Buckling-restrained Brace System Research Articles

Enhancing vibration energy dissipation and self-powered sensing in high-rise buildings using origami-inspired triboelectric nanogenerators and buckling-restrained braces

This study introduces a novel Buckling-Restrained Brace (BRB) design, incorporating Origami-inspired structures (OS) with triboelectric nanogenerators (TENGs), creating an intelligent BRB system for both vibration damping during seismic events and self-powered sensing. Rooted in the Miura-tube pattern, we conducted an extensive array of mechanical tests, encompassing varying contact shapes, external resistances, and excitation frequencies. Addressing the challenge of motion synchronicity in the OS base, we introduce an enhanced Miura-tube OS-TENG, featuring reinforced stiffness in the origami structure's creases and panels. Our experiments revealed that the signal strength of these refined devices proportionally escalates with the number of integrated tribo-pairs. Further vibrational analysis of a two-story frame equipped with this enhanced Miura-tube OS-TENG underscored its potential as a sophisticated intelligent BRB. Experiments demonstrated a significant 31.21 % reduction in structural acceleration and a strong correlation between the device's voltage output and the building's dynamic response, with a 90.40 % regression fit. Within the examined range of excitation frequencies 3–15 Hz, the average accuracy of predicting structural acceleration using intelligent BRBs is 92.90 %. This work not only meets the essential demand for vibration mitigation through the innovative use of intelligent OS-TENG BRB systems but also significantly advances the integration of TENG-based self-powered sensors in structural health monitoring frameworks.

Enhancing seismic performance of buckling-restrained brace frames equipped with innovative bracing systems

Nowadays, to improve the performance of conventional bracing systems, in which, buckling in the pressure loads is the main disadvantage, the buckling-restrained brace (BRB) is introduced as a solution. In this study, the performance of the BRB system was improved with innovative lateral-resisting systems of double-stage yield buckling-restrained brace (DYB), and a combination of DYB improved with shape memory alloy (SMA) materials (DYBSMA). The proposed systems have been verified and implemented in the 2- to 12-story elevation steel buckling-restrained brace frames (BRBFs). To evaluate their effects on the seismic performance, two types of analysis including nonlinear dynamic analysis (NDA) and incremental dynamic analysis (IDA) were performed considering design-based earthquakes (DBE) and maximum considered earthquakes (MCE) levels for far-field ground motions. The results showed that the BRB system in all BRBFs had the highest values of residual drift ratio (RDRMed) demands, while implementing innovative DYBSMA can considerably reduce the values of RDRMed compared to other lateral-resisting systems. In addition, under MCE level, the BRB-DYBSMA system had lower values of the interstory drift ratio (IDRMed) and RDRMed demands (e.g., the IDRMed reduced by 79.67% and 18.5% compared to BRB and DYB systems, respectively), and can be introduced as the best lateral-resisting system. Therefore, the proposed BRB-DYBSMA system can effectively reduce the IDRMed and RDRMed demands, as result, higher performance levels can be achieved, as well as, the collapse probability occurrence over 1 and 50 years impressively decreased.

Seismic performance of two-story three-bay reinforced concrete frame equipped with K-configured buckling restrained braces

This study presented experimental and numerical investigations into the seismic performance of reinforced concrete (RC) frames equipped with buckling restrained brace (BRB) systems in the central span. The study evaluated the effectiveness of the K-configured BRB system in strengthening the RC frame for engineering construction applications in the seismic region. A 1/3-scaled, three-span, two-story, RC frame was designed in accordance with seismic design requirements and tested under low-reversed lateral cyclic loading. A finite element model of the BRB-equipped RC frame was created using ABAQUS and validated by comparing the numerical and experimental results. The validated model was also modified by removing the BRBs to create the bare RC frame. Seismic behaviors of the bare and RBR-equipped RC frames were numerically examined and compared in terms of failure modes, hysteretic response, ductility, energy dissipation, strength degradation, and stiffness deterioration. The results indicated that the BRB-equipped RC frame achieved a plastic hinge failure mechanism at the beam ends with no severe concrete damage in the supporting columns. Furthermore, the use of the K-shaped BRB in the central span improved the load-carrying capacity by up to 80% and the energy dissipation capacity by up to 50%. Parametric studies were also conducted to investigate the influence of critical design parameters and provide design suggestions for potential improvement in the RC frame's ductility and energy dissipation capacity.

