On the effect of near-field excitations on the reliability-based performance and design of base-isolated structures

• Effect of near field excitations on the reliability of base-isolated systems is explored.
• Hysteretic behavior of the isolators is calibrated with experimental data.
• Effect of near-field ground motions is significant in terms of the isolators cost.
• Protection of the superstructure and control of base responses are conflicting objectives.
• Proposed methodology is a valuable tool for the analyst and designer.

This work explores the effect of near-field excitations on the reliability-based performance and design of base-isolated systems. In particular base-isolated buildings under uncertain excitation are considered in this work. A probabilistic logic approach is adopted for considering the variability of future excitations. Isolation elements composed by rubber bearings are used in the present formulation. The non-linear behavior of the bearings is characterized by a biaxial hysteretic model which is calibrated with experimental data. The performance of the isolated system is defined in terms of the isolators deformations and the superstructure interstory drifts and absolute accelerations. First excursion probabilities are used as measures of system reliability. Two example problems involving large finite element building models are presented to illustrate the ideas set forth.