长期监测中藏式古建筑木梁应变-温度模型分析

针对藏式古建筑木梁的构造和受力特点,通过在梁端施加非线性弹簧,建立了温度作用下的简化力学模型.该模型考虑了梁端反力对梁的二阶弯矩作用,建立了温度作用下梁底跨中顺纹方向应变的理论模型,并将一年内的温度循环分为四段进行分别计算.以某藏式古建筑监测工程中的木梁为例进行了实例计算,结果表明一年之后应变增量回到了初始值,但升温段和降温段的曲线没有重合而是分成了两部分.将应变的计算值与实测值相对比,二者吻合较好.最后,对影响温度作用下应变增量的各个结构参数进行了参数分析,研究表明,不同温度起点的设定对分析结果没有影响,木材的弹性模量对应变影响最大,燕尾榫的拉压刚度影响最小.

Strain-temperature Model Analysis of Tibetan Ancient Timber Beam in Long-term Monitoring

According to the construction and loading features of Tibetan ancient timber beam,a nonlinear spring was added at the end of the beam and the simplified mechanical model of temperature effect on the timber beam was established. Considering the second order of the counterforce of beam end,a theoretical model of the strain in the grain direction of the mid-span beam bottom under temperature effect was proposed. The strain in a temperature cycle was divided into four parts for calculations. A timber beam of a Tibetan ancient building from a monitoring system was employed as a calculation example. The results show that the strain returns to the initial value in a temperature cycle,while the curves of the temperature rising stage and temperature decreasing stage are not coincident but divided into two parts. The calculated strain curve matches well with the measurement. Finally,the parameter analysis of the structure parameters affecting the strain variations was proceed,and the results show that the different starting temperature makes no difference for the analysis results. Elasticity module is the most sensitive parameter,while the tension and compression stiffness of the dovetail joint is the least sensitive parameter.