High-damping fiber-reinforced elastomeric seismic isolator in different boundary conditions: An experimental insight

Abstract

Seismic isolation reduces structural vulnerability and is an effective retrofitting solution. The commonly used steel-reinforced elastomeric isolators (SREIs) consist of several rubber pads interspersed with steel laminas for vertical reinforcement. However, SREIs are expensive, making them economically-unjustified for ordinary residential buildings, especially in developing countries. Fiber-reinforced elastomeric isolators (FREIs) offer a lighter alternative with thin fiber layers instead of steel laminas. FREIs can be applied to the structure in bonded (traditional), unbonded, or partially bonded configurations. Unbonded FREIs (UFREIs) are cost-effective as they are not bonded or fastened to thick connection steel plates. Furthermore, they are inherently more flexible in lateral directions and thus require relatively less rubber material to offer the same seismic isolation performance as traditional elastomeric isolators. However, UFREIs cannot resist tensile forces and may slip under certain loads, limiting their use in situations with overturning or high vertical accelerations. To address these limitations, partially bonded applications (PBFREIs) bond only a reduced area of the rubber device to the connection steel plates. PBFREIs retain beneficial characteristics of both unbonded and bonded applications, such as improved lateral flexibility, and resistance to uplift forces and slip. The possibility of UFREI applications remains promising, particularly in developing countries, due to their low cost, ease of fabrication and installation. This paper proposes a FREI made of high-damping rubber and glass fiber fabrics, and examines its performance in bonded, partially bonded, and unbonded applications. As a unique feature, the material and geometrical characteristics of the FREIs are identical. A comparative analysis, including experimental testing, highlights the strengths and weaknesses of each application typology. The paper also provides a detailed explanation of the design process, encompassing rubber compound development, fabrication, and experimental characterization of the device.