Significantly Improved Seismic Protection by Adaptive Base Isolators with Variable Low to High Friction Performance

To ensure best seismic protection of structures for various seismic conditions, base isolators need to perform according to specific seismic requirements. These base isolators are commonly designed mainly for the MCE level. By doing so their efficiencies are poor with regards to soft breakaway at DBE, which means that due to static friction significant acceleration may be transferred to the superstructure already before the first isolator displacements occur. These systems are even locked-up. This shortcoming can only be improved if the friction within the devices is not constant at different yield levels. This approach allows generating the same structural isolation system for the MCE as conventional devices but significantly improves structural performance for breakaway and for low to medium seismicity. The isolation performance of a new adaptive curved surface slider is explained in terms of absolute structural acceleration and device´s displacements, computed as function of the ground shaking level and compared to the conventional devices. Additionally a reference of Zubiran Hospital in Mexico will be presented.