BYG DTU. European Spruce picea abies graded by Chinese visual rules. Hilmer Riberholt. Rapport R ISSN ISBN

Transcription

1 BYG DTU Hilmer Riberholt Europen Spruce pice bies grded by Chinese visul rules DANMARKS T E K N I S K E UNIVERSITET Rpport BYG DTU R ISSN ISBN

2 Europen Spruce pice bies grded by Chinese visul grding rules Hilmer Riberholt Deprtment of Civil Engineering DTU-bygning Kgs. Lyngby

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4 Europen spruce strength for glulm 2 / 15

5 Europen spruce strength for glulm 3 / 15 Contents 1 Bckground 3 2 Objective 3 3 Method of documenttion 4 4 Visul strength grding rules in the Chinese glulm stndrd nd in the Europen grding stndrds Evlution nd comprison of grding requirements 7 5 Europen spruce pice bies, Strength nd stiffness Generl EN Stndrds Test results with Europen spruce 8 6 Alloction into species groups bsed on lmintion properties 11 7 Conclusions 13 8 References 14 1 Bckground The Chinese stndrd for structurl glulm glued lminted timber under preprtion nd intended to be published in the ner future contins visul strength grding rules for the bords or plnks to be used for the production of the glulm. Further, it hs defined 4 species groups, where the strongest species hve been llocted to SZ1 nd the wekest to SZ4. Severl Europen wood species relevnt for glulm production re listed in the drft Chinese glulm stndrd. The suggested lloction of the Europen species is reltively similr to the one in the Jpnese glulm stndrd, which ws evluted yers go. From Europen tests doubts hve been rised concerning the documenttion of the lloction of the Europen spruce pice bies - into the 4 species groups. The new tests show tht EU spruce should be llocted into better species clss. In Europe lot of informtion on the strength nd stiffness properties of glulm hs emerged recently becuse of the elbortion nd the implementtion of the Europen hrmonised glulm stndrd EN supported by the strength clss stndrd EN 1194 for use by the design of glulm structures in ccordnce to Eurocode 5, EN 1995 prt 1 nd 2. Therefore, it is found correct to contribute with this informtion to the clssifiction of Europen spruce in the Chinese glulm stndrd. 2 Objective The objective of this pper hs been to document the strength of Europen spruce, pice bies - when visully strength grded in ccordnce to the rules in the drft Chinese glulm stndrd nd by compring with the strength profiles of tht stndrd to be ble to llocte the Europen spruce into the correct species groups defined in the stndrd.

6 Europen spruce strength for glulm 4 / 15 3 Method of documenttion The visul strength grding rules in the Chinese glulm stndrd hve grding requirements which differ from those used in Europe, but not very much. However, the Europen visul strength grding rules hve typiclly 2 or 3 grde clsses, for which the strength properties hve been determined. Therefore, it is possible by estimtion to plce the Chinese visul strength grding clsses mong the similr Europen clsses for which the strength nd stiffness properties hve been determined by stndrdised methods. This provides bsis for good estimte of the strength nd stiffness of Europen spruce visully strength grded in ccordnce with the rules in the Chinese glulm stndrd. The strength nd stiffness properties obtined in this wy cn be compred with the requirements to the chrcteristic vlues stted in the Chinese glulm stndrd for the very lmintions nd such comprison cn form the bsis for llocting Europen spruce pice bies into the correct species group. 4 Visul strength grding rules in the Chinese glulm stndrd nd in the Europen grding stndrds The selected visul strength grding stndrds re described in prtly the Nordic rules used in Scndinvi nd Finlnd /INSTA 142 Nordic visul strength grding rules for timber/,prtly the Germn rules used in Germny nd Austri /DIN Strength grding of wood prt 1: Coniferous swn timber/ nd prtly the French stndrd NF B /Régles d utilistion du bois dns les constructions: Clssement visul pour employ en structure pour les principles essence résineuses et feuillues/. The strength properties of coniferous timber grded by these rules re well defined from lrge scle testing in ccordnce with the Europen testing stndrd EN 408, which is similr to the interntionl drft testing stndrd /ISO/CD 8375 ISO/TC 165 N414 Timber structures Glued Lminted Timber test Methods: Determintion of Physicl nd Mechnicl Properties/. The tble 4.1 gives comprison between the requirements ccording to the Chinese visul strength grding rules stted in the drft Chinese glulm stndrd, tble nd the Europen ones. For groups of knots knot cluster the definition of the knot dimeter rtio is different in the 3 stndrds. See figure 4.1 for the exct definitions. In order to be ble to compre the requirements to the knot dimeter rtio trnsformtion of the requirements to the definition in the drft Chinese glulm stndrd hs been performed. In INSTA 142 the requirement to knot cluster is defined s the sum of the dimeters of the knots in the wide side plus the knots in the 2 edges. This hs been trnsformed to Σd knot /b by using typicl lmintion cross section of 40x150 mm. See figure 4.1 nd the Annex A.

