Seismic study of lead-rubber bearing application in Kutai Kartanegara steel arch bridge

The basic concept of the application of base isolation is by extending the natural period of the structure in order to provide lower seismic acceleration. The paper focuses on the investigation of the application of lead-rubber bearings (LRBs) instead of pot bearings in a new Kutai Kartanegara steel arch bridge located in East Kalimantan province. Even though the bridge is known located in Seismic Zone 1 (the zone with the least seismic risk as per SNI 2833-2013), the study was extended for other higher risk seismic zones, namely Seismic Zones 2, 3, and 4. With the aid of Midas software, the analyses of the bridge structures were carried out and it can be concluded that the higher the seismic risk, the more effective the use of LRBs in dissipating the earthquake energy before transmitting to the bridge superstructure. The reductions of seismic base shears obtained from the analyses were between 23.10 and 44.67 percent and 17.07 and 31.47 percent in the longitudinal and transverse directions, respectively. However, the application of LRBs has a consequence of increasing the horizontal displacements of the bridge, which can be solved by introducing either larger expansion joints or passive dampers. In order to validate the seismic responses, the bridge was analyzed using Time History Analysis (THA) by imposing seven earthquake ground motions, which were scaled to a spectral design of Padang as a requirement by the Indonesian code.