Shake table tests of highway bridges installed with unbonded steel mesh reinforced rubber bearings

Abstract Previous earthquakes in China have caused significant seismic damage in short-to-medium span highway bridges due to the uncontrollable sliding of unbonded laminated rubber bearings (ULNRs). This paper investigates the soundness of replacing the ULNRs in these bridges with novel unbonded steel mesh reinforced rubber bearings (USRBs). Distinct from ULNRs that use rigid steel plates, USRBs are reinforced by flexible high-strength steel meshes to enable large and stable rollover deformations when subjected to strong earthquakes. To this end, shake table tests have been carried out for a two-span steel girder bridge that is isolated by ULNRs and USRBs, respectively. The test bridge was designed with a scale factor of 1/15 by maintaining the similarity of the deck mass, pier longitudinal stiffness, and bearing lateral stiffness for a typical prototype bridge in high seismic zones in China. Various types of sensors were used to monitor the dynamic responses of the bridge when excited by four different sets of earthquake motions. Test results show that USRBs not only exhibit a higher isolation efficiency in limiting the deck inertia force, but also outperform ULNRs in controlling the sliding of the bearings. Moreover, a phenomenological material model is utilized to simulate the hysteretic behavior of the USRBs, where the bridge’s time-history responses have been validated against the experimental outcomes. This paper illustrates that the use of USRBs can be a cost-effective, robust, and reliable substitute for the ULNRs to enhance the seismic resilience of the transportation infrastructure in China.