Zhuojin Pipe Fitting Co., LtdFinite Element Analysis of Axial Compression Capacity of Square Steel Tube Coal Gangue Concrete Short Columns
Literature Overview
This paper by Zhang Yuzhuo and colleagues from Shenyang Jianzhu University and Southeast University, published in the Journal of Shenyang Jianzhu University (Natural Science) in 2024 (Vol. 40, No. 2, pp. 284-292), investigates the axial compression behavior of square steel tube concrete columns filled with coal gangue aggregate concrete. The study employs ABAQUS finite element analysis to examine the influence of design parameters and coal gangue aggregate replacement rates on axial compression capacity, and proposes a modified capacity calculation formula incorporating a coal gangue replacement rate influence coefficient.
Core Technical Approach
The research addresses an important sustainability challenge in construction: the utilization of coal gangue, a byproduct of coal mining, as a replacement for natural aggregates in concrete. By incorporating coal gangue coarse aggregates into steel tube concrete columns, the study explores the structural feasibility of using industrial waste materials while maintaining adequate structural performance.
The methodology follows a systematic approach:
- Finite element model development — ABAQUS models of square steel tube coal gangue concrete short columns were developed.
- Model validation — The FE models were validated against experimental test results to confirm accuracy.
- Stress and load distribution analysis — Stress distributions and load sharing between the steel tube and concrete core were analyzed.
- Parametric study — A controlled variable method was used to analyze the effects of design parameters at five different coal gangue replacement rates.
- Capacity formula development — A modified axial compression capacity formula was proposed based on the GB 50936-2014 code framework.
Key Technical Parameters and Results
| Parameter | Range/Value |
|---|---|
| Column type | Square steel tube concrete |
| Coal gangue replacement rates | 5 levels |
| Steel ratio range | 7.4% to 20.3% |
| Maximum capacity reduction | Less than 14% |
| Average capacity increase from steel ratio | 68.85% |
| Calculation error with modified formula | Less than 5% |
| Reference code | GB 50936-2014 |
The parametric study revealed several important findings:
- Coal gangue replacement effect — Axial compression capacity decreases with increasing coal gangue replacement rate, but the maximum reduction does not exceed 14%. This indicates that coal gangue aggregate concrete can be used in steel tube concrete columns with only modest capacity reduction.
- Steel ratio dominance — The steel ratio (ratio of steel tube cross-sectional area to total cross-sectional area) has the most significant influence on axial compression capacity. Increasing the steel ratio from 7.4% to 20.3% results in an average capacity increase of 68.85% across all replacement rates.
- Formula accuracy — The proposed modified formula, incorporating a coal gangue replacement rate influence coefficient, achieves calculation errors less than 5% when compared with the FE analysis results.
Finite Element Model Considerations
The accuracy of finite element analysis for steel tube concrete columns depends on several critical modeling aspects:
- Material constitutive models — The concrete and steel material models must accurately represent the nonlinear behavior under compression, including the confinement effect provided by the steel tube.
- Interface modeling — The bond-slip behavior between the steel tube and concrete must be properly modeled to capture the load transfer mechanism.
- Mesh refinement — Adequate mesh density is required, particularly in regions of high stress gradient such as the column ends and the steel-concrete interface.
- Boundary conditions — Realistic boundary conditions must be applied to simulate the test setup, including end plate constraints and displacement control.
The validation of the FE model against experimental results is essential for establishing confidence in the parametric study results. The study reports satisfactory agreement between FE predictions and experimental measurements, confirming the model's reliability for parametric analysis.
Engineering Practice and Sustainability Implications
The findings of this study have significant implications for sustainable construction practice. Coal gangue is a major industrial waste material in coal-producing regions, and its utilization in concrete reduces landfill burden and conserves natural aggregate resources. The study demonstrates that steel tube concrete columns with coal gangue aggregate concrete can achieve adequate structural performance with only modest capacity reduction.
From a design perspective, the proposed modified capacity formula provides a practical tool for engineers to design steel tube concrete columns with coal gangue aggregate concrete. The formula's integration with the existing GB 50936-2014 code framework ensures compatibility with current design practices and facilitates adoption.
Key engineering considerations for implementing coal gangue aggregate concrete in steel tube columns:
- Coal gangue quality — The physical and chemical properties of coal gangue must be controlled to ensure consistent concrete performance.
- Mix design optimization — The concrete mix design must be optimized for each coal gangue replacement rate to achieve the target strength and workability.
- Durability assessment — The long-term durability of coal gangue aggregate concrete, particularly resistance to carbonation and chloride ingress, must be evaluated.
- Construction quality control — Proper concrete placement and compaction within the steel tube are critical for achieving the expected structural performance.
Study Insights and Reflections
This study makes a valuable contribution to the field of sustainable steel tube concrete structures. The finding that coal gangue replacement rates up to the tested levels cause only modest capacity reduction (less than 14%) is encouraging for the practical adoption of industrial waste materials in structural applications.
The dominance of steel ratio as the primary capacity parameter is consistent with the fundamental behavior of steel tube concrete columns. The steel tube provides both direct compression resistance and confinement to the concrete core, and increasing the steel ratio enhances both mechanisms. This finding suggests that for applications requiring high capacity, increasing the steel ratio is more effective than optimizing the concrete properties.
The proposed modified capacity formula with a coal gangue replacement rate influence coefficient is a pragmatic approach that maintains the simplicity of the existing code formula while accounting for the specific effects of coal gangue aggregate. The less-than-5% calculation error indicates good predictive accuracy, which is sufficient for practical design purposes.
One limitation of the study is the focus on short columns under axial compression. In practice, steel tube concrete columns are often subjected to combined axial compression and bending, and the behavior under such loading conditions may differ from the pure compression case. Future research should extend the investigation to eccentric loading and flexural behavior to provide a more comprehensive design framework.
Additionally, the long-term performance of coal gangue aggregate concrete under sustained loading and environmental exposure deserves further investigation. Creep, shrinkage, and durability behavior under marine or aggressive environments are critical for the long-term serviceability of steel tube concrete structures.
The study exemplifies the integration of environmental sustainability with structural engineering, demonstrating that industrial waste materials can be effectively utilized in structural applications with appropriate design modifications. This approach aligns with the growing emphasis on sustainable construction practices and circular economy principles in the engineering community.