Seismic protection of vulnerable equipment with semi-active control by employing robust and clipped-optimal algorithms

Critical non-structural equipments, including life-saving equipment in hospitals, circuit breakers, computers, high technology instrumentations, etc., are vulnerable to strong earthquakes, and the failure of these equipments may result in a heavy economic loss. To guarantee function of vulnerable equipment during earthquake; peak acceleration and peak base displacement response of system should be limited to allowable levels. Traditional and passive control strategies cannot afford these contradictory targets in same time for broad range of ground motions. In recent years, semi-active control systems have been introduced as an adaptable and reliable alternative to control response under both limitations with low power supply. In this paper, efficacy of smart semi-active controlled floor isolation system which consists of a rolling pendulum system and a semi-active controlled magnetorheological (MR)-damper to control seismic response of equipment has been investigated by using clipped-H_2/LQG and clipped-H_∞ algorithms. The effectiveness of these algorithms was examined for equipment stand on raised floor due to floor motions in seven stories building. The results demonstrate semi-active control effectively decrease response acceleration and velocity of equipment in compare to passive strategy and hold its relative displacement to floor in least value. Furthermore it was shown semi-active control strategy with clipped-H_∞ algorithm in controlling seismic response of equipment compare to clipped-H_2/LQG algorithm and passive strategy (isolation system) have better performance in protecting equipment.