7 Europen spruce strength for glulm 5 / 15 Tble 4.1. Visul requirements to the strength grdes in the drft Chinese glulm stndrd, INSTA 142, DIN nd NF B The left column sttes the grding stndrd nd the grding requirements re mentioned in one or some of the 4 columns to the right. The Europen requirements hve been put in the columns, where they best fit those of the drft Chinese glulm stndrd. No req. signifies tht the stndrd hs no requirement to this type of defect. Chinese grde I II III IV Dimeter rtio of knot groups (knot cluster). For ll grding rules trnsformed to = Σd knot /b nd summtion over knots on the surfce with the lrgest sum of knots s in the drft Chinese glulm stndrd. For DIN it hs been ssumed tht ⅔ of the knot sum re on the side with the lrgest dimeter sum. Drft glulm stndrd INSTA 142 LT30 LT20 DIN C30 C24 NF B , STI, STII 20% 17% 33% 32% 40% 43% 50% 51% 65% 50% Dimeter rtio of knots in the edge - the nrrow side - of timber member. d knot /thickness No req. No req. Drft glulm stndrd INSTA 142 LT30 LT20 DIN C30 C24 NF B , STI, STII No req. 67% No req. 50% No req. Dimeter rtio of mx. knot in the wide side of timber member 17% Drft glulm stndrd INSTA 142 LT30 LT20 DIN C30 C24 NF B , STI, STII Inclintion of grin Drft glulm stndrd INSTA 142 LT30 LT20 DIN C30 C24 NF B , STI, STII Decy Drft glulm stndrd INSTA 142 LT30 LT20 DIN C30 C24 NF B , STI, STII Checks rdil Drft glulm stndrd INSTA 142 LT30 LT20 DIN C30 C24 NF B , STI, STII Ring checks Drft glulm stndrd, I nd II III nd IV INSTA 142 LT30 LT20 20% 17% <30mm 25% 25% 1:17 1:14 Not llowed Not llowed Not llowed 1:14 Not llowed Allow-knot 1) No req. 33% 40% 33% 1:12,5 1:10 1:10 Not llowed Allow-knot Not llowed No req. 80% No req. 67% 50% 50% <40mm 1:8 1:8 1:8 1:4 Not llowed Allow-knot Not llowed Not llowed Very smll checks llowed with llowed up to length of 0,5 m over 3 m length Check through the bord llowed up to length of 0,5 m over 3 m length Allowed Check through the bord llowed up to length of 2 times the bord width Grde I nd II: Not llowed Grde III nd IV: Width<25% of width but not closer to the edge thn 25% of width LT30 not llowed.

