The Kobe earthquake is considered to be one of the most devastating and costly natural disasters in recent history considering the number of buildings destroyed, the number of people killed and injured, the size of the affected area, and the extent and severity of damage to a wide range of structural types. As a result, important questions have been raised about earthquake preparedness, disaster response, seismic design and codes of practice, and upgrading of earthquake-resistant structures. This paper presents an overview of this earthquake, investigates the extent and types of damage caused, studies the factors behind each type of damage, and highlights important lessons learnt from this earthquake. Protective measures and future research that should be undertaken in Japan, and all countries that are at seismic risk, are recommended in order to reduce damage and casualties in future seismic events.
A new fuzzy control method for the reduction of the dynamic response of structures is presented, and is compared with the instantaneous optimal control method. The control forces are determined from preformulated fuzzy rules regarding the velocity and the acceleration of the system. The triangular membership function and the mini-max-gravity method are used in the fuzzyfication and the defuzzyfication process, respectively. In these processes, no material property of the structure such as the mass matrix or the stiffness matrix are needed. This characteristic nature is definitely different from that of optimal control algorithms. Numerical examples are shown in order to compare the performances both of the proposed fuzzy control method and the optimal control method. It appeared that the fuzzy control method is quite useful as regards reliability and robustness.
SUMMARYAn algorithm to calculate direct velocity feedback gain with limited number of sensors is developed in a simple way such that a certain performance index is minimized according to QN control method. If a limited number of velocity outputs can be measured, full velocity responses of the whole structure can be interpolated based on the mode shapes. By deÿning the performance index function as a combination of the structure's velocity responses and control forces only, feedback gain can be determined according to QN control method with the external excitation being taken into account throughout the entire algorithm. Control forces are then regulated by the time-invariant feedback gain matrix. The e ective location of the active control devices for a building structure subjected to intermediate-storey excitation has been determined to be in the three oors adjacent to the vibration source. Hence for the purpose of this paper, only the optimal placement of sensors is veriÿed. It is shown in this paper that if the dynamic behaviour of the structure is well described by a mathematical model, su cient response reduction e ect can be achieved according to the new DVFC algorithm, and the degradation of control performance due to time delay can also be veriÿed.
In seismic isolation system for lightweight structures, sufficient effect is not acquired when laminated rubber bearings are used. It is because that the pressure on the surface is small. Since sliding base isolators expect the performance even when the pressure on the surface is small, sliding base isolators are used for lightweight structures. Generally, the frictional coefficients of sliding base isolators are assigned in the range 0.01-0.10. However, it is examined by three-dimensional finite element method that it is effective in the case of a big earthquake even if the frictional coefficients are 0.20. The purpose of this study is to examine the effect of base-isolated structures using sliding bearings by experimental and analytical methods. The experiment by horizontal earthquake excitation (modified JMA KOBE 1995) was conducted, and the frictional coefficient was identified. As a result, the values are identified around 0.20. By using the identified frictional coefficients, the response reduction effect of multi-degree-of-freedom system model is investigated by a simulation. The responses are reduced by in the range 50-80%.
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