Abstract
Reinforced concrete (RC) beam–column joints are vulnerable to brittle failure under seismic actions due to their limited deformation capacity, posing a threat to the overall safety of RC frames. To address this issue, this study proposes and evaluates a novel strengthening strategy for RC joints using an engineered cementitious composite (ECC) shell, forming a beam–column joint with an ECC shell (BCJES). The mechanical behavior of the BCJES under cyclic loading was investigated through a refined finite element (FE) model. The FE model, validated against test results, enabled a systematic parametric study to quantify the effects of ECC shell height and thickness, longitudinal reinforcement ratio (at the beam region), and axial compression ratio on seismic performance. Results demonstrate that the proposed ECC shell markedly enhances the seismic capacity of RC joints. Increasing the longitudinal reinforcement ratio from 0.05% to 0.2% improved peak load from 33.87 to 85.58 kN (152%), while increasing shell thickness from 30 to 90 mm enhanced peak load by 11.9%. However, a saturation effect was observed, as further thickening the shell to 150 mm resulted in only a 2.46% gain. Based on the parametric results, this study, for the first time, establishes a quantitative predictive model for the ultimate bearing capacity of BCJES using multiple linear regression (R²= 0.943). Furthermore, a new theoretical shear–capacity model incorporating both main and lateral diagonal bracing mechanisms is developed. Theoretical predictions agree well with FE simulations and experimental results, with maximum deviations of only 7.5% and 7.9%, respectively, confirming the reliability of the proposed approach. These findings highlight the potential of the ECC shell as an effective and practical seismic-strengthening solution for RC joints, offering new insights for performance-based design and retrofit strategies.
Data availability
All data generated or analysed during this study are included in this published article.
Abbreviations
- RC:
-
Reinforced Concrete
- ECC:
-
Engineered Cementitious Composite
- BCJES:
-
Beam–Column Joint with an ECC Shell
- FE:
-
Finite Element
- R2:
-
Coefficient of Determination
- CFRP:
-
Carbon Fiber-Reinforced Polymer
- UHPC:
-
Ultra-High-Performance Concrete
- SRC:
-
Steel Reinforced Concrete
- CDP:
-
Concrete Damaged Plasticity
- VIF:
-
Variance Inflation Factor
- DW:
-
Durbin-Watson
- COV:
-
Coefficient of Variation
- fcu :
-
Cubic compressive strength
- ft :
-
Tensile strength
- fb :
-
Flexural strength
- Ec :
-
Elastic modulus
- ν:
-
Poisson’s ratio
- β:
-
ECC strength reduction coefficient
- fc,c :
-
Compressive strength of ECC in column
- fc,b :
-
Compressive strength of ECC in beam
- hc :
-
Height of the column section
- Ag :
-
Cross-sectional area of the column
- ws :
-
Effective height of the web section
- ac :
-
Height of the compression zone at the end of the column
- θh :
-
Angle between the web and the horizontal direction
- n1,n2 :
-
Quantities of longitudinal rebar at the top and bottom of the beam
- bb :
-
Width of the beam section
- F:
-
Ultimate bearing capacity of BCJES
- A:
-
Height of the ECC shell
- B:
-
Thickness of the ECC shell
- C:
-
Longitudinal reinforcement ratio
- D:
-
Axial compression ratio
- N:
-
Axial force
- MECC1,MECC2 :
-
Bending moments of the left and right sections of the main diagonal braces of ECC
- ML1,ML2 :
-
Bending moments of the left and right sections of the transverse diagonal brace
- Fy :
-
Yield load
- Fp :
-
Peak load
- Fu :
-
Ultimate load
- Δy :
-
Yield displacement
- Δu :
-
Ultimate displacement
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Funding
This study is supported by two funds: The Fundamental Research Funds for the Central Universities (2572024BR07) and Science and Technology Project of Department of Transportation of Heilongjiang Province (HJK2023B001).
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Ziwang Xiao and Lifeng Wang wrote the main manuscript text， and Rikang Huang prepared the Figs. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19. All authors reviewed the manuscript.
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Xiao, Z., Wang, L. & Huang, R. Seismic performance of reinforced concrete beam column joints strengthened with ECC shells. Sci Rep (2026). https://doi.org/10.1038/s41598-026-39753-4
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DOI: https://doi.org/10.1038/s41598-026-39753-4