Experimental and numerical investigations on an assembled self-centering buckling-restrained brace with high post-yield stiffness

In order to facilitate the replacement of damaged components and prevent the weak-story mechanism of frame structure after strong earthquakes, a novel assembled self-centering buckling-restrained brace (ASC-BRB) is proposed in this paper. The proposed bracing system is comprised of the buckling-restrained brace (BRB) system and the self-centering (SC) system. The SC system consists of two sets of steel strands and one group of disc springs stacked in series to achieve the goal of large deformability and post-hardening behavior. The detailed configuration, fundamental working mechanism, and restoring force model of the ASC-BRB are first presented. Different from SC systems with bilinear elastic behavior of existing SC-BRBs, the SC system of ASC-BRB exhibits trilinear elastic behavior due to its special configuration. Then, quasi-static tests are conducted to validate the effectiveness of the proposed ASC-BRB. The experimental results indicate that the ASC-BRB has a flag-shaped hysteretic response with excellent self-centering capability, stable energy dissipation capability, and appreciable deformation capacity with a maximum ductility coefficient of 25.58. More importantly, the specimen can exhibit the anticipated post-hardening behavior. The refined numerical model of ASC-BRB is established and verified by the experimental results, which can effectively analyze the mechanical behavior of the main components of ASC-BRB, making up for the deficiency of the tests. According to the problems discovered in the tests and numerical analyses, an improved configuration of the ASC-BRB is proposed and validated by the numerical simulation of the BRB system before and after improvement. The numerical results indicate that the improved BRB system exhibits more stable hysteretic behavior, and the stress levels of the inner and outer tubes become much lower after replacing 1-shaped cores with steel angle cores.

Study on numerical seismic performance evaluation of 3D building frame with smart self-centering BRBs system

Structures are generally designed to withstand the applied loads safely. However, in order to secure the stability of structures from earthquakes, which are unpredictable natural disasters, seismic damage reduction technology is required, and various technologies are being developed so far. Recently, to resist seismic loads, new materials are used to reinforce structural members, or technologies to control vibration by applying seismic devices are being developed. In particular, Shape Memory Alloy (SMA), also known as a smart alloy, has a unique re-centering capacity that exhibits a flag-shaped hysteresis curve, so when applied in a structural system, it can provide safer structural performance with higher serviceability. In this study, to prove the structural stability of the SMA buckling restrained brace (BRB) system to which the seismic isolation is applied, a study was conducted to evaluate the seismic performance according to the structural material, type, and device. Response of SMA BRB and base isolation system has been calibrated by following quasi-static and dynamic loading test and substantially matches empirical results. A prototype steel frame has been designed by following standard code which has a single-story basement assumed to be surround by well graded sandy soil. In addition, two different column system has been considered namely as, Hollow Steel Section (HSS) and Concrete Filled Steel Tubes (CFST). For the nonlinear dynamic analysis, two sets of 11 bidirectional artificial earthquakes were considered, and the interstory drift ratio (IDR) and residual interstory drift ratio (RIDR) were considered as main performance evaluation parameters. In moderate ground motion, the performance of the SMA BRB was found to be higher compared to the steel BRB and base isolation system due to its superior self-centering capacity. However, in strong ground motions, periodic damage degrades the performance of the SMA BRB, which was found to be nearly identical to the steel BRB, but still superior to the base isolation system. This performance evaluation study will help to understand design aspects of seismic protection systems for similar types of building frames.

