胶合木梁湿度变化导致横纹应力和开裂的研究

项目名称： 胶合木梁湿度变化导致横纹应力和开裂的研究

项目编号： No.50878067

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 祝恩淳

作者单位： 哈尔滨工业大学

项目金额： 30万元

中文摘要： 本项目基于传热传质理论，综合考虑木材湿胀干缩、粘弹性蠕变和机械吸附蠕变性质，研究了胶合木受弯构件在荷载与湿度、温度联合作用下产生横纹应力的机理和长期工作性能。建立了计算胶合木受弯构件应力场、温度场和湿度场的有限元模型，用以预测胶合木构件的长期工作性能。并通过胶合木曲梁的短期承载力试验和不同周期的相对湿度变化与荷载联合作用下的长期承载试验研究，对有限元分析结果予以验证。根据断裂力学和损伤力学理论，研究了胶合木构件在荷载与湿度、温度联合作用下裂纹的产生、扩展机理及其对承载能力的影响，建立了胶合木构件考虑温湿度导致横纹应力的开裂准则和强度准则，提出了胶合木的弹脆性损伤模型和考虑时间效应的蠕变损伤模型，发展了计算荷载和湿度变化联合作用的简化蠕变开裂计算方法。同时，对胶合木生产制作过程中层板的选择、叠放顺序、年轮朝向等影响横纹应力的因素进行了优化研究，寻求减缓胶合木构件在制作和使用过程中横纹应力的措施。

中文关键词： 胶合木；横纹应力；蠕变；开裂准则；温湿度

英文摘要： Based on theories of heat transfer and moisture transfer, moisture-induced stress perpendicular to grain in Glulam beams under combined actions of moisture variations and load and the long-term performance of Gluam beams were investigated, taking into account shrinking,swelling,viscoelastic creep and mechano-sorption of wood.Finite element models simulating temperature, moisture content and stress distribution in the beams were developed, then the long-term performance of Glulam beams was thus predicted. A series of tests of curverd Glulam beams both under short-term loading and under combined actions of moisture variations and load were conducted, and the finete element models so developed and the analytical results were also validated by the tests. By using theories of Fracture Mechanics and Damage Mechanics, initiation and propagation of cracks and the effect on the load carrying capacity were investigated, the criteria for fracturing and strength design due to moisture-induced stress perpendicular to grain were established. An elastic brittle damage model and creep damage model taking duration of load into consideration was developed and the simplilfied calculation method for the comnied actions of load and varying moisture or relative humidity was established. In addition, factors afecting stress perpendicular to grain like requirements for the laminas and pattern of lamina stacking were optimised to enhance quality of Glulam production, wasys to mitigate the moisture-induced stress in both production and service were sought.

英文关键词： Glulam; stress perpendicular to grain; creep; fracture criterion;temperature and humidity