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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/64798


    Title: 受震鋼筋混凝土之鋼筋截斷設計研究;Investigation on Steel Bar Cut-off Design for RC Beams Subjected to Seismic Loading
    Authors: 王偉軒;Wang,Wei-Hsuan
    Contributors: 土木工程學系
    Keywords: 鋼筋截斷;耐震行為;耐震設計;拉力外移;cut-off;curtailment;seismic behavior;seismic performance design;tension shift
    Date: 2014-07-24
    Issue Date: 2014-10-15 14:25:44 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 本研究旨在探討鋼筋截斷混凝土矩形梁之耐震行為,並檢討目前建築規範之鋼筋截斷規定是否適用於耐震設計。

    在本研究中,一共製作四支鋼筋混凝土梁。混凝土強度為280 kgf/cm^2,主筋降伏強度為4200 kgf/cm^2。梁斷面一共六支八號主筋,一支梁作為對照組,並未做任何截斷。另外三支矩形梁,採用上下層各三支的雙鋼筋設計,中間兩支主筋設計截斷。截斷設計一共有兩種,上層主筋參考美國混凝土協會出版之標準ACI 318-11規範中的截斷設計;下層主筋則根據紐西蘭標準NZS3101:2006設計截斷,額外考慮拉力外移的效應,因此截斷長度較長。採用此種設計方式主要原因為ACI規範於耐震設計並未提及鋼筋截斷之細則,因此目前耐震結構之鋼筋截斷仍採用一般設計方式。但此種設計法截斷長度較短,一旦遭遇地震力,會產生鋼筋的握裹滑移現象,導致混凝土梁握裹破壞。

    ACI 318-11規範同時規定鋼筋截斷處必須配置超額剪力筋,以防止撓曲剪力裂縫在該處產生,在本研究中在其中兩支有截斷的矩形梁中分別採用兩種不同的方式設計:第一種為截斷處一個有效深度的範圍內以d/4的間距配置三號繫筋於被截斷的主筋上,第二種為截斷處一個有效深度的範圍內以d/4的間距配置二號封閉箍筋。採用此種設計目的在於探討兩種超額剪力筋對於鋼筋滑移的防止,其效果的差異。

    最後,本研究提供建議,對於結構物的耐震設計若有鋼筋截斷的需求,應考慮拉力外移的效應,一般建議增加一斷面有效深度,避免因鋼筋截斷長度不足,而導致鋼筋產生滑移,造成鋼筋握裹破壞。
    ;The purpose of this study is to understand the seismic behavior of rebar cut-off RC beams subjected to seismic loading, and to investigate if current building codes for rebar cut-off designs are adequate during seismic activities.

    In this study, four RC beams are tested. The properties of the four beams are described as follows: the concrete compression strength of the concrete is 28 MPa and the yield strength for longitudinal reinforcement is 420 MPa. One beam is used as a control beam where no rebars are curtailed. The other three beams have longitudinal curtailed rebar according to code ACI 318-11 (American Concrete Institute). The curtailed beams have three #8 rebars placed on both upper and lower sides of the beam, and the center bar is curtailed. The curtailment of the two sets of rebar has two different designs. Both designs follow the code described in ACI 318-11, but the second design includes consideration of tension shift which is adopted from NZS 3101:2006. The second design is adopted to overcome the lack of detail in ACI 318-11 with regard to rebar cut-off in seismic performance design. Thus, the conventional design of rebar cut-off may lead to bond slipping due to insufficient cut-off distance when the beam is subjected to seismic loadings.

    Excess transverse reinforcements are required in the region of the cut-off section by ACI 318-11. Two different types of transverse reinforcements are added and compared in the test. The first type is a #3 tie hooked on the center bar; the second type is a #2 closed hoop. This design allows the contribution of the transverse reinforcement to be observed with regard to prevention of bond slipping, and the results from both types are compared.

    Finally, this study provides some recommendations for rebar cut-off design. The consideration of tension shift for rebar cut-off design of RC beams is necessary. Conventional cut-off design according to ACI 318-11 is inadequate because the general structure has to consider shear effect during an earthquake. Therefore, an additional length of effective sectional depth should be taken into account when the rebar cut-off is designed.
    Appears in Collections:[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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