Niel C. Van Engelen

Development of Design Code Oriented Formulas for Elastomeric Bearings Including Bulk Compressibility and Reinforcement Extensibility

AbstractThe introduction of alternative reinforcement types for elastomeric bearings has rendered it necessary to consider the extensibility of the reinforcement as an additional design parameter. The extensibility of the reinforcement reduces the lateral restraint on the elastomer and, similar to the compressibility of the elastomer, influences important design parameters such as the compression modulus and bending modulus. Neglecting the compressibility of the elastomer or the extensibility of the reinforcement may result in an unconservative overestimation of these design parameters. Existing analytical solutions, which have been developed based on the pressure solution, are usually not suitable for design purposes. In this study, the analytical solutions for infinite strip, circular, square, and annular pad geometries are expanded and simplified to form geometry-specific approximations that account for reinforcement extensibility and bulk compressibility. The derived approximations closely and conserv...

Model of the Shear Behavior of Unbonded Fiber-Reinforced Elastomeric Isolators

AbstractIn this paper, an analytical model is developed and used to predict the horizontal behavior of unbonded fiber-reinforced elastomeric isolators (FREIs). An advantageous feature of unbonded FREIs is the ability to undergo rollover due to the lack of flexural rigidity of the reinforcement and the unbonded support conditions of the isolator. The rollover causes a characteristic softening, followed by stiffening, as the initially vertical faces of the isolator come into contact with the upper and lower supports—defined as full rollover. The force-displacement relationship is modeled by dividing the isolator into three sections: a central section, which experiences pure shear, and two rollover sections, which experiences combined shear and bending. The displacements of the rollover section are used to establish the curved deformed profile and predict full rollover. The model is evaluated with experimental data from four unbonded FREI designs. A parametric study is conducted to determine the influence of...

Correcting for the Influence of Bulk Compressibility on the Design Properties of Elastomeric Bearings

AbstractThe compression and bending modulus of elastomeric bearings, commonly applied as vibration isolators, are important design considerations. Analytical solutions have demonstrated that the sensitivity to the compressibility of the elastomer can be significant and begins at relatively low shape factors. These analytical solutions, which include the effects of compressibility on the compression and bending modulus, are often complex and not suitable for design purposes. Alternatively, an ad hoc approximation has been recommended that expresses the compression and bending modulus, including the compressibility of the elastomer, by assuming incompressibility and correcting with the bulk modulus. It is demonstrated that the ad hoc approximation provides an unconservatively large value of the compression and bending modulus for infinite strip, square, circular, and annular pad geometries. A correction factor to the ad hoc approximation is determined by expanding and simplifying the analytical solutions. T...

Shear Strain Demands in Elastomeric Bearings Subjected to Rotation

AbstractIn seismic base isolation applications, fiber reinforcement was initially proposed as a potential cost-saving alternative to conventional steel reinforcement in laminated bearings. Steel re...

Simplified Approximations for Critical Design Parameters of Rectangular Fiber-Reinforced Elastomeric Isolators

AbstractAnalytical solutions for critical design properties of elastomeric bearings, such as the compression modulus, bending modulus, and maximum shear strain due to compression or rotation, inclu...