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http://dx.doi.org/10.4334/JKCI.2016.28.5.611

Behavior of 550MPa 43mm Hooked Bars Embedded in Beam-Column Joints  

Bae, Min-Seo (Division of Architecture and Urban Design, Incheon National University)
Chun, Sung-chul (Division of Architecture and Urban Design, Incheon National University)
Kim, Mun-Gil (Division of Architecture and Urban Design, Incheon National University)
Publication Information
Journal of the Korea Concrete Institute / v.28, no.5, 2016 , pp. 611-620 More about this Journal
Abstract
In the construction of nuclear power plants, only 420 MPa reinforcing bars are allowed and, therefore, so many large-diameter bars are placed, which results in steel congestion. Consequently, re-bar works are difficult and the quality of RC structures may be deteriorated. To solve the steel congestion, 550 MPa bars are necessary. Among many items for verifying structural performance of reinforced concrete with 550 MPa bars, the 43 mm hooked bars are examined in this study. All specimens failed by side-face blowout and the side cover explosively spalled at maximum loads. The bar force was initially transferred to the concrete primarily by bond along a straight portion. At the one third of maximum load, the bond reached a peak capacity and began to decline, while the hook bearing component rose rapidly. At failure, most load was resisted by the hook bearing. For confined specimens with hoops, the average value of test-to-prediction ratios by KCI code is 1.45. The modification factor of confining reinforcement which was not allowed for larger than 35 mm bars can be applied to 43 mm hooked bars. For specimens with 70 MPa concrete, the average value of test-to-prediction ratios by KCI code is 1.0 which is less than the values of the other specimens. The effects of concrete compressive strength should be reduced. An equation to predict anchorage capacity of hooked bars was developed from regression analysis including the effects of compressive strength of concrete, embedment length, side cover thickness, and transverse reinforcement index.
Keywords
hooked bar; bond; bearing; transverse reinforcement; embedment length; anchorage strength;
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