Hamid Ganjehei - Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Panam Zarfam - Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Mohsen Ghafory-Ashtiany - International Institute of Earthquake Engineering and Seismology, Tehran, Iran

Highway bridges are amongst the most expensive, most widely used, and most vital infrastructures subject to the earthquake hazard. Seismic demand for bridges can be reduced by adding isolation systems. Lead-Rubber Bearing (LRB) isolators are widely used isolating devices whose optimal utilization studied in this article by using the Genetic Algorithm (GA). In this research, the analysis and design of deck-isolated bridges using Lead Rubber Bearings (LRBs) is carried out in accordance with the construction site, AASHTO criteria, and procedural rules for seismic bridge design. The LRB properties, along with the piers dimension selected as optimization variables. These variables’ values applied in objective function using AASHTO design equations as constraints. Various pier heights and LRB placement scenarios regarded for assessing the sensitivity of optimum results. According to the results of the investigation, the research subject was repeated for not using LRB isolators in the side spans. Finally, a comparison of all the results showed that the larger LRB demands increased the effectiveness of LRBs in absorbing input vibrations and mitigating the bridge’s seismic demand by about ۲۰ to ۵۰ percent. Also, it showed that it is more economical to exclude LRBs from abutment supports and limit their usage to the inner supports of the deck.

Isolated bridge, Lead Rubber Bearing (LRB), Optimization, Genetic algorithms (GA)