本研究主要是探討台製#8螺紋節高拉力(SD685)鋼筋截斷，是否適用於現今ACI318-11[1]與NZS3101-2006[2]所規定之設計方式。初步研究階段，乃設計三組矩形斷面RC懸臂梁，受反覆荷載實驗來探討耐震行為差異。其中，RC梁混凝土強度為35MPa，梁主筋上下層各3根#8螺紋節高拉力鋼筋，一組梁主筋為完全未截斷，箍筋採#4螺紋節高拉力鋼筋(SD785)，配筋方式符合ACI318-11耐震規定。另二組梁主筋，上層1-#8按ACI318-11截斷設計作截斷，而下層1-#8按NZS3101-2006作截斷設計。此二組主筋截斷之梁試體，一組採SD785#4高拉力箍筋，另一組則採SD420#4一般拉力箍筋。
由實驗結果得知，規範ACI318-11之截斷設計結果，因截斷點不足，以致在極限狀況下，截斷筋尚未降伏，影響梁整體之耐震能力。另外，在不同箍筋強度情況下，使用高拉力SD785箍筋之試體與使用SD420箍筋之試體，其耐震能力皆足夠且無太大之差異。對於，若截斷設計得宜，有無截斷之鋼筋混凝土梁，在降伏載重、勁度與韌性無太大差異。

The purpose of the experimental study is to investigate seismic behavior of the new RC beams with high-strength (SD675MPa) screw bars, curtailed according to the design of ACI318-11[1] and NZS3101-2006[2]. Three cantilever beams subjected to cyclic loading were adopted for the pilot test. #8 SD685 screw bars (3-#8 set at upper bars and 3-#8 set at bottom bars) and #4 SD785/420 deformed bars were used in the test specimens. Furthermore, the #4 bars as transverse hoops were designed according to the seismic specification of ACI318-11. One beam without beam bar cut-off as a control specimen and the other two with 1-#8 beam bar curtailment at upper bars (ACI cut-off design) and at bottom bars (NZS cut-off design) were adopted for the test specimens. To realize the effect of transverse hoop strength on beam seismic performance, one beam designed using high strength #4 hoops whereas the other using normal strength #4 SD420 hoops.
Test results showed the cut-off design specified in ACI318-11 did not apply to the curtailment of high-strength screw-type #8 reinforcement. This is because the cut-off point of the #8 reinforcement is not lengthy enough. However, the cut-off design provided from NZS3101-2006 could be feasible for the curtailment of the high strength steel. Further study on the curtailed design of such high strength steel reinforcement is required. It was also repealed the curtailed beams with different hoop strengths, #4 SD785 and #4 SD420, had similar seismic behavior.

[1] ACI Committee 318, Building Code Requirement for Structural Concrete, ACI318-11 & Commentary, American Concrete Institute, 2011.

[2] Standards Association of New Zealand, NZS 3101: New Zealand Concrete Structures Standard, Part 1- the Design of Concrete Structures, Part 2- Commentary on the Design of Concrete Structures, New Zealand, 2006.

[3] Aoyama, H., Design of Modern Highrise Reinforced Concrete Structures, Imperial College Press, 2001, pp.104-112.

[4] ACI Committee 374, “Acceptance Criteria for Moment Frames Based on structural Testing and Commentary (ACI 374.1-05)” American Concrete Institute, Farmington Hills, MI, 2005, pp. 1-9.

[5] Paulay, T, and Priestley, M.J.N., Seismic Design of Reinforced Concrete and Masonry Building, John Wiley & Sons, New York, 1992.

[6] Ferguson, P.M., and Matloob, F.N., “Effect of Bar Cutoff on Bond and Shear Strength of Reinforced Concrete Beams.” Journal of the American Concrete Institute, July 1959, pp.5–23.

[7] Lee, J. Y., Choi, I. J., and Kim, S. W., “Shear Behavior of Reinforced Concrete Beams with High-Strength Stirrups.” ACI Structural Journal, V. 108, No. 5, Sep.-Oct. 2011, pp. 620-629.
[8] 中國土木水利工程學會，混凝土工程設計規範與解說，土木401-100，2011。
[9] 許禎祐，「有鋼筋截斷之RC梁耐震行為探討」，國立中央大學，碩士論文，民國一百零一年。