| Pagoda is a historical and religious architecture,is a valuable historical and cultural heritage of all mankind.Pagodas not only preserved the ancient production technology,materials and construction technology of historical information.Meanwhile,it is also the microcosm of the history,culture,art,religion,politics,diplomacy,economy and society aspects in our country.At present,the existing masonry pagodas structures that are very old and affected by natural disasters and man-made serious destruction,It is urgently necessary for disaster protection performance.However,for the particularity of the tower structure protection,a lot of problems,especially the tower structure damping technique and protection theory is not perfect,the in-depth study is very necessary.In this paper Xiaoyan Pagoda is the research object,which is an outstanding representative of brick tower with thick eaves,and the following research work has been carried on:(1)By investigatiion of the relevant historical archives and the field measurement,the current status of the Pagodas have been analyzed comprehensively and furtherly researched the structure material composition,structural features of the historical restoration and current injury situation.By the scene for the Xiaoyan Pagoda structure dynamic characteristics test,we analysed the main dynamic characteristics and the characteristics of the disaster,and according to the results of the acient similar wall model in the text,we adopted the limit displacement and ultimate bearing capacity evaluation method,evaluated the seismic performance of the structure of the Xiaoyan pagoda.Results showed that the structure of the Xiaoyan pagoda mortar is mainly composed of clay,lime,orange,yellow,and glutinous rice paste,the mortar strength 0.4 MPa,the compressive strength of tower body is about 0.7 MPa,it shows that the characteristics of a lower intensity and serious damage,poor seismic performance,exists the whole collapse risk especially under the 8 degrees to flame,herein,It urgently needs to take a new damping control method for improving the reliability of earthquaketake.(2)48 group of shape memory alloy(SMA)mechanical properties test were carried out,the loading rate,cyclic loading frequency,strain amplitude and the wire diameter on superelastic SMA material mechanics performance was studied resectively,probed into the corresponding change regularity and the corresponding solutions to the larger factors is given.Based on Brinson constitutive model,at the same time,this paper proposes a rate related model simplified constitutive relation,and the corresponding simulation has been done.Then on the basis of experiment,by using the genetic algorithm of artificial neural network of neurons in the right/threshold optimization,a new constitutive model is established.Results showed that the proposed constitutive model can well reflect the mechanical behaviors of SMA materials;simulation results are in good agreement with the test results,but the latter adaptation is wider,and has more precise calculation precision,especially in the SMA material mechanics performance is superior in the dynamic analysis.(3)Aiming at the actual status of the Xiaoyan pagoda structure and the main characteristics of the tower structure seismic protection,combining with the materials special mechanical properties of the SMA and the working principle of the suspension pendulum suspension of the SMA in dangling composite damping system,we developed a new shape memory alloy-suspension pendulum damping system(abbreviated to SMA-SPDS),which does not affect the original ancient pagoda and historical information,facilitate integration and can reduce the earthquake response of the tower structure.And 36 kinds of working conditions of simulated earthquake shaking table test were carried out,we mainly studies the 9 kinds of different quality,long and SMA wire prestrain on SMA-SPDS damping effect,the influences of the phase analysis of the principle,further the working performance and effectiveness of the SMA-SPDS are discussed in this paper and tested its control effect and effectiveness.In addition,based on the modal analysis of multi degree of freedom system,the Xiaoyan pagoda structure decoupling for multiple single degree of freedom system,using the theory of fixed point for SMA-SPDS layout position,the best tuning,optimal damping ratio and engineering design optimization,and the parameters set up corresponding engineering optimization calculation method.Results indicated that the researches and development of the SMA-SPDS are adjustable frequency and damping control,the system performance is stable,easy to integrate,its damping effect is obvious,therefore it can better meet the demand of the tower structure of shock absorption.(4)According to field testing material composition and mechanical properties of the structure of the tower body,24 pieces of simulation of the 4 groups of the Xiaoyan pagoda tower structure of gelled material cementation and 2 set of a total of 12 analog block is designed and produced to simulate the Xiaoyan pagoda tower structure material of masonry block respectively,and the corresponding mechanical properties test were carried out,and the Xiaoyan pagoda prototype structure material properties in the model structure implementation method in the making is further researched.Then,on the basis of the researches,four simulation of the Xiaoyan pagoda tower body structure wall specimens is designed and producted;we adopted low reversed cyclic loading test to research the the relationship between the failure pattern of Xiaoyan pagoda tower body structure and the interlayer displacement Angle.Combining with the existed the results of our researches and the protection of cultural relics value and significance,we puts forward the Xiaoyan pagoda tower structure various damage states of the interlayer displacement Angle limitation of recommended interval;which can be served as reference in the damage assessment of similar structure of masonry pagodas.(5)Based on the similarity theory of model structure design,we designed a geometric similarity ratio of 1/10 of the Xiaoyan pagoda model structure,developed three matching SMA-SPDS,tested 39 kinds of working conditions of simulated earthquake shaking table test.Studied the setting and not-seting SMA-SPDS model structures under seismic action at the bottom of the tower body,middle and top of relative displacement and acceleration,etc.,In this paper,we discussed the main characteristics of the earthquake response of the tower body structure and the corresponding failure mechanism and the law,and examined the SMA-SPDS damping effect.The results showed that the set after the SMA-SPDS,the dynamic characteristics of tower body structure and deformation law can be obviously changed,model structure of acceleration and relative displacement were significantly reduced,especially at the top and middle lower more,usually can reduce about 20%,and the decrease of the relative displacement is especially significant,the top can reach more than 25%.In addition,the experimental results also indicated that the more earthquakes,the more obvious shock absorption effect of SMA-SPDS,and which explains the researches and development of the SMA-SPDS can effectively reduce the earthquake response of the tower structure and which is a kind of new type of suspension system,deserves further research and application.(6)In Xiaoyan pagoda prototype based on the measured data of the existing structure,Simulink toolbox of MATLAB software is adopted for establishling the simulation model of the structure of the Xiaoyan pagoda prototype,and designing for the prototype structural damping control need of SMA-SPDS,setting and not-setting SMA-SPDS simulation calculation and analysis;In setting the project under the premise of the optimization goal,using the modal control theory,the SMA-SPDS in the Xiaoyan pagoda set the position of the prototype structure,number,SMA-SPDS parameters of engineering optimization problems are discussed in this paper,and the Xiaoyan pagoda prototype structure set SMA-SPDS engineering optimization arrangement scheme.The results showed that after the optimal placement of the engineering,the Xiaoyan pagoda at the top of the prototype structure damping effect of relative displacement and acceleration are above 43%,and shock absorption effect is very obvious,which can be used for reference in the engineering application. |
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