||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.
|| ACI Committee 318, Building Code Requirements for Structural Concrete, ACI318-71 & Commentary, American Concrete Institute ,1971.|
 ACI Committee 318, Building Code Requirements for Structural Concrete, ACI318-95 & Commentary, American Concrete Institute, 1995.
 ACI Committee 318, Building Code Requirements for Structural Concrete, ACI318-05 & Commentary, American Concrete Institute, 2005.
 ACI Committee 318, Building Code Requirements for Structural Concrete, ACI318-14 & Commentary, American Concrete Institute, 2014.
 ACI Committee 374, Acceptance Critiria for Moment Frames Based on Structural Testing and Commentart (ACI 374.1-05), American Concrete Institute, 2005, pp. 1-9.
 ACI Committee 374, Guide for Testing Reinforced Concrete Structural Elements under Slowly Applied Simulated Seismic Loads(ACI374.2R-13), American Concrete Institute, 2013, pp. 1-18.
 ACI Committee 408, State of the Art Report: Bond under Cyclic Loads (ACI408.2R-92), American Concrete Institute, 1992.
 Orangun, C. O., Jirsa, J. O., and Breen, J. E., “The Strength of Anchored Bars: A Reevaluation of Test Data on Development Length and Splices,” Research Report No. 154-3F, Center for Highway Research, The University of Texas at Austin, Tex., Jan., 1975, 78 pp.
 João Luís Domingues Costa, “Reinforced Concrete under Large Seismic Action,” Tekniske Universitet, Danmarks, 2003.
 ACI Innovation Task Group 4, Report on Structural Design & Detailing for High Strength Concrete in Moderate to High Seismic Applications, American Concrete Institute (2007).
 NIST GCR 14-917-30, Use of High-Strength Reinforcement in Earthquake-Resistant Concrete Structures, National Institute of Standards and Technology, 2014.
 Ferguson, P. M., and Thompson J. N., 1962, “Development length of high strength reinforcing bars in bond” ACI JOURNAL, Proceedings V. 5, NO.7, July, pp. 887-922.
 NZS3101, Concrete Structual Standard, The design of Concrete Structures & Commentary on the Design of Concrete Structures, New Zenland Standard, 2006.
 洪立彥，｢New RC梁撓曲剪力行為研究｣，國立中央大學，碩士論文，民國一百零三年。
 國家地震工程研究中心，「高強度鋼筋混凝土結構設計手冊(初稿) 」，民國一百零四年。