论文标题:应用形状记忆合金进行古塔结构抗震保护的理论和试验
Theoretical and Experimental Research on Seismic Protection of Ancient Pagoda Structures Based on Shape Memory Alloy
论文作者
论文导师 王社良;周福霖,论文学位 博士,论文专业 结构工程
论文单位 西安建筑科技大学,点击次数 61,论文页数 171页File Size13302K
2008-03-01论文网 http://www.lw23.com/lunwen_164893492/
mosque pagoda;; SMA damper;; seismic energy dissipation;; shaking table test;; FEA
中国现存古塔大多都融合了外来文化与中华传统建筑艺术的精华,是我国古建筑的杰出代表。现存古塔不仅具有宝贵的文物价值,同时也是各地风景名胜区域和历史文化名城的重要组成部分,不但反映了我国古建筑的科学和技术成就,同时也记录了当时的历史信息和建造工艺等,是古代劳动人民智慧的结晶,也是人类宝贵的历史文化遗产。 古塔保护研究是文物保护的一项重要工作。然而,我国对现存古塔结构的抗震机理与保护技术研究较少,目前尚无科学有效的损伤监控和保护方法,并且古塔结构的保护研究还要涉及历史学、考古学及建筑学等诸多领域,是一个多学科交叉的研究课题。因此,深入研究我国现存古塔结构的抗震保护理论和工程应用方法,具有重要的社会意义和实用价值。 本文首先对我国广州怀圣寺光塔的历史变化和工程现状进行了全面的现场检测与长期监测,研究了光塔结构的材料组成、构造形式以及目前存在的倾斜和裂缝等问题,同时对光塔结构的动力特性进行了实测,掌握了光塔结构的主要受力特性和灾变特点,并采用有限元分析方法,对该塔结构的动力特性、7度小震及中震时的地震反应进行了比较深入的研究,探讨了该塔抗震保护的关键问题,提出了采用形状记忆合金(简写为SMA)阻尼器被动控制系统进行该塔抗震控制的保护方案。其次,进行了SMA丝的温控拉伸试验,研究了超弹性SMA丝的主要力学性能,着重探讨了环境温度、加载速率、应变幅值和循环加载次数等因素对超弹性SMA材料在奥氏体初始状态下加卸载循环时等效割线刚度、最大单圈循环消能能力和等效阻尼比等力学性能的影响,得到了相应的变化规律。在此基础上,针对光塔结构抗震保护的特殊性,设计了3种消能能力较好和适用性较强的SMA阻尼器,并分别进行了3种SMA阻尼器在不同工况下的消能能力试验,研究了环境温度、加载频率、加载行程和合金丝长度等因素对其消能能力的影响,分析了其变化规律和适用性。 接着,以Brinson本构模型为基础,提出了相应的SMA材料本构模型的有限元求解方法,编制了相应的计算机分析程序,并对SMA材料的相变超弹性性能和阻尼器的消能能力进行了非线性有限元分析,研究了其力学性能随环境温度等因素变化的一般规律,并与主要试验结果进行了对比分析,两者吻合较好,表明有限元分析结果可反映SMA材料和3种阻尼器的主要力学特征。同时,针对光塔结构的主要受力和变形特点,并且遵循“保护第一”和“修旧如旧”的古建筑保护原则,设计了1种性能良好的SMA阻尼器被动控制系统,提出了将其安装于光塔结构以提高光塔结构抗震性能的保护方案,探讨了SMA阻尼器被动控制系统的安装方式,建立了确定SMA阻尼器被动控制系统数量的计算方法。 最后,根据光塔原型结构的实际情况,以模型试验的相似关系为基础,设计并制作了一个相似系数S,为1/10的光塔模型结构,并先后进行了未安装和安装A、B型SMA阻尼器被动控制系统光塔模型结构的地震模拟振动台试验,研究了模型结构在3种不同工况下,主塔顶部和小塔顶部的相对位移、层间位移角和加速度以及塔体开裂等光塔结构的主要地震反应,测试了SMA阻尼器被动控制系统在地震激励下的变形能力和消能能力等工作性能,分析了相应的控制机理和控制规律,并从总体上评价了光塔模型结构抗震保护前后的性能变化和保护效果。此外,本文还在试验的基础上,采用有限元软件ANSYS10.0,分别对光塔模型结构和原型结构在3种不同地震波输入下的地震反应进行了分析,并在既定优化目标下对SMA阻尼器被动控制系统的特性参数和光塔结构与SMA阻尼器被动控制系统的集成方式进行了优化分析及探讨,深入了解了安装SMA阻尼器被动控制系统后,光塔结构的减震效果和动力特性变化的一般规律。 理论和试验研究结果均表明,目前光塔原型结构的总体抗震性能较差,存在多处不同的内部缺陷或薄弱环节,难以承受或再次承受地震、飓风等强灾害的袭击,亟需采取措施进行抗震保护。SMA材料具有较好的超弹性性能,利用其研制的A、B和C型SMA阻尼器均具有较好的消能能力,并且能够实现制品的小型化,是一种古建筑抗震保护的新方法。安装SMA阻尼器被动控制系统后,主塔顶部和小塔顶部的相对位移及加速度都有明显降低,其中相对位移的降低尤为显著,并且地震烈度越高,降低幅度越大,说明文中所提SMA阻尼器被动控制系统和控制方法具有较好的消能减震效果,可以有效地提高光塔结构的抗震能力,值得进一步开发和推广应用。 文中所得结论不仅可为光塔原型结构的抗震保护提供理论依据和技术支撑,而且对其它历史建筑的保护和修复也具有一定的参考意义。
The majorities of Chinese present ancient pagodas all mix together the highlighted arts of foreign cultures and traditional architectures of China, and are typical masterpieces of ancient buildings. The existing ancient pagodas are not only of precious value of cultural relics but also are important components of each resort and each famous city for its history and culture. Their presence could reflect the achievements of science and technology in ancient buildings of China as well as recording historical information and construction craft etc., is attributed to wisdoms of ancient labors, and is also mankind"s priceless cultural relics of history. The ancient pagoda protecting research is a major task of cultural relic protection. However, the research on seismic mechanism and protection technology is scarcely launched for existing ancient pagoda structure. There is still no scientific and effective method to monitor its damage and protect it. Furthermore, the ancient pagoda protection research is concerned with history, archaeology, architecture etc., and thus is a intercourse research topic. As a matter of fact, the deep investigation to seismic protection theory and application methods in engineering will be of great social significance and practical value. Firstly, in this paper the historical changes and engineering situations have be fully tested and long monitored on site for Huaisheng Mosque Pagoda in Guangzhou of China; then, the material constituents, detailing types, existing inclination and crack etc. are studied. In the meanwhile, the dynamic characteristics of mosque pagoda structure are actually measured, and the main load bearing characteristics and disaster features are mastered. By the use of FEA(Finite Element Analysis), the dynamic characteristics of this pagoda, and seismic responses in the minor earthquake and moderate earthquake of 7 degree are comparatively deeply researched; the key problems of seismic protection are explored for the pagoda, and a passive control system with SMA(Shape Memory Alloy) dampers is put forward to carry out a protection scheme on seismic control of the pagoda. Secondly, the tensile experiments of temperature control on SMA wire are conducted, the primary mechanical properties of superelastic SMA wire are investigated, and the influence of such factors is accentuated as environmental temperature, loading rate, strain amplitude, loading cycles etc. on the equivalent secant stiffness, the maximum single-cycle energy dissipation capacity, and equivalent damping ration etc. when the superelastic SMA wire is subjected to loading and unloading cycles at the initial state of austenite; the