基于摇摆柱的古建筑木结构柱脚节点力学模型研究

在古建筑木结构中，木柱通常直接平摆浮搁于础石之上，形成只有受压而无受拉能力的柱脚节点。在地震作用下，木柱会发生摇摆，柱脚为半刚性节点。为研究地震作用下古建筑木结构柱脚节点的摇摆机理，对柱脚节点的受压状态进行分析，并对木柱的摇摆过程进行分类，给出了不同摇摆过程的判定条件，建立了柱脚节点的弯矩-转角（M-θ）力学模型；通过与柱脚节点的弯矩-转角曲线试验结果进行对比，验证了该力学模型的正确性；将该M-θ力学模型应用于古建筑木结构的地震分析中，分别建立了柱脚半刚性连接和铰接的数值模型，并与振动台试验结果进行对比。研究结果表明：木柱的摇摆过程可分为全截面弹性摇摆、小截面弹塑性摇摆、大截面弹塑性摇摆以及全截面弹塑性摇摆等4类；采用M-θ力学模型得到的柱脚节点弯矩-转角曲线计算结果与拟静力试验结果的差异在10%以内；与铰接的柱脚节点相比，采用柱脚半刚性连接计算的古建筑木结构在地震作用下的动力响应更接近振动台试验结果，结构的加速度峰值、位移峰值与振动台试验结果的差异均在20%以内。

Study on mechanical model of column footing in ancient timber structure based on rocking column

Timber columns are usually placed on the foundation directly in ancient timber structures, forming a column footing with compression capacity only and without tension capacity. Column footing is a semi-rigid joint when timber column rocks under the earthquake. To study the rocking mechanism of the column footing, firstly, the compression state of column footing was analyzed and the rocking process was classified. The judgment conditions of different rocking processes were proposed, and the moment-rotation (M-θ) mechanical model of column footing was established. Then, the mechanical model was validated by comparing it with the test results. Finally, the M-θ mechanical model was applied to the seismic analysis of ancient timber structures. The semi-rigid connection model and hinged model of the column foot were established and compared with the shaking table test results, respectively. The results show that the rocking process of timber columns can be divided into four types: elastic rocking of the full section, the elastic-plastic rocking of the small section, the elastic-plastic rocking of the large section, and the elastic-plastic rocking of the full section. The differences between the calculated results of the M-θ mechanical model and quasi-static test results are within 10%. Compared with the hinged column footing, the semi-rigid connection model results is closer to the dynamic response of the timber structure under earthquake. The differences between the results of the shaking table test and semi-rigid connection are within 20% for both peak acceleration and peak displacement.