Verification of Depth Adjustment Factor in Eurocode 5 for Tropical Hardwood Timbers

The depth adjustment factor for bending strength stated in Eurocode 5(EC5)is only applicable to timbers having a characteristic density below 700 kg/m^(3).However,most Malaysian timbers are hardwood,some with a characteristic density reaching above 700 kg/m^(3).Therefore,the objective of this study was to examine whether the depth adjustment factor stipulated in EC5 is valid for Malaysian hardwood timbers.Six timber species were selected for this study,namely Kapur(Dryobalanops C.F.Gaertn.),Kempas(Koompassia Maingay ex Benth.),Keruing(Dipterocarpus C.F.Gaertn.),Light red meranti(Shorea Roxb.ex C.F.Gaertn.),Geronggang(Cratoxylum Blume)and Balau(Shorea Roxb.ex C.F.Gaertn.).The determination of bending strength and characteristic density was conducted according to BS EN 408:2010 and BS EN 384:2016,respectively.A graph for mean bending strength vs.(150/h)was plotted for each timber species.The power function was selected to analyze the relationship between the two variables.The power of the regression equations varied depending on the characteristic density of the timber species.For species with a characteristic density below 700 kg/m^(3),such as Kapur,Keruing,and Light red meranti,the power was between 0.16 to 0.17.In contrast,for species having a characteristic density above 700 kg/m^(3),namely Kempas and Balau,the power was higher at 0.23 and 0.24,respectively.Geronggang was an exception to this pattern.These values are close to the depth adjustment factor given in EC5,which is 0.2.Based on the results,it can be suggested that the adjustment factor of 0.2 is also applicable to Malaysian hardwood timbers with a characteristic density above 700 kg/m^(3).

Bending,Compression and Bonding Performance of Cross-Laminated Timber(CLT)Made from Malaysian Fast-Growing Timbers

This study investigated the bending,compression as well as the bonding performance of CLT panels made from fast-growing timber species,i.e.,Laran(Neolamarckia cadamba)and Batai(Paraserianthes falcataria).The variables studied were timber species(Laran and Batai),layers of lamination(3-layer and 5-layer),loading direction in bending(in-plane and out-of-plane),loading direction in compression(x-,y-,and z-axis)and different treatment conditions for bonding performance test.The desired outputs of this study were bending and compression properties(strength and stiffness)as well as bonding performance(block shear strength,wood failure percentage and delamination value).The bending and compression test were conducted according to EN16351:2015 and EN408:2012,respectively.On the other hand,the bonding performance test was determined by block shear and delamination test based on EN16351:2015 and EN14374:2004,respectively.Prior to block shear test,the samples were subjected to three different treatment conditions.The results showed that CLT made from 3-layer Laran timber,loaded at out-of-plane direction exhibited the highest bending properties.Contrarily,CLT made from 5-layered Batai timber,loaded at in-plane direction showed the lowest bending properties.Laran samples for compression loaded at x-axis exhibited the best compressive properties.Generally,Laran CLT showed greater bonding performance determined by shear test compared to Batai CLT for both 3-and 5-layer panels.On the contrary,delamination results showed that Batai CLT demonstrated better bonding performance compared to Laran CLT.In terms of bonding performance measured by wood failure percentage(WFP),most samples under various treatment conditions showed WFP≥80%except for samples under wet condition with WFP≤60%.