考虑边界非理想的铁路桥梁挠度影响线分析与损伤识别

It is difficult to achieve the influence line analysis accurately and damage detection exactly of assembled railway bridge girder because the boundary conditions are somewhere between the rigid and articulation connections. The non-ideal supporting conditions were considered in the assembled girder structure, a girder model of the elastic supported boundary with rotational restraint was established to simulate the actual prefabricated assembled beam. The initial uncertainty parameters of the girder section were introduced based on the lognormal distribution. The analytical expression of the deflection influence line of arbitrary beam section was deduced by the force-method, and the damage identification method of the assembled girder structure based on the influence line of deflection was proposed. A three-span continuous composite steel girder bridge was established as a simulation example to verify the proposed method. The positions of measuring points of deflection influence line, location and degree of regional damage and testing noise were studied to provide theoretical basis for the analysis of deflection influence line and damage identification of assembled girder structures. The results show that the proposed indicator can locate and quantify the local damage of the span and its adjacent span of a precast assembly railway bridge with non-ideal boundary. The proposed indicator had a superior noise resistance and it is susceptible to damage of the middle span of the girder and longitudinal girders. Based on the influence lines measuring, the continuity of the supports in the assembled girder bridge can be evaluated. The method in this paper can provide theoretical reference for the deflection influence lines analysis and damage identification of the actual railway bridges.