某钢结构桥梁火灾后检测评估和安全鉴定

Inspection, Evaluation and Safety Identification for a Steel Bridge Experienced a Fire Disaster

某桥为双层刚性悬索连续钢桁梁桥,2017年12月23日晚20:14遭受火灾。为了解火灾后桥梁结构状况,指导桥梁维修处治,对火灾后桥梁现场进行初步鉴定,采用高精度全站仪对损伤区域钢横梁的变形进行测量,通过里氏硬度计测试受损构件的硬度,采用有限元法计算钢结构的过火温度并分析火场温度下结构的位移和应力。结果表明:现场未发现钢梁屈服变形、混凝土桥面板剥落露筋现象,初步鉴定结构受损较小;受火后钢梁变形满足规范要求,受火区域钢结构材质强度变化不大;桥面系温度场最高温度为294.036℃,钢纵、横梁应力均未超过屈服应力,位移满足规范要求;安全性鉴定结果判定该桥受火后钢结构材料及结构性能未受或仅受轻微影响,可不采取措施或仅采取提高耐久性的措施。

The bridge is a combined rigid suspension and continuous steel truss structure, with an upper and a lower decks.One day in 2017,about 20:14 at night,a fire started on the bridge.To examine the condition of the bridge structure after the fire damage and direct the remedial of the bridge,the bridge site was investigated.The high-precision total station was used to test the deformation of steel cross beams in the zones damaged,the Leeb hardness testers were used to test the hardness of the damaged components,and the finite element method was used to calculate the temperature of the steel structure in the fire and the displacement and stress of the structure under the combustion.The results show that the steel beams did not experience yield deformation.The concrete in concrete slabs did not spall and no exposed reinforcement were seen.The preliminary inspection demonstrated that the structure had been slightly damaged.The deformation of the steel beams met the code requirements.The hardness of the materials in the steel structure burned showed minor change.The maximum temperature in thermal field of the deck system was 294.036 ℃.The stresses in the stringers and cross beams did not exceed the yielding stress and the deformation met the code requirements.According to the identification, the material of the steel structure and the performance of the structure were not influenced or just slightly influenced by the fire.Remedial measures were not quite necessary,or just taking measures to improve the durability of the structure was enough.