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There is always a need to improve the structures for many reasons, including changing the use, changing the design regulations, increasing the life of the structure, and improper implementation of the structures. One of the most influential parameters in the selection of the improvement method is the lateral stiffness of the target structure, which is determined according to the lateral bearing system of the structure. There are many methods for improving structures, including the use of steel jackets to increase the load capacity of columns and the use of FRP fibers, etc. The transfer of ground movement to the structure can be controlled with the help of the base seismic isolator system at the base of the structure; the base seismic isolator isolates the upper structure from the ground shaking movements so that the destructive forces of the earthquake do not enter the building or to a significant extent be reduced. The Malaysian Rubber Materials Research Company in England has produced a type of elastomer with high damping. Using this elastomer, a rubber seismic isolator system with high damping has been used for the seismic isolator of buildings. In some systems, the Teflon layer is used to cause slippage between steel sheets. A central lead core is provided to control lateral displacement and return the system to its original state. Progressive failure is the failure of the entire structure, or a relatively large part of it, caused by events that damage a part of the structure and the inability of adjacent members to redistribute the overload through a path that can maintain the stability and continuity of the entire structure. Progressive failure may occur as a result of abnormal loading such as explosion, severe fire, vehicles hitting a part of the structure, etc. The lateral bearing system is part of a structure that is responsible for resisting lateral loads and directing them from a safe path to the foundation (lateral forces can include wind, earthquake, or other forces). Earthquake-resistant elements should be considered in such a way that the torsion caused by these effective and resistant forces in the floors is minimized. For this purpose, it is suitable for the distance between the center of mass and the center of stiffness in each floor and extension to be less than 5% of the dimension of the building in that extension.
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