8 Europen spruce strength for glulm 6 / 15 LT20: Width<25% of width but not closer to the edge thn 25% of width DIN C30 C24 Not llowed NF B , STI, STII Non mentioned Spirl grin Drft glulm stndrd Not llowed within 100 mm from finger joints INSTA 142 LT30 LT20 Not llowed t finger joints DIN C30 C24 Not llowed t finger joints NF B , STI, STII Not llowed t finger joints Width of nnulr rings, verge over the outer prt of the cross section <6 mm <6 mm Drft glulm stndrd INSTA 142 LT30 LT20 DIN C30 C24 NF B , STI, STII <6 mm <5 mm <4 mm < 6 mm <6 mm <8 mm <6 mm < 8 mm Definition of knot dimeter rtio in knot cluster in drft Chinese glulm stndrd. However the drft considers ll knots over length of 200 mm. The knot pttern typiclly results in tht the lrgest sum occurs on the spwood side i.e R kc b Definition of knot dimeter rtio in knot cluster in INSTA 142 b R kc Definition of knot dimeter rtio in knot cluster in DIN R kc 2b Figure 4.1 Definition of knot dimeter rtio in knot cluster consisting of knots over length of 150 mm.

9 Europen spruce strength for glulm 7 / 15 The specil requirements in the drft Chinese glulm stndrd to pith in rdit pine hs not been delt with, since they re not relevnt to Europen spruce pice bies. In INSTA 142 nd DIN there re requirements to single knot in the wide side of timber member. Such requirements re not stted in the drft Chinese glulm stndrd. Further, there re in INSTA 142 requirements to top rupture which is the result of the brking of the top of coniferous tree when it is growing. An upper brnch of the tree substitutes the top shoot resulting in locl inclined grin. This defect is not so common but rther severe so it is not llowed for LT30 nd only over the middle of the cross section in LT20. The grde S7 defined in DIN hs not been evluted becuse it llows lrger knots thn ny of the 4 Chinese visul grdes. In EN 1912 S7 hs been llocted into clss C Evlution nd comprison of grding requirements It ppers from tble 4.1 tht there is no fixed reltion between ny Chinese visul grde nd Europen grde. Thus it is necessry to perform n estimtion in order to stte which Europen visul grde results in similr strength properties of the timber when grded in ccordnce to the Chinese visul grding rules. From experience gined during testing of glulm produced from pice bies the knots typiclly cuse the filure. Inclintion of grin is not so pronounced in the rupture surfces nd the other defects re of less significnce. For pine e.g. pinus sylvestris the inclintion of grin cn influence the strength to higher degree. From comprison of the mximum llowed defects, nd hving focus on the mximum knots, it is estimted tht the visul strength grding in ccordnce to the 3 different grding methods should result in tht Chinese grdes cn be relted to the Europen ones s Grde I should result in timber being * s strong s ST I Grde II should result in timber being * little stronger thn LT30 Grde III should result in timber being * s strong s C30 Grde IV should result in timber being * s strong s LT20 * s strong s ST II * stronger thn C24. For the evlution in the following chpters it hs been ssumed tht Grde I = ST I Grde II = LT30

