考虑边界非理想的铁路桥梁挠度影响线分析与损伤识别

Influence Line Analysis and Damage Detection of Railway Bridge Deflection with Non-ideal Boundaries

铁路桥梁多为装配式桥梁,因其边界条件介于理想铰支与固支边界间的非理想状态,而较难实现影响线分析与损伤识别。考虑装配式铁路桥的非理想支承特性,建立带转动约束和竖向弹性支承边界的主梁模型,以模拟实际预制装配式铁路桥梁主梁,并引入基于对数正态分布模型的主梁截面初始不确定性参数。通过力法原理推导了该主梁挠度影响线的解析表达式,进而提出考虑边界非理想的铁路梁损伤识别方法。采用实测某装配式3跨连续组合梁桥挠度影响线,评价该桥的承载能力,同时对所提方法进行验证,并研究了挠度影响线测点位置、局部损伤位置与程度、测试噪声对主梁挠度影响线的影响。结果表明:基于所提出的影响线指标可以定位、定量边界非理想的装配式铁路连续梁桥某跨及其临跨的局部损伤,且更易于识别主梁跨中与纵梁结构损伤,指标抗噪性良好;实测影响线可用于评价装配式连续梁桥中支座连续性的强弱,为实际铁路桥梁的挠度影响线分析与损伤识别提供理论借鉴。

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.