古建筑木结构关键节点受力性能分析及其等效有限元模型研究

Mortise-tenon, Dougong, Dougong-column cap joint and column foot joint are the critical joints of ancient timber structure, and they play important roles in the structural overall performance. Mechanical properties and equivalent finite element models of the critical joints are quite important to the analysis of structural overall performance and structural state assessment. This project will focus on two kinds of critical joints which are floating column foot joint and Dougong-column cap joint, of which research results are still rare at present. Firstly, establish the mechanical conceptual models which can descript the stress state and swing mechanism of the joints as well as force type, transmission mechanism and failure mode of the joint constituent components. Secondly, based on the refined finite element model and full scale model tests, mechanical properties of the joints, critical parameters which mostly influence the property of the joints and connections between the joint constituent components will be analyzed deeply. Finally, establish the equivalent finite element models which can descript the mechanical characteristics of the joints and the experimental characteristics of the contacts between the joint constituent components. The quantitative relationship between model parameters and joint parameters should also be determined. The obtained equivalent finite element model can provide basis for the overall structural analysis.

柱-枋、梁-檩等榫卯节点、斗拱、斗拱-柱头连接节点、柱脚节点等是古建木构的关键节点，对结构整体特性起着决定性作用。对关键节点进行受力性能分析，建立适用于结构整体分析的等效有限元模型是准确分析结构整体受力性能和评估结构状态的前提。本项目拟针对目前研究成果尚不多见的平摆浮搁柱脚节点及斗拱-柱头连接节点开展节点受力性能及其等效有限元模型方面的研究。首先建立能够反映这两类关键节点受力状态、摇摆机理以及节点中各组成部件承力类型、传力机制和破坏模式的力学概念模型，清晰描述节点在整体结构中的力学作用；而后基于节点精细化有限元模型和足尺模型试验对节点受力性能、关键参数以及组成部件间的连接关系进行深入分析；最后建立能够较精准地反映这两类连接节点整体受力特性及各组成部件接触面实验特征的节点等效有限元模型，并确定模型参数与节点参数之间的定量关系，为古建木构整体分析提供计算依据。

柱-枋、梁-檩等榫卯节点、斗拱、斗拱-柱头连接节点、柱脚节点等是古建木构的关键节点，对结构整体特性起着决定性作用。对关键节点进行受力性能分析，建立适用于结构整体分析的等效有限元模型是准确分析结构整体受力性能和评估结构状态的前提。本项目针对平摆浮搁柱脚节点、榫卯节点和斗拱节点开展受力性能及其等效有限元模型方面的研究。（1）柱脚节点：提出了能够反映古建筑木构架未滑移摇摆状态下平摆浮搁柱脚节点在整体结构中的受力特点、摇摆机理以及节点中各组成部件承力类型、传力机制和破坏模式的理论分析模型；通过理论分析、足尺试验和数值模拟，得到了柱脚节点在水平往复荷载作用下的运动特点和变形特征以及承载力、滞回耗能、刚度特性和延性等力学特性，建立了适用于结构整体分析的等效有限元模型；（2）榫卯节点：现存古建筑木结构榫卯节点组成部件间大多存在缝隙，处于不同程度的松动状态，通过榫头卯口间不同缝隙值的足尺透榫节点拟静力试验，研究了松动节点的滞回性能、刚度特性、耗能及延性，并提出了松动节点抗弯刚度模型；根据现场量测与统计分析，得到了古建筑木结构榫卯节点缝隙概率分布模型，对考虑榫卯缝隙分布的单榀单跨木构架进行了单调加载有限元分析，得到了木构架典型荷载-位移曲线；（3）斗拱节点：总结了典型历史时期的斗拱节点与其所在木构架的构造特征与演变规律，对斗拱节点的传力机制进行了概念分析；对殿堂型木构架代表唐代建筑佛光寺东大殿的斗拱层构造进行详细解读，建立了考虑实际几何构造、木材正交异性本构关系以及组成部件间静动摩擦关系的佛光寺东大殿一榀构架精细化有限元模型，对斗拱和木构架的传力机理与变形特征进行了深入分析。