【作者】 张锡成；

【导师】 赵鸿铁；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2013， 博士

【摘要】 木结构古建筑在地震作用下的动力分析是其加固修缮的关键依据，也是古建筑结构保护亟需解决的难点问题。本文在定性分析木结构古建筑基本结构特性及抗震概念设计思想的基础上，对按照《营造法式》制作的一个单层单开间殿堂结构当心间模型进行了单向地震激励下的振动台试验，定量研究了殿堂结构在地震作用下的动力特性及地震反应特点；基于构件的恢复力特征建立了殿堂结构的空间有限元杆系模型，并进行了有限元动力时程分析；同时提出了综合考虑柱础滑移隔震、半刚性榫卯节点的特性及斗栱层耗能减震性能等木结构古建筑基本结构特点的简化计算模型；在动力非线性时程分析的基础上采用IDA方法对其抗倒塌性能进行了研究。本文完成的主要研究工作有：（1）从木结构古建筑的结构选型、结构体系布置、结构特殊构件和结构措施的使用等方面入手，探讨了其抗震概念设计思想，研究表明：木结构古建筑平面形状简单、规则，柱网布置对称，平面及竖向刚度均匀，严格限制房屋长宽比及高宽比，结构体型的选取符合当前抗震概念设计原则；柱平置浮搁于础石之上、构件之间采用榫卯连接、斗栱及大质量屋盖的采用使得木结构古建筑成为多重隔震减震的结构系统；“材份制”及“斗口制”等古典模数设计方法不仅确保了结构的安全性，而且同时考虑了木材蠕变与松弛对结构性能的不利影响；“侧脚”、“生起”等特殊构造做法及柱间斜撑和雀替的使用提高了结构的抗震性能，“抬梁式”屋架是一种“替力梁架”。（2）对缩尺比为1:3.52的单开间殿堂式木结构模型进行了振动台试验，研究了在不同地震激励作用下柱脚、柱架顶面及屋盖的相对位移及加速度反应特点，分析了结构的动力特性、破坏模式、动力抗侧刚度的变化趋势及各层次的滞回耗能特点，得到了以下结论：随着结构损伤的不断累积，模型的自振周期及阻尼比随地震动强度的增加而逐渐增大，其波动范围分别为T=0.49~0.67s，ζ=2.9%~4.6%；柱脚滑移及榫卯变形具有隔震减震作用，而铺作层的隔震作用主要取决于地震波频谱特性及结构自振频率之间的相对比例关系；当名义PGA分别为300gal、400gal、600gal、900gal时，柱架的最大侧移角分别为1/70、1/50、1/35、1/21，柱架具有比现代结构更强的变形能力；随着地震强度的增大，结构整体刚度呈现出逐渐下降的趋势，其波动范围为0.346~0.028kN/mm；由榫卯节点连接的柱架侧移变形引起的能量耗散最大，柱脚滑移及铺作层变形的能耗较小且较为接近。（3）建立了基于木结构古建筑结构特征及构件恢复力特性的空间杆系有限元模型，提出用正比于单元初始刚度的单元阻尼矩阵[c]_e=2ζ[k]_e/ω代替经典的Rayleigh阻尼以模拟古建筑中榫卯及斗栱的阻尼性能，进行了动力非线性时程分析，并与试验结果进行了对比，验证了计算模型的可靠性。在此基础上，对殿堂式木结构古建筑结构动力性能进行了参数分析，结果表明：柱脚刚接或者铰接后结构的整体加速度放大系数明显大于原始结构，在一定程度上削弱了木结构古建筑的抗震能力；斗栱的设置可明显延长结构的自振周期且具有减震作用，斗栱刚度越大，其耗能减震作用越弱；结构阻尼比的增加可有效降低木结构古建筑的地震反应；屋盖质量的增加会延长结构自振周期并增大结构相对位移反应，且有助于提高斗栱的耗能减震能力。（4）提出了可以同时考虑柱脚滑移、榫卯半刚性连接及铺作层隔震作用的简化动力计算模型，建立了以水平位移（动力自由度）为未知量的集中质量模型并给出了各状态下的动力方程及统一表达式，给出了体系啮合及滑移两种状态之间转变的临界状态判定条件；采用Wilson-θ法对所建立的集中质量模型进行弹塑性时程分析，利用MATLAB软件编制了相应的弹塑性程序，并通过计算值与试验值的对比验证了程序的可行性。（5）提出了柱脚滑移倒塌的相对位移判定准则及柱架层间倒塌的最大层间位移角判定准则，采用IDA分析方法对两种倒塌机制进行了研究，结果表明：普通地震波作用下木结构古建筑不易出现柱脚滑移倒塌破坏现象；长周期地震波作用下层间倒塌为最可能出现的倒塌机制，长周期地震波的危害性比普通地震波更大。更多还原

