| Summary: | 碩士 === 逢甲大學 === 土木及水利工程研究所 === 88 === At this time, passive control is a relatively mature technology in improving seismic resistance of structures and being applied to many structures in earthquake active regions of the world. However, the accurate prediction of the seismic behavior of passively controlled structures depends strongly on the accuracy of the mathematical model of the highly nonlinear properties of passive control devices. Furthermore, the behavior of soil-structure interactions during seismic excitations is quite complicated and important after the installation of passive control devices.
The passive control consists of base isolation and the energy absorption system. Base isolation systems such as high damping rubber bearings (HDRB) are highly effective in protecting structures and their contents from earthquake damage. The HDRB can lengthen the natural vibration period of the structure and provide supplemental damping. Nevertheless, the highly nonlinear mechanical behavior of the HDRB is quite complex. In this thesis an extensive series of experimental tests to identify the mechanical characteristics of the HDRB are presented. By re-deducing the Wen’s model and including the rate dependent effects, an advanced analytical model in an incremental form for the HDRB is proposed. The proposed model reveals that the mathematical model is in a good agreement with the experiment results, especially at the large shear strains. Shaking table tests also show that the structural responses were remarkably reduced by the HDRB system during earthquake simulations.
The use of energy-absorbing devices such as lead extrusion dampers (LED) to dissipate the seismically induced energy is one of the most economical and effective ways to mitigate seismic effects on structures. Two of the major difficulties for the mathematical modeling of the damper are the temperature effect and the deterioration phenomenon of energy-absorbing capacity during earthquakes. In this paper, an advanced finite-element formulation for the LED has been developed to account for aforementioned effects. The correlations between numerical and experimental results show very good agreement.
In order to ensure the safety of structures, it is demanded to know the interactive behavior between the structure equipped with LEDs and the unbounded foundation during earthquakes. To this end, a time-domain procedure, based on the finite-element and the infinitesimal finite-element cell methods, has been presented to address the interactive behavior of a structure equipped with LEDs, and the foundation with an unbounded far field. Quite different phenomena have been observed in numerical exercises between structures with and without considering their interplay. It is implied from this study that interaction effects are of importance between structures equipped with LEDs and unbounded soil medium. It is also found that the efficiency of LEDs in reducing seismic energy is very dependent on the flexibility of the soil and that interaction effects should be taken into account to gain insight into the actual behavior of the whole system and to ensure structural safety under seismic loadings.
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