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A new approach to seismic base isolation using air-bearing solutions

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posted on 2023-08-30, 14:49 authored by Mohammad Hossein Harbi Monfared
Earthquake, the natural phenomena, is conceived by the movement of the tectonic plates that induce shocks and impulse of devastating magnitude at ground level. Reducing losses during an earthquake has always been one of the most critical concerns of humans in earthquake prone areas. The main goal has been always to attenuate the shocks induced by ground motions on man-made structures. Two approaches have been conducted; increasing the earthquake resistant capacity of a structure, and reducing the seismic demands on a structure. With regard to the concept of reducing seismic demands on a structures, seismic base isolation is considered as an efficient method in mitigation of earthquake damages. A proper base isolation framework offers a structure great dynamic performance and in this way, the structure will be able to remain in elastic mode during an earthquake. On the other hand, not all isolation systems can provide the target structure with efficient seismic performance. The majority of currently available isolation systems still have some practical limitations. These limitations affect the functionality of a structural system and impose some restrictions to its proper use and protection level, causing it not to achieve anticipated level of performances. In this dissertation, an innovative seismic isolation system is proposed and investigated via laboratory tests and computer simulation to introduce a practical and effective seismic isolation system. The proposed system has aimed to modify some drawbacks of current seismic isolation system whilst at the same time keeping their advantages. The innovative isolation system in this study incorporates air-bearing benefits together with roller bearings and bungee cords in a complex system for horizontal base isolation. An experimental study was carried out to test a scale structure model (1/10th in length) as a case study for this research, to observe the behaviour of the structure with and without isolation system and to extract the dynamic characteristics of the structure by measuring fundamental frequencies and damping through a free vibration test. Computer simulation was conducted to simulate the dynamic behaviour of the structure when it is subjected to three different types of earthquakes; and with different base vi configurations (fixed base and base isolated). The simulation was performed to gain an insight into the performance of the proposed isolation system under the given structure. Results from computer simulation were compared and validated with findings from experimental tests. It was confirmed that the present isolation system offers a significant reduction in acceleration demand in the structure leading to the reduction of base shear and consequently the level of damage to the structure. Results revealed that the proposed isolation system is able to mitigate the seismic responses under different ground motion excitations while exhibiting robust performance for the given structure. Furthermore, the system can also be used to isolate sensitive equipment or hardware in buildings affected by seismic shocks.



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