# Effectiveness of LRB in Curved Bridge Isolation:
## 1 Introduction  
An LRB is an isolation system that is composed of multiple layers of rubber and steel plates with a central lead core. It is more effective for structural seismic isolation, as reported by [PERSON] and [PERSON] [1]. [PERSON] [2] studied the ability of the lead core to provide hysteresis energy dissipation which can protect the structure from the frequency of earthquake damage. Later, LRBs (Figure 1) were widely used for the isolation of buildings ([PERSON] and [PERSON]; [PERSON] et al.) [3] and bridges ([PERSON]; [PERSON] and [PERSON]) [4; 5]. [PERSON] [6] reported that lead plug bearings significantly increased damping compared to laminated rubber bearings. However, after the lead plug is inserted, part of the self-centering performance of the laminated rubber bearing is lost. [PERSON] et al. [7] pointed out that the hysteresis loop of the lead rubber bearing is stable under repeated loading. [PERSON] and [PERSON] [8] considered LRBs for seismic isolation of a continuous bridge. The ductility of the bridge pier is compared with the energy dissipation capacity of the LRB. [PERSON] et al. proposed a design method for LRBs for bridges [9; 10; 11]. The main advantage of this method is that it is based on the elastic response spectrum commonly used in the design. [PERSON] et al. [12]showed that LRBs have almost no strain rate dependence in a wide frequency range, including typical seismic frequencies. In addition, these have stable behavior under repeated loads, independent of temperature. [PERSON] et al. [13] experimentally studied the effects of axial load and strain rate on the performance of full-size lead-core elastic bearings used in bridges. A numerical model was developed to check bearing response with changes in key performance variables. [PERSON] et al. [14] investigated the effect of changes in the mechanical properties of the LRB on the response of the seismic isolation system. Changes in the mechanical properties of the vibration isolator significantly affected the shear strain of the vibration isolator and the acceleration response of the superstructure. [PERSON] et. al. [15] concluded with the potential application and future challenges with regards to filler and their polymer composites. [PERSON] et al. [16] studied the effects of LRBs and ground motion characteristics on the response of isolated bridges. The critical parameters were the ground motion characteristics. The ratio of peak ground acceleration to peak ground speed (PGA/PGV) was represented as the damage index. In elastomer-based isolation systems, LRBs are critical elements. In this type of bearing, the rubber provides lateral flexibility to prolong the structure's life, whereas the lead core releases energy during the cyclic movement of an earthquake [17]. [PERSON] and [PERSON] [18] established the calculation formula and an appropriate range of design parameters systematically. This comprises the diameter and height of the lead, the effective design deflection, the equivalent linear model, the shear strain of the LRB, the initial stiffness, and the secondary stiffness. [PERSON] and [PERSON] [19] determined that the axial and shear coupling response of the LRB plays an important role in the safety of an insulated base building. A simple amplification factor of 2.5 was proposed to increase the axial capacity of the LRB when the deformation by shear reached the maximum total displacement. Such a simple amplification factor can result in a low probability of LRB failure during an earthquake. [PERSON] and [PERSON] [20] concluded that the deterioration of laminated elastomeric bearings and shear keys might play a significant role in evaluating the performance of bridge constructions. Compared to the combined LRB and elastomeric bearing system, the overall design displacement was reduced for all LRBs, as mentioned by [PERSON] and [PERSON] [21].