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Title |
Anchorage Performance of SD600 Reinforcing Bars in Compression in Exterior Beam-Column Joints Subjected to Reversed Cyclic Loading
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Authors |
천성철(Sung-Chul Chun) ; 성민규(Min-Kyu Seong) |
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DOI |
https://doi.org/10.4334/JKCI.2021.33.6.619 |
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Keywords |
압축정착; 반복하중; 보-기둥 접합부 compression anchorage; cyclic loading; beam-column joint |
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Abstract |
To verify a new design equation of a compression development length proposed by previous studies, two exterior beam-column connections, C40-BCJ and C70-BCJ, were tested with a variable of concrete compressive strength of 40 and 70 MPa. Both top and bottom bars of the beams had a standard hook in tension, conforming to KDS 14 20 52 except for the development length. The development length of bars in compression is longer than that of hooked bars in tension in KDS 14 20 52; however, the proposed equation was used in this study instead of KDS 14 20 52 provisions of development length of bars in compression. The two specimens showed joint shear failures after beam flexure strengths were fully developed with yielding of beam bars. High joint aspect ratios of 1.14 and 1.41 for C40-BCJ and C70-BCJ, respectively, may cause joint shear failure. Especially, C70-BCJ, having a higher joint aspect ratio, showed more significant damage of the joint. However, two specimens satisfy the criteria of moment frames required in ACI 374 and are thought to have sufficient resistance against reversed cyclic loading. At 3.0 % drift ratio, the beam bars yielded and a residual deformation was measured in the tensile side after the applied load was removed. Under reversed loading, crack gaps in the tensile side at the previous loading did not close and only the beam bars resisted the applied compression. Therefore, compressive stresses of the bars may be higher than calculated stresses according to the method used determine the nominal flexural strength. Bars with a compression development length according to the equation proposed by previous studies have sufficient anchorage capacities.
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