- 期刊
鋼筋混凝土偏心梁柱接頭之抗剪強度設計
Design of Shear Strength for Eccentric Beam-Column Joints
摘要
現行之ACI 318-11規範[1]參考了ACI-ASCE 352規範委員會[2]之多項建議，定義梁柱接頭之剪力計算強度為平均剪應力容量與接頭有效面積之乘積。但多年之使用經驗顯示，ACI 318-11規範[1]對偏心梁柱接頭抗剪有效寬度之規定過於嚴苛。本研究探討四種接頭有效寬度的計算方式，其中包含ACI 318-11[1]、ACI 352R-02[2]、AIJ Guidelines[3]與NZS 3101[4,5]等規範。本文除了以資料庫實驗結果比較各規範有效寬度之差異，更進一步地提出接頭有效寬度之公式。本文提出的接頭有效寬度可反映各種矩形梁柱接頭之幾何尺寸變化差異，並可合理預測資料庫之偏心及同心梁柱接頭的剪力強度。本文所建議之接頭有效寬度，除可供接頭剪力強度設計之經驗公式使用外，其亦具有力學意義，而能應用在接頭剪力強度預測之解析模型中。此外，依據現有之同心外部（T形）梁柱接頭實驗結果，本文也重新強調工程師在接頭區內需將梁主筋彎鉤延伸至柱核心區遠端錨定的重要性。
並列摘要
The current ACI 318-11 building code, which adopts many recommendations from ACI-ASCE Committee 352, defines the nominal joint shear strength of a beam-column connection as the product of the average shear stress capacity and the effective joint area. Past experience did indicate that the ACI 318-11 provisions on the effective joint width of the eccentric beam-column joints are too strict. This study critically evaluates four sets of effective joint width provisions, available in ACI 318-11, ACI 352R-02, AIJ Guidelines, and NZS 3101, as well as the companion provisions for average shear stress capacity. Comparisons and experimental verifications have been made among the code provisions; and more general expressions of effective joint width are proposed for design. The proposed effective joint width considers various sizes of rectangular joints and gives consistent strength estimations for both concentric and eccentric beam-column connections. Since the proposed effective joint width possesses the physical meaning of concrete crushing, it can be used both in the ACI 318-11 design method and the associated analytical procedures. Furthermore, based on available research data for concentric exterior (T-shaped) beam-column connection specimens, this study re-emphasizes engineers to extend beam longitudinal bars to the far face of the confined column core.