10 Europen spruce strength for glulm 8 / 15 Grde III = grde C30 Grde IV = LT20 nd ST II Grde IV = stronger thn C24. This ssumption hs the consequence tht the lloction of Europen wood species into the Chinese species groups SZ1 to SZ4 will be done conservtively. 5 Europen spruce pice bies, Strength nd stiffness 5.1 Generl EN Stndrds With the implementtion of the Europen timber code, Eurocode 5 lot of full size testing of pice bies hs been conducted to verify its strength nd stiffness properties. Timber with dimensions relevnt for the production of glulm hs primrily been tested in tension becuse ccording to the Europen system the bending strength of the glulm is determined form the tensile strength of the lmintions. However, in some cses the bending strength hs lso been determined. The stndrd EN 338 sttes the strength clsses used for full size Europen structurl timber. The stndrd EN 1912 specifies how pice bies nd other timber species grded ccording to the different visul grdes used in Europe hve been llocted into the strength clsses defined in EN 338. Tble 5.1 gives the informtion for the relevnt grdes. Tble 5.1 Strength clsses defined in EN 338 nd some visul grding methods llocted into the strength clsses. Chrcteristic vlues i.e. 5% percentiles of the strength properties nd men vlues of the E-moduli. Strength clss f m,k, MP f t,k, MP E men, GP Visul grdes C S7 C ST-III C S10, ST-II C S13, ST- The tests conducted within the lst yers hve ll hd the objective to document certin strength clss of the visul grdes used for the testing. 5.2 Test results with Europen spruce The full size tests conducted with pice bies hve ll been performed in ccordnce with EN 408 which specifies tht the timber shll be conditioned t climte of (20±2) o C nd (65±5) % reltive humidity. The spn in bending tests shll be 18 times the depth h of the timber. The free length of the specimen for tensile tests shll contin the defect nd shll be t lest 9 times the mximum cross-sectionl dimension.

11 Europen spruce strength for glulm 9 / Smll cler specimens of pice bies The mechnicl properties of smll cler specimens of pice bies hve been tken from the most reputed nd well known book on such properties, nmely: /Technologie des Holzes und der Holzwerkstoffe. By F. Kollmnn. Springer Verlg, Berlin. 1951/ Tble Mechnicl properties of smll cler specimens ccording to Kollmnn, Unit Pice bies Minimum Men Mximum Dry density g/cm 3 0,30 0,43 0,64 E-modulus from bending kp/cm Tensile strength, prllel to grin kp/cm Compression strength, prllel to grin kp/cm Bending strength, prllel to grin kp/cm Sher strength, prllel to grin kp/cm Further, French tests conducted recently hve resulted in the properties in tble Tble Mechnicl properties of pice bies mesured from smll cler specimens of the sizes indicted. Mesurements on French pice bies Testing with full size structurl timber Test results hve been collected from growth regions in Northern Europe to growth regions in the Centrl to South-western Europe. Tests with pice bies from the Nordic countries, Finlnd, Norwy nd Sweden The strength nd stiffness vlues re documented in the SP report /Lmintions for glued lminted timber Estblishment of strength clsses for visul strength grdes nd mchine settings for glulm lmintions of Nordic origin/ pieces of timber 40x145 mm from 8 swmills in Sweden, Norwy nd Finlnd hve been tested. The vlues of E, f m nd f t hve been determined in ccordnce to the test stndrd EN 408. The verge vlues of these properties hve been tken from the report. The chrcteristic vlues hve been determined ccording to the rther conservtive methods on EN 384, so they re rther conservtive.

12 Europen spruce strength for glulm 10 / 15 Tble Strength nd stiffness properties of pice bies from the Nordic countries. Stndrd with the visul grding rules nd the grdes Modulus of elsticity, MP Bending strength, MP Tensile strength, MP Men 5% Men 5% Men 5% INSTA 142 LT ,1 31,3 37,7 22,1 INSTA 142 LT ,8 22,2 28,3 15,3 Tests with pice bies from Frnce The strength nd stiffness vlues from over 1000 specimens in sizes relevnt for glulm production re documented in report from CTBA Centre Technic du Bois et Ameublement in Frnce received by E-mil. The growth regions re the hilly prts t the centrl nd est prt of Frnce. The visul grding rules re defined in the French ntionl stndrd NF B The verge vlues of the properties hve been tken from the report. The chrcteristic vlues hve been determined s 5% percentiles. The tensile strength hs been determined by the sfe rule tht it is 60% of the bending strength. Tble Strength nd stiffness properties of pice bies from the Frnce. Stndrd with the visul grding rules nd the grdes Modulus of elsticity, MP Bending strength, MP Tensile strength, MP Men 5% Men 5% Men 5% NF B ST-I ,6 NF B ST-II ,4 NF B ST-III ,0 Tests with pice bies from Austri The strength nd stiffness vlues re documented in the report /IFP 2.3 Lrge dimension timber Mechnicl potentil of bords of spruce for glulm production/ from the Technicl University of Grz. Totl 2200 pieces of timber were tested in tension of which some hd been mchine strength grded nd some hd been visully grded. Further, 300 mchine grded pieces in four point bending were tested but not in ccordnce with present stndrds. The visul grding rules re defined in DIN The vlues of E, f m nd f t hve been determined in ccordnce with the test stndrd EN 408. The verge vlues of these properties hve been tken from the reports performed since 2001 where the Europen test stndrds nd methods for determintion of strength properties hd found their finl form. The chrcteristic vlues hve been determined ccording to EN with confidence level of 75%.

