Experimental and Numerical Study on Reinforced Concrete Columns Strengthened with Lightweight Alkali-Activated Slag Concrete and X-Type Encased Steel
Abstract
1. Introduction
2. Axial Compression Test of Composite-Strengthened Column
2.1. Design of Columns
2.2. Column Fabrication and Material Testing
2.3. Experimental Phenomena and Analysis
2.4. Comparison of Axial Compression Load–Strain Curves
2.4.1. Comparison of Axial Compressive Load–Strain Curves for Different Strengthening Layers
2.4.2. Comparison of Axial Compressive Load–Strain Curves for Different Forms of Encased Steel
2.4.3. Derivation of Axial Compressive Bearing Capacity Formula for Composite Strengthened Columns with Encased Steel
3. Numerical Simulation of X-Type Encased Steel Composite Reinforced Column
3.1. Model Building
3.1.1. Material Constitutive Model
3.1.2. Unit Type, Interaction, and Boundary Conditions
3.2. Simulation Results and Analysis of Axial Compression
3.2.1. Typical Damage Modes of Columns
3.2.2. Comparative Analysis of Axial Compressive Load Strain Curves
3.2.3. Error Analysis of Axial Compressive Bearing Capacity
3.3. Simulation Results and Analysis of Small Eccentric Compression
3.3.1. Validation of Small Eccentric Compression Model
3.3.2. Typical Damage Modes of Strengthened Columns
3.3.3. Comparison of Lateral Deflection Distribution Curves Along the Height of Column
3.3.4. Comparative Analysis of Ultimate Bearing Capacity
3.4. Simulation Results and Analysis of Hysteresis Performance
3.4.1. Validation of Horizontal Reciprocating Loading Model
3.4.2. Skeleton Curve
3.4.3. Energy Dissipation Coefficient and Cumulative Energy Dissipation
4. Conclusions
- (1)
- The LAASC lightweight strengthening material proposed in this study has a density of only 1850 kg/m3, representing a 25% weight reduction compared to conventional concrete. Under the same encased steel form, columns using the LAASC strengthening layer achieve an axial compressive bearing capacity of 2312.5 kN, which is 37% higher than that of columns with ordinary concrete strengthening layers. Notably, even if the LAASC strengthening layer shows cracking damage, there will be no significant fragments falling off, and it demonstrates superior ductility.
- (2)
- The improved simplified formula for the axial compressive bearing capacity of the proposed encased-steel composite-strengthened columns in this study achieves error control within 5% between the calculated and experimental values, demonstrating effective applicability to engineering practice. In addition, the X-type encased steel strengthening method and its formula are not only applicable to square section columns but also to rectangular section columns.
- (3)
- When performing axial compression simulation analysis of strengthened columns using ABAQUS finite element software, the difference between the simulated values and experimental values of columns A1 and A2 is the largest but still remains within 10%. Among them, column B1 shows the smallest error of only 0.5%. Furthermore, simulation results under small eccentric compression indicate that the new-type composite-strengthened columns can effectively control flexural deformation when resisting small eccentric loading, reducing lateral deflection by 30% to 35%, and their bearing capacity only decreases by 22% to 24% compared to axial compression.
- (4)
- Under horizontal reciprocating loading, column A3, featuring the LAASC strengthening layer, demonstrates a substantial increase in cumulative energy dissipation, with a 35.7% improvement compared to columns A1 and A2. This highlights that LAASC surpasses traditional concrete in energy dissipation during deformation. Notably, despite column B1 having a batten plate spacing double that of column A3, the diagonal bracing effect of its X-type batten plate is pronounced, making for a 13.1% increase in total energy dissipation relative to column A3.
- (5)
- Although the proposed X-type encased steel strengthening form has better lateral performance than the traditional encased steel strengthening form, its complex details make it difficult to apply in practical engineering. Meanwhile, higher precision is also required during the manufacturing process.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Column Number | Section Size/mm2 | Angle Steel Size/mm | Thickness of Batten Plate/mm | Forms of Steel Cladding | Concrete Strengthening Layer |
---|---|---|---|---|---|
A0 | 150 × 150 | \ | \ | \ | \ |
A1 | 250 × 250 | ∟30 ×30 × 3 | 3 | Horizontal batten plate | C40 |
A2 | 250 × 250 | ∟30 ×30 × 3 | 3 | Horizontal batten plate | BMSCC |
A3 | 250 × 250 | ∟30 ×30 × 3 | 3 | Horizontal batten plate | LAASC |
B1 | 250 × 250 | ∟30 ×30 × 3 | 3 | X-1 type batten plate | LAASC |
B2 | 250 × 250 | ∟30 ×30 × 3 | 3 | X-2 type batten plate | LAASC |
Component | fy | fu | Es |
---|---|---|---|
Longitudinal reinforcement | 376 | 551 | 196,000 |
Hoop reinforcement | 254 | 377 | 196,000 |
Encased steel | 248 | 373 | 196,000 |
MgO | Citric Acid | Magnesium Sulfate Heptahydrate | River Sand | Water |
---|---|---|---|---|
596.7 | 6.0 | 331.3 | 1492.0 | 360.0 |
Slag Powder | Silica Fume | Fly Ash | Hollow Glass Microspheres | Water Glass | NaOH | Quartz Sand | Water |
---|---|---|---|---|---|---|---|
746.7 | 106.7 | 213.4 | 80.0 | 198.7 | 49.3 | 533.3 | 330.7 |
Column Number | fcu1/MPa | fcu2/MPa | ρ/(kg/m3) |
---|---|---|---|
A0 | 31.5 | / | / |
A1 | 31.5 | 40.5 | 2500 |
A2 | 31.5 | 41.5 | 1960 |
A3 | 31.5 | 81.8 | 1850 |
B1 | 31.5 | 81.8 | 1850 |
B2 | 31.5 | 81.8 | 1850 |
Column Type | Nexp/kN | Nfem/kN | Nexp/Nfem | Ng/kN | Nexp/Ng |
---|---|---|---|---|---|
A0 column | 550.0 | 590.0 | 0.93 | 543.4 | 1.01 |
Only strengthened with horizontal batten plate encased steel | / | 762.0 | / | 741.3 | 1.03 |
Only strengthened with X-type batten plate encased steel | / | 786.0 | / | 792.9 | 0.99 |
A1 column | 1685.0 | 1845.7 | 0.92 | 1645.5 | 1.02 |
A2 column | 2000.0 | 1845.7 | 1.08 | 1804.4 | 1.09 |
A3 column | 2312.5 | 2370.5 | 0.98 | 2216.3 | 1.04 |
B1 column | 2325.0 | 2331.6 | 0.99 | 2235.9 | 1.04 |
B2 column | 2350.0 | 2382.9 | 0.99 | 2283.3 | 1.03 |
Category | Eccentricity Distance to Column Width Ratio | Ultimate Bearing Capacity/kN | Lateral Deflection During Complete Destruction/mm |
---|---|---|---|
Experimental | 1/5 | 576 | 12.3 |
FEM | 1/5 | 566 | 11.6 |
Column Number | Ultimate Bearing Capacity/kN | Increase Times |
---|---|---|
A0 | 330.3 | \ |
A1 | 1322.4 | 4.0 |
A2 | 1350.8 | 4.1 |
A3 | 1772.3 | 5.4 |
B1 | 1762.5 | 5.3 |
B2 | 1807.5 | 5.5 |
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Zhu, J.; Wen, Z.; Li, Y.; Hou, X.; Lu, Y. Experimental and Numerical Study on Reinforced Concrete Columns Strengthened with Lightweight Alkali-Activated Slag Concrete and X-Type Encased Steel. Buildings 2025, 15, 1692. https://doi.org/10.3390/buildings15101692
Zhu J, Wen Z, Li Y, Hou X, Lu Y. Experimental and Numerical Study on Reinforced Concrete Columns Strengthened with Lightweight Alkali-Activated Slag Concrete and X-Type Encased Steel. Buildings. 2025; 15(10):1692. https://doi.org/10.3390/buildings15101692
Chicago/Turabian StyleZhu, Jing, Zijie Wen, Yuankai Li, Xiaomeng Hou, and Yiqi Lu. 2025. "Experimental and Numerical Study on Reinforced Concrete Columns Strengthened with Lightweight Alkali-Activated Slag Concrete and X-Type Encased Steel" Buildings 15, no. 10: 1692. https://doi.org/10.3390/buildings15101692
APA StyleZhu, J., Wen, Z., Li, Y., Hou, X., & Lu, Y. (2025). Experimental and Numerical Study on Reinforced Concrete Columns Strengthened with Lightweight Alkali-Activated Slag Concrete and X-Type Encased Steel. Buildings, 15(10), 1692. https://doi.org/10.3390/buildings15101692