Verification Processes for. (CLT) in the Frame of EN. Graz University of Technology. Speaker: holz bau forschungs gmbh, Graz

Transcription

1 Verification Processes for Cross Laminated Timber (CLT) in the Frame of EN 1995 Robert A. Jöbstl Speaker: Thomas Bogensperger Institute for Timber Engineering and Wood Technology Graz University of Technology holz bau forschungs gmbh, Graz 1

2 Introduction: ti Cross Laminated Timber CLT a Wood Based Product Bending under loads perp. p to Plane Shear loads in Plane Conclusion and open points 2

3 Timber Solid Construction: Single family house Dringel-Techt 3

4 Timber Solid Construction: Single family house Dringel-Techt 4

5 Timber Solid Construction: Single family house Dringel-Techt 5

6 Timber Solid Construction: Single family house Jeitler 6

7 Timber Solid Construction: Wiskeymaker's house in St. Nikolai Styria/Austria Foto-Quelle: Arch. G. Mitterberger, Graz 7

8 Cross Laminated Timber CLT a wood based product One possibility of definition of wood based products: degree of desection and orientation of base-material Wood based products Degree of desection Board Veneer Strand Fiber cross parallel cross parallel cross parallel random Cross Laminated Glue Laminated Timber Timber 8

9 Cross Laminated Timber CLT a wood based product One possibility of definition of wood based products: degree of desection and orientation of base-material Wood based products Degree of desection Cross Laminated Timber Board Veneer Strand Fiber cross parallel Glue Laminated Timber cross parallel cross parallel Ready-made products have defined material values (strength, stiffness) but not the base material random 9

10 Cross Laminated Timber CLT a wood based product One possibility of definition of wood based products: degree of desection and orientation of base-material Wood based products Degree of desection Cross Laminated Timber Board Veneer Strand Fiber cross parallel Glue Laminated Timber cross parallel Glue Laminated Timber: cross parallel random Bearing model (=function) material values of boards leeds to material values of GLT 10

11 Cross Laminated Timber CLT a wood based product One possibility of definition of wood based products: degree of desection and orientation of base-material Wood based products Degree of desection Cross Laminated Timber Board Veneer Strand Fiber cross parallel Glue Laminated Timber cross parallel cross parallel random Cross Laminated Timber: modified, new Bearing model material values of Boards leeds to material values of CLT special behavior of CLT is taken into account by this new bearing model No intensive test procedures of huge elements in production control are needed later 11

12 Introduction: ti Cross Laminated Timber CLT a Wood Based Product Bending under loads perp. p to Plane Shear loads in Plane Conclusion and open points 12

13 Bending in Plane Bearing Model f m,c,05 34,00 33,00 32,00 31,00 30,00 29,00 28,00 27,00 26,00 25,00 19 # series 1u f m,g,05 = 29,0 N/mm² 5% fractile and k sys of edge normal strength f m,c 29,8 31,3 1,14 27,3 1,09 1,1 32,6 1,19 1, ,25 1,20 1,15 1,10 1,05 1, ,00 5% fractile Number of parallel lamellas system effect proposal k sys k sys 13

14 Bending in Plane Bearing Model New proposal p for GLT - Bearing Model: proposal for CLT - Bearing Model on the same basis: 14

15 Bending in Plane Test Method 4-point-bending test according to EN 408: According to EN 408: a f h with 1 a1 fa1 6 1,5 15

16 Bending in Plane Test Method 4-point-bending test according to EN 408: bending failure requested For bending failure we need at least a bending stress of 95%- quantile while (rolling) shear stress is 5%-quantile at a maximum glulam l e.g.: GL 24 visually graded COV = 35% CLT f m,c,k = a f t0,l,k 0,80 = 2, ,82 = 24,5 N/mm 2 f mck = 0,80 = 0,8 = 2 m,c,k a CLT f t0,l,k 3, ,9 N/mm 95% quantile (assuming normal distribution): fmc,,05 f mc,,95 1 1,645 COVm 40,3 N / m² 1 1,645 COV m N/mm 2 16

17 Bending in Plane Test Method 4-point-bending test according to EN 408: bending failure requested (Rolling) shear strength of cross layers: Without groovings: f 150N/ v,9090,c,k = 1,50 N/mm 2 With groovings: f v,9090,c,k = 0,70 N/mm 2 acc. to approval for Merk Example for groovings 17

18 Bending in Plane Test Method 4-point-bending test according to EN 408: bending failure requested v,9090, c F Seff 2 2 fv,9090, c,05 Ieff b F I b S eff F F a1 fa 1 h M f mc,,95 W eff mc, fa 1 Weff Weff Weff F h eff 18

19 Introduction: ti Cross Laminated Timber CLT a Wood Based Product Bending under loads perp. p to Plane Shear loads in Plane Conclusion and open points 19

20 Shear force in plane Bearing Model The mass product Cross Laminated Timber (CLT) Length 16 m Width 3 m Thickness mm Layers 3 9 (21) Finger Joint Rigid glued (same lamella as for GLT) Butt joint Gaps 0 6 mm Rigid glued Dry cracks effective width?! 20

21 Shear force in plane Bearing Model Mechanism I: Mechanism II: 21

22 TUG test configuration Mechanism I Shear force in plane Test Configuration Test configuration with symmetric shear block (2 tested cross sections) F/2 F/2 F/2 F Shear forces Test configuration F Local failure 22

23 Shear force in plane Test Configuration TUG test configuration Mechanism I FEM Investigation F/4 Local failure F/2 F Shear forces F/4 23

24 Shear force in plane Test Configuration Shear Strength value for mechanism I f = 10 v, k [N/mm²] Remark: Value still in discussion! Load displacement behaviour 24

25 Shear force in plane Test Configuration TUG test configuration Mechanism II shear stresses in the gluing interface Detail of test specimen M T I P a Torsional moment polar sectional moment of gluing interface I P = a4 6 dimension of RVE 2004: diploma thesis G. Jeitler Versuchstechnische Ermittlung der Verdrehungs- kenngrössen von orthogonal verklebten Brettlamellen 25

26 Coverage of tests Shear force in plane Test Configuration Shear strength value for mechanism II Shear stresses in the gluing interface f f = T, k [N/mm²] Remark: Value generally accepted! 26

27 Introduction: ti Cross Laminated Timber CLT a Wood Based Product Bending under loads perp. p to Plane Shear loads in Plane Conclusion and open points 27

28 Conclusion and open points Conclusion Bearing models like for bending loads perp. p to plane or shear loads in plane - are needed for huge elements like CLT Test procedures must be new defined (shear loads in plane) or at least adapted (bending loads) from well known configurations (EN 408 configuration) 28

29 Conclusion and open points open points Bearings models for tension and compression forces should be still established. Interaction formulars between tension/compression with bending should be investigated t in future. Bending strength near local support (e.g. column support) with its typical moment peaks has to be investigated. Compression strength perpendicular to grain and factor k c90 c,90 For some special cases tensile strength behavior perpendicular to grain is needed d e.g. curved elements. 29

30 Thank You for Your Attention Contact: DI Robert Jöbstl Dr Thomas Bogensperger Institute for Timber Engineering g and Wood Technology Graz University of Technology Inffeldgasse 24 A-8010 Graz r.joebstl@tugraz.at tel.: bogensperger@tugraz.at tel.: