Journal of the Architectural Institute of Korea Structure & Construction (대한건축학회논문집:구조계)

Architectural Institute of Korea (대한건축학회)
권호 표지
DOI QR코드

DOI QR Code

Flexural Strengthening of Damaged Reinforced Concrete (RC) Beams using Externally Post-tensioning Steel Rods

손상입은 철근콘크리트 보의 외적 포스트텐셔닝에 의한 휨 보강

  • 이수헌 (경북대학교 융복합시스템공학부) ;
  • 이희두 (경북대학교 건설환경에너지공학부) ;
  • 이창수 (스마트 E&C) ;
  • 신경재 (경북대학교 건설환경에너지공학부)
  • Received : 2016.08.04
  • Accepted : 2017.06.12
  • Published : 2017.07.28
⟨ Previous Next ⟩

Abstract

An experimental work was undertaken to observe and assess the behavior of damaged reinforced concrete (RC) beams with external post-tensioning steel rods. Six simply supported beams - two control beams and four comparable beams post-tensioned using externally steel rods - were tested in three-point bending. The main parameters are the diameter of external post-tensioning rods (${\phi}22mm$ and ${\phi}28mm$) and the ratio of tension steel reinforcement (${\rho}=0.0106$ and 0.0166). For the post-tensioned beams, V-shaped profiles were used with a deviator located at the bottom of mid-span, and the post-tensioning force was applied to beams in order to overcome the low load-carrying capacity and existing deflection. The post-tensioning force acting on the steel rods was applied by tightening nuts of anchorage and its value was monitored by attached strain gauges. The initial strain of about $2000{\mu}{\varepsilon}$ was chosen for post-tensioning force because it is about the maximum strain that two adult men can apply without struggle. Test results indicate that the externally post-tensioning increased the load-carrying capacity by about 40~101% and the flexural stiffness by about 27~43% compared to control beams. On the other hand, the larger steel reinforcements and external rods of the section disturbed the yielding of external rod at ultimate strength.

Keywords

Acknowledgement

Supported by : 한국연구재단

References

  1. American Concrete Institute (ACI) Committee 318 (2011). Building Code Requirements for Structural Concrete (ACI 318-11) and Commentary, Farmington Hills, MI, USA.
  2. Federal Emergency Management Agency (FEMA). (1997). Commentary on the Guideline for the Seismic Rehabilitation of Buildings, FEMA-274, Washington, DC, USA.
  3. Han, S.H., Hong, K.N., Shin, B.G., Lim, J.M., & Kwak, S.H. (2011). Characteristics of shear behavior of reinforced concrete beams strengthened with near surface mounted CFRP strips, Journal of the Korea Institute for Structural Maintenance and Inspection, 15(5), 178-189. https://doi.org/10.11112/jksmi.2011.15.5.178
  4. Harajli, M.H. (1993). Strengthening of concrete beams by external prestressing, PCI Journal, 38(6), 76-88.
  5. Lee, S.-H., Lee, H.-D., Shin, K.-J., & Kang, T.H.-K. (2014a). Shear strengthening of continuous concrete beams using externally prestressed steel bars, PCI Journal, 59(4), 77-92. https://doi.org/10.15554/pcij.09012014.77.92
  6. Lee, S.-H., Shin, K.-J., & Kang, T.H.-K. (2014b). Non-iterative moment capacity equation for reinforced concrete beams with external post-tensioning, ACI Structural Journal, 111(5), 1111-1122.
  7. Lee, S.-H., Shin, K.-J., & Kang, T.H.-K. (2015). Flexural strengthening of continuous concrete beams using external prestressed steel bars, PCI Journal, 60(1), 68-86.
  8. Ministry of Land, Infrastructure and Transport (MOLTI) & Korea Agency for Infrastructure Technology Advancement (KAIA). (2006). Reinforcing Method of Architectural Structures Using High-strength Bars and Tensile-force Measurement Device.
  9. Naaman, A.E., & Breen, J.E. (1990). External Prestressing in Bridge, ACI Special Publication SP-120, American Concrete Institute (ACI), Detroit, MI, USA.
  10. Park, R., & Paulay, T. (1975). Reinforced Concrete Structures, John Wiley & Sons, New York, USA.
  11. Priestley, M.J.N., Seible, F., & Calvi, G.M. (1996). Seismic Design and Retrofit of Bridges, John Wiley & Sons, New York, USA.
  12. Rabbat, B.G., & Sowlat, K. (1987). Testing of segmental concrete girders with external tendons, PCI Journal, 32(2), 86-107.
  13. Shin, K.-J., Kim, Y.-J., & Moon, J.-H. (2007). An experimental study on flexural behavior of RC beams strengthened with hi-strength bars(3), Journal of the Korea Concrete Institute, 19(3), 351-358. https://doi.org/10.4334/JKCI.2007.19.3.351
  14. Shin, K.-J., Kim, Y.-J., & Moon, J.-H. (2008). A study on flexural behavior of RC beams strengthening with high-strength bars according to the reinforcing ratio, Journal of Architectural Institute of Korea (Structure & Construction), 24(5), 51-58.
  15. Shin, K.-J., Kwak, M.-K., Heo, B.-W., Na, J.-M., & Oh, Y.-S. (2006a). An experimental study on the flexural behavior of RC beams strengthened with high-strength bars(1), Journal of the Korea Concrete Institute, 18(4), 527-534. https://doi.org/10.4334/JKCI.2006.18.4.527
  16. Shin, K.-J., Kwak, M.-K., Bae, K.-W., Oh, Y.-S., & Moon, J.-H. (2006b). An experimental study on flexural behavior of RC beams strengthened with hi-strength bars(2), Journal of the Korea Concrete Institute, 18(4), 603-610. https://doi.org/10.4334/JKCI.2006.18.5.603
  17. Shin, H.-M., & Lee, J.-H. (2015). Reinforced Concrete, 11th Edition, Dong Myeong Publisher.
  18. Virlogeux, M.P. (1982). External prestressing, IABSE Proceedings, International Association for Bridge and Structural Engineering, 101-108, Zurich, Switzerland.