StructFlow
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Technical overview

Cloud computation for high-strength reinforced concrete section analysis

This overview describes the scope of analysis covered by the StructFlow calculation core, the research and codes it is based on, and its relationship to the original New RC research program.

StructFlow R&D Team · SUHUL LLC・Updated

Abstract

StructFlow is a cloud section analysis platform based on Taiwan New RC high-strength reinforced concrete research, covering the biaxial strength of rectangular and circular columns and structural walls, moment–curvature analysis, and cantilever retaining wall design. The calculation core has been verified by professors and is compared point by point with the actual output of the original research program; while keeping results consistent, the cloud version improves the precision and speed of the compression zone calculation and provides more stable load checking through a continuous demand/capacity ratio. This paper is a technical overview; the complete design basis and check procedure are provided in the calculation report after sign-up.

Keywordshigh-strength reinforced concrete・New RC・biaxial interaction surface・demand/capacity ratio・fiber section analysis・retaining wall

1Research background

Since the 2010s Taiwan has promoted research on New RC, a new type of high-strength reinforced concrete that pairs high-strength concrete with high-strength reinforcement to reduce member sizes and reinforcement quantities in tall buildings [9, 10]. High-strength materials require recalibration of conventional design parameters and of confinement behavior [15, 16], and the related research programs are mostly distributed as desktop executables, which are difficult to integrate, update, and trace in engineering practice.

The goal of StructFlow is to turn such research programs into tools for daily use without changing their mechanical results.

2Section strength

Concrete in compression is modeled with the equivalent rectangular stress block [3, 4], with parameters modified for high-strength concrete according to New RC research [10], applicable up to the 100 MPa class of fc′. The compression zone is computed directly and exactly, with none of the discretization error of conventional fiber slicing; the strength reduction factor and axial load limit depend on the confinement type (tied or spiral).

3Biaxial interaction surface

P–M meridians are computed at each neutral-axis angle and assembled into a three-dimensional interaction surface; the sampling scheme is the same as in the original, so results can be compared point by point with the original output.

P–M interaction diagrams of a structural wall (strong and weak axes)06,00012,00018,00024,00030,000-2,0001,6675,3339,00012,66716,33320,000M (tf·m)P (tf)θ = 0° (about x-axis)θ = 90° (about y-axis)
Fig. 1Design strength curves of the default structural wall case at θ = 0° and 90°, illustrating the difference in capacity between the strong and weak axes (computed by the calculation core).

4Continuous demand/capacity ratio

Check results determined from discrete sample points jump with the sampling angle. StructFlow obtains a continuous, stable demand/capacity ratio from the design strength surface, and can check tens of thousands of ETABS-exported load cases at once; the original criterion is retained alongside for comparison with earlier results.

5Moment–curvature analysis

Fiber section analysis accounts for both the cover and the confined core. Core concrete uses the Mander confined concrete model [1, 2]; the HUNG model describes high-performance fiber-reinforced cementitious composites (HPFRCC) [11, 12]; the UHPC jacket model is used to evaluate UHPC jacket retrofit [13, 14].

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. 2Moment–curvature curves of the same section (60 × 60 cm, fc′ 700 kgf/cm², P = 0.1fc′Ag) under four concrete models, computed by the calculation core.

6Cantilever retaining walls

Per [5, 6]: stability is checked with safety factors and members are designed for strength; seismic earth pressure follows Mononobe–Okabe theory [7], and reinforcement is selected automatically.

Cantilever retaining wall section and stem moment envelopeStem moment (tf·m/m)Static MuSeismic MuDesign strength φMn
Fig. 3Stem moment envelope of the default cantilever retaining wall (computed by the calculation core).

7Cloud architecture and performance

The calculation core runs only in the cloud; the browser only sends inputs and receives results. This protects the research results and ensures that all users run the same version of the calculation core, whose version number is printed on the calculation report for traceability.

Table 1Calculation performance (rectangular column 80 × 80 cm with 16 #10 bars)
OperationScaleTime
Interaction surface2,622 pointsabout 4 ms
Interaction surface (high resolution)12,558 pointsabout 8 ms
Load combination check2,000 casesabout 80 ms
Moment–curvatureone curveabout 60 ms

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