TEMTIS seminar Horsens 2008 Eurocode 5: Compression perpendicular to the Grain H J Larsen Denmark A J M Leijten TU-Eindhoven – The Netherlands T A C M van der Put TU-Delft – The Netherlands

TEMTIS seminar Horsens 2008 Acknowledsments Based on paper for CIB-W by H J Larsen, Denmark A J M Leijten, TU-Eindhoven – The Netherlands T A C M van der Put, TU-Delft – The Netherlands

TEMTIS seminar Horsens 2008 Problem Introduction of a ”scientific” test method and definition for compression perpendicular to grain has halved the characteristic strength

TEMTIS seminar Horsens 2008 Problem Introduction of a ”scientific” test method and definition for compression perpendicular to grain has halved the characteristic strength Many traditional structures and details e. g. in timber frame houses will no longer be acceptable

TEMTIS seminar Horsens 2008

Standard Test Methods 51x51x152mm ASTM – D143 Australian (technological ) test 45 European (scientifical) test EN 408 Poussa et all. Proc.:CIB-W : paper Compressive strength =

TEMTIS seminar Horsens 2008 Standard Test Methods Compressive stress

TEMTIS seminar Horsens 2008 Definition Compressive strength European test EN 408 Compressive strength 1% off-set 1 %

TEMTIS seminar Horsens 2008 Comparison of test results Ref: Poussa et al. Helsinki CIB-W18 paper

TEMTIS seminar Horsens 2008 Proposal Thelandersson & Mårtensson and others Regard exceedance of scientific compression strength as violation of a serviceability state (and not an ultimate limit state)

TEMTIS seminar Horsens 2008 Limit states Ultimate limit states Serviceability limit states

TEMTIS seminar Horsens 2008 Ultimate limit states Failure of whole structure or part of it Precise internationally agreed definitions On the whole agreed safety level

TEMTIS seminar Horsens 2008 Topping-up day

TEMTIS seminar Horsens 2008 Next day - failure

TEMTIS seminar Horsens 2008 Failure (at least in lower story)

TEMTIS seminar Horsens 2008 Failure (at least in lower story)

TEMTIS seminar Horsens 2008 Deformations preceding failure

TEMTIS seminar Horsens 2008 Serviceability limit states Unacceptable behaviour at normal use

TEMTIS seminar Horsens 2008 Serviceability limit states Unacceptable behaviour at normal use, e. g. visually unacceptable

TEMTIS seminar Horsens 2008 Serviceability limit states Unacceptable behaviour at normal use, e. g. visually unacceptable

TEMTIS seminar Horsens 2008 Serviceability limit states Unacceptable behaviour at normal use, e. g. visually or functionally unacceptable deformations

TEMTIS seminar Horsens 2008 Serviceability limit states In most cases: No precise requirements Criteria fixed by designer in agreement with client National tradition and taste

TEMTIS seminar Horsens 2008 Serviceability limit states Formally it is not required to perform a serviceability verification as long as it is possible to perform the ultimate state verification

TEMTIS seminar Horsens 2008 Serviceability, compression perp. It is difficult, to put it mildly, to understand why exceeding a marginal deformation in a block compression test should be taken as the governing criteria for structures where much larger deformations are normally acceptable and loaded in a completely different way.

TEMTIS seminar Horsens 2008 Serviceability, compression perp. It is difficult, to put it mildly, to understand why exceeding a marginal deformation in a block compression test should be taken as the governing criteria for structures where much larger deformations are normally acceptable and loaded in a completely different way. Especially when the use of the Serviceability limit state is accepted only half heartedly and without a proper definition and understanding

TEMTIS seminar Horsens 2008 Eurocode design equation EN Impirical model Hilmer Riberholt Incomplete, discontinous, strange jumps

TEMTIS seminar Horsens 2008 New design equation EN :2005/A1 Blass and Görlacher based on Borg Madsen (2000 ) l + 60mm l ef =

TEMTIS seminar Horsens 2008 Alternative Model Based on Van der Put (1986) Slip-line theory

TEMTIS seminar Horsens 2008 Alternative Model Slope 1:1 for 1% off-set Slope 1:1,5 for 10% deformation

TEMTIS seminar Horsens 2008 Alternative Model Based on Van der Put (1986) Slip-line theory (Schoenmakers)

TEMTIS seminar Horsens 2008 Model comparison A B C D E F Test results reported by many authors Test A: n = 418 Tests B to F: 1% n= 582 (52 samples) 10% n= 125 (23 samples) -Solid wood -Glued laminated wood Load cases reported

TEMTIS seminar Horsens 2008 Comparison 1 % off-set

TEMTIS seminar Horsens 2008 Model comparison

TEMTIS seminar Horsens 2008 Comparison

TEMTIS seminar Horsens 2008 Comparisons ln(model/test)=ln(R) ideally: ln(R)=0  R=1 n = 582Van der PutEC 5 Mean- 0,04- 0,36 Standard deviation 0,170,20

TEMTIS seminar Horsens 2008 Model evaluation

TEMTIS seminar Horsens 2008 Model evaluation

TEMTIS seminar Horsens 2008 Conclusion Compression perpendicular to grain The evaluation of both models show that Van der Put model is far more accurate in predicting accurately the bearing strength perpendicular to the grain than the model currently in Eurocode 5/A1.

TEMTIS seminar Horsens 2008 Proposal for EC5 adoption Compression perpendicular to grain Deformation limit 1% Deformation limit 10% for h < 4 b

TEMTIS seminar Horsens 2008 Proposal for EC5 adoption Compression perpendicular to grain Deformation limit 1% Deformation limit 10% for h < 4 b

TEMTIS seminar Horsens 2008 Restriction Formally verified only for continously supported beams

TEMTIS seminar Horsens 2008 Restriction Formally verified only for continously supported beams Not too difficult to extend to concentrated supports

TEMTIS seminar Horsens 2008 Future Formally verified only for continously supported beams Not too difficult to extend to concentrated supports No tests for unsupported loads

TEMTIS seminar Horsens 2008 Future Tests needed for unsupported loads !