Zhuojin Pipe Fitting Co., LtdProgressive Collapse Resistance of Steel Tube Concrete Composite Frame with Infill Walls
Literature Overview
This paper by Wang Jingxuan, Yang Yong, and Shen Yajun (2021), published in the Journal of Zhengzhou University (Engineering Science), investigates the progressive collapse resistance of steel tube concrete (STC) composite frame structures with infill walls. Using ABAQUS/Explicit numerical analysis, the study examines the middle-column failure scenario and evaluates how infill walls influence the collapse resistance mechanism and capacity of the composite frame.
Core Technical Content
Numerical Modeling Approach
The numerical model employs explicit dynamic analysis in ABAQUS/Explicit, which is appropriate for capturing the nonlinear dynamic response during progressive collapse. The modeling considerations include:
| Modeling Aspect | Method/Model | Justification |
|---|---|---|
| Steel material | Von Mises yield criterion with kinematic hardening | Captures cyclic plasticity |
| Concrete material | Concrete Damaged Plasticity (CDP) model | Represents cracking and crushing |
| Infill wall masonry | Brittle damage model with Mohr-Coulomb failure | Captures diagonal compression failure |
| Steel-concrete interface | Penalty-based coupling with friction | Simulates bond-slip behavior |
| Wall-frame interface | Mortar joint modeling with tension cutoff | Represents semi-rigid connection |
The model was validated against experimental data from other researchers, confirming the reasonableness of the constitutive models and constraint formulations.
Collapse Resistance Mechanism
The study identifies three distinct stages in the progressive collapse process under vertical loading:
- Beam mechanism stage: After the middle column fails, the adjacent beams develop plastic hinges and carry load through flexural resistance. The infill walls contribute significantly during this stage by providing additional lateral support and restricting beam deflection.
- Catenary mechanism stage: As deflections increase, the beams develop axial tension at their ends, creating a catenary action that provides additional load-carrying capacity. The infill walls' contribution diminishes as they begin to crack and lose integrity.
- Failure stage: When the combined beam and catenary mechanisms can no longer sustain the load, progressive collapse occurs.
Effect of Infill Walls
The research demonstrates that infill walls significantly enhance the progressive collapse resistance, particularly during the beam mechanism stage. The infill walls develop diagonal compressive struts that provide lateral support to the frame, effectively increasing the load path redundancy. The local damage pattern of the infill walls shows characteristic diagonal cracking and crushing, consistent with the strut action mechanism.
Engineering Practice Implications
From a steel pipe and welding engineering perspective, the progressive collapse resistance of STC composite frames has several practical implications:
- Steel tube specifications: The steel tubes used in the composite columns and beams must have adequate ductility to develop the required plastic hinges. The elongation and reduction of area must meet minimum requirements as per GB/T 8162 or GB/T 8163.
- Welding quality: The welds in the steel tubes (longitudinal and circumferential) must be free of defects that could initiate brittle fracture under cyclic loading. Non-destructive testing (RT or UT) of all welds is recommended.
- Connection design: The connections between steel tubes and concrete or between steel tubes and infill walls must be designed to ensure proper load transfer. Welded connections between steel tubes and end plates should be full-penetration groove welds.
- Material compatibility: The steel tubes and infill wall masonry must be compatible in terms of thermal expansion and corrosion resistance to ensure long-term structural integrity.
Key Questions and Reflections
The paper raises important questions about the role of infill walls in progressive collapse resistance. While the numerical results clearly show that infill walls enhance collapse resistance, the practical question is how much of this contribution can be relied upon in design. Infill walls are often considered non-structural elements, and their contribution to progressive collapse resistance is not typically included in design codes. This paper provides a strong argument for reconsidering this assumption.
The numerical modeling approach is robust, but the accuracy of the results depends on the quality of the input parameters and the validation against experimental data. The use of ABAQUS/Explicit is appropriate for this type of analysis, but engineers should be aware of the computational cost and the need for careful time-step control.
Study Insights and Implications
This research contributes significantly to the understanding of progressive collapse resistance in STC composite frames with infill walls. For engineers involved in steel pipe supply and fabrication, the key takeaway is that the material properties and welding quality of the steel tubes directly influence the collapse resistance of the structure. The ductility of the steel tubes is particularly important for developing the catenary mechanism, which provides the ultimate load-carrying capacity.
The paper also highlights the importance of considering infill walls in progressive collapse design. While this is a structural engineering consideration, it has implications for the design of steel tube connections and the overall structural configuration. Engineers should advocate for the inclusion of infill wall effects in progressive collapse assessments, as this can lead to more efficient and safer designs.