| The primary failure leading to collapse is identified as unseating of superstructures at the expansion joints and abutments. If seismic force on the structure is large enough to fail the bearings, then the superstructure becomes vulnerable to unseating at the supports. Collapse-proof systems is a new method for seismic design and retrofitting, and the main purpose is to prevent the girders form falling off their supports. Collapse-proof systems of bridges consist of unseating prevention devices, seismic restrainers and adequate seat length. More and more seismic damages have attracted more and more experts, at home and abroad, to study on collapse-proof systems, and acquire many achievements, but there are many problems about new damping material and restrainers' study, the mechanical ability of restrainers and unseating prevention devices, the design methods of the collapse-proof system etc., moreover, the collapse-proof system has not ever been researched in China, probably there are many usages in engineering, but they are all on experience, not on theory, and are not consistent with the Seismic Standard of China. So these problems are required to be solved and completed.In this paper, the major aim is that exploiting new restrainers and unseating preventing devices - lead viscoelastic restrainers (LVER) and unseating preventing devices (LVEPD) and establishing analysis design method about prevention collapse system, the following work is done:(1) Experimental Study on Properties of the (Lead) Viscoelastic Restrainers and Unseating Preventing DevicesAccording to the results of experiment on viscoelastic restrainers under different frequencies, strain amplitudes and viscoelastic layer's thickness, the effect of the laws concerning frequency, strain amplitude and viscoelastic layer's thickness on the behavior of the restrainers are obtained; Experiment on LVER and LVEPD, study their energy absorption behavior, and find different parameters' effect laws.(2) Experimental Study on Properties of the Fluid Viscous Dampers (Restrainers)According to the results of experiment on viscous restrainers under different frequencies, strain amplitudes and the area of the shear section, the effect of the laws concerning frequency, strain amplitude and the area of the shear section on the behavior of the restrainers are obtained. The application range of equations for mechanic capability of dampers was confirmed.(3) Research on Adequate Seat LengthThough change the data of modal bridges, two approaches including response spectrum-based approach and static-based approach were introduced and compared, the of them was discussed, and the better method for usage in engineering was found; the methods to extend seat length were introduced.(4) Research on Design Theories and Methods of Unseating Prevention DevicesBased on the seismic standard of China, the design theories of unseating prevention devices were presented, according to the response spectrum of random loading and the fortify intensity at expansion joints, the design method was put forward. In the light of the use of unseating prevention devices at home and abroad, the choice and methods for installation of the devices are introduced and compared.(5) Research on the Design Method for (Viscoelastic) RestrainersBased on the factors effected the usage of restrainers, the design methods for the restrainers in use are analyzed, and a new design method is put forward based on response spectrum method. The method is tested with time history analysis. According to the design idea of unseating prevention devices, the static-based approach for restrainer devices is suggested.(6) Experimental Study on Properties of the Compression Bumpers According to the results of experiment on rubber type restrainers under differentmaterial and type, the hysteresis curves for studying the dissipation characters and mitigation effect of the devices is obtained to find out the better devices. Based on the experiment, the design method and calculating model are proposed.(7)...
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