足尺毛竹梁长期蠕变性能研究

Study on long-term creep performance of full-culm Moso bamboo beam

为研究足尺毛竹梁的长期蠕变性能,分析了已有的试验数据,进一步探究毛竹梁在长期荷载作用下的蠕变规律。从微观层次分析了竹材蠕变性能随环境湿度、温度变化而改变的机理;以强度储备、蠕变速率以及相对挠度作为控制指标,评估了毛竹梁的蠕变性能;对毛竹梁蠕变模型开展了适用性研究,并基于蠕变模型的挠度预测给出了毛竹梁的建议应力比。结果表明:环境中湿度和温度的变化会引起竹材的物理性质发生变化,从而改变竹材的蠕变性能;应力比较小的毛竹梁蠕变性能总体上符合工程使用要求;将Burger模型中表征黏性变形的线性函数改进为幂函数,改进的Burger模型结合了Burger模型和幂律模型的特点,能更好地模拟毛竹梁的蠕变性能。最后,基于蠕变模型的长期变形预测值,建议了毛竹梁应力比不应大于0.50,以防止原竹建筑在50年的设计基准期内产生过大的蠕变变形。

In order to study the long-term creep performance of full-culm Moso bamboo beams,the existing test data were analyzed,and the creep law of full-culm Moso bamboo beam under long-term load was further explored.The mechanism that the creep performance of bamboo changes with the environmental humidity and temperature was analyzed from the microscopic level.The creep performance of Moso bamboo beam was evaluated by adequate strength,creep rate and fractional deflection.The applicability of creep models of Moso bamboo beam was studied,and the recommended stress ratio of Moso bamboo beam was given based on the deflection prediction of creep models.The results show that the changes of humidity and temperature in the environment would cause changes in the physical properties of bamboo,thus changing the creep performance of bamboo.The creep performance of Moso bamboo beam with small stress ratio generally meet the engineering requirements.The viscosity deformation in Burger model is modified as a linear function of time to a power function,and the modified Burger model combines the characteristics of Burger model and power function model,which can better simulate the creep performance of Moso bamboo beam.Finally,based on the long-term deformation prediction of the creep model,it is suggested that the stress ratio of Moso bamboo beam should not be greater than 0.50 to prevent excessive creep deformation of the original bamboo building in the 50 year design reference period.