Diagnosis for Grouted Condition of Transverse Prestressing Tendon in PC Bridges in-Service using Impact Elastic Wave Methods
| Autor: | Takefumi Ito, Yoshifumi Nagata, Akira Shiratori, Hiroshi Ueki |
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| Rok vydání: | 2014 |
| Předmět: | |
| Zdroj: | Concrete Research and Technology. 25:57-64 |
| ISSN: | 2186-2745 1340-4733 |
| Popis: | Prestressing bars or prestressing wires are employed as transverse prestressing tendons in cross-beams and concrete slabs of prestressed concrete (PC) bridges. The ducts for inserted tendons are normally grouted. Inadequately grouting, however, may lead to tendon corrosion and breakage. The breakage of tendons sometimes results in the projection of a torn portion from the bridge, causing a serious public safety hazard. The impact Elastic Wave Methods technique was employed to study the effect of voids in post-tensioning grouted ducts of PC bridges in service. Two indices were introduced to evaluate inadequately grouted ducts for transverse prestressing. One is the velocity of the elastic wave propagated in the tendon, and the other is the presence of high frequency components observed at the beginning portion of the received wave. After confirming the applicability of the technique for detecting inadequately grouted ducts for transverse prestressing, it was demonstrated that the technique can also be applied for inspecting restored ducts after re-grouting. Further, it may be possible to improve the reliability of the diagnosis by taking into account the rise time of the received waves.PC橋の横締めは横桁および床版に存在し，PC鋼棒またはPC鋼線が最近まで用いられてきた。これらのPC鋼材はシース内にグラウトを充填して防食機能を維持しているが，グラウトの充填が不充分であると水，空気などの侵入により腐食し，破断してPC鋼棒については突出する事故が散見される。このためグラウトの充填状態を診断する手法の開発が維持管理を行う際に必要となる。筆者らは，衝撃弾性波法を用いてPC鋼棒またはPC鋼線で横締めされた２種類の実橋の横桁について，弾性波伝幡速度と受信波前方に存在する高周波波形(前方高周波振幅波)の有無を評価指標としたグラウトの充填診断手法を開発して，その実用性を確認することができた。また，本手法はグラウトの充填不足のシース内に再注入する工事の検査手法にも適用できることを示した。 PC鋼棒では伝播波形の最大振幅に至るまでの立上り時間を新たな評価指標として考慮すれば診断の信頼性が更に向上することを明らかにした。 |
| Databáze: | OpenAIRE |
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