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The near field ground motions have a high amplitude pulse like at the beginning of the seismogram which are significantly influenced by the rupture mechanism and direction of rupture propagation. This type of ground motion cause higher demands for engineering structures and its response spectrum is dramatically different than far field spectra.

Tabriz is one of the ancient cities in

Azerbaijan province with many industrial factories, financial centers and historical monuments in North-West of Iran. In this region, North Tabriz Fault which has a well known history of intense seismic activity is passing through in close distance of urban area. In this regard investigation of near field ground motion effect on current practice seismic design spectrum in this region is necessary.

Hence, probabilistic seismic hazard analysis is carried out using appropriate attenuation relationship to consider near field effect. The peak ground acceleration (PGA) and several spectral accelerations (SA) over bedrock are estimated for different return periods and maps of iso acceleration contour lines are provided to indicate the earthquake hazard in different points of

Tabriz city.

Afterward, the generated horizontal equal-hazard spectrums considering near field effect are compared with different spectrums developed base on simple pulses model for near field motion. Both types spectrum used to verify current practice seismic design spectrum of Iranian code (2005) and International Building Code (IBC 2000). The results reveal the long-period structures which are seismically designed based on current practice seismic codes are in high risk to be damaged during near fault ground motion.

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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.