Zhuojin Pipe Fitting Co., LtdPerformance Analysis of Perforated Triple Rectangular Steel Tube Buckling-Restrained Braces
Literature Overview
This research by Lin Yihuang, Zhou Yun, Cao Yongsheng, and Zhuang Zixuan from Guangzhou University, published in the Journal of Earthquake Engineering (2025, Vol. 47, No. 5, pp. 1128-1137), investigates a novel perforated triple rectangular steel tube buckling-restrained brace (PTRBRB) through finite element analysis using ABAQUS. Funded by the National Natural Science Foundation of China (Grant No. 51978184), this study represents a significant advancement in seismic energy dissipation device design, addressing the need for braces that combine high energy dissipation capacity with controlled yielding behavior and reliable buckling prevention.
Core Technical Findings
The PTRBRB demonstrates excellent seismic energy dissipation characteristics with full, symmetric, and stable hysteresis curves. The study systematically examines the influence of perforation position, number of perforations, perforation ratio, steel tube clearance, and end connection methods on the mechanical and energy dissipation performance. The key finding is that perforations on the web panels are recommended, with an optimal perforation ratio range of 35% to 50%.
Parametric Study Results Summary
| Parameter | Influence on Mechanical Performance | Influence on Energy Dissipation | Recommended Range |
|---|---|---|---|
| Perforation Position (Web vs. Edge) | Web preferred | Web provides fuller hysteresis | Web panels |
| Number of Perforations | Minor effect | Minor effect | Design-dependent |
| Perforation Ratio | Significant effect | Minor effect | 35% to 50% |
| Steel Tube Clearance | Minor effect | Minor effect | Standard tolerances |
| End Connection Method | Minor effect | Minor effect | Standard designs |
Technical Analysis of PTRBRB Design
Structural Configuration
The PTRBRB incorporates three concentric rectangular steel tubes with a yielding core unit. The perforations are introduced to achieve specific design objectives: controlling the yielding location to predetermined zones, enabling simultaneous multi-point energy dissipation, and managing the interaction between the core unit and the surrounding restraint tubes.
The concept of "fixed-point yielding and multi-point simultaneous energy dissipation" is particularly innovative. By introducing perforations at strategic locations, the designer can direct plastic deformation to predetermined zones, creating multiple yielding regions that activate simultaneously. This approach enhances the predictability of brace behavior during seismic events and provides more uniform energy dissipation along the brace length.
Effect of Perforation Ratio
The perforation ratio emerges as the most influential parameter among those studied. When the perforation ratio is too small, the maximum equivalent plastic strain concentrates at the end connection segments rather than in the intended yielding zones. This behavior is undesirable because end connections are typically designed for force transfer rather than energy dissipation, and concentrated plastic deformation at these locations can lead to premature connection failure.
Conversely, when the perforation ratio is excessively large, the core unit perforated segments experience in-plane instability. This failure mode represents a critical limitation, as it indicates that the perforated regions have insufficient local stiffness to resist the compressive stresses developed during cyclic loading. The recommended range of 35% to 50% represents the optimal balance between achieving controlled yielding and maintaining structural stability.
Web Perforation versus Edge Perforation
The study clearly demonstrates that web panel perforations outperform edge perforations. PTRBRBs with edge perforations exhibit non-full hysteresis curves, indicating reduced energy dissipation efficiency. Both the compressive bearing capacity and energy dissipation capacity are diminished when perforations are placed on the edges rather than the webs. This finding is physically intuitive: edge perforations compromise the tube's bending stiffness more significantly than web perforations, leading to earlier local buckling and reduced overall structural capacity.
Engineering Practice Integration
Design Guidelines for PTRBRB Implementation
Based on the findings of this study, the following design guidelines can be established for practical engineering applications:
- Perforations should be placed on web panels rather than edges to maintain optimal energy dissipation characteristics.
- The perforation ratio should be maintained within the 35% to 50% range to ensure proper yielding location and prevent instability.
- The number of perforations, steel tube clearance, and end connection method have minimal influence on performance, providing designers with flexibility in these aspects.
- The PTRBRB configuration is suitable for applications requiring predictable, repeatable energy dissipation behavior under cyclic seismic loading.
Comparison with Conventional BRBs
| Feature | Conventional BRB | PTRBRB |
|---|---|---|
| Yielding Pattern | Diffuse or unpredictable | Fixed-point, multi-point |
| Hysteresis Curve | Variable fullness | Consistently full and symmetric |
| Energy Dissipation | Single or few zones | Multiple simultaneous zones |
| Design Predictability | Moderate | High |
| Weight Efficiency | Standard | Enhanced through perforation |
| Buckling Resistance | Core unit restrained | Multi-tube restraint with perforation control |
Key Questions and Reflections
The study raises several important questions for further investigation. First, the long-term fatigue behavior of PTRBRBs under repeated seismic events warrants attention. The perforated regions, while designed for controlled yielding, may accumulate damage over multiple loading cycles, potentially leading to progressive degradation of energy dissipation capacity.
Second, the study focuses on quasi-static cyclic loading through finite element simulation. The response of PTRBRBs under dynamic seismic loading with varying frequency content may differ, particularly regarding the activation sequence of multiple yielding zones. The inertial effects of the perforated segments during high-frequency loading could influence the overall brace response.
Third, the practical fabrication considerations for PTRBRBs deserve attention. The introduction of perforations adds complexity to the manufacturing process, requiring precise cutting, deburring, and inspection. The quality of perforation edges is critical, as stress concentrations at perforation boundaries could initiate cracks under cyclic loading.
This research represents a meaningful contribution to the field of seismic energy dissipation devices. The PTRBRB concept offers a refined approach to BRB design that addresses the limitations of conventional configurations through intelligent perforation strategies. The clear parametric guidelines provided by this study enable practical implementation while maintaining the performance advantages demonstrated through finite element analysis.