Advanced Materials Research Vols. 255-260

Abstract: Three dimensional seismic responses of an isolated spatial beam string structure are studied by applying the non-linear finite element theory. The filtering effect of the main structure, which amplifies the ground input, is investigated. The results indicate that the vertical rare earthquake has great influence on the isolated spatial beam string structure, and stresses of cables, frames and slab shells under vertical rare earthquake are all much greater than that under gravity load. Results of non-linear time history analysis show that elements’ stresses are in elastic stage, thus the spatial beam string structure with isolation keeps safe under rare earthquake.

Abstract: With a special structure system and architectural shape, Kelamayi Exhibition Building has a quite complicated seismic response and dynamic behavior. Based on performance-based seismic design method, vibration characteristics and seismic response under different earthquakes are researched in this paper. Elastic-plastic model is made, and elastic-plastic time history analysis of structure subjected to strong earthquake is carried out, to verify the bearing capacity of the structure according to aseismic behavior indexes. The results of static analysis and elastic-plastic time history analysis show that, the maximum storey drift angle is less than the limit value 1/100. Parts of the structure is in plastic, but not deep, and can be put into use after some repairment. In a word, Kelamayi Exhibition Building can meet the requirement of seismic fortification and fixed aseismic behavior indexed, and have enough seismic bearing capacity.

Abstract: Based on interaction analysis of subgrade, foundation and upper structure, considering the effect of foundation deformation on upper structure loading behavior, the influence of soil stiffness on structure and foundation design is studied in this paper. With the finite element model of subgrade, foundation and upper structure, and the assumption of Winkler elastic foundation beam, the interaction between each other is calculated by ETABS and SAFE, in which the performance of subgrade deformation is simulated by surface spring.

Abstract: According to Fast Fourier Transform we can work out main frequency of vertical vibration wave. Combining natural frequency of vibration of the structure we evaluate whether isolation layer have effect. Combine with a multi-tower with a large base structure located above subway, We use time history method and consider different vertical tensile-compressive stiffness of rubber bearing, Storey acceleration response of the structure under vertical earthquake and subway vibration was calculated. The result shows that it have no effect that isolation layer with regard to vertical earthquake, but have obvious effect to reduce subway vibration, At the same time, storey acceleration response is reduced markedly, comfort level can be increased greatly.

Abstract: The analysis on earthquake response of one multi-tower isolation structure with an enlarged base in rare earthquake and aftershocks was carried out using elastic time history analysis method. It includes the damping effect of structure, plastic deformation of members and plastic hinges distribution in structure. The results show that isolation structure comes to plastic state under rare earthquake lighter, vertical elements remain flexible under earthquake aftershocks, the plastic hinges on horizontal members are deepen, but the structure can meet the requirement while it is renovated. Plastic hinges first appear in the bottom of structure, then they gradually develop upwards, Plastic hinges are generated at the ends of beams, but not occur in columns and walls. The displacement of structure under rare earthquake is mainly concentrated on isolation layer and it can take energy consumption by large displacement.

Abstract: A simple and efficient direct displacement-based design (DDBD) method is introduced to base isolated (BI) structures. Assuming the vibration mode of superstructure to be the shear type and considering the BI structure to be an equivalent single degree of freedom (ESDOF) system with spring and damper at the seismic isolation layer. The acceleration response spectrum in Chinese code is converted to displacement response spectrum. Corresponding to the design displacement, the equivalent period is obtained. The relationship of the deign displacement, equivalent period, equivalent stiffness and base shear of the system can be derived from the given formulations. Then, the distribution of the base shear along the floors is obtained. This method has been applied to the design of a 12-story BI structure with lead rubber bearings in high intensity zone in Suqian city, Jiangsu province. The results show that the method is feasible for the design of BI structures.

Abstract: Analytical study was conducted to investigate effect of friction dampers on vibration control of steel frame structures. The friction dampers installed in a ten-storey sample frame structure have two levels of fictional resistances. Unlike the conventional friction damper which has one frictional resistance, the friction dampers with variable resistances (VRFD) can apply two levels of frictional resistances, the lower resistance of which is attended to absorb the seismic energy by a moderate earthquake or a strong wind, and the higher one of which is expected to dissipate the seismic energy induced by a severe earthquake. The time-historey analytical results of the sample frame have indicated that the VRFD could not only mitigate the seismic response of the frame structure under a moderate earthquake more effectively than the conventional frictional damper, but also provide the same level of damping effect to the structure under severe earthquake as the conventional one.

Abstract: This paper expounded the basic principle of the base-isolated structures. Established the equations of motion of single particle and multi-particle base isolation structural system. Adopted multi-layer and high-level framework groups, added laminated rubber bearings in the bottom respectively, input EL Centro seismic waves, and then the modal, time-history, base shear are compared and analyzed. By comparing the results obtained: base-isolated structure used in high-rise building can decrease a certain degree of the seismic response, in the multi-layer building the effect was more apparent. It also confirmed that the application of base isolation on multi-layer and high-level framework in the existing conditions still had some limitations.

Abstract: The failure behavior and the vulnerable position of the rigid frame bridge are analyzed by nonlinear response analysis, based on incremental dynamic analysis (IDA). The damage index, applying for long-span continuous rigid frame bridge with high pier, is studied. The seismic vulnerability problem of the whole bridge is analyzed by fiber model. The strain was used for damage index of piers. The displacement was used for damage index of bearings. According to the studies above, the fragility curves are established based on integral performance of the bridge.

Abstract: In the isolation system, the design of vertical bearing member under the isolation devices needs higher safety reliability than the upper structure because of the importance of it. A method of considering second-order moment caused by superstructure horizontal shift is put forward, so that to analysis the stress and strain in the FEM of cantilever column. Analysis result of the FEM lead to the following conclusions that this method can effectively balance the decrease of stiffness, which is caused by the shift of superstructure on the isolators.