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Practical Research Work on Diagnosis and Strengthening for ASR Deteriorated Bridge Piers with Fracture of Steel Reinforcement

ASR劣化桥墩钢筋断裂诊断加固实践研究

基本信息

批准号：
16360218
负责人：
TORII Kazuyuki
金额：
$ 9.28万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Research results obtained in this study are summarized as follows ;(1)Investigation on fracture of steel bars in ASR-affected structuresResearch works revealed that the embrittle fracture of steel bars at the bending corner of stirrup or bent-up steel bars, due to excessive expansion of concrete due to ASR, occurred in the pillow beam or footing of piers and the abutment in bridges located in Ishikawa Prefecture, leading to the significant loss of structural integrity of concrete elements.(2)Mechanisms of fracture of steel bar due to ASRIn the pillow beam or foundation of bridge pier, a lot of stirrup steel bars fractured at the bending corners, without any elongation of steel bar. The fracture surface of steel bar seemed to be very flat and smooth, which indicated the typical embrittlement fracture of steel bar. Whether or not the fracture of steel bars may be associated with the stress corrosion cracking and/or the hydrogen embrittlement fracture was discussed.(3)Asset management for ASR-deteriorated bridgesFor all bridge piers located in Ishikawa prefecture, which is considered to be the most serious ASR case in Japan, the degree of deterioration of bridge pier due to ASR was investigated by the visual inspection of cracking. Corresponding to the classification of ASR deterioration level of each bridge pier, the repair/strengthening method and maintenance procedure were proposed.(4)Strengthening and monitoring of ASR-deteriorated bridge piersIn the case study of the pillow beam of Kashima Bridge and the foundation of Tokuda No.2 Bridge in Ishikawa Prefecture, the degree of deterioration of bridge pier due to ASR was also investigated by the non-destructive inspection. Based on the classification of ASR deterioration level of each element, the most appropriate strengthening methods were adopted for them. In the maintenance of these bridges, the monitoring using crack sensors was successfully applied in order to ensure the daily safety of these bridges.

本研究取得的研究成果概括如下：(1)受ASR影响的结构中钢筋断裂的调查研究工作表明，由于ASR引起的混凝土过度膨胀，在石川县桥梁的枕梁或桥墩基脚和桥台处发生了箍筋或弯曲钢筋弯曲角处的钢筋脆性断裂，导致了桥梁的脆性断裂。 (2)ASR引起的钢筋断裂机理在桥墩枕梁或基础上,大量箍筋钢筋在弯角处发生断裂,且没有任何钢筋伸长。钢筋断口看上去非常平坦、光滑，表明钢筋属于典型的脆性断裂。讨论了钢筋断裂是否与应力腐蚀开裂和/或氢脆断裂有关。(3)ASR劣化桥梁的资产管理对于位于日本ASR最严重案例的石川县的所有桥墩，通过目视裂纹检查来调查ASR引起的桥墩劣化程度。针对各桥墩ASR劣化程度的分级，提出了修复/加固方法和维护程序。(4)ASR劣化桥墩的加固与监测以鹿岛大桥枕梁和石川县德田二桥基础为例，通过无损检测的方法，对桥墩ASR劣化程度进行了研究。根据各元素ASR劣化程度的分类，对其采取最合适的强化方法。在这些桥梁的维护保养中，裂缝传感器监测得到了成功应用，保证了桥梁的日常安全。