Masonry construction is the most popular and suitable for housing purposes in almost all developing countries. BASE ISOLATION in the form of pure friction is the simplest (P-F) among all ISOLATION so far developed which can easily applied to low cost brick masonry buildings. The effect of the earthquake ground motion on the behaviour of ISOLATION system is investigated analytically by using a synthetic accelerogram that is compatible with the design spectrum of IS 1893 (Part 1): 2002 corresponding to the level of maximum considered earthquake in the most severe seismic zone (PGA=0.36g). It is observed that, maximum reduction in spectral acceleration occurs with decrease in coefficient of friction at the cost of increased BASE sliding displacement. But for structures with Tn<0.2 sec maximum sliding displacement is 50mm for coefficient of friction 0.1. As most of masonry buildings are stiff structures with time period less than 0.2 second the sliding displacement are within plinth projection of 75. Hence P-F ISOLATION is one of the best alternatives for reducing earthquake energy transmission to super structure during strong earthquake leading to lesser damages in masonry buildings.

Hybrid control system composed of a BASE ISOLATION system and a magneto-rheological damper so-called smart BASE ISOLATION is one of effective semi-active control system in controlling the seismic response of structures. In this paper, a design method is proposed for designing the smart BASE ISOLATION system in order to achieve an effective performance under multiple earthquakes. The BASE mass, the BASE stiffness and the weighting parameter of H2/linear quadratic Gaussian control algorithm, which is used to determine the desired control force, have been considered as the design variables and different earthquake records have been considered as design earthquakes. First, the optimum values of these variables under each of the considered earthquakes have been determined by using the genetic algorithm and then, an optimum control system has been designed with multiple earthquakes-BASEd design approach. The defined design objective is minimizing the peak BASE drift while the peak inter-story drift has been constrained. For numerical simulation, smart BASE ISOLATION system is designed for controlling a four-story shear frame. The results show that when the control system designed for a specific earthquake is subjected to another earthquake, difference between the performance of this control system and the optimal case under that earthquake is considerable. Hence, the specific earthquake-BASEd design approach is an inappropriate design procedure for smart BASE ISOLATION. Also, it has been found that control system designed BASEd on multiple earthquakes-BASEd design approach shows effective performance in controlling the response of structure under a wide range of earthquakes.

In this paper a new isolating system is introduced for short to mid-rise buildings. In comparison to conventional systems such as LRB and HRB, the proposed system has the advantage of no need to cutting edge technology and has low manufacturing cost. This system is made up of two orthogonal pairs of pillow-shaped rollers that are located between flat bed and plates. By using this system in two perpendicular directions, building can move in all horizontal directions with respect to its foundation. Due to the pillow shape of the roller, this system has self-centering capability which causes it to return to its original position after the earthquake. The rolling friction force between pillows and their bed creates some damping in the system which prevents it from further oscillation after earthquake excitations diminish. The purpose of this study is to evaluate the proposed ISOLATION system’s performance under different earthquake excitations. First of all general features of the proposed isolators have been introduced followed by the analytical equations of the system. Vertical bearing capacity and the effects of the thickness of pillows has been investigated using ABAQUS software. It has been shown that for a pair of pillows of 58 cm width, 45 cm height and 100 cm length the vertical load bearing capacity of the system is more than 300 tons. The period of system with respect to the height and radius of curvature of the rollers, and seismic response of a building, assumed as a rigid body resting on isolators, has been studied subjected to simultaneous effects of horizontal and vertical excitations. It has been shown that the proposed system can reduce the absolute acceleration in the building around 78% in average, while the building’s maximum displacement is around 1.77 times of the ground in average.

It is both impractical and uneconomic to design a structure that remains elastic throughout severe ground motions. The main seismic design philosophy of a fixed-BASE structure is that minor structural damages are acceptable as long as the structure does not collapse. Hence, seismic BASE ISOLATION provides a better alternative in earthquake structural design. This paper presents finite element analysis carried out to investigate the feasibility of applying locally produced elastomeric rubber bearing BASE isolators in seismically isolating non-ductile precast concrete wall structures from earthquake excitations. The precast wall structures were analyzed in terms of in-plane and out-of-plane ISOLATION effects due to dynamic lateral loads. Ground excitations from three classifications of acceleration history BASEd on different a/v ratios were used in dynamic analyses of the structures. The results showed that although the BASE isolator had successfully reduced most of the critical structural responses such as floor acceleration and BASE shear demand, relative inter-story drift reduction as compared to fixed-BASE structure was not significant. Current design philosophy for seismic BASE ISOLATION should be urgently revisited. Imperative discussion and review of the feasibility in utilizing BASE isolators as seismic mitigation plan for seismic prone areas are presented.

The response of a multi-story space frame structure resting on non-linear BASE ISOLATION system, subjected to bi-directional harmonic and seismic ground motions are studied. A four-storey space frame structure with consistent mass system having six degrees of freedom (three translations along x, y, z-axes and three rotations about these axes) at each node is considered for study. The effect of ISOLATION damping and the excitation frequency on the response of a BASE isolated structure is investigated. The effect of excitation frequency, ISOLATION period, superstructure time period and superstructure damping on the optimum ISOLATION damping is also studied in this paper. It is shown that the above parameters have significant effects on optimum ISOLATION damping. The response of isolated system is found to be less in comparison to the corresponding response without ISOLATION system, implying that the ISOLATION is effective in reducing acceleration and forces of the system.