Seismic Retrofitting of Tied Arch Bridge with Friction Pendulum Isolation Bearings

On September 28, 2018, a 7.4 M earthquake hit Palu, Central Sulawesi, Indonesia, causing damage to many bridge infrastructures. Dolago Bridge located at Parigi, 37 km from Palu, is one of the bridges affected by the earthquake. The bridge consists of three spans with a total length of 111.2 m and the middle span is a reinforced concrete tied-arch structure with a span length of 70 m. In this paper, an analytical study for seismic retrofitting using friction pendulum bearings (FPB) is presented. The proposed retrofitted system is intended to have better performance and efficient structural retrofit compared to the conventional non-isolated retrofitting strategy. Recently, there has been limited study on using FPB on seismic retrofitting systems on tied-arch bridges. The non-linear time history analysis (NLTHA) was used to analyze the existing and retrofit system using seven pairs of ground motion records representing the seismic site conditions. Seismic bridge evaluation using the new seismic bridge design code with design earthquake of 1000 years return period was conducted by evaluating several parameters including superstructure displacement and acceleration, base shear, D/C Ratio of bridge components, and bearing capacities, as well as plastic hinge formation. The results showed that the use of FPB can improve bridge performance thus minimizing potential damage and reducing the number of bridge components that need to be retrofitted.