Zhuojin Pipe Fitting Co., LtdPushover Test Study on Masonry Structures Constrained by Steel Tube Bundle Shear Walls
Literature Overview
Chen Yong et al. (2020), published in the Journal of Zhejiang University (Engineering Science), present experimental and analytical studies on masonry structures reinforced with steel tube bundle shear walls as edge members. The research was funded by the National Key R&D Program and addresses the seismic retrofitting and new construction challenges for masonry buildings through innovative composite wall systems.
Core Technical Points
Steel Tube Bundle Shear Wall Configuration
The steel tube bundle shear wall system comprises multiple steel tubes bundled together with concrete infill, creating a composite shear wall element that provides lateral resistance while constraining adjacent masonry panels. This configuration offers advantages over conventional reinforced concrete shear walls in terms of construction speed, material efficiency, and compatibility with masonry construction methods.
Pushover Test Results
| Test Parameter | Specimen 1 (Edge Member Type A) | Specimen 2 (Edge Member Type B) |
|---|---|---|
| Peak lateral load capacity | Higher | Lower |
| Displacement at peak load | Moderate | Higher |
| Failure mode | Masonry debonding followed by diagonal cracking | Progressive diagonal cracking |
| Energy dissipation capacity | Moderate | Higher |
| Ductility ratio | Lower | Higher |
Equivalent Diagonal Strut Model
The study validates two simplified models for representing masonry panel behavior:
- Single strut model: Considers one compressive diagonal strut per panel. Simple but underestimates capacity and overestimates stiffness in early loading stages.
- Three-strut model: Distributes the compressive force across three diagonal struts (two compression struts and one tension strut equivalent). Provides better correlation with test results when parameters are properly calibrated.
| Model Parameter | Single Strut | Three Strut (Recommended) |
|---|---|---|
| Effective strut width | Full panel width | Fraction of panel width |
| Strain compatibility | Poor | Good |
| Load-displacement correlation | Underestimates initial stiffness | Accurate throughout loading range |
| Applicable loading range | Elastic to early inelastic | Full inelastic range |
Engineering Practice Considerations
Welding and Steel Tube Specifications
The steel tube bundle shear wall involves critical welding operations:
- Steel tube selection: Round steel tubes per GB/T 8163, typically φ114-φ219 mm with 4-8 mm wall thickness, Grade 20# or Q345B
- Lateral binding welds: Steel tubes are welded at regular intervals (typically every 600-900 mm) using fillet welds. GTAW or FCAW processes are preferred for the narrow inter-tube access.
- Connection to floor slabs: The tube bundle is connected to floor and roof slabs through embedded steel plates welded to the tube exterior. These connections must accommodate thermal expansion and seismic displacements.
- Weld inspection: Given the safety-critical nature of shear walls, 100% MT or PT inspection of all welds is recommended, with RT sampling per GB/T 3323 for full-penetration welds.
Masonry-Steel Interface Behavior
The pushover test reveals a critical failure sequence:
- Initial debonding between masonry panel and steel tube bundle edge members
- Formation of diagonal compression struts within the masonry panel
- Progressive cracking and crushing of masonry along the diagonal compression zone
- Final failure by masonry crushing and steel tube local buckling
This sequence indicates that the masonry-steel interface bond is the weakest link in the composite system. Proper detailing of the interface (mechanical interlock, chemical adhesive, or grout) is essential for achieving the full composite action predicted by the three-strut model.
Key Questions and Reflections
The research raises important questions about the practical implementation of steel tube bundle shear walls in masonry construction:
- Construction methodology: How are the steel tubes installed relative to masonry construction sequence? Pre-installed tube bundles require precise positioning before masonry laying, while post-installed bundles require interface preparation and bonding treatment.
- Quality assurance of masonry-steel bond: Unlike conventional reinforced concrete where the bond is continuous through concrete placement, the masonry-steel interface involves discrete masonry units with mortar joints. The bond uniformity is inherently variable and difficult to control.
- Code compliance: Current seismic design codes (GB 50011) do not specifically address steel tube bundle shear walls as masonry edge members. Engineers must rely on rational analysis and test-verified design approaches, which may require special design review.
Study Insights and Outlook
This research demonstrates that steel tube bundle shear walls can effectively enhance the lateral load resistance of masonry structures while maintaining compatibility with traditional masonry construction methods. The three-strut model provides a practical analytical tool for design engineers. Future development should focus on standardized connection details, construction quality control procedures, and code provisions to facilitate widespread adoption in seismic retrofitting and new construction applications.