摘要(英) |
The purpose of this study is to discuss the rebar cut-off design of New RC beams by means of cyclic testing on the beams with high-strength SD690 reinforcing steel bars. The steel strength of current empirical equations related to rebar cut-off design in ACI318-14 is limited to 420 MPa. Meanwhile, the rebar cut-off design is not specified in seismic resistance chapter. Therefore, this study performed the testing on the cantilever beams subjected to cyclic loading to verify the validation of ACI rebar cut-off design applied to New RC beams and the seismic performance of the New RC beams with the rebar curtailment.
Four 350 mm wide x 450 mm deep and 2.4 m long cantilever beams are adopted in the study. The beam bars are arranged with 3- SD 690 #8 in the top and 3- SD 690 #10 in the bottom. One is a control specimen without beam bar cut-off, called as HR-Y0. The other three specimens are RC beams with one SD 690 #10 rebar being curtailed, which are HR-Y1, HR-Y1-M (subjected to monotonic loading only), and HR-Y2, respectively. The development length of SD 690 #10 is calculated using recent ACI 318 empirical equation. The results of beam bar termination location for these three beams are: HR-Y1 and HR-Y1-M have l_d curtailed length (measured from the beam fixed end), and HR-Y2 has a longer curtailed length, l_d+d (the concept adopted from NZS 3101-06).
The results indicated that all the specimens (HR-Y0, HR-Y1, and HR-Y2) satisfied the minimum seismic performance required by ACI 374.2r-13. HR-Y1 appeared an obvious beam bar slip until the DR=3.5%, then the loading strength was suddenly reduced to 2/3 nominal flexural strength. HR-Y1-M appeared obvious bar slip until the DR=7.5%. The difference between HR-Y1 and HR-Y1-M is mainly due to the cyclic and monotonic loading effect on the beam bar debonding. The seismic performance of HR-Y2 (the beam bar cut-off length is l_d+d) has very similar behavior to the control specimen HR-Y0 (without beam bar curtailment). These two specimens are tested until DR=7.0% when the flexural failure is occurred at the beam fixed end, i.e. the plastic hinge zone. |
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