The Study Of The Dynamic Characteristics Of Diseased Structures In Earthen Ruins ——Taking Suoyang City As An Example

As a key protected culture,the earthen ruins carry a long history and a splendid culture,and it is a physical example of China's status as an ancient civilization.In the northwest of the country,the arid natural conditions are allowed for the preservation of the earthen ruins.However,the earthen ruins is endangered due to environmental factors such as war,earthquakes,wind and rain erosion,as well as the human factors(human destruction and unreasonable protection),the conservation for the earthen ruins cannot be delayed.Existed in the work of the earthen ruins with erosion and fractural disease was conducted by reinforcing protection measures.However,with the actions of earthquake dynamic response mechanism and diseased problems,the dynamic characteristics of the earthen ruins still need further research.In view of the above key problems,the paper explores the following research work by combining fieldwork,indoor tests,field vibration tests,theoretical derivation and numerical calculations The experimental modal parameters,theoretical modal parameters and numerical modal parameters were obtained.Those parameters of three methods were compared and verified.The influence of the earthen ruins topographic characteristics,material characteristics and structure characteristics on their dynamic characteristics was analyzed,and achieved the corresponding research results as follows:(1)Combined with literature,field investigation and the theory of structural mechanics,the diseased structure of the earthen ruins is defined and classified.The relationship between structural stability,structural dynamic characteristics and disease of rammed wall site is clarified.The influence of different disease structures on structural dynamic characteristics is analyzed;Laboratory experiments were carried out on the samples to analyze the characteristics of the earthen ruins.(2)Taking the rammed earthen wall of Suoyang ancient City as the object to conduct vibration tests.The obtained results can reflect the structure vibration characteristic parameters(displacement,velocity and acceleration)of modal testing,determine the characteristics of the wall and the sites of masonry structure system(natural frequencies,mode shapes and damping ratio).The influence law for the damaged structure on the dynamic characteristic parameters of the structure is obtained.Meanwhile,based on the theoretical analysis method and numerical simulation,the modal parameters of the earthen ruins structure under the action of dead weight were given based on the characteristics of erosion and crack disease by conducting damaged wall.(3)Experimental modal parameters were obtained by field tests,the use of relevant theoretical formula was derived theoretical modal parameters,and the numerical modal parameters were obtained by using finite element software.The work is about to compare and verify three kinds of modal parameters for the earthen ruins,so as to obtain the dynamic characteristics between the material features,morphology and structure characteristics.The influence law of the damage characteristics of the erosion and crack on the overall stability of the structure is deduced by combining numerical calculation and theoretical formula.Furthermore,the mechanism of dynamic response and damage under earthquake action is determined,and the preliminary evaluation method of seismic stability for the earthen ruins based on dynamic characteristic parameters is given.This paper is based on the Project of National Key Research and Development Program(Research on The Mechanism and Control Technology of Earthen Ruins Structural Instability under Static and Dynamic Loads).The research result will provide a basic for the initial evaluation of the seismic strengthening and protection of different diseased earthen ruins.Meanwhile,it can also provide the scientific basis for the research of seismic reduction and strengthening protection for the earthen ruins in Northwest China.