Abstract
Base isolation has been used as one of the most wildly accepted seismic protection systems that should substantially dissociate a superstructure from its substructure resting on a shaking ground, thereby sustainably preserving entire structures against earthquake forces as well as inside non-structural integrities. Base isolation devices can operate very effectively against near-fault (NF) ground motions with large velocity pulses and permanent ground displacements. In this study, comparative advantages for using lead-rubber bearing (LRB) isolation systems are mainly investigated by performing nonlinear dynamic time-history analyses with NF ground motions. The seismic responses with respects to base shears and inter-story drifts are compared according to the installation of LRB isolation systems in the frame building. The main function of the base LRB isolator is to extend the period of structural vibration by increasing lateral flexibility in the frame structure, and thus ground accelerations transferred into the superstructure can dramatically decrease. Therefore, these base isolation systems are able to achieve notable mitigation in the base shear. In addition, they make a significant contribution to reducing inter-story drifts distributed over the upper floors. Finally, the fact that seismic performance can be improved by installing isolation devices in the frame structure is emphasized herein through the results of nonlinear dynamic analyses.
Highlights
A number of catastrophic building failures due to severe and impulsive earthquakes have taken place worldwide since last few decades
The LRB1 frame model presents a similar ascent slope pattern as the LRB2 frame model on the occasion of increasing scale factors, but has larger statistical values owing to more flexible behavior displayed at the lead-rubber bearing (LRB) isolator
Larger mean values and standard deviations are found at the LRB1 frame model
Summary
A number of catastrophic building failures due to severe and impulsive earthquakes have taken place worldwide since last few decades. The most common base isolation devices used over many years by engineers are lead-rubber bearing (LRB) isolators which combine isolation function and energy dissipation in a single compact unit [16,17] Such LRB isolator devices provide vertical load support, horizontal flexibility, supplemental damping, and centering force to the structure from earthquake attack. The low damping elastomers constructed with elastomeric rubber bearings generally behave as an elastic manner toward external response They can instantly supply isolation capacity, additional flexibility, and elastic recentering force to the LRB isolator device [20]. Notwithstanding that seismic performance for the base-isolated building under the NF ground motion leads many engineers and scientists to attract sufficient interest, there is a lack of proper research until now to implement the LRB isolator devices practically used in the actual frame building. Statistical investigation based on analysis results should be conducted in order to fairly verify the effectiveness of the LRB base isolation system in the multi-story building structure
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