高拉力鋼筋混凝土梁鋼筋截斷設計之研究

he Study on the Rebar Cut-off Design for New RC Beams using High Strength Steel Reinforcement

歐陽文浩(Wun-Hao Ou Yang)

指導教授 ： 王勇智

國立中央大學/工學院/土木工程學系/碩士(2014年)

摘要

本研究設計五組矩形斷面RC懸臂梁，受反覆荷載實驗來探討有截斷鋼筋之New RC梁耐震行為，並檢討目前ACI設計規範在鋼筋截斷規定是否適用於高拉力鋼筋截斷設計。
在本實驗中，New RC梁混凝土強度原設計強度為40MPa，而實際測試強度為55MPa。梁主筋上下層各3根#8高拉力SD685螺紋節鋼筋，箍筋採#3普通拉力SD420鋼筋。兩支梁為控制組，#8主筋為完全未截斷試體，其中一支梁主筋為普通拉力SD420鋼筋，另一支梁主筋為高拉力SD685鋼筋。另三組為主筋截斷之試體，一組為按照ACI318-11規定做截斷設計。另外兩組試體為按照耐震規範細則建議，主筋強度以1.25倍降伏標稱強度做設計，試體荷載方式分為單向荷載及反覆荷載。
由本研究之結果與前人之研究之結果比較得知，混凝土梁受力時產生之剪力斜裂縫造成之拉力外移，會造成設計之有效握裹長度減少，在截斷設計時，應考慮其影響。故建議主筋強度以1.25倍降伏標稱強度做設計，以延伸主筋握裹發展長度，將可以避免截斷之主筋發生握裹滑移破壞，以達到構件所需求的設計目標。

關鍵字

梁 ； 高拉力鋼筋 ； 鋼筋截斷 ； 耐震行為 ； 拉力外移

並列摘要

In the research, five reinforced concrete beams with high strength steel reinforcement are tested by cyclic loadings to observe their seismic performance and to verify the availability of the recent ACI 318 code on the high strength rebar cut-off design.
The original concrete strength 40 MPa was adopted for the testing whereas the concrete cylindrical strength was measured up to 55 MPa. The difference of the concrete strength could influence the design for the rebar cut-off length. For all the five tested beams, 3-#8 bars are placed on the top and on the bottom of the beam section, respectively. One beam belonged to normal RC beam with SD420 #8 beam bars, different from the rest of four beams belonged to New RC beams with SD685 #8 bars. The yielding strength of the transverse reinforcement for all the tested beams is 420 MPa. Two beams including the normal RC are not curtailed for comparison. As for the three curtailed beams, one beam is curtailed adopted from ACI318-11 building code, and other two are revised from the original design. That is the yielding strength in the ACI empirical equation of the development length is replaced by taking 1.25 times the nominal yield strength of the steel reinforcement.
According to the result, the diagonal flexure-shear cracks cause the effect of the tension shift of the high strength steel reinforcement severe. Thus, it causes the rebar development length increase. This effect shall be cared when the steel reinforcement curtailment is considered. It is suggested that 1.25 times the nominal yield strength of the beam longitudinal bars might take into account when the development length of steel reinforcement was evaluated.

並列關鍵字

New RC beams ； high strength steel reinforcement ； rebar cut-off ； seismic behavior ； tension shift

參考文獻

[6]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。

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

[4]Y.C. Wang , “Analytical and Experimental Study on Seismic Performance of RC T-beams with Design Deficiency in Steel Bar Curtailment ”Engineering Structure, vol. 25, 2003, pp. 215-227.

[2]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。

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