Design recommendations for self-centering buckling restrained braces

Self-centering buckling-restrained braces (SC-BRBs) have typical flag-shaped hysteresis. Differing from conventional buckling-restrained braces (BRBs) which can result in significant residual drifts, the SC-BRB incorporates additional prestressing elements, so that it can recenter after earthquakes, which is critical for seismic resilience. Current seismic design procedures can be used to calculate the key properties of conventional braces (e.g. BRB), but they cannot be used to determine the additional hysteretic properties of SC-BRB braces. To achieve a comprehensive understanding of the performances of SC-BRB systems and develop their design recommendations, this paper conducted a parametric study of two typical SC-BRB systems, using a 12-story steel braced frame office building. Then, the overall behavior of the SC-BRB system was compared with those of a BRB system and two self-centering energy dissipative brace systems. The selection of SC-BRB properties appeared to be a tradeoff between demands on component properties and seismic performances. The criteria for proportioning the system were suggested. Numerical results showed that, although the SC-BRB systems had smaller residual drifts than the BRB system, they generated more significant high-mode effect than the other comparable systems.

Study and Comparison of the Performance of Steel Frames with BRB and SMA Bracing

Designing steel structures with Concentric Braced Frame (CBF) lateral systems has been common in recent decades. This type of bracing has a quite unstable and complicated behavior in relatively intense earthquakes. This study tries to improve the seismic behavior of steel frames with CBF braces equipped with Shape Memory Alloy (SMA) and Buckling Restrained Braces (BRBs). In this manner, a multi-story building with inverted V chevron bracing was considered. Nonlinear time-history analyses have been performed using OpenSEES software. The dynamic responses of frames with SMA and BRB braces were compared. The results showed that the SMA and BRB braces provide energy dissipation in the nonlinear zone and can reduce maximum interstory drift. The comparison of those bracing systems revealed that implementing SMA in braces also led to a reduction in permanent displacement of the structures due to the elasticity property of the SMA bracing system. The energy dissipation of structures with the BRB system was higher than that of structures with the SMA bracing system.

Replaceable fuse buckling-restrained brace (BRB): Experimental cyclic qualification testing and NLFEA modeling

Building in seismically active regions subjected to lateral forces requires adequate strength and stiffness to resist such forces. Numerous studies have shown that braces perform better against axial loads than conventional braces if inhibited from buckling with a restraining mechanism. This system is called Buckling Restrained Braces (BRBs), enhancing energy dissipation when added to a structure. Contrary to the conventional BRBs, this paper presents testing a newly patented type of BRB system consisting of a stainless-steel core bar inserted into a buckling inhibiting unit made of mild steel pipe filled with grout and connected to a novel end restrained unit so-called fingers. The new system provides easy replacement of the core (dissipation unit) and end units if replacement is needed after a significant seismic event. Six BRB samples of three different cross-sections of core units were subjected to uniaxial cyclic loading following the AISC 341 qualification testing protocol. Only full-threaded core and smooth shaved core bars passed the qualification test out of three cross-sections. The successful tests showed a stable hysteretic response in the tension and compression phase of loading and a significant ductility of µ=4. Overall load-deformation responses, ductility, overall stiffness, and energy dissipation were analyzed and compared for the BRBs tests. The threaded cross-sectional type of core bar showed the highest energy dissipation and attained ductility compared to the other types of tested bars. A 3D NLFEA model of the best performing BRB specimen was created using the commercial software package ABAQUS. It exhibited notable agreement with the experimental results. The produced high-fidelity NLFEA models are a solid basis for a future more comprehensive parametric investigation campaign.

Proportioning of self‐centering energy dissipative braces

AbstractSelf‐centering energy dissipative (SCED) braces are designed to limit the maximum story drifts in buildings during earthquakes and to nearly eliminate residual drifts. The key properties of conventional braces (eg, strength, stiffness) can be determined with current seismic design procedures, but additional criteria are needed to select the hysteretic properties of SCED braces (eg, prestressing level, fuse activating deformation). Past investigations of the seismic performance of the SCED braced frames selected brace characteristics to match the hysteretic characteristics of buckling restrained braces (BRB). However, those characteristics may not be achieved because the performance of the SCED system is constrained by the elongation capacity of the post‐tensioned tendons. To develop recommendations for proportioning SCED braces, the researchers conducted a parametric study on the properties of two typical SCED systems, using a nine‐story steel braced frame office building. The seismic performances of the SCED systems were then compared with that of a BRB system including an analysis without property uncertainty and an analysis with uncertainty using Monte Carlo simulation. Based on the cost and seismic performances of SCED systems designed using various characteristics, recommendations are proposed for proportioning the SCED systems. Besides having much smaller residual drifts, the SCED systems had a smaller likelihood of exceeding a maximum story drift of 3% and less drift concentration compared with the BRB system, though they generated larger floor accelerations and forces in connections and adjacent members. The property uncertainty increased the residual drift of the SCED systems.

