敲擊回音法應用橋面版損傷之探討

國內主要公路的橋梁有部份是採薄版密梁方式設計，為因應車流需要，往往會於橋梁兩側拓寬，形成兩代橋(two generations bridge，又稱拓建橋)，由於少數橋梁於新舊接合處的角隅端版(end of plate)，會發生大小不等裂紋，且修補後又有多處重復出現。本研究針對其中兩座橋梁經全面性於角隅端版處以敲擊回音(impact echo method)檢測裂縫及頻譜，並配合目視檢測的判斷，進行裂縫可能原因的探討，結果推論如下: 1.頻譜檢測大多能測到複合版厚度，說明瀝青層(asphalt layer)與混凝土版黏結(bonding)情況尚佳，推論瀝青層非造成裂縫主因。 2.多數裂縫皆已貫穿橋面版，由於裂縫皆產生於端版處，研判應可能為橋面版採單向版(one-way slab)設計，然而端版處因為有端隔梁(end of cross beam)的存在，車載時變為雙向版力學行為，因而使角隅承受較大剪力使角隅臨界斷面處因二次彎矩而龜裂。 3.角隅筋不在結構設計範圍，角隅裂縫短期內安全無慮，長期影響使用功能及劣化速率。 4.建議後續修護或設計時，橋面版應配置「角隅補強筋」或可改善。

關鍵字

敲擊回音系統；頻譜；目視檢測；角隅補強

並列摘要

Parts of highway bridge design within Taiwan are using thin slab with compact girder. Due to the traffic needs, usually the government will widen the side, forming a two generation bridge. Within the connection point of some of these bridges, crack will occur in the end of plate area, and this kind of reconstruction will happen regularly. This research aims to use the approaches of impact echo methodto inspect the crack and frequencyspectrum, with the help of visual inspection, further discussing the reason of the crack. Here are some inferred conclusions: 1.The frequency spectrum can usually detect the thickness of compound slab, which explained the asphalt layer are able to bond with the concrete layer quite successfully, further proven that the asphalt layer is not the main reason causing the crack. 2.Most of the crack had gone through the slab and happen in the end of plate. According to this phenomenon, it is concluded that the crack was cause by the one-way slab design. When in traffic, it changes to two-way slab behavior, for that reason, the corner of the plate undertake a larger shear force, therefore the crack and secondary moment was occur. 3.The corner of the steel was not in the structure design region,consequently the crack will not have much effect in safety in short time. However, it will affect the bridge’s function and deterioration rate. 4.Suggestion to solve this problem is when maintaining or designing the bridge, embedding steel in the slab corner in order to prevent the crack from happening.