国产杉木不同层板厚度对正交胶合木力学性能的影响

Effect of Different Laminate Thickness on Mechanical Properties of Cross-Laminated Timber Made from Chinese Fir

【目的】研究国产杉木不同层板厚度对正交胶合木(CLT)力学性能的影响,以拓宽速生材杉木在木结构建筑领域的应用范围,促进CLT在国内的发展。【方法】在国产杉木CLT整体厚度不变的前提下,研究不同层板厚度对CLT抗弯和抗剪性能的影响,结合抗弯试验结果,运用CLT静力学分析理论对CLT试件进行抗弯性能计算并比较。【结果】在CLT整体厚度不变的前提下,3层CLT试件的抗弯刚度最大,5层和7层CLT试件的抗弯刚度分别降低11%和18%。5层CLT试件的抗弯强度相比3层CLT试件提高18%,相比7层CLT试件提高36%,5层和7层CLT试件的抗剪强度相比3层CLT试件分别提高2.6%和16%。抗弯刚度理论分析与试验结果趋势相同,而抗弯强度理论分析得出层数越多其值越高,试验结果显示5层优于7层;以5层CLT试件为例,保持整体厚度不变,增加奇、偶层厚比例,CLT试件的力学性能均有一定比例上升,理论分析与试验结果具有相同趋势。【结论】在整体厚度不变的前提下,CLT层板越厚,CLT结构的抗弯刚度越佳,抗剪强度越差,破坏模式越单一,5层CLT试件的抗弯强度最佳;在一定比例范围内,增加奇、偶层厚比例,可有效提高CLT试件的抗弯和抗剪性能。

【Objective】This research was implemented to study the influences of different laminate thicknesses of Chinese fir(Cunninghamia lanceolata)on the mechanical properties of cross-laminated timber(CLT),and to expand the application range of Chinese fir in the field of wood structure construction and further promote the development of CLT in China.【Method】Under the premise that the overall thickness of the domestic Chinese fir CLT remains unchanged,the effects of different layer thicknesses on the CLT bending and shearing properties were studied.Combined with the bending test results,the existing CLT statics analysis theory was used to perform the above tests on the CLT specimens.The bending performances under different conditions were also calculated and compared.【Result】Under the premise of an unchanging total thickness,bending stiffness of the three-layer CLT specimens was the highest,and the five-layer and seven-layer specimens were reduced by 11%and 18%,respectively.The bending strength of the five-layer CLT specimens was increased by 18%compared with the three-layer specimens,which was 36%higher than that of the seven-layer specimens.The shear strength of the five-layer specimens and the seven-layer specimens was increased by 2.6%and 16%,respectively,over the three-layer specimens.The trend of the theoretical analysis of the bending stiffness was the same as the test results,however,the theoretical analysis of the bending strength showed that the higher the number of layers,the higher the value,the test results showed that the five layers were better than the seven layers.When the five-layer specimens was taken as an example,under the premise of overall thickness unchanged,increasing odd and even layer thickness ratio could effectively improve the bending and shear properties of CLT specimens in a certain percentage range.Theoretical analysis had the same trend as the experimental results.【Conclusion】The results showed that under the premise of overall thickness unchanged,the thicker the CLT laminated,the better the bending stiffness was,the worse the shear properties presented,and the single failure mode was.The 5-layer CLT specimen had the best bending strength;within a certain ratio range,increasing the ratio of odd and even layer thickness could effectively improve the bending and shear resistance of the CLT specimen.