Assessment of the E031 code boundary limits for accurately capturing critical responses in base-isolated buildings

Resumen

In Peru, the seismic design code mandates the use of seismic isolation in essential type A1 buildings located in the highest seismic zones (3 and 4). Natural rubber bearings, both with and without lead cores, are the most used; however, their dynamic properties can vary significantly due to various factors, which are considered in the design using Lambda property modification factors. This study aims to analyze the influence of these variations on the response of the isolation system and to evaluate the sufficiency of the limits established by Peruvian code E031, known as the “Upper Bound” and “Lower Bound”, in capturing the critical seismic responses of these structures. To achieve this, a comprehensive parametric analysis was conducted to investigate how variations in the dynamic properties of the isolators affect the overall response of the isolation system. The equivalent lateral force analysis procedure was used to assess these impacts. As a result, curves were generated illustrating the variation in key parameters such as base shear force, effective damping, maximum displacement and lateral restoring force in different scenarios. The findings reveal that certain states of variation lead to more critical responses than those indicated by the Upper and Lower Bounds specified in the standard.  This suggests that the current criteria may not adequately encompass all possible scenarios, highlighting an urgent need for a review and update of the code to ensure the safety and effectiveness of base-isolated building designs in seismic-prone areas.