Issue 31

C.L. dos Santos et alii, Frattura ed Integrità Strutturale, 31 (2015) 23-37; DOI: 10.3221/IGF-ESIS.31.03 27 behaviour of the connection. With respect to this connection, 6 specimens failed at the side members and 4 failed at the centre member. Fig. 5 illustrates the two referenced failure modes, with the final rupture characterized by cracks propagating in the RL system. When the rupture occurs in the centre member of the connection, it corresponds to a higher ductile behaviour because the crack is preceded by some embedding of the centre member in the dowel. The failure due to cracking of the lateral members corresponds to a global brittle behaviour, with the (3/4) displacement not exceeding 2 mm (see Fig. 4b). (a) (b) (c) Figure 4 : Experimental results: (a) load-(1/2) displacement; (b) load-(3/4) displacement; (c) load-(1/2)-(3/4) joint slip. Tab. 2 summarizes the average strength and ductility values from the tests: ultimate load, F max ; maximum (1/2) displacement, D (1/2)max ; maximum (3/4) displacement, D (3/4)max ; stiffness from (1/2) displacement, k 1 ; stiffness from (3/4) displacement, k 2 and stiffness from (1/2)-(3/4) displacement, k 3 . Experimental average ultimate loads were computed for each one of the two possible failure modes. It is interesting to note that the average ultimate loads are very close to each other, independently of the observed failure modes. However, the majority of the failures were observed on the side members, which may be justified by some size effect. The volume of material involved in the lateral members is twice the volume of the material of the centre member around the dowel; therefore failures are most likely to occur at the side member, for similar stress conditions leading to failure in both members. Tab. 2 also includes estimates of the failure loads according to the EC5 [3]. According to this design code, the connection strength per shear plane and per fastener is obtained by the expression (1), for the side members: v,R h,1 1 F f t d  (1) and according expression (2), for the case of failure at the centre member: v,R h,2 2 0.5 F f t d  (2) where v,R F is the load carrying capacity per shear plane and per fastener; h,i f and i t are, respectively, the embedment strength and the thickness of wood member i ( 1 i  for side members; 2 i  for centre member) and d is the dowel