鋼筋混凝土十字形樁帽之抗剪強度：以四樁承載之樁帽為例

Shear Strengths of Reinforced Concrete Cross-Shaped Pile Caps: Taking the Pile Caps with Four Piles as an Example

本研究共製作9 座鋼筋混凝土十字形樁帽進行試驗，探討混凝土強度、樁心間距及撓曲鋼筋參數等對十字形樁帽剪力傳遞行為之影響。本研究並以軟化壓－拉桿 (Softened strut-and-tie, SST) 模型及ACI 規範之壓－拉桿 (Strut-and-tie, ST) 模型做為分析工具，來預測9 座鋼筋混凝土十字形樁帽之抗剪強度。研究結果顯示，抗壓強度81.3 MPa 之高強度混凝土樁帽其抗剪強度約為抗壓強度28.0 MPa 之普通強度混凝土樁帽抗剪強度之1.5 倍。樁帽之抗剪強度隨著剪跨－深比之增加而降低。樁帽之抗剪強度會隨著撓曲鋼筋參數之增加而增加。SST模型及ACI 規範之ST 模型皆能精確預測鋼筋混凝土樁帽之抗剪強度。ST 模型無法預測十字形樁帽之破壞模式。

In this study, a total of 9 reinforced concrete cross-shaped pile caps were produced for experiments to investigate the effect of concrete strength, pile centroid spacing and flexural steel bar parameters on the shear transferred behavior of the cross-shaped pile cap. In this study, the softened strut-and-tie (SST) model and the strut-and-tie (ST) model of the ACI Code were used as analysis tools to predict shear strength of 9 reinforced concrete cross- shaped pile caps. Research results show that the shear strength of the high-strength concrete pile caps with a compressive strength of 81.3 MPa is about 1.5 times that of the normal-strength concrete pile caps with a compressive strength of 28.0 MPa. The shear strength of the pile caps decreases as the shear span-to-depth ratio increases. The shear strength of the pile cap will increase with the increase of the flexural reinforcement parameters. Both the SST model and the ST model of the ACI Code can predict the shear strength of reinforced concrete cross-shaped pile caps well. The ST model cannot predict the failure mode of the cross-shaped pile cap.