During the previous major seismic events, the unseating of the bridge superstructure was caused by large relative displacements which exceeded the bridge seat length. Therefore, this paper aims to introduce a multi-level unseating prevention device (MLUPD) to control deck movement. This device is capable of providing lateral resistance force with different performance levels of bridge girder movement in order to limit relative displacement between the superstructure and substructure. The device consists of a combination of a number of springs with different or equal length depending on the bearing type assembled inside each other in parallel to demonstrate multi-levels of stiffness. The design procedure and working mechanism of the device are based on the code of practice. In this study, the MLUPD prototype was fabricated and installed in two different configurations of the steel frame for testing under pushover and cyclic loading to evaluate the MLUPD performance. Additionally, the device performance was also assessed using numerical study.

Hence, a constitutive model for the developed MLUPD was derived. Then, the analytical model of the bridge with and without MLUPD device was codified by the finite element program in order to evaluate the seismic performance of the bridge equipped with the developed device. The experimental and finite element results of the MLUPD prototype revealed that the device is capable of unseating prevention through the multi-level performance.

In addition, the results indicate that the developed system demonstrated a significant force resistance in two frame configurations. Moreover, the numerical results of bridge time history analysis in terms of girder displacement, pier base shear and drift ratio demonstrated that the bridge seismic behavior is enhanced by utilizing the developed device along with different bearing cases.

在先前的重大地震事件中，桥梁上部结构的不固定是由超过桥座长度的较大相对位移引起的。因此，本文旨在介绍一种用于控制甲板运动的多级防坐装置（MLUPD）。该装置能够以不同的桥梁梁运动性能水平提供横向阻力，以限制上部结构和下部结构之间的相对位移。该设备由多个弹簧组成，这些弹簧的长度不同或相等，具体取决于彼此平行组装的轴承类型，以显示多级刚度。该设备的设计程序和工作机制是基于实践准则的。在这个研究中，制造MLUPD原型并将其安装在钢架的两种不同配置中，以便在推覆和循环载荷下进行测试以评估MLUPD性能。此外，还使用数值研究评估了设备性能。

因此，得出了所开发的MLUPD的本构模型。然后，通过有限元程序对带有或不带有MLUPD装置的桥梁的分析模型进行了编码，以评估配备有该装置的桥梁的抗震性能。MLUPD原型的实验和有限元结果表明，该设备能够通过多级性能来确保安全。

另外，结果表明，所开发的系统在两个框架配置中显示出显着的抗力性。此外，桥梁时程分析的数值结果在梁位移，桥墩基础剪力和漂移比方面都表明，通过使用该开发的装置以及不同的轴承箱，可以提高桥梁的抗震性能。