Research Status and Application of Buckling Restrained Brace Technology

For the past four decades, researchers have worked upon and developed a bracing system. called the buckling restrained brace (BRB) for frame braced structures. This system counteracts compression from buckling during strong earthquakes. The system has the advantages of a common brace and damper, providing lateral stiffness to the structure under frequent earthquakes. Seismic energy can be dissipated by the steel core yield, under both rarely expected and moderate earthquakes. This paper is devoted to the concept of BRB, its components, characteristics, and its current deficiencies. It also discusses the current limitations and estimates the developing trend of this technique. It has a certain reference value for in-depth studies on BRB system.

Toggle buckling-restrained brace systems and a corresponding design method for the seismic retrofit of bridge bents

Based on the structural fuse concept, easily replaceable fuses are designed to sustain seismic demand and dissipate seismic energy while keeping RC bridge bents elastic, so the retrofitted bents have a very low displacement demand. Buckling-restrained braces (BRBs) are common fuses used in the seismic retrofit of bridge bents. However, the energy dissipation capacity of BRBs cannot be fully utilized under a small displacement if the diagonal or inverted-V configurations are adopted. Combining the structural fuse concept with toggle brace mechanisms, this paper studied a toggle BRB system that can amplify the effect of damper devices. The system was designed to keep the RC bridge bents elastic through the increased energy dissipation capacity of the BRBs. Several key parameters, including the displacement amplification factor and the steel core length-to-total length ratio, were discussed. The admissible values of the displacement amplification factor for different bents were plotted with contour lines. In addition, a displacement-based design procedure was proposed that ensured the bents achieved the target performance under a design-level earthquake. Two design examples were illustrated: a bent that failed in a flexural mode and another bent that failed in a flexural-shear mode. Finally, the feasibility of the design procedure was validated with nonlinear time history analyses.

Seismic Response Analysis of Multi-Story Steel Frames Using BRB and SCB Hybrid Bracing System

Multi-story steel frames are popular building structures. For those with insufficient seismic resistance, their seismic capacity can be improved by installing buckling-restrained braces (BRBs), which is known for high energy dissipation capacity, and the corresponding frame is denoted as BRB frame (BRBF). However, BRBFs are frequently criticized because of excessive residual deformations after earthquakes, which impede the post-event repairing work and immediate occupancy. Meanwhile, self-centering braces (SCBs), which were invented with a particular purpose of eliminating residual deformation for the protected structures, underwent fast development in recent years. However, the damping capability of SCBs is relatively small because their hysteresis is characterized by a flag shape. Therefore, this paper aims to combine these two different braces to form a hybrid bracing system. A total of four combinations are proposed to seek an optimal solution. The multi-story steel frames installed with BRBs, SCBs, and combined braces are numerically investigated through nonlinear static and dynamic analyses. Interested seismic response parameters refer to the maximum story drift ratios, maximum floor accelerations, and residual story drift ratios. The seismic analysis results indicate that the frames using the combined bracing system are able to take the advantages of BRBs and SCBs.

Seismic design and performance analysis of buckling‐restrained braced RC frame structures

SummaryDue to the stable hysteretic behavior, buckling‐restrained braces (BRBs) have been increasingly adopted in reinforced concrete (RC) frame structures to develop a dual structural system (BRB‐RCF). This study proposed an alternative strength‐based design approach that decomposes the dual BRB‐RCF system into two independent RC frame and BRB system using the BRB‐carrying story shear ratio. The design of RC frame is performed in an integrated manner by considering the BRB postyielding force demands. Three RC frames with five, 10, and 15 stories were employed as prototype structures, and seven story shear ratios ranging from 0.1 to 0.7 were used to generate a total of 21 structural modes. The material usage, maximum axial compression ratio of columns, and elastic interstory drift ratio were compared for different story shear ratios. Nonlinear dynamic analysis of the BRB‐RCFs subjected to 12 ground motions were carried out. The seismic response including the maximum interstory drift ratio, hysteretic energy dissipation ratio, and actual BRB‐carrying story shear ratio were systematically assessed for different design story shear ratios. Based on the considerations of material usage and seismic performance, it is suggested that the design BRB‐carrying story shear ratio should be in the range of 0.3 to 0.5.

