Many damages to the structure of bridges occurred during the past earthquakes are mostly the result of underestimation of SEISMIC forces. For this reason, SEISMIC ISOLATION can be effectively used in designing or retrofitting the bridges in high SEISMIC zones. The objective of this paper, along with the study of characteristics of electrometric isolator that can be manufactured in the country, is to briefly present design guidelines of these isolators and to investigate the effects of key parameters like elastic stiffness, inelastic stiffness and yielding force of isolators on SEISMIC performance of five typical highway bridges. Based on the results obtained in this research, SEISMIC isolators have a significant role in reduction of SEISMIC forces and displacements of the typical bridges, protecting sub structural elements which are usually weak and brittle. The larger the bridge lateral stiffness, the more effective will be the SEISMIC ISOLATION. The primary elastic stiffness and yield force of isolators are the key factors in ISOLATION efficiency and its hysteretic damping.By decreasing the elastic stiffness of isolators, the bridge response will decrease while the absolute displacement of the bridge deck will increase. This drawback can be compensated by increasing yielding force and damping of isolators by inserting other types of passive devices. Optimum design can be found through numerical investigation. It is eventually concluded that elastomeric SEISMIC isolators can be effectively used in designing new bridges or retrofitting existing bridges, according to the performed design and analysis of bridges in this paper. Experimental studies on SEISMIC isolators are recommended as a complementary to numerical procedure to ensure desired lateral performance of isolated bridges.

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.

In the last two decades, there has been an increasing interest in structural engineering control methods. Shape memory alloys and SEISMIC ISOLATION systems are examples of passive control systems that use of any one alone, effectively improve the SEISMIC performance of the structure. Characteristics such as large strain range without any residual deformation, high damping capacity, excellent re-centering, high resistance to fatigue and corrosion and durability have made shape memory alloy an effective damping device or part of base isolators. A unique characteristic of shape memory alloys is in recovering residual deformations even after strong ground excitations. SEISMIC ISOLATION is a device to lessen earthquake damage prospects. In the latest research studies, shape memory alloy is utilized in combination with SEISMIC ISOLATION system and their results indicate the effectiveness of the application of them to control the response of the structures. This paper reviews the findings of research studies on base ISOLATION system implemented in the building and/or bridge structures by including the unique behavior of shape memory alloys. This study includes the primary information about the characteristic of the ISOLATION system as well as the shape memory material. The efficiency and feasibility of the two mechanisms are also presented by few cases in point.

This paper introduces an improved ISOLATION system for aboveground storage tanks (ASTs). In this system, the tank shell is supported by a ring of vertical ISOLATION systems (VIS) that dampen the rocking motion of the tank shell caused by dynamic loads. On the other hand, the forces in the vertical direction caused by the overturning moment are isolated as an alternative to the common horizontal system used for shear base ISOLATION of ASTs. The effects of the proposed vertical ISOLATION system on the SEISMIC responses of the contained liquid are examined using various tank dimensions and earthquake ground motions. The finite element model (taking into account fluid-structure interaction effects) is used to simulate the contained liquid, as well as the tank shell. The results indicate that the new system could efficiently reduce the main SEISMIC design parameters of the tanks, including base shear, overturning moment, and SEISMIC stress in the tank shell. The sloshing wave height, however, is not significantly affected.

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 application of SEISMIC ISOLATION system in developing countries was generally associated with important and special structures, but nowadays it seems necessary the relevance of this technology in residential homes, schools and hospitals where the replacement cost due to earthquake damage can be very significant. It is more imperative in developing countries such as Iran, which are located in areas prone to earthquakes. In this regard, SEISMIC ISOLATION system by rubbersoil mixture has been proposed in 2008 year for developing countries as a new method with distinctive advantages such as low cost. In this paper, the efficiency of this new SEISMIC ISOLATION system has been evaluated in nearfault area with or without forward directivity effect. Based on the results of this paper, performance of RSM depends on nearfault earthquake characteristics in addition to properties of RSM layer and super structure. Consequently, in design process of these systems, significant effect of characteristics of nearfault ground motions on SEISMIC demand reduction should be assessed carefully.

SEISMIC response of isolated bridge under several earthquake ground motions is presented in this paper. Non-linear time history analysis is carried out for both non-isolated and SEISMICally isolated bridge. Lead rubber bearing is employed to observe the isolated bridge behavior. Takeda trilinear model is used to model the mechanical behavior of the pier and simple elastic model is applied to model remaining portion of the bridge. Four different earthquake ground motions are considered and applied at the longitudinal direction of the bridge. It is found that the effectiveness of base ISOLATION technique is highly influenced by the properties of the isolated bridge as well as by the ground motion. It is also revealed that to understand and design efficient isolated bridge system, analyzing the ground acceleration in frequency domain could be more efficient than time domain approach.