13 Europen spruce strength for glulm 11 / 15 Tble Strength nd stiffness properties of pice bies from Austri. Stndrd with the visul grding rules nd the grdes Modulus of elsticity, MP Bending strength, MP Men 5% Tensile strength, MP Men 5% Visully grded DIN S13 = C ,1 22,0 DIN S10 = C ,0 15,9 Mchine stress grded DIN 4074 MS13 = C ,8 22,1 DIN 4074 MS10 = C ,6 14,4 Only the strength nd stiffness dt from visully grded timber will be used by the comprison in chpter 6. The strength nd stiffness dt of mchine stress grded hve lso been stted in tble to show tht the 5% percentile of the tensile strength is lrger thn the chrcteristic vlue llocted to the strength clsses by EN 338. The sme pplies to the men vlue of the E-modulus. Tests with pice bies from Germny The strength nd stiffness vlues from 1048 bending specimens nd 1526 tensile specimens in sizes relevnt for glulm production re documented in report / Europen Spruce dt (pice bies) / from the Technicl University in Munich, Germny received by E-mil. The bending tests were performed with the worst growth defect in the tension side, which hs resulted in little lower vlue thn if they hd been positioned rndomly, pproximtely 7 % to 12 % lower. The growth regions re within Germny. The visul grding rules re defined in DIN The verge vlues of the properties hve been tken from the report. The chrcteristic vlues hve been determined s 5% percentiles. Tble Strength nd stiffness properties of pice bies from the Frnce. Stndrd with the visul grding rules nd the grdes Modulus of elsticity, MP Bending strength, MP Tensile strength, MP Men 5% Men 5% Men 5% DIN S13 = C ,2 33,8 38,6 19,6 DIN S10 = C ,9 23,4 29,2 14,1 DIN S7 = C ,3 18,8 24,9 11,9 6 Alloction into species groups bsed on lmintion properties Tble in the drft Chinese glulm stndrd sttes the requirements to the verge vlues nd the 5% percentile vlues of the modulus of elsticity, the bending strength nd the tensile strength of the grded lmintions. The required vlues re repeted t the top of tble 6.1. These strength nd stiffness vlues cn be compred with the results of very comprehensive test series with timber grded into the LT20 nd LT30 clsses documented in the SP report

