In recent years, interest in low-cost seismic isolation systems has increased. The replacement of the steel reinforcement in conventional elastomeric bearings for a carbon fiber reinforcement is a possible solution and has garnered increasing attention. To investigate the response of fiber-reinforced elastomeric bearings (FREBs) under seismic loads, it is fundamental to understand its mechanical behavior under combined vertical and horizontal loads. An experimental investigation of the components presents complexities due to the high loads and displacements tested. The use of a finite element analysis can save time and resources by avoiding partially expensive experimental campaigns and by extending the number of geometries and topologies to be analyzed. In this work, a numerical model for carbon fiber-reinforced bearings is implemented, calibrated, and validated and a set of virtual experiments is designed to investigate the behavior of the bearings under combined compressive and lateral loading. Special focus is paid to detailed modeling of the constituent materials. The elastomeric matrix is modeled using a phenomenological rheological model based on the hyperelastic formulation developed by Yeoh and nonlinear viscoelasticity. The model aims to account for the hysteretic nonlinear hyper-viscoelastic behavior using a rheological formulation that takes into consideration hyperelasticity and nonlinear viscoelasticity and is calibrated using a series of experiments, including uniaxial tension tests, planar tests, and relaxation tests. Special interest is paid to capturing the energy dissipated in the unbonded fiber-reinforced elastomeric bearing in an accurate manner. The agreement between the numerical results and the experimental data is assessed, and the influence of parameters such as shape factor, aspect ratio, vertical pressure, and fiber reinforcement orientation on stress distribution in the bearings as well as in the mechanical properties is discussed.
Seismic isolation achieved by placing a flexible layer between the structure to protect and the foundation has proven to reduce the seismic demand. Recently fiber reinforced elastomeric bearings (FREBs) consisting of alternating layers of elastomeric material and carbon or fiber glass fabric have awakened interest as a replacement for the conventional steel reinforced elastomeric bearings (SREBs). FREBs bring advantages as a reduction of production and transport costs, while maintaining a high bearing capacity. In the current work, an automated workflow for optimizing both the costs and bearing capacity is presented. The methodology includes using design of experiments techniques to reduce computation cost, building metamodels based on the generated data, optimizing the multi‐objective problem, validating the optimal model and finally using reliability based design optimization to find the optimal solution under uncertainty. Design variables and constraints, as well as a composite objective function that minimizes the production and transport costs and maximizes the vertical stiffness have been defined. The presented method can serve as basis for the extension of the problem to assess the horizontal performance of FREBs.
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