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UHPC jacket retrofit of existing columns: research highlights and how to evaluate

Ultra-high-performance concrete (UHPC) jacketing is one way to strengthen existing reinforced concrete columns. This post summarizes what recent research focuses on and how to evaluate the effect at the design stage.

ResearchStructFlow R&D Team · SUHUL LLC・Published ・1 min read

1What is UHPC

Ultra-high-performance concrete (UHPC) has very high compressive strength and, thanks to its fibers, good tensile and deformation capacity; its applications and design methods in structural engineering have continued to develop in recent years [12].

2Strengthening existing columns

Wrapping an existing column in a layer of UHPC increases confinement and shear strength and improves ductility. Full-scale tests have examined seismic performance under high axial load [13], and have also compared cast-in-place and precast UHPC shells for strengthening shear-deficient columns [14].

3How to evaluate at the design stage

Moment–curvature curves before and after strengthening show directly how the ultimate curvature and curvature ductility change, and serve as a basis for choosing the jacket thickness and scheme. The StructFlow UHPC jacket model corresponds to this research and can be plotted alongside the unstrengthened section.

Moment–curvature curves for four concrete models0.000.050.100.150.20050100150200250Curvature φ (1/m)M (tf·m)Unconfined（μφ ≈ 3.25）Mander confined, K = 1.3（μφ ≈ 19.21）HUNG (HPFRCC)（μφ ≈ 12.01）UHPC jacket（μφ ≈ 8.79）
Fig. 1Moment–curvature comparison of the same section under the unconfined, Mander confined, HPFRCC, and UHPC jacket models (computed by the calculation core).

References

  1. Mander, J. B., Priestley, M. J. N., & Park, R. (1988). Theoretical stress-strain model for confined concrete. Journal of Structural Engineering, 114(8), 1804–1826. doi:10.1061/(ASCE)0733-9445(1988)114:8(1804)
  2. Popovics, S. (1973). A numerical approach to the complete stress-strain curve of concrete. Cement and Concrete Research, 3(5), 583–599. doi:10.1016/0008-8846(73)90096-3
  3. Whitney, C. S. (1937). Design of reinforced concrete members under flexure or combined flexure and direct compression. ACI Journal Proceedings, 33(3), 483–498. doi:10.14359/8429
  4. ACI Committee 318. (2019). Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19). American Concrete Institute. doi:10.14359/51716937
  5. 內政部（Ministry of the Interior, Taiwan）. (2023). 建築物混凝土結構設計規範（Design Specifications for Concrete Structures of Buildings），112 年 8 月 10 日修正發布，113 年 1 月 1 日生效. nlma.gov.tw
  6. 內政部（Ministry of the Interior, Taiwan）. (2023). 建築物基礎構造設計規範（Design Specifications for Foundations of Buildings），112 年 6 月 20 日修正發布，113 年 1 月 1 日生效. nlma.gov.tw
  7. Mononobe, N., & Matsuo, H. (1929). On the determination of earth pressure during earthquakes. Proceedings of the World Engineering Congress, Vol. 9, Tokyo, 177–185.
  8. Sutherland, I. E., & Hodgman, G. W. (1974). Reentrant polygon clipping. Communications of the ACM, 17(1), 32–42. doi:10.1145/360767.360802
  9. National Center for Research on Earthquake Engineering (NCREE). 台灣新型高強度鋼筋混凝土（Taiwan New RC）專區. ncree.niar.org.tw/service/newrc
  10. Chiu, C.-K., Hung, C.-C., Lin, K.-C., Liu, K.-Y., Lee, H.-J., Cheng, M.-Y., et al. (2019). Design Guideline for Building of High-Strength Reinforced Concrete Structures (Draft), NCREE-19-001. National Center for Research on Earthquake Engineering.
  11. Hung, C.-C., & Li, S.-H. (2013). Three-dimensional model for analysis of high performance fiber reinforced cement-based composites. Composites Part B: Engineering, 45(1), 1441–1447. doi:10.1016/j.compositesb.2012.08.004
  12. Hung, C.-C., El-Tawil, S., & Chao, S.-H. (2021). A review of developments and challenges for UHPC in structural engineering: Behavior, analysis, and design. Journal of Structural Engineering, 147(9), 03121001. doi:10.1061/(ASCE)ST.1943-541X.0003073
  13. Shao, Y., Kuo, C.-W., & Hung, C.-C. (2021). Seismic performance of full-scale UHPC-jacket-strengthened RC columns under high axial loads. Engineering Structures, 243, 112657. doi:10.1016/j.engstruct.2021.112657
  14. Hung, C.-C., Kuo, C.-W., & Shao, Y. (2021). Cast-in-place and prefabricated UHPC jackets for retrofitting shear-deficient RC columns with different axial load levels. Journal of Building Engineering, 44, 103305. doi:10.1016/j.jobe.2021.103305
  15. Ou, Y.-C., Alrasyid, H., Haber, Z. B., & Lee, H.-J. (2015). Cyclic behavior of precast high-strength reinforced concrete columns. ACI Structural Journal, 112(6), 839–850. doi:10.14359/51687911
  16. Shen, W.-C., & Hwang, S.-J. (2023). Confinement reinforcement of high-strength reinforced concrete tied columns under high axial load. ACI Structural Journal, 120(3), 145–155. doi:10.14359/51738505

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