Study On The Dynamic Analysis And Standardization For Cable-unseating Prevention Devices Of Highway Bgidges

Cable-unseating prevention devices is the final security instrallment in the collapse-proof system of highway bridges,which cable-unseating prevention devices is the measure which prevent the beam to fall in the longitudinal direction if the rank of seismic force is surpassed L₂. Unseating prevention devices has applied in the practical bridges and has the corresponding standar of design in overseas, but the research of this device has just started in our country. Probably, there are many usages in engineering, but they are all on experience ,not on theory, and aren't consistent with the Seismic Standar of China.In this paper, the application and development of the present situation, the type and the suitable condition about unseating prevention devices at home and abroad have been introduced, the design method is discursed also, moreover, specified the elementary theory of design calculation by means of static theory which carried on unseating prevention devices by Doctor ZhuWenzheng. The research project is the beam bridge which span is from 20m to 50m, while paralled wire and prestressed strand with unbonded tendons is used as the cable, the analysis of the non-liner time history has been carried on, altogether, the correlation influence in the preasure of the unseating prevention devices has been analyed. It is one kind of impuls when seismic force acts on the unseating prevention devices. The pressure on the unseating prevention devices is mainly related to the moving value of design, the length and diameter of the cable, the condition of the field and the acceleration of ground motion. The relationship between the pressure on the unseating prevention devices and the designed moving value or the length of the cable has been elaborated in detail, the most important influence factor is the designed moving value. By means of one calculation example, the character of the pressure on the unseating prevention devices and the influence to the structure rigidity after stressed has specifically analyzed by all kinds of loadcase combinations. The rang of one span weight has been projected, which based on the practical bridges and standar drawings of the medium-scale span of the beam bridge. According to the basic principle ststic theory, the diameter and strands of the paralled wire and prestressed strand with unbonded tendons weer standardized and produced the result by the form, in addition, the application method of the standardized result has been explained also. In the process, allows the beam to be separated from the substructure, while there are no pressure on the cable from the seismic impulse function also, only is W/2 function received. In this paper, the nuseating prevention devices which has the function of restrainer hasn't certainly involved.