正交胶合木滚动剪切性能评价及影响机理研究

Modern timber structure has the outstanding advantages, such as energy conservation and environmental protection, however, modern timber structure also has some disadvantage, such as low building height. Cross-laminated timber (CLT) is an innovative engineering wood product, which has provide the material source and chance for developing mid-rise and high-rise buildings. The research of using CLT as the structural material of building has become the research hotspot and development strategy of timber structure industry, especially in Europe and North American. Rolling shear strength and stiffness in CLT has been identified as a key issue that may control the design and performance of CLT floor or wall systems. The influence mechanisms of rolling shear in CLT have been studied in this project, which include the microscopic structure of wood, cross section macroscopic structure of timber, CLT structural parameters and CLT manufacture. The relationships between cross section macroscopic structure and rolling shear was quantified and the single factor effect and multi-factor coupling effect on rolling shear were evaluated in this product. The digital image correlation (DIC) method was used to evaluate the shear strain of rolling shear and bending failure modes of CLT, and a new evaluation method of rolling shear has been developed which met the actual loading environment, product dimension and structure. The modification of rolling shear properties was studied finally. The aims of this product are to provide theoretical explain for master the rolling shear properties in CLT, scientific theory of CLT mechanical properties for developing mid-rise building and high-rise building, and speed the development of mid-rise building and high-rise building in China.

现代木结构建筑具有节能、环保等突出特点，但也存在建筑高度低等不足。新型工程木:正交胶合木为发展中高层木建筑提供了材料来源和发展契机。目前，利用正交胶合木作为主要承重材料建造中高层木建筑研究已成为世界，尤其是欧洲和北美木结构行业研究热点和重要发展战略。滚动剪切性能是正交胶合木作为楼板和墙体构件的结构设计和力学性能的关键因素。项目从木材微观构造、锯材横切面宏观构造、产品构造参数和生产工艺等角度全面阐明滚动剪切性能影响机理，定量化锯材横切面宏观构造参数与滚动剪切性能的关系，评价单一因素影响和多因素对滚动剪切性能的耦合效应，采用数字图像相关法分析滚动剪切变形的全场应变和弯曲失效模式，建立一种与实际受力、尺寸和构造等因素相符合的新型滚动剪切评价方式，研究改善滚动剪切性能。研究成果将为科学理解正交胶合木滚动剪切性能提供理论依据，为国内发展中高层木建筑提供材料性能科学依据，促进国内中高层木结构建筑发展。

随着中高层木结构建筑在全世界范围内的发展，正交胶合木（Cross-laminated timber, CLT）方面研究已成为相关行业研究的热点和战略发展方向，滚动剪切性能是CLT作为楼板和墙体构件的结构设计和力学性能的关键因素。. 项目通过CLT滚动剪切破坏微观分析，揭示了木材早晚材分界处、木射线等滚动剪切破坏机理；通过不同密度、不同管孔类型、不同宽窄木射线、不同早晚材过渡的CLT横向层锯材的滚动剪切性能测试评价，总结得到了锯材横切面宏观构造特征对CLT横向层滚动剪切性能影响规律及不同树种在CLT材料应用的可行性；研究了CLT典型构造特征（宽厚比、横向层缝隙、侧面是否涂胶和层数）以及生产工艺（胶粘剂种类、涂胶量和压力）对CLT滚动剪切性能单一和耦合影响；试验研究了压缩、浸渍等改性方法对CLT滚动剪切性能的影响；采用滚动剪切性能较好的国内木材和工程木（重组竹和结构用OSB等）研发了滚动剪切性能和抗弯性能都优于普通锯材CLT的混合结构CLT，如将重组竹同时作为横向层和表层平行层时，CLT梁弯曲弹性模量和强度分别提高24%和64%，建立了适合混合CLT抗弯力学性能计算和有限元模型，得到了优化的胶合生产工艺，申请竹木复合CLT发明专利1项；采用DIC技术，测试了CLT滚动剪切过程全场位移，揭示了破坏裂纹发展规律；采用声发射和DIC技术，分析了CLT发生滚动剪切破坏时的损伤演化和破坏特征，利用聚类分析探究该状态下不同损伤的声发射特征；评价了压弯和压剪等CLT滚动剪切测试方法对其滚动剪切性能的影响，获得了CLT滚动剪切测试方法的实用新型专利；项目还研究了不同横向层厚度占比等重要因素对CLT销槽承压性能的影响，建立了基于横向层厚度占比等因素的CLT销槽承压性能计算公式；试验研究了不同组坯结构的HCLT的横纹承压破坏机理和强度。. 项目研究成果，为科学理解CLT滚动剪切性能提供了理论依据，研发的混合结构CLT将在国内相关企业进行转化和应用；项目研究进一步完善了国内CLT方面研究，对国内CLT产品和建筑等方面研究和发展具有很大的促进作用。