| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 107 === The purpose of this study was to investigate and analysis the correlation between the dynamic and static bending properties of China fir (Cunninghamia lanceolata) laminae using visual grade method, ultrasonic wave method, tap tone method and static bending test. Laminae after ACQ preservative treatment (K4 and K5 grade) was to construct homogeneous and heterogeneous-grade structural glued laminated timber, and evaluate the effect of preservative treatment and laminae configuration on the bending properties, shear properties, delaminating properties, longitudinal compressive properties, radial and tangential shrinkage.
The correlation between the dynamic and static bending properties determined by non-destructive method and static bending test of control groups and ACQ-treated laminae was high (R2 = 0.60-0.78). The result also showed that the dynamic MOE is higher than the static MOE of laminae (DMOEu＞DMOEf＞MOE), however, the values of DMOEf determined by tap tone method were very close to the values of MOE. It is feasible to use the non-destructive method for mechanical grading of laminae and preservative treated laminae.
The variation of the average MOE and DMOE values of ACQ preservative-treated laminae (K4 and K5 grade) compared with the control group were about ±15 %. The MOE and MOR of preservative-treated homogeneous and heterogeneous-grade structural glued laminated timber were lower than the control groups by about 12.06-20.13%. However, the differences of MOE and MOR values between preservative-treated groups and control groups were not significant according to ANOVA analysis. The longitudinal compressive strengths of preservative-treated homogeneous-grade glulam were lower than the control groups by about 25.63-32.18%, and there was a significant difference among preservative-treated groups and control groups. It is speculated that the effect of preservative treatment on the bending properties of glulam was not significant. The difference of the average radial and tangential shrinkages between most preservative-treated China fir laminae and control groups was not significant according to ANOVA analysis. To evaluate the physical properties and mechanical properties of China fir glulam, the effect of preservative treatment is not significant. And the result of this study maybe can provide reference for the use of China fir structural glued laminated timber.
In addition, the MOE and MOR of homogeneous-grade structural glued laminated timber were higher than heterogeneous-grade structural glued laminated timber, but there was not a significant difference among homogeneous-grade glulam and heterogeneous-grade glulam. Design the configuration of heterogeneous-grade glulam, placing the laminae of lower MOE grades in the middle layer which strengths still can conform the standard of CNS 11031 structural glued-laminated timber. And it also can effectively utilize the medium-to-low grades laminae.
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