Lateral Local Compression Performance of Square Hollow Sandwich Concrete-Filled Steel Tubes

Literature Overview

This paper by Yang Youfu and Meng Chunyuan from the State Key Laboratory of Coastal and Offshore Engineering at Dalian University of Technology, published in the Journal of Architecture and Civil Engineering in 2015 (Volume 32, Issue 4, pages 92-98), investigates the lateral local compression performance of square hollow sandwich concrete-filled steel tubes (SHS-CFST). The study combines experimental testing with nonlinear finite element analysis using ABAQUS software, and was supported by the Liaoning Provincial Natural Science Foundation (Project No. 2013020125). The research is classified under TU398 and focuses on a novel composite structural system that combines the advantages of steel tubes, concrete, and hollow sandwich construction.

Core Technical Content

The square hollow sandwich CFST represents an innovative structural concept where a concrete-filled square steel tube is further reinforced with an external hollow sandwich layer. This configuration aims to improve the lateral local compression resistance of the member, which is a critical design consideration for members subjected to concentrated loads from girders, beams, or equipment supports. The authors conducted experimental tests on six specimens and performed corresponding finite element simulations to analyse the structural behaviour under lateral local compression loading.

Experimental Parameters and Test Setup

The study systematically varied two key geometric parameters: the ratio of the compression bar width to the specimen outer edge length (which represents the intensity of the local load) and the hollow rate of the sandwich layer (which affects the weight and stiffness of the external reinforcement). The results demonstrate that the square hollow sandwich CFST exhibits good mechanical performance under lateral local compression, and that the finite element simulation results are in good overall agreement with the experimental results.

Interpretation of Technical Points

The lateral local compression performance of steel tube members is governed by the web crippling mechanism, where the steel wall buckles inward under the concentrated load. The addition of the concrete core provides some resistance to this buckling through the confinement effect, but the hollow sandwich layer offers additional benefits by increasing the effective wall thickness and providing a more uniform load distribution. The hollow rate parameter is particularly interesting because it allows for a trade-off between weight reduction and structural performance; a higher hollow rate reduces the weight but may decrease the load-bearing capacity, while a lower hollow rate provides more structural capacity at the cost of increased weight.

The finite element modelling approach using ABAQUS is particularly well-suited for this type of analysis because it can accurately capture the non-linear behaviour of both the steel and concrete materials, as well as the complex contact and interaction between the different structural components. The use of non-linear analysis is essential because the failure mechanism involves significant plastic deformation and potential buckling, which cannot be captured by linear elastic models.

Process and Standards Analysis

The manufacturing of square hollow sandwich CFST members involves several critical process steps, including the fabrication of the inner steel tube, the casting of the concrete core, the fabrication of the outer hollow sandwich layer, and the assembly of the composite member. The quality of each step directly affects the structural performance of the final member. Relevant standards include:

The experimental testing procedures should comply with GB/T 228.1 for tensile testing, GB/T 7314 for hardness testing, and GB/T 1499 for welding inspection of steel tubes.

Integration with Engineering Practice

The square hollow sandwich CFST concept has potential applications in bridge construction, building structures, and industrial facilities where lateral local compression is a critical design consideration. The key advantages of this system include improved load-bearing capacity, reduced weight compared to solid sandwich construction, and enhanced ductility due to the composite action of the steel and concrete components. For engineering practice, the following considerations are important:

1. The connection details between the hollow sandwich layer and the inner CFST member must be carefully designed to ensure effective load transfer and prevent delamination under cyclic loading.
2. The hollow rate should be optimised based on the specific structural requirements; a hollow rate of 30-50% typically provides a good balance between weight reduction and structural capacity.
3. The finite element model should be validated against experimental data for each specific geometry and loading condition before being used for design purposes.

Key Questions and Reflections

The study raises important questions about the long-term behaviour of the hollow sandwich layer under environmental exposure, particularly regarding corrosion of the steel components and durability of the concrete. The interaction between the hollow sandwich layer and the inner CFST member under fire conditions also warrants further investigation. Additionally, the study focuses on static loading; the behaviour under dynamic or impact loading, which is relevant for seismic design and accidental load scenarios, remains to be explored.

Study Insights and Implications

This paper demonstrates that the square hollow sandwich CFST is a promising structural system for applications requiring high lateral local compression resistance. The combination of experimental and numerical approaches provides a comprehensive understanding of the structural behaviour and validates the finite element modelling methodology. The key implication for practising engineers is that the hollow sandwich concept can significantly improve the performance of CFST members under concentrated loads, but careful attention must be paid to the design of connections, the optimisation of geometric parameters, and the validation of numerical models against experimental data. Future research should focus on extending the analysis to combined loading conditions, dynamic loading, and long-term durability assessment.