Journal of the Korea Concrete Institute (콘크리트학회논문집)

Korea Concrete Institute (한국콘크리트학회)
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Behavior and Capacity of Compression Lap Splice in Unconfined Concrete with Compressive Strength of 40 and 60 MPa

횡보강근이 없는 40, 60 MPa 콘크리트에서 철근 압축이음의 거동과 강도

  • Chun, Sung-Chul (Architectural Technology Research Team, Daewoo Institute of Construction Technology, Daewoo E&C Co., Ltd.) ;
  • Lee, Sung-Ho (Architectural Technology Research Team, Daewoo Institute of Construction Technology, Daewoo E&C Co., Ltd.) ;
  • Oh, Bo-Hwan (Architectural Technology Research Team, Daewoo Institute of Construction Technology, Daewoo E&C Co., Ltd.)
  • 천성철 ((주)대우건설 기술연구원 건축연구팀) ;
  • 이성호 ((주)대우건설 기술연구원 건축연구팀) ;
  • 오보환 ((주)대우건설 기술연구원 건축연구팀)
  • Published : 2009.06.30
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Abstract

A compression lap splice can be calculated longer than a tension lap splice in high strength concrete according to current design codes. New criteria for the compression lap splice including the effects of concrete strength are required for practical purpose of ultra-high strength concrete. Characteristics of compression lap splice have been extensively investigated and main parameters are derived. In addition, an experimental study has been conducted with column specimens in concrete strength of 40 and 60 MPa. The strength of the compression lap splice consists of bond and end bearing and two contributors are combined. Therefore, combined action of bond and end bearing should be assessed. Compared with tension splices, concrete strength significantly affects the strength of compression splices due to short splice length and existence of end bearing. Test results show that the splice strength can be evaluated to be proportional to square root of compressive strength of concrete. The stress states of concrete surrounding spliced bars govern the strengths of bond and end bearing. Because the axial stress of the concrete is relatively high, the splice strength is not dependent on clear spacing. End bearing strength is not affected by splice length and clear spacing and is expressed with a function of the square root of concrete strength. The failure mode of specimens is similar to side-face blowout of pullout test of anchors and the strength of end bearing can be evaluated using the equation of side-face blowout strength. Because the stresses developed by bond in compression splices are nearly identical to those in tension splices, strength increment of compression splices is attributed to end bearing only.

현행 기준식에 따르면 초고강도콘크리트에서는 철근 인장이음길이보다 압축이음길이가 더 길어지는 현상이 발생된다. 초고강도콘크리트의 경제적 실용화를 위해 합리적인 압축이음강도의 평가가 필요하다. 이를 위해 압축이음의 거동 특성을 분석하고 영향인자를 도출하였으며, 설계강도 40, 60 MPa 콘크리트에 대한 압축이음 실험을 수행하였다. 압축이음강도는 부착과 지압으로 구성되고, 부착과 지압의 복합 거동에 의해 발현되므로, 압축이음 거동특성 및 강도평가를 위해서는 부착과 지압이 함께 존재하는 상태에서의 연구가 수행되어야한다. 인장이음과 달리 압축이음은 이음길이가 짧고 지압의 존재로 인해 콘크리트 강도의 영향이 크다. 실험결과 압축이음강도는 콘크리트의 제곱근에 비례하는 것으로 평가되었다. 부착과 지압 모두 주변 콘크리트의 응력상태에 따라 결정되는데, 콘크리트의 축방향 응력이 높기 때문에 철근 순간격 증가에 따른 이음강도 증가는 거의 없다. 지압강도는 이음길이와 철근 순간격에 무관하며, 콘크리트 강도의 제곱근의 함수로 표현할 수 있다. 파괴양상이 측면파열파괴와 유사하므로 지압강도는 앵커의 측면파열파괴 강도식을 활용하여 평가가 가능하다. 부착에 의해 발현되는 강도는 인장이음의 경우와 유사하므로, 인장이음강도에 비해 향상된 압축이음강도는 단부 지압효과로 설명될 수 있다.

Keywords

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Cited by

  1. Components of compression splice resistances in high-strength concrete vol.69, pp.10, 2017, https://doi.org/10.1680/jmacr.16.00412
  2. Behavior and Capacity of Compression Lap Splice in Confined Concrete with Compressive Strength of 40 and 60 MPa vol.21, pp.4, 2009, https://doi.org/10.4334/JKCI.2009.21.4.389
  3. Compression Lap Splice Length in Concrete of Compressive Strength from 40 to 70 MPa vol.21, pp.4, 2009, https://doi.org/10.4334/JKCI.2009.21.4.401