Side-Face Blowout Failure of Headed Bars in High-Strength Concrete

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Title: Side-Face Blowout Failure of Headed Bars in High-Strength Concrete

Author(s): Hye-Jung Sim and Sung-Chul Chun

Publication: Structural Journal

Volume: 119

Issue: 5

Appears on pages(s): 3-16

Keywords:

DOI: 10.14359/51734834

Date: 9/1/2022

Abstract:
The design provisions of ACI 318-19 for the development length of headed bars do not distinguish different failure modes and limit concrete compressive strength to 70 MPa (10 ksi). Failure types regarding headed bars terminating in an exterior beam-column joint can be classified into side-face blowout, concrete breakout, pullout, or joint shear failure. The anchorage capacity of headed bars depends on the failure mode. In this study, a side-face blowout strength of headed bars in high-strength concrete over 70 MPa(10 ksi) was investigated. Thirty-two simulated exterior beamcolumn joints were tested using 80 and 120 MPa (11.6 and 17.4 ksi) concrete of design compressive strength. Side-face blowout failure was anticipated by preventing the other failure modes. Two descriptive equations were developed based on the test results including previous studies. One is expressed as the summation of two terms representing the contributions of head bearing and bond, while the other is xpressed as a single term of total anchorage strength, similar to the design equation of ACI 318-19. Using the two proposed equations, the design yield strength of headed bars against side-face blowout failure can be safely developed in highstrength concrete up to 120 MPa (17.4 ksi).

Related References:

1. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.

2. Shao, Y.; Darwin, D.; O’Reilly, M.; Lequesne, R. D.; Ghimire, K. P.; and Hano, M., “Anchorage of Conventional and High-Strength Headed Reinforcing Bars,” SM Report No. 117, The University of Kansas Center for Research, Inc., Lawrence, KS, 2016, 334 pp.

3. Chun, S.-C., “Components of Side-Face Blowout Strengths of Headed Bars in Exterior Beam-Column Joints,” ACI Structural Journal, V. 116, No. 2, Mar. 2019, pp. 159-169. doi: 10.14359/51711141

4. Chun, S.-C.; Choi, C.-S.; and Jung, H.-S., “Side-Face Blowout Failure of Large-Diameter High-Strength Headed Bars in Beam-Column Joints,” ACI Structural Journal, V. 114, No. 1, Jan.-Feb. 2017, pp. 161-172. doi: 10.14359/51689161

5. Thompson, M. K.; Jirsa, J. O.; and Breen, J. E., “Behavior and Capacity of Headed Reinforcement,” ACI Structural Journal, V. 103, No. 4, July-Aug. 2006, pp. 522-530.

6. ASTM A970/A970M-18, “Standard Specification for Headed Steel Bars for Concrete Reinforcement,” West Conshohocken, PA, 2018, 10 pp.

7. Choi, C. M., “Strength of Headed Bars Anchored in CCT Nodes,” master’s thesis, Mokpo National University, Mokpo, Korea, Feb. 2014, 70 pp.

8. Joint ACI-ASCE Committee 352, “Recommendations for Design of Beam-Column Connections in Monolithic Reinforced Concrete Structures (ACI 352-02),” American Concrete Institute, Farmington Hills, MI, 2002, 38 pp.

9. ISO 6892-1, “Metallic Materials — Tensile Testing — Part 1: Method of Test at Room Temperature,” International Organization for Standardization, Geneva, Switzerland, 2019.

10. Hwang, H.-J.; Park, H.-G.; and Yi, W.-J., “Nonuniform Bond Stress Contribution Model for Evaluation of Bar Development Length,” ACI Structural Journal, V. 114, No. 4, July-Aug. 2017, pp. 839-849. doi: 10.14359/51689446

11. Hwang, H.-J.; Park, H.-G.; and Yi, W.-J., “Development Length of Standard Hooked Bar Based on Non-Uniform Bond Stress Contribution,” ACI Structural Journal, V. 114, No. 6, Nov.-Dec. 2017, pp. 1637-1648. doi: 10.14359/51700918

12. Furche, J., and Elingehausen, R., “Lateral Blow-Out Failure of Headed Studs Near a Free Edge,” Anchors in Concrete—Design and Behavior, SP-130, American Concrete Institute, Farmington Hills, MI, 1991, pp. 235-252.

13. Bashandy, T. R., “Application of Headed Bars in Concrete Members,” PhD dissertation, The University of Texas at Austin, Austin, TX, 1996, 302 pp.


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