古建筑木结构多尺度建模方法及抗震性能分析

Multi-scale modeling method and seismic behavior analysis for ancient timber sutrctures

在保证计算精度前提下,为降低抗震性能计算的有限元分析费用,采用通用有限元软件ANSYS建立了古代木结构非线性有限元模型。深入探讨了利用多尺度建模方法解决古代木结构抗震计算问题。为实现宏观结构模型和局部微观模型界面的变形协调,采用了多点约束法,将榫卯节点域作为关键区域用实体单元进行精细尺度建模,对梁柱构件非关键区域则采用梁单元进行建模。基于木框架和直榫节点拟静力试验数据,对比了多尺度模型和实体单元模型在破坏模态和滞回曲线的异同点,验证了该界面连接方法的有效性。基于多尺度建模方法,选取某在役期内的古代木结构边跨框架进行弹塑性动力时程分析,并比较了实体单元模型和多尺度模型的地震响应及计算效率。结果表明:多尺度有限元模型能很好地模拟古代木结构的边界条件以及整体结构的动力响应,同时还可大幅提高计算效率,能够在计算精度和计算效率之间寻找到一个平衡点,为古代木结构抗震分析提供有力的技术支持。

In order to ensure the accuracy of finite element seismic analysis of ancient timber structure and to improve computational efficiency,a nonlinear finite element model was established by using the general finite element software ANSYS and the anti-seismic calculation problem was also discussed based on multi-scale modeling method. By using the multiple point constraint method（ MPC）,the deformation at the interface between structural macroscopic models and local microscopic models were compatible well with each other. Solid element was used to construct the model of mortise-tenon joint which was chosen as a key area of the whole structure. The models of beam and column in the noncritical area were constructed by using the beam element. To verify the effectiveness of the interface connection method by using MPC,the multi-scale finite element models and three dimension solid element models were established to analyze the failure modes and hysteretic loops based on the quasi-static test data of timber frame and mortise-tenon joints. Finally,elasto-plastic time-history analysis was performed on an exterior timber framework of an existing ancient timber building based on multi-scale method. The computational efficiency and earthquake response were compared between the solid model,beam element model and multi-scale model. The result shows that the multi-scale finite element model,with good computational efficiency,can simulate the boundary conditions of timber components and dynamic response of the whole structure. This indicates that the use of multi-scale model is a balanced solution between computational precision and efficiency,which can provide a solid and powerful technical support for seismic analyses of ancient timber structures.