Strength optimization of transverse retrofitting device for seismic isolated bridge based on seismic repair cost ratio

Abstract

At present, the application of seismically isolated bridges is widespread. However, the elongation of the period of isolated bridges often leads to large displacements in the superstructure and significant residual displacements after earthquakes, which results in high repair costs or even bridge collapse. Therefore, various retrofitting measures for laminated rubber-bearing isolated bridges have emerged. The selection and design of these retrofitting measures are crucial to the response of bridges. In this study, three types of retrofitting devices are considered: concrete shear key, steel cable, and superelastic shape memory alloy (SMA) cable. The performance of different retrofitting devices is compared using the annualized seismic repair cost ratio (ASRCR) analysis and incremental dynamic analysis (IDA). Then the ASRCR analysis based on probability is used to optimize the strength of the retrofitting device. The results demonstrate that SMA cables and steel cables demonstrate similar effectiveness in reducing the fragility of bearings, but the superior self-centering ability of SMA cable significantly reduces the residual displacements of bearings. Furthermore, a mathematical model is developed to evaluate the economic benefits of seismic isolated bridges equipped with SMA cables and the strength of SMA cables can be designed rapidly by this model.