corresponding variation law is obtained. Based on this, aiming at the speciality of seismic protection for the pagoda, three kinds of dampers with high energy dissipation capacity and adaptability are designed, and the corresponding energy dissipating experiments are respectively carried out in different cases. The effect of those factors including environmental temperature, loading frequency, loading travel and the length of SMA wire is studied on their energy dissipating capacity, and the varying regularity and practicability is yielded. Then, according to Brinson"s constitutive model, the corresponding finite element solution to the constitutive model of SMA is addressed, and the computer analysis program is complied correspondingly; a nonlinear FEA is conducted on the phase transformation superelasticity of SMA material and the energy dissipation capacity of dampers; the variation laws of their mechanical properties with environmental temperature etc. is researched. Compared to experimental results, both are in a good agreement, which indicates that the FEA results can permit a reasonable reflection of the main mechanical characteristics of SMA material and three dampers. Meanwhile, in the light of the principal load carrying and deformation features, combined with the ancient building protecting principle "First protect" and "Repair like the old", a desirable passive control system with SMA dampers is designed; a protection scheme that this supplemental system in the mosque pagoda structure can improve the earthquake resistance of the pagoda is proposed; the erection ways are subsequently investigated for the passive control system with SMA dampers; the computational procedure to determine the quantity of this control system is established. Lastly, in accordance with the actual situations of the prototype structure of mosque pagoda, based on the similar relation of model experiments, a model structure of mosque pagoda with a similar coefficient of 1/10 is designed and fabricated. Earthquake simulating shaking table tests are performed on the model structure of pagoda in the cases the AB type passive control system with SMA dampers is erected or unerected. The leading earthquake responses like the relative drift at the top of the main tower and the small tower, interstory drift ratio, acceleration, and cracking process of the pagoda"s body etc. are studied. The operational behaviors involving the deformation capacity and energy dissipation capacity is tested for passive control system with SMA dampers under the earthquake excitation, and the corresponding control mechanism and regularity is also analyzed. Furthermore, the performance changes and protection effectiveness is comprehensively evaluated while the model structure of pagoda is seismically protected or not. Additionally, on the basis of experimental results, through the utilization of FEA software ANSYS 10.0, the analyses are made respectively on earthquake responses of the model structure and prototype structure in 3 different earthquake wave inputs. The characteristic parameters of the passive control system with SMA dampers and the integration modes between the mosque pagoda structure and the control system are optimized at the predetermined optimal objective. The usual regularity of vibration reducing effectiveness of mosque pagoda structure and the dynamic characteristic change is profoundly acquainted with after the mosque pagoda structure is supplemented by the passive control system with SMA dampers. Both the theoretical and experimental results indicate that so far the mosque pagoda structure exhibits a bad seismic performance, is present of quite a few various inner imperfections and weak parts, which enables this kind of structure not to experience earthquake, etc. It is urgent to take some measures to protect its seismic performance. Because the material of SMA possesses excellent superelasticity, A type, B type and C type SMA dampers made of it are provided with desirably good energy dissipation capacity, the miniaturized product can be realized, and it is a newly developed method to seismically protect ancient buildings. After the erection of the passive control system with SMA dampers, the relative drift and acceleration at the top of the mail tower and small tower are obviously reduced especially for the relative drift; the earthquake magnitude is higher, the decreasing amplitude is greater, which demonstrates that the passive control system with SMA dampers advanced herein could fulfill the valid seismic energy dissipation, effectively strengthen the seismic capacity of mosque pagoda structure and is worth further exploiting and extensively applying. The concluding remarks in this paper could not only provide a theoretical foundation and technical support, but provide references for protection and repair of other historical buildings.
|