14 Europen spruce strength for glulm 12 / 15 /Lmintions for glued lminted timber Estblishment of strength clsses for visul strength grdes nd mchine settings for glulm lmintions of Nordic origin, dted 1998/. Tble 6.1 of this report sttes the relevnt strength nd stiffness vlues in the bove mentioned Chinese glulm stndrd tble together with the verge vlues nd the chrcteristic vlues reported in the SP report. The chrcteristic vlues re men vlues of the properties determined from timber visully grding by either the production site or the lbortory, however, these vlues differ only slightly. Tble 6.1. Strength nd stiffness properties relevnt for comprison with the properties of pice bies. Species nd visul grdes Modulus of elsticity, MP Bending strength, MP Tensile strength, MP SZ1 SZ2 SZ3 SZ4 Men 5% Men 5% Men 5% I ,9 39,7 31,4 23,5 II I ,5 35,8 27,9 21,1 III II I ,1 33,3 26,0 19,6 III II I ,2 30,9 24,0 18,1 III II ,2 28,9 23,0 17,2 III ,3 26,5 21,1 15,7 INSTA 142 LT ,1 31,3 37,7 22,1 INSTA 142 LT ,8 22,2 28,3 15,3 DIN C30 AUS ,1 22,0 DIN C30 D ,2 33,8 38,6 19,6 DIN C24 AUS ,0 15,9 DIN C24 D ,9 23,4 29,2 14,1 DIN C16 D ,3 18,8 24,9 11,9 NF B ST I ,6 NF B ST II ,4 It ppers from tble 6.1 tht the strength nd stiffness properties of pice bies in the strength clsses C24 nd C30 grown in Germny nd Austri re lmost identicl. The mechnicl properties of timber from the Nordic countries nd from Frnce cn t be compred directly becuse different visul grding criteri hve been used. However, the generl trend is the sme tht there ppers to be not much difference in the mechnicl properties if the timber hd been grded using the sme visul grding rules. So the differences in the mechnicl properties cused by different growth regions re negligible. Considering tht the chrcteristic bending, tension nd compression strength of glulm is correlted to the chrcteristic tensile strength of the lmintions nd tht the E-modulus of the glulm is very closely correlted to tht of the lmintions it ppers tht the strength nd stiffness of lmintions produced from Europen spruce, pice bies fulfil the requirements to Chinese species nd visul grdes s follows: ST I nd LT30 corresponds to C30 corresponds to SZ1/II or SZ2/I SZ2/III or SZ3/II or SZ4/I

15 Europen spruce strength for glulm 13 / 15 C24 corresponds to LT20 corresponds lmost to ST II corresponds hrdly to C16 hs lower strength thn SZ4/III SZ4/III SZ4/III SZ4/III Since the visul requirements of the grde French grde ST I correspond to the Chinese visul grde I the Europen spruce pice bies hs to be llocted to species clss SZ2 if greement between the strength nd stiffness profiles shll be resonble. Since the visul requirements of the Nordic grde LT30 corresponds to the Chinese visul grde II the Europen spruce pice bies hs to be llocted to species clss SZ1 if greement between the strength nd stiffness profiles shll be resonble. Since the visul requirements of the grde C30 corresponds to the Chinese grde III the Europen spruce pice bies hs to be llocted to species clss SZ2 if greement between the strength nd stiffness profiles shll be resonble. Since the visul requirements of the grdes C24, LT20 nd ST II correspond to the Chinese grde IV, which is lower thn the clsses mentioned in the tble 6.1, the Europen spruce pice bies cn t be llocted to ny species group. However, the results indicte tht it t lest shll be llocted to species clss SZ3 or better. As expected the clss S7 = C16 hs lower strength thn required by ny Chinese grde. The lloction of pice bies should be done bsed on the comprisons between the mechnicl properties of visully grded timber where the grding criteri re most similr. This is the cse for the Europen visul grdes ST I, LT30 nd C30, wheres the Europen visul grdes LT20, C24 nd ST II re similr to the Chinese visul grde IV for which no strength nd stiffness dt re stted in the Chinese glulm stndrd. So it cn be concluded tht bsed on the comprisons between the strength nd stiffness properties of the Europen visul grdes ST I, LT30 nd C30 nd the Chinese visul grdes I, II nd III it cn be concluded tht pice bies Europen spruce should be llocted into species group SZ2. A similr comprison between the Europen visul grdes LT20, C24 nd ST II nd the Chinese visul grde IV indictes the sme. 7 Conclusions It is cler tht there re severl similrities between the visul strength grding requirements to lmintions for glulm in the drft Chinese glulm stndrd nd the Europen stndrds. In order to hve greement between the chrcteristic strength nd stiffness properties listed in the drft Chinese glulm stndrd nd the mesured strength nd stiffness properties of lmintions produced from Europen spruce, pice bies, using the visul grding rules in the drft Chinese glulm stndrd the wood species pice bies should be llocted into species group SZ2 s defined in the drft Chinese glulm stndrd.

