Studies On Dynamic Properties Of Subsoil-foundation-silo Structure Interaction System And Vibration Reducing Measures Of Silo Structure

This dissertation focuses on the establishment of the Semi-Analytical Model of the Subsoil-Silo Structure Interaction System. Based on this model, the rules of definite vibration and random vibration of the system and the vibration reducing analytical method for the silo structure have been studied systematically.First, the Semi-Analytical Model of the Subsoil-Silo Structure Interaction System is postulated, considering the following three interactions: the interaction between structure and foundation, the interaction between foundation and subsoil, and the interaction between silo wall and bulk materials. The characteristics of subsoil from the interface of subsoil and the structure to infinitely remote region are fully taken into account in the subsoil model. As a result, the difficulty in selecting the parameters of ABC in FEM method can be avoided. The bulk material in the silo structure is simulated by using viscous fluid, with the interflow in the bulk material, the movement between bulk material and the silo wall, the undulation on material surface, and the effect of the interior friction of material being considered.Second, based on the analytical model, the study on definite vibration and random vibration of the subsoil-silo structure interaction system is carried out in time domain and frequency domain, respectively. In definite vibration analysis, the generalized nodal load column matrix is first obtained by computing the earthquake acceleration. Then, the result in frequency domain is deduced by taking a Fourier transform. Multiplying it by the frequency responding matrix of the system, the generalized nodal displacement values in frequency domain are obtained. By an inverse Fourier integral transform, the time domain values were obtained. In time domain analysis, the generalized nodal displacement values can be obtained by multiplying the previously mentioned generalized load vector and the pulse responding matrix of the system. Both in frequency domain and in timedomain, after the generalized displacement values are gained, according to the basic principles of elastic mechanics, the displacement fields, strain fields and stress fields of this system are obtained consequentially. In random vibration analysis, the response results of the system under the random action of seismic ground motion are deduced both in frequency domain and in time domain, too. In frequency domain, the power spectrum density function matrices of generalized nodal load and generalized nodal displacement values are obtained in order, afterwards the power spectrum density function matrices of displacement fields, strain fields and stress fields of the system are instituted successively. In time domain, the correlation functional matrices of generalized nodal load and generalized nodal displacement values are obtained in order, then correlation functional matrices of displacement fields, strain fields and stress fields are set up one after another.Finally, an analysis on the design of vibration isolation is carried out. The subsoil and silo structure are proposed to be separated by adopting a special designed vibration isolation layer (VIL). In analyzing the VIL, the semi-analytical element is established. The whole VIL is deemed as a concrete model, instead of traditionally simplified massless spring-damper model. Hence, the weight of the VIL and the layout of rubber bearings are taken into account. And also, the three translational motion components and three rotational motion components of the seismic ground motion are considered, so the weakness in traditional analytical method which considers only one translation component can be overcome.The advantages of the method proposed in this doctoral dissertation are that it considers the three components of earthquakes, provides a clearer concept, generate more reliable results, and involves lesser work on computation. Moreover, time-history analyses on the subsoil-silo structure interaction system before and after the adoption of VIL are done by using the semi-analytical method considering the action of seismic ground motion of El Centro earthquake waves.