利用敲擊回音法量測鋼筋混凝土版受高溫後之裂縫深度

Abstract

本研究主要目的是利用敲擊回音法探知鋼筋混凝土版受高溫後之裂縫深度，並探討鋼筋混凝土版在受高溫時，加以不同的載重條件、承受不同的加溫最高溫度與加溫之延時，其裂縫深度的發展。而在試驗中，發現鋼筋混凝土版受高溫後損害之裂縫多為垂直方向且待試體自然冷卻後裂縫變得十分細微，故以敲擊回音法直接量測其裂縫深度有所困難。因此改以敲擊回音法量測鋼筋混凝土受高溫後之應力波速度的變化配合鑽心取樣觀察試體裂縫深度，及將試體切片重新量取應力波速，找出波速度與裂縫深度之關係。 研究結果包含各種不同變因對鋼筋混凝土版受高溫後之內部溫度、裂縫深度的影響、強度的折減與溫度的關係、應力波速度變化與強度折減的關係、火害深入試體內部的程度、應力波速度與裂縫深度的關係趨勢。初步結果發現利用敲擊回音法量測受高溫後鋼筋混凝土版之應力波速度，估計其裂縫深度是可行的。

The purpose of this study is to evaluate the crack depth of concrete slab exposed to elevated temperature by impact-echo method, and to investigate the effects of parameters such as loading conditions, fire temperatures and duration. In experiments, the direction of most cracks after exposed to high temperature is vertical and the size of cracks became smaller after cooling. It was difficult to measure the crack depth directly by impact-echo method. Therefore, combing the impact-echo method and core boring was used, to determine the relationship between wave speed and crack depth. The results of this study included the effect of temperature in slab and crack depth, relationship among strength, temperature, wave speed and crack depth. In Summary, it is feasible to measure the wave speed of concrete slab exposed to high temperature by impact-echo method to estimate the crack depth.