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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 40993 (09)
- University: Sharif University of Technology
- Department: Civil Engineering
- Advisor(s): Bakhshi, Ali
- Abstract:
- In the past few decades, shaking tables are widely used to evaluate system response of structures under seismic excitations. These devices are used without any fundamental research performed on a shaking table system as an entity model. In most of these studies for simplicity, it is assumed that there exist no considerable vibration and displacement around the shaking tables, and no attention is paid to the peripheral substances such as soil settled under the foundation.
In this thesis, result of ambient vibration test on shaking table system (solid deck, concrete foundation and soil layer) has been presented. Precise sensors known as low frequency and high accuracy accelerometers have been utilized to record vibration of benchmark points on ground and foundation for finding modal parameters of the complicated model. Dynamic properties of system such as vibratory natural period and modal shapes and modal damping coefficients are found with the help of recorded vibrations and finite element software and using theory of random vibration methods and modal analysis. The result depended on soil conditions, foundation properties and the type of input seismic excitation. Due to soil- foundation-structure interactions which has significant effects on dynamic response and behavior of structure and embedded foundation of shaking table and then on overall system. In fact, in order to calculate the response error of the shaking table system, there is a need to perform comprehensive study with parametric analysis for significant soil-foundation-structure interactions by considering different conditions. Considering the effects of actuators on response and accuracy of its input on total response, soil shear velocity change, viscous boundary effect on foundation response, shaking table system effect on response of structure located on the deck, are among the parameters considered in this research. The result of studies demonstrates that the effect of viscous boundary and actuator on foundation response, are the most significant effects on the response of the system. Using simplified analytical models and ambient vibration tests are appropriate practical ways to find dynamical characteristics, which depend on behavior of material and combination of different parts of system together that cannot consider all of them in analytical model at the same time. There are always differences between analytical models and actual models. Determining these dynamical characteristics directly by performing experiments on shaking table systems and comparing them with analytical results, we can find the accuracy of results and then make judgment on whether they are acceptable or not.
- Keywords:
- Ambient Vibration ; Soil-Structure Interaction ; Dynamic Properties ; Shaking Table Test ; Modal Analysis
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