Analysis On Dynamic Response Of Mega Frame With Isolated And Suspended Substructure Considering Soil-Structure Dynamical Interaction

The requirements of structural system become higher and higher along with the developing of high-rise buildings, especially super-high buildings. Comparing with buildings in common use, the high-rise buildings have the higher risk because of the higher building costs, highly centralized person and property and multivariate building function. As a result, the higher requirements for anti-seismic performance and building functions applicability of building structure system are increasingly pop out. One of the important projects is to search a new structure system with more safety, economic, reliable and suitable for building function to advance high-rise and super-high buildings. As well as the studying on megaframe with suspended and isolated substructures system plays an important role in casting a brick to attract jade and making a little contribution for it. The megaframe with suspended and isolated substructure system integrates respective advantages of megastructure, suspension structure and isolation technology, therefore the safe reliability and use of comfort of high-rise and super-high buildings could be ensured effectively. The soil around fonudation of structure is one of the most important influenced factors of structural dynamic properties. Therefore, it is of great significance and application value to develop the analysis on dynamical response of megaframe with suspended and isolated substructure considering soil-structure dynamical interaction.First of all, the dynamical properties testing for soil with different soil patterns and confining pressure shows that the more depth of soil layer embedment, the larger confining pressure, the tighter soil particle contact, the larger slope of backbone curve, and shear modulus and shear wave speed increase remarkablely. On the contrary, the damping ratio decreases. The dynamical properties of soil are the basis for analyzing soil-structure dynamical interation.Secondly, dynamic properties of suspended and isolated structure are studied by theoretical analysis and numerical calculation means. It is feasible to simplify suspended and isolated structure as single mass system based on the analysis of its dynamic characteristic depending on mass ratio and stiffness ratio, the equivalent principle and formulas are provided, and then the analytic process can be quite simplified. On the other hand, the experimental investigation on dynamic characteristics of suspended and isolated structure is completed to verify the conclusion and equivalent design formulas above. The experiment shows that the equivalent design procedure proposed in this paper is very effective.Thirdly, the analysis on amplitude-frequency and phase-frequency response of megaframe with single or multi segments suspended and isolated substructures reveal the principle that structure vibration controlled by phase separation between megastructure and substructure. At the same time, vibration control effect could be optimal if the mass ratio, frequency ratio between mega and substructure and damping ratio of substructure get optimum values in the certain scope. On the other hand, contrastive analysis on finite element modal of different forms of megaframe with suspended substructures shows that the natural vibration period of megaframe with suspended and isolated substructures is remarkable lager than the others, and it is beneficial for structure to avoid earthquake. Contrastive analysis on response-time history shows that megastructure relative displacements and substructure absolute acceleration are remarkable little than megaframe with free or conventional suspended substructures, and they close relate to safety and amenity of structure. Because of the existing of isolated layer, the seismic response of megaframe with isolated and suspended substructures damp rapidly, it shows that the most seismic importing energy is damped by isolated layer, and then the better vibration control effect could be achieved.Finaly, the analysis on dynamical time history response of megaframe with different suspended sunstructure and site condition shows that soil layers have the effect of low frequency amplification and high frequency filter as the communication media of earthquake wave. The seismic reponse control objectives of megaframe with suspended and isolated substructures considering soil-structure dynamical interaction get the advantage over the rigid foundation assumption, and then structure parameters design without considering soil-structure dynamical interaction is relatively safty and conservative.The strategies of vibration control in megaframe with isolated and suspended substructure is based on the dynamical properties of itself, structure safty and amenity are magnificent remarkablely batter than the other structures and vibration control methods. On the other hand, it is a prospective philosophy in the vibration control in high-rise buildings.