مقاله انگلیسی رایگان در مورد جداسازی لرزه ای نیمه فعال در زلزله های نزدیک گسل – الزویر 2019

Introduction

Structural control systems can be used in modern engineering practice to protect structures from destructive effects of earthquakes. Structural control systems are mainly categorized as passive, active, semi-active, and hybrid systems. The basic concept of passive control systems is to lower the effective earthquake forces by elongating the fundamental period of the structure, thereby, lowering both the floor accelerations and the inter-story drift ratios to keep them within desired limits. The main challenge that such systems face is the large displacement requirements of the isolation system in case of nearfault earthquakes [1], which may exceed practical and economical limits [2]. Such large base displacements may even exceed the seismic gap, thus, posing serious risks [3]. Providing high passive isolation damping may be of help but such a solution may cause increase in floor accelerations and inter-story drifts depending on the earthquake characteristics [4]. Various other studies [1,5–7] also revealed that additional damping that is necessary for controlling base displacement may not guarantee good performance in structural response under the near-fault earthquakes, which would be a problem for missioncritical buildings such as hospitals that house vibration-sensitive contents [2,8]. Thus, active or semi-active isolation systems that can adapt to earthquake excitations of different frequency contents are necessary. Although active control systems are effective, they require very high power to operate [9,10]. Moreover, adding mechanical energy actively to the building may cause stability problems to the structure [11–13]. These drawbacks increase the interest in semi-active control systems, which can provide the proper amount of damping without causing any stability problems. Also, they need much less power to operate than the active control systems [12,13]. Symans et al. [14] showed that both isolation displacement and superstructure response can be limited by such adaptive base isolation systems. Likewise, [15–17] confirmed that the safety performance of a seismic isolation system that is equipped with semi-active dampers are quite high and it is effective in simultaneously limiting both base displacement and superstructure responses. On the other hand, it is known that the mechanical properties of isolators can vary due to the variation in temperature, ageing, contamination, or scragging [18–20]. Likewise, the mechanical properties semi-active control devices can vary. Researchers [18,19,21] have evaluated the effect of variability in passive isolation system parameters on the response of superstructure. The results emphasized the significance of variability of these parameters on the response of isolated buildings. At this point, it can be said that probabilistic seismic risk analysis, which takes such uncertainties into account, is the best method for determining the realistic seismic performance of seismically isolated buildings equipped with semi-active control systems. Due to the difficulty of describing the probabilistic characteristic of the whole problem analytically, the Monte-Carlo Simulation technique can be used as a convenient alternative. It is an accurate method for conducting safety and reliability analysis [22] that is based on mathematical modeling and recursive computer analysis in which the uncertainty is taken into account by defining random variables to follow certain probabilistic distributions.