鋼筋混凝土樁帽剪力強度之評估

SHEAR STRENGTH PREDICTION FOR REINFORCED CONCRETE PILE CAPS

由樁帽及基樁所構成之樁基礎，係藉由基樁穿越軟弱土層而將建築物之載重傳遞到深層之堅硬土壤以確保結構安全。鋼筋混凝土樁帽之設計，除了須具有足夠的厚度以避免剪力破壞外，並須配置適量的撓曲鋼筋以確保樁帽不會發生撓曲破壞。本研究根據軟化壓－拉桿模型，建議一簡化分析方法來計算鋼筋混凝土樁帽之剪力強度。藉由試驗值和分析值之比對，以探討分析方法之精確性，經由試驗數據之測試比對發現，美國ACI規範斷面法及本研究所建議之分析方法，皆能均勻地預測鋼筋混凝土樁帽之剪力強度，惟美國ACI規範斷面法對於剪力跨度與有效深度比值較小之樁帽會得到不保守地剪力強度預測。

The pile foundation consisting of pile caps and piles transfers the load of the building to the deep hard soil by means of piles that pass through the soft soil layers to ensure structural safety. The design of the reinforced concrete pile caps should provide sufficient thickness to avoid shear failure as well as an appropriate amount of flexural reinforcement to avoid flexural failure. In this study, a simplified analytical method was proposed based on the softened strut-and-tie model to calculate the shear strength of reinforced concrete pile caps. The prediction precision of the proposed analytical method and the section method of the ACI Code are verified by comparing the experimental and analytical values. According to the experimental verification, it is found that both methods can obtain uniform predictions for the shear strength of the reinforced concrete pile caps. However, the section method of the ACI Code may be non-conservative for pile caps with relative low shear span-to-depth ratios.