00694 Pouyan Zarnani - Timber Design Society

More documents

Recommendations

Info

LVL groups No. of rows by columns Row spacing Table 1: Configuration for the tested connections on LVL Column spacing Rivet penetration Member thickness Member width End distance Bottom distance Edge distance (N R*N C) S p S q L p b W d a d z d e (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) BRG1-L 25 15 28.5 90 220 75 17 58 BRG2-L 25 15 28.5 126 220 75 35 58 BRG3-L 25 15 28.5 180 220 75 62 58 BRG4-L 25 15 28.5 126 300 75 35 98 BRG5-L 25 15 28.5 126 370 75 35 133 BRG6-L 8*8 25 15 28.5 126 220 100 35 58 BRG7-L 25 15 28.5 126 220 125 35 58 BRG8-L 25 15 53.5 126 220 50 10 58 BRG9-L 25 15 53.5 126 220 50 10 58 BRG10-L 25 15 53.5 180 220 50 37 58 BRG11-L 25 15 53.5 216 220 50 55 58 BRG12-L * 25 15 53.5 216 220 50 55 58 BRG13-L 25 15 53.5 180 300 50 37 98 BRG14-L 8*6 25 15 53.5 180 370 50 37 133 BRG15-L 25 15 53.5 180 220 75 37 58 BRG16-L 25 15 53.5 180 220 100 37 58 BRG17-L 50 15 53.5 126 220 75 10 88 4*8 BRG18-L 25 15 28.5 126 220 75 35 73 BRG19-L 25 15 53.5 180 260 50 37 93 MIG20-L 6*6 25 15 78.5 216 220 50 30 73 MIG21-L 25 15 78.5 216 220 75 30 88 MIG22-L 25 15 53.5 180 300 75 37 128 MIG23-L 4*6 25 15 28.5 180 220 75 62 88 DUG24-L DUG25-L 8*6 6*6 25 25 28.5 126 260 125 35 43 25 25 53.5 180 260 125 37 68 DUG26-L 25 25 78.5 216 260 125 30 93 4*4 * In all groups except BRG12, rivets were installed on the faces of the specimen. In BRG12, rivets were driven into the other sides of the specimen with the same configuration as BRG11. Glulam groups No. of rows by columns Row spacing Table 2: Configuration for the tested connections on glulam Column spacing Rivet penetration Member thickness Member width End distance Bottom distance Edge distance (N R*N C) S p S q L p b W d a d z d e (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) BRG1-G 8*8 25 15 53.5 135 225 75 14 60 BRG2-G 8*6 25 15 53.5 180 225 75 37 60 BRG3-G 6*8 25 15 28.5 135 225 75 39 75 BRG4-G 4*8 50 15 53.5 135 225 75 14 90 MIG5-G 4*6 25 15 78.5 230 225 75 37 90 DUG6-G 6*6 25 25 53.5 180 270 125 37 73 Note: In all groups, rivets were installed on the faces of the specimen. (a) (b) Fig. 10: Material property tests; (a) Tensile strength - European testing standards EN 408:2003 [13], (b) Shear strength - AS/NZS 4063.1 [14] by Lindsay [15]
Test groups with tightly spaced rivet pattern exhibited a failure with a brittle manner (Fig. 11). A sudden plug shear failure happened while a block of wood bounded by the rivets perimeter was pulled away from either one side or both sides of the specimens. As shown in Table 3 and 4, in BRG test series the failed block thickness t block were observed at approximately 0.85L p which corresponds to the elastic deformation of the rivets since no plastic deflection was observed as in Figure 11a. However, in MIG test series, there was a considerable decrease on t block with visible distortion of the rivets (Fig. 11b). This failure mode is defined as mixed mode since the wood fails before final yielding of the rivets. In this case the load-carrying capacity of the wood is based on the stiffness and strength of the tensile and shear planes corresponding to the effective depth of the wood, t ef,y . 5 VALIDATION OF NEW ANALYSIS AND COMPARISON WITH OTHER MODELS Strength predictions of the current tests and tests from the literature were made using the new analytical method to compare it with codes equations and other analytical models. The CSA O86-09 [3], Eurocode 5 [5] and the prediction model proposed by Stahl et al. [6] were used in the comparison. Using the U.S. (NDS) code [4], results in similar predictions as the O86 code ones after correcting for limit state definition since the rivets are adopted from CSA [6]. 5.1 CURRENT TEST DATA Based on the proposed analysis, in the BRG test groups (Table 3 and 4), the wood strength for t block =t ef,e was lower than the rivets yielding strength P r and consequently the failure mode was brittle. However, in the MIG test groups, the wood strength for t block = t ef,e was more than the rivets strength. The strength of the connection was thus checked for the possible mixed or ductile modes of failure. Since in these test series the wood strength for t block =t ef,y was weaker than the rivets strength, therefore a mixed mode failure occurred for the connection with a load carrying capacity less than the rivets resistance. As shown in Table 3 and 4, there is very good agreement between the predictions and observations for the thickness of the failed block, the governing failure mode, and the strength of the connection. Fig. 12 shows the strength predictions of the experimental groups using the new analysis and the predictions from O86-09, EC5 and Stahl’s method. The proposed analysis results in more precise predictions with a correlation coefficient (r 2 ) of 0.91 and a mean absolute error (MAE) of -2.6% and standard deviation (STDEV) of 9.8%. (a) (b) t block ~t ef,y (Mode IV) Brittle plug shear t block ~t ef,y (Mode III m) t block ~t ef,y (Mode IV) Brittle plug shear Figure 11: Thickness of the failed block in LVL and glulam; (a) Brittle failure mode, (b) Mixed failure mode
Page 1 and 2: PREDICTVE ANALYTICAL MODEL FOR WOOD
Page 3 and 4: the lateral blocks and is Atl 2tef
Page 5: Grain 1200 mm Load F [kN]nt mm thic
Page 9 and 10: Predicted Average Strength [kN] Pre

00694 Pouyan Zarnani - Timber Design Society

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?