412 TJ.Dais,PA.Claisse/Constnuction and Building Materials 14(00)47-417 25 20 10 0.4 F.m Stirness K. slip st Fnee 0.1 Fast 0.00 1.00 200 3.00 4.00 5.00 6.00 7.00 8.00 Joint Slip (mm) Fig4.Typical load-slip respon ofjointitestandidcnticeationofcalculhiedtetparameters in Fig.4.The following 0h. the base wood ma the maximum load in for all but the Parallam samples.The coefficient of kN achieved by the variation (CV)of a set of results has been denned as the its Th the standa ted area of the fastener; Ki,the initial stiffness of the joint in kN/mm d from a are comparable although some solid samples exhibited and lip respons extreme (in exc 10 mm at failure).I K,the stiffness of the joint in kN/mm,determined be comeffect on npatentdcu from a line r regre n analy 0I stiffness.and slip at maximum load was much less response during th variable in the glulam.The Microlam samples per- spe The initial stiffness for the joint,representing 'bed- bited les 6 ad (orin?品 slip at ne jomnt,and able).The Parallam samples wer ticularly disap 11 The embedment strength is calculated according to the pointing,exhibiting the widest variations in results,but relationship: this is due to the presence of internal voids (visible during rge varia ton in 人-器 a Its of s ples P-B-1 and P-B-3 which had a low than average density. where d is the diameter of the bolt(12 mm),and t is Fig.7 shows the embedment strength of all the the thickness of the e【est sample(44士1mm samples plotted against their de ty.Th result pana aneanhipse plywood. For solid timberf=0.082(1-0.01d)p givingf=0.072p 412 T.J. Da¨is, P.A. Claisse rConstruction and Building Materials 14 2000 407 ( ) ]417 Fig. 4. Typical load-slip response of joint test and identification of calculated test parameters. shown in Fig. 4. The following parameters were ob￾tained from the load-slip response: v Fmax , the maximum load in kN achieved by the joint, and the corresponding slip in mm; v f , the embedment strength in Nrmm2 , defined as h Fmaxrprojected area of the fastener; v K , the initial stiffness of the joint in kNrmm, i determined from a linear regression analysis of the load-slip response after any initial slip and 0.4 F ; est and v Ks, the stiffness of the joint in kNrmm, determined from a linear regression analysis of the load-slip response during the reloading stage 0.1 to 0.4 F . est The initial stiffness for the joint, representing ‘bed￾ding-in’ following joint fabrication, is 60]70% of the reload working stiffness of the joint, and is used to Ž . determine non-recoverable deformation of the joint. The embedment strength is calculated according to the relationship: Fmax f hs dt where d is the diameter of the bolt 12 mm , and Ž . t is the thickness of the test sample 44 Ž . "1 mm . A summary of the embedment strength and stiffness results is shown in Figs. 5 and 6, respectively. On these graphs all of the samples are shown in order to indicate the spread of the data. Other test results, including modes of failure are listed in Tables 2]5 for each of the base wood materials. The embedment strengths were very consistent with low coefficients of variation for all but the Parallam samples. The coefficient of variation CV of a set of results has been defined as Ž . the ratio of its mean to the standard deviation Ž . sny1 of the results. The joint stiffness values, however, are much more variable-both within a material group, and between groups. The glulam and solid timber results are comparable although some solid samples exhibited extreme ductility in excess of 10 mm at failure . It can Ž . be concluded that the glueline had no apparent detri￾mental effect on joint strength or stiffness, in fact the stiffness, and slip at maximum load was much less variable in the glulam. The Microlam samples per￾formed consistently better in both strength and, espe￾cially, stiffness terms. They also exhibited less slip at maximum load although it was four times more vari- Ž able . The Parallam samples were particularly disap- . pointing, exhibiting the widest variations in results, but this is due to the presence of internal voids visible Ž during fabrication , the relatively large variation in . sample density, and the influence of the relatively poor results of samples P-B-1 and P-B-3 which had a lower than average density. Fig. 7 shows the embedment strength of all the samples plotted against their density. These results follow a linear trend consistent with the embedment￾density relationships given in EC5 for solid timber and plywood. For solid timber fh,0,k k s0.082 1Ž . y0.01d r giving fhs0.072 r