16 Europen spruce strength for glulm 14 / 15 8 References. Some of the documents re vilble s Word files or pdf files. Their nmes re listed fter the document. DIN Sortierung von Holz nch der Trgfähigkeit. Strength grding of wood prt 1: Coniferous swn timber. Dted June Germn stndrd EN 338:2003. Structurl timber Strength clsses. EN 384:2004. Structurl timber Determintion of chrcteristic vlues of mechnicl properties nd density. EN 408:2003. Timber structures Structurl timber nd glued lminted timber Determintion of some physicl nd mechnicl properties EN 1194:1999. Timber structures Glued lminted timber Strength clsses nd determintion of chrcteristic vlues EN 1912:2004. Structurl timber Strength clsses Assignment of visul grdes nd species EN :2004, prt 1 nd 2. Eurocode 5. Design of timber structures EN 14080:2004. Timber structures Glued lminted timber Requirements. Europen Spruce dt (pice bies). Technicl University in Munich, Germny. Received by E- mil FILE NAME: D_europen_lmelle_3010PK.pdf IFP 2.3 Lrge dimension timber Mechnicl potentil of bords of spruce for glulm production. Technische Universität Grz, Holz.Bu forschungs gmbh. Austri. November FILE NAME: Bericht_gesmt_ pdf INSTA 142 Nordic visul strength grding rules for timber ISO/CD 8375 ISO/TC 165 N414 Timber structures Glued Lminted Timber test Methods: Determintion of Physicl nd Mechnicl Properties. Dted Lmintions for glued lminted timber Estblishment of strength clsses for visul strength grdes nd mchine settings for glulm lmintions of Nordic origin. SP Swedish Ntionl Testing nd Reserch Institute, Building Technology, Trätek. SP Report 1998:38. 2 FILE NAMES: SP Report _Chpter1-4.pdf AND - SP Report _Chpter ppendices.pdf NF B Régles d utilistion du bois dns les constructions: Clssement visul pour employ en structure pour les principles essence résineuses et feuillues. Appliction rules for structurl timber. Visul clssifiction of the min coniferous nd deciduous timber species. French stndrd. FILE NAME: spin épicé NFB pdf Report received by E-mil from CTBA Centre Technic du Bois et Ameublement in Frnce. November nd December FILE NAMES: French dt pice bies.doc AND - Epicé commun ou Europen Spruce GB.pdf Technologie des Holzes und der Holzwerkstoffe. By F. Kollmnn. Springer Verlg, Berlin. 1951

17 Europen spruce strength for glulm 15 / 15 Annex A. The trnsformtion of grding requirements for knot groups in INSTA 142 nd DIN 4074 to the mesurement method of the JAS glulm stndrd. DIN Requirement: side,mx side,min 2b edge 33% Trnsformed requirement Similr to side,mx side b, mx side,min 1 / side,mx edge/ side, mx b side, min / side 66 %, mx 66% edge / side, mx _side,min / _side mx = 0,4 _edge / _side,mx = 0,15 C30 C24 Trnsformed requirement to the side with mx knots. 0,33 0,5 _side,mx / b = 43% 65% Inst 142 Requirement: side,mx edge side, llowed edge, llowed k side b k edge t Trnsformed requirement side,mx b k side k edge t/ b edge / b k side 0,5 k edge t/ b LT30 LT20 Typiclly b = 150 k_side 0,25 0,4 t = 40 k_edge 0,5 0,8 _side,min / _side mx = 0,4 _edge / _side,mx = 0,15 Trnsformed requirement to the side with mx knots. _side,mx / b = 32% 51%