Direct Loss-based Design of Low-rise Buildings Base Isolated with Lead Rubber Bearings

Seismic base isolation has gained popularity in the last decades. As a result, many structures are now equipped with base isolation systems to offer enhanced seismic performance and meet the needs of risk-aware stakeholders. However, a robust performance-based seismic design of these types of structures is generally not carried out due to the iterative nature of common design approaches and the time/computational resources required for such iterations, which are incompatible with the preliminary design phase. This work offers an overview of a simplified methodology for the seismic design of low-rise structures equipped with lead rubber bearing isolators to achieve a predefined level of earthquake-induced economic loss while complying with a predefined minimum level of structural reliability. The main advantage of the proposed methodology is that it requires no design iterations. The procedure is enabled by Gaussian-process-regression-based surrogate probabilistic seismic demand modelling of equivalent single degree of freedom systems (i.e., the probability distribution of peak horizontal displacements and accelerations on top of the isolation layer conditional on different ground-motion intensity levels). Combined with simplified loss models for the base isolation system and the structural and non-structural components of the superstructure, this approach allows mapping a range of structural configurations to their resulting seismic performance and loss. A designer can then select one of the identified combinations of the strength of the superstructure and properties of the isolation system conforming with the reliability requirements and loss target and consequently detail the superstructure and isolation system accordingly. This work introduces the implemented surrogate probabilistic seismic demand models, provides an overview of the Direct Loss-based Design procedure for low-rise base-isolated structures, and illustrates its application for a base-isolated 3-storey shear wall building.