SEISMIC PERFORMANCE PREDICTIONS of CANDIDATE YIELDING METALS and METAL ALLOYS INSTEAD of LEAD for LRBs

Base-isolation is a well-known technique used in earthquake-resistant structures and isolation devices sustainably preserve the entire structure by reducing earthquake energy transmitted to the structure. Lead Rubber Bearings (LRBs) are the most widely used devices as base-isolators, because of their seismic performance, stability, and being economical. LRBs are essential for structural sustainability, but they also have some characteristics that should be considered to improve sustainability. People are likely to be exposed to various forms of lead material, which is highly toxic and used extensively in LRBs, not only when it is damaged or needs replacement after major earthquakes, but also at each stage of lead's entire life cycle, from production to recycling. Due to the toxic properties of lead, which is also used in various parts of the structures, it is often possible to obtain outcomes equivalent to the results expected from the use of lead material with the use of alternatives, while the situation is quite different for the use of alternatives in LRBs. The necessity of alternative materials to provide various mechanical properties by complying with certain limits complicates the search for alternative materials. In addition, the seismic isolator system must be examined in detail, since the damping performance of alternative materials together with other materials in the composite structure of LRBs does not depend only on the mechanical properties of the alternative core material. It is important to consider not only the mechanical properties of alternative materials, but also the state of toxicity which is one of the properties to be avoided, thermal properties, and even recrystallization, which is often overlooked. The recrystallization property of lead, which starts at values lower than room temperature for lead, which increases its ductility, is one of the properties that make it difficult to find an alternative to lead. In this study, the properties of lead material were accepted as the lower limit for the mechanical properties of alternative core materials. On the other hand, it is necessary to have an upper limit for the mechanical properties of alternative materials in order not to damage the other components that make up the isolator, and in this context, to protect the structural form and stability of the isolator. For this reason, in addition to the results obtained from the performance analysis, plastic deformation-related outputs of the steel shims are also presented with additional evaluations.