| 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.
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