FINITE ELEMENT ANALYSIS OF WOODEN BEHAVIOR OF COMPRESSIVE STRAIN INCLINED TO THE GRAIN (PART 4): NUMERICAL ANALYSIS OF DEFORMATION BEHAVIOR AT CLT-GLULAM JOINTS WITH CONSIDERATION ON INCLINATION OF ANNUAL RINGS

<p> Recently, application of Cross Laminated Timber (CLT) for medium and high-rise wooden structure is spreading rapidly even in Japan. It has been proposed not only CLT panel structures but also structures combined CLT panel with frame members which is used wood-based materials such as Glued Laminated Timber (Glulam) or Laminated Veneer Lumber (LVL) and so on. In a case of CLT is used as wall column and Glulam is used as beam, it is important that appropriate evaluation of deformation property between CLT and Glulam.</p><p> Wood has strong anisotropy, and material characteristics are completely different when subject to compressive stress in longitudinal direction or direction that perpendicular to the grain. Especially, it is known that stiffness and strength become low value in the case subject to partial compressive strain in direction of perpendicular to the grain. To evaluate deformation property of wooden structures, it is important that transact unique characteristics of wood such as mentioned above properly.</p><p> In this paper, the yield criterion and strain hardening rule using non-dimensional stresses for orthotropic materials such as wood proposed in previous papers are applied to numerical analysis of CLT-Glulam joint and comparison between result of analysis and experiment are shown.</p><p> Firstly, partial compression test of glulam is conducted and compared with numerical analysis. It is shown that method for decide material properties for analysis, which is that a certain value is decided from material experiment and other properties are calculated using ratio among material properties of wood proposed in previous studies. From the result of numerical analysis, stiffness and strength have not improved even though increase in size of specimen contrary to expectations.</p><p> Reason of the above result is expected to effect of inclination of annual rings in the end grain. Accordingly modeling method considering inclination of annual rings in the end grain is proposed and numerical experiment applied the method is performed. From the result of numerical experiment, if effect of inclination of annual rings is not considered, it is confirmed that obtained value from analysis is bigger than experimental value. In the case that width of glulam is 210mm, by the effect of inclination of annual rings, decrease 55% (from 519.05 N/mm² to 235.59 N/mm²) in Young’s modulus and 22% (from 2.74 N/mm² to 2.14 N/mm²) in yield stress. Moreover, result of compression test is shown and it is verified that Young’s modulus and yield stress decrease relatively even though size of specimen increase by effect of inclination of annual rings.</p><p> Finally, based on the above discussions, numerical analysis of partial compression test is conducted once again. The result of analysis is well corresponding to experimental result and appropriateness of the proposed method is confirmed. In the case that width of glulam is 150mm, by adjusting input data for analysis to experimental result, difference between analysis and experiment is only 1% (analysis: 701.26 N/mm², experiment: 711.05 N/mm²) in Young’s modulus and 6% (analysis: 3.73 N/mm², experiment: 3.96 N/mm²) in yield stress. It is clarified that whether considering inclination of annual rings in the end grain or not have great effect on result of numerical analysis. According to the result, effect of inclination of annual rings would be remarkable if width of glulam become larger and a part which annual rings inclining become wider.</p>