【Abstract】 Dynamic analysis of ancient timber buildings under seismic excitations is criticalfor its rehabilitation, and also a difficult problem need to be solved. In this paper, thestructural characteristics and seismic conceptual design ideas of the ancient timberbuildings are qualitatively analyzed. Then a single-storey and intermediate-bay palacehouse was fabricated according to Yin Zao Fa Shi, and shaking table tests wereconducted under unidirectional earthquake excitations. The dynamic characteristics andseismic responses of this palace house are quantitatively studied. Based on hystereticbehaviors of structural members, a3-D beam-spring FEM model was established. And asimplified calculation model was put forward, taking into account of the basic structuralfeatures of ancient timber buildings such as sliding isolation of column root, semi-rigidcharacteristics of mortise-tenon joints, and energy dissipation mechanism of Dou-gonlayers. On the basis of dynamic nonlinear time-history analysis, the collapseperformance was studied using IDA method. The main research work this paperaccomplished is as follows:(1) By analyzing the structural configuration, layout of structural system andconstructional measures, the seismic conceptual design ideas of ancient buildings arediscussed. The results show that: The ancient buildings have a simple and regular planelayout, a symmetry column grid so that the planar and vertical stiffness distributeuniformly. The aspect ratio is strictly limited. The shape of the structure iscorresponding to existing principles on seismic concept design. Columns simple placingon top of plinth, mortise-tenon connections between structural members and the use of Dou-gon and heavy roof make the ancient timber buildings a multi-layered system ofthe vibration isolation and shock absorption. The classical modulus design methods‘Cai-fen’ and “Dou-kou” not only ensure its structural safety, but also take into accountof the adverse effects of wood creep and relaxation on the structural performance. Thespecial constructional measures such as “Ce-jiao” and “Sheng-qi”, the use of diagonalcolumn and “Que-ti” improve its seismic performance greatly. The use of “raised-beam”roof achieves the purpose of saving material.(2) A single-bay palace house with a scale ratio1:3.52was fabricated and shakingtable tests were conducted. Displacement and acceleration responses at column root,column head and roof top were studied under different input seismic excitations. Thedynamic characteristics of the structure, failure mode, dynamic lateral stiffness andhysteretic energy features were analyzed. Those following conclusions are made:The range of natural period and damping ratio of the test model is0.49~0.67s and2.9%~4.6%respectively. The sliding of column foot and deformation of mortise-tenonjoints play a role in vibration isolation. But the isolation role of Dou-gon layers dependsprimarily on relative value between the spectral characteristics of the seismic wave andthe structure’s natural frequency. When the nominal PGA reached to300gal,400gal,600gal and900gal, maximum deformation angle of wooden frame reached to1/70,1/50,1/35and1/21respectively, showing a greater deformation capacity than modernstructures. With the increase in seismic intensity, the overall stiffness of the structuregradually decreased, with a range of0.346~0.028kN/mm. The lateral deformation ofwooden frame dissipates most of the seismic energy. By contrast, the sliding of columnroot and deformation of Dou-gon dissipates less energy.(3) A3-D beam-spring FEM model was established based on structural features ofthe ancient timber structures and restoring force characteristics of structural members.Element damping matrix proportional to its initial stiffness was put forward to simulatethe damping mechanism of mortise-tenon joints and Dou-gon sets, instead of usingclassic Rayleigh damping. Dynamic nonlinear time-history analysis was conducted tocompare with experimental results, which verified the reliability of the calculationmodel and selection of parameters. On this basis, parametric analysis was conducted ondynamic performance of palace buildings. The results show that: whether the column roots are rigid or hinged, acceleration amplification factor of the structure significantlysurpasses the original structure, which weakens the seismic capacity of ancient timberbuildings. The settings of Dou-gon can significantly prolong the natural period of thestructure and present a function on shock absorption. The larger the stiffness ofDou-gon is, the weaker the ability of shock absorption becomes. The increase ofstructural damping ratio ζ can effectively reduce the displacement and accelerationresponses of the structure. The increase of roof mass prolongs the natural period of thebuilding, and magnifies the relative displacement. Roof mass is also helpful inimproving the ability of shock absorption of Dou-gon.(4) A simplified calculation model was put forward to take into account of sliding ofcolumn root, semi-rigid connection of mortise-tenon joints, shock isolation of Dou-gonlayers. An aggregate mass model was established and a unified motion equation was putforward to represent different status of sliding and stick phase. And the critical conditionwas give between the two phases. Nonlinear time-history analysis according toWilson-θ method was conducted using MATLAB. The comparison between calculationvalues and experimental results shows its feasibility.(5) The collapse criterions of both collapse due to sliding of column root andinterlayer collapse due to lateral deformation of wooden frame are put forward. Thesetwo collapse mechanisms are studied using IDA method, and results show: the slidingcollapse is less prone to happen under common seismic excitations. The most likelycollapse mechanism under long period seismic waves is the interlayer collapse. Thelong period seismic waves are more hazardous than common ones.更多还原