- Introduction to Buckling-Restrained Braces (BRB)
- Why BRBs Were Developed
- Components of BRBs
- BRB Seismic Performance
- Recent Innovations in BRBs
- Comparison of Traditional Braces with BRBs
- Advantages of BRBs Over Conventional Bracing Systems
Buckling Restrained Brace (BRB) is a critical component in strengthening structures against earthquakes, and this article aims to explore its significance. We will start by defining BRB and discussing its emergence, then examine its components and how it operates during seismic events. A comparison with traditional braces will follow, as well as a look at the latest advancements and innovations in the design and materials used in Buckling Restrained Braces (BRB), including high-performance concrete and shape memory alloys. Finally, we will help you understand the importance of using these braces in your structures.
 Why Should You Read This Article?
This article will answer the following questions, which are essential for every civil engineer to understand:
- What is a Buckling Restrained Brace (BRB)?
- Why was the Buckling-Restrained Brace (BRB) developed?
- What are the main components of a Buckling-Restrained Brace?
- How does BRB perform in earthquakes?
- What are the differences between Buckling-Restrained and traditional braces?
What is a Buckling Restrained Brace (BRB)?
A Buckling-Restrained Brace is a bracing system designed to control vibrations and seismic forces in structures. Unlike traditional braces, Buckling Restrained Braces (BRB) prevent buckling, meaning they efficiently absorb compressive and tensile forces without bending or losing effectiveness during an earthquake.
Typically, BRBs consist of a steel core surrounded by a buckling-restrained casing. This casing allows the core to remain intact under high pressures, preventing buckling and cracking. Due to their high energy absorption capacity and stable hysteresis behavior, Buckling Restrained Braces (BRB) are recognized as one of the best options for seismic strengthening.
The Emergence of Buckling Restrained Brace (BRB)
Before the introduction of Buckling Restrained Braces (BRB), traditional braces would buckle when subjected to compressive forces from earthquakes, leading to a significant reduction in the load-bearing capacity of structures and increased damage. Engineers sought solutions that could manage the tensile and compressive behavior of materials effectively and prevent buckling.
The emergence of Buckling Restrained Brace (BRB) in recent decades has effectively resolved this issue. With a resilient casing, Buckling Restrained Braces (BRB) exhibit consistent performance under both tension and compression, preventing sudden stiffness reduction. This feature has made BRBs a fundamental component of seismic-resistant systems.
Components of Buckling Restrained Brace (BRB)
BRBs consist of the following key components:
- Steel Core: This part withstands tensile and compressive forces.
- Buckling-Restrained Casing: Typically made of materials like concrete or steel, it protects the core from compressive forces.
- Separator Layer: This separates the steel core from the casing, preventing the direct transmission of lateral forces.
- End Connections: These transfer seismic forces to the brace and then to the main structure.
The combination of these components allows the brace to function without buckling during an earthquake while maintaining stable behavior.
Behavior of Buckling Restrained Brace (BRB) in Earthquakes
One of the most crucial features of BRBs is their ability to maintain stable behavior under cyclic and seismic loads. Tests have shown that these braces can absorb significant energy without buckling or losing stiffness. Due to their special design, BRBs perform exceptionally well against seismic oscillations and prevent large deformations.
Recent research indicates that using high-performance fiber-reinforced concrete (UHPFRC) and ultra-high toughness cementitious composites (UHTCC) as buckling-restrained casings has improved the seismic performance of BRBs, enhancing load-bearing capacity and reducing earthquake-related damage.
Comparison of Traditional and Buckling-Restrained Braces
Compared to traditional braces, Buckling Restrained Brace (BRB) offer the following advantages:
- Prevention of Buckling: Traditional braces buckle under compressive forces, while BRBs prevent this issue with their resilient casing.
- Increased Energy Absorption: Due to stable hysteresis behavior and high energy absorption capacity, BRBs perform better against earthquakes.
- Improved Cyclic Performance: Innovative materials like UHTCC and UHPFRC enhance the lifespan and cyclic performance of BRBs.
- Reduced Weight: New designs utilizing hollow steel cores reduce the weight of BRBs without compromising effectiveness.
Advantages of Buckling Restrained Braces (BRB) over Convergent and Divergent Braces
BRBs have several advantages over Convergent Braces (CBF) and Divergent Special Braces (EBF):
- Prevention of Buckling: CBF and EBF buckle under pressure, while BRBs maintain stability.
- Higher Energy Absorption Capacity: BRBs absorb more seismic energy, enhancing structural resilience.
- Better Seismic Performance: Buckling Restrained Braces (BRB) show consistent performance during cyclic loading, especially in strong earthquakes.
- Stability in Large Deformations: Unlike CBF and EBF, BRBs can handle large cyclic loads without losing efficiency.
- Better Control of Story Drift: BRBs effectively control story drift due to their high energy absorption and stable performance.
In summary, Buckling Restrained Braces (BRB) outperform CBFs and EBFs, particularly during severe seismic events, ensuring enhanced safety and stability for structures.
Cumulative Nonelastic Ductility in Buckling Restrained Brace (BRB)
Cumulative nonelastic ductility is a critical feature in bracing systems like Buckling Restrained Braces (BRB), referring to the ability of the brace to withstand plastic deformations without significant loss of strength. This characteristic allows the brace to repeatedly enter the plastic (nonelastic) region under large cyclic loads and maintain optimal performance.
Cumulative nonelasticity means that during prolonged earthquakes or multiple loading cycles, the brace can endure significant deformations without failure or serious damage. This cumulative deformation does not lead to stiffness reduction, allowing the brace to continue absorbing energy. Cumulative nonelastic ductility is an essential metric for assessing the durability and effectiveness of braces against seismic forces. A brace with high cumulative nonelastic ductility can withstand severe seismic loads without collapsing or losing effectiveness, thereby reducing the vulnerability of the structure.
In Buckling Restrained Braces (BRB), this feature is ensured by preventing buckling and maintaining stable behavior against both tensile and compressive forces, making Buckling Restrained Braces (BRB) a suitable choice for enhancing the cumulative nonelastic ductility of structures.
Innovations and Recent Research in Buckling Restrained Brace (BRB)
Recent research indicates that the use of new materials such as shape memory alloys and multilayered steel cores has significantly improved BRB behavior. Hybrid systems combining Buckling Restrained Braces (BRB) with these materials have reduced story drift and enhanced seismic performance.
For instance, enhanced BRBs with UHTCC have shown a 13% increase in load-bearing capacity and delayed crack initiation, as demonstrated by Tang et al. in 2024. Additionally, BRBs with multiple steel cores, introduced by Zhang et al., optimize weight and strength while providing better energy dissipation capacity.
Conclusion
Buckling Restrained Braces (BRB) are among the best options for enhancing structural resistance against earthquakes. With multiple advantages such as preventing buckling, increasing energy absorption, and improving cyclic behavior, these braces are rapidly gaining prominence in the construction industry. The use of innovative materials and hybrid designs has made BRBs a fundamental tool for seismic retrofitting.
