweled T-joint ( d =14 mm): (a) centre member; (b) side members. Figure 2 : Test apparatus adopted for the T-connections. Tests were performed on an INSTRON ® machine, model 1125, rated to 100 kN, under crosshead displacement control. Four linear variable differential transducers (LVDT) were used to measure the displacements (see Fig. 2): two LVDTs (1 and 2) were attached to the centre member to measure the displacement between a section of this member and the machine base; the other two LVDTs (3 and 4) were directly connected to the dowel ends in order to measure the displacement between the dowel and the base of the machine. The LVDTs used in the experimental program were from Applied Measurements ® with the reference AML/EU ± 10-S10 (measurement range of ±10 mm). The data were acquired by means of a SPIDER ® 8-30 system. A loading–unloading-reloading procedure was adopted, as suggested in the EN26891 standard [18]: firstly, specimens were loaded until 40% of the maximum estimated load ( F est ), and the crosshead position held for 30s; after this stage, specimens were unloaded until 0.1 F est , and the crosshead position again maintained for 30s; finally, specimens were reloaded until failure. Preliminary tests showed a maximum load of 16500 N. These strength values were the basis for planning the final tests, namely, for the definition of the initial loading cycles according to the procedures provided on the EN26891 standard. The connection was tested with a displacement rate of 0.3 mm/min. Wood densities were measured for each specimen member before testing. The average density was 612.8±30.7 kg/m 3 . Wood members used in T-joint tests were placed in the laboratory several weeks before testing to allow the wood a) b)