钢结构桥梁的失效高强螺栓腐蚀产物特性研究

Research on the Corrosion Products of Fracture Failure High-strength Bolt Used in Steel Structure Bridge

目的研究在重庆湿润气候环境腐蚀条件下,朝天门大桥断裂高强螺栓的腐蚀特性及其影响因素。方法根据朝天门大桥2013—2018年发现的81颗脱落断裂的高强螺栓在桥梁不同位置、时间发生脱落断裂的时空及类型分布统计分析结果,选取具有代表性的6个样品。同时,开展模拟重庆市湿润气候环境下高强螺栓的腐蚀试验,采用Q8直读光谱仪、扫描电镜、EDS、XRD等,对失效高强螺栓及模拟腐蚀环境下的高强螺栓表面腐蚀产物的化学组成、微观形貌进行分析,探讨高强螺栓失效与环境腐蚀之间的关系。结果断裂失效螺栓断口表面、全新螺栓表面及芯部的化学成分分析结果表明,断裂失效螺栓和全新螺栓芯部的元素均为Fe、C、Mn、Si,元素分布均匀,而失效高强螺栓断口表面及模拟腐蚀环境下的高强螺栓表面腐蚀产物的元素种类较多,主要为铁和氧元素。失效高强螺栓及模拟腐蚀环境下的高强螺栓的表面腐蚀产物EDS能谱分析结果表明,腐蚀产物中有S、Cl、Al、Si、K等元素的存在,XRD物相分析结果显示,存在大量的Fe、Mn、Si等元素的氧化物及硫化铁。结论高强螺栓的断裂失效与大气腐蚀(酸雨)、工业尘埃、道路扬尘等环境污染有关。

Bolt corrosion is one of the important factors threatening the long-term security and stable operation of bridges.In order to determine the reason of bolt corrosion,according to the statistical analysis results of the spatial and temporal distribution and type distribution of 81 high-strength bolts which were found in Chaotianmen Bridge from 2013 to 2018,6 representative samples were selected.The relationship between failure of high-strength bolt and environmental corrosion was discussed,corrosion test of high strength bolt under simulated humid climate in Chongqing were carried out.The chemical composition and micro morphology of the corrosion products were analyzed by using Q8 direct reading spectrometer,SEM,EDS,and XRD.The chemical composition analysis results show that both the elements of the failed bolts’core and the new bolts’core are Fe,C,Mn and Si,which are uniformly distributed,while elements of the corrosion products on the surface of fracture failed bolt sand the high strength bolt under simulated corrosion environment are various and serious segregation,and are mainly of oxygen and Fe.Apart from rust,the EDS results show that there were S,Cl,Al,Si,K and other elements in the corrosion products,and the XRD results show that there are iron sulfide,oxides of manganese,silicon and other oxides.It is speculated that the fracture failure of high-strength bolts is related to atmospheric corrosion(acid rain),industrial dust,road dust and other environmental corrosion.