Assessing and quantifying the earthquake response of reinforced concrete buckling-restrained brace frame structures

Due to the stable hysteretic behavior, buckling-restrained braces (BRB) have been increasingly adopted in reinforced concrete (RC) frame structures to develop a dual structural system. This investigation aims to quantify the seismic behavior of newly-constructed reinforced concrete BRB frames (RC-BRBFs). The force–deformation characteristic of dual RC-BRBFs is firstly presented and the yield displacement is derived using the story shear ratio resisted by BRB system. The seismic design procedure of dual systems for different BRB configurations (including single diagonal, V-type and inverted V-type), is developed using the performance-based plastic design approach by considering BRB postyield behavior, design target drift and global yield mechanism. 126 RC-BRBF structures corresponding to different story numbers, BRB configurations and story shear ratios are designed. The influence of story shear ratios on the design results is analyzed. The seismic response of structures subjected to 22 ground motions is investigated and compared in terms of yield mode, maximum interstory drift ratio, BRB maximum ductility and cumulative ductility, and residual drift ratio. The relationship between actual and design normalized story shear of BRBs is demonstrated and a fitting equation is proposed to quantify the actual story shear ratios. The analytical results of the present study can provide quantified insights to the seismic design of RC-BRBF structures.

Hysteretic performance of inverted-V patterned BRB systems considering vertical pre-compression effects

Buckling-restrained braces (BRBs) could be installed in pares in high-rise frames or long-span structures, forming inverted-V patterned BRB systems, and the pre-compression effects are inevitably introduced into the BRB systems due to the vertical loads transmitted from upper structures. This paper presents the investigations on hysteretic performances of the inverted-V patterned BRB systems subjected to lateral cyclic loadings and vertical pre-compression. First, a parametric study via finite element (FE) analyses is conducted, considering the parameters including: pre-compression factors, vertical translational rigidity ratios, angles of the BRB systems and material properties of the BRB cores. According to the FE results, design recommendations are provided for practical designs of the BRB system and each individual BRB member. Then, based on the evaluation of the vertical and horizontal loading effects applied to the roof of a long-span structure equipped with the BRB system, formulas are proposed for designing of the long-span roof subjected to pre-compression as well as lateral earthquake effects. Finally, design procedures for the BRB system and the long-span roof are provided, which are further demonstrated by a practical design example.

Seismic Response of Multi-Storey Building with Buckling Restrained Brace System

Buckling Restrained Braces (BRBs) are made up by a steel core surrounded by a buckling restraining system, coated with an unbonding material. The buckling restrained system prohibits steel core from buckling when in compression. Experimental studies have been carried out to study the behavior of BRBs. Experimental results showed that the BRB exhibit stable hysteresis response with substantial energy dissipation and ductility. Therefore, seismic performance of buildings or other structure can improve effectively by using BRBs. In this work, numerical studies of eleven models were conducted using ETABS software. The numerical tests were carried out in different scenarios, i.e. building the model with a conventional brace system, building models with partial BRBs system and building models with BRBs system. From both equivalent static analysis and response spectrum analysis main findings are the effects of yielding core length on partial replaced BRBs system and BRBs system buildings are significant in controlling or altering base shear, maximum storey displacement and storey drift, and time period. Also, BRBs are effective in reducing the axial force for column and footing.

Design and full‐scale experimental evaluation of a seismically endurant steel buckling‐restrained brace system

SummaryThis paper presents the results of 12 full‐scale tests on buckling‐restrained brace (BRB) specimens. A simple‐to‐fabricate all‐steel encasing joined by high‐strength bolts was used as the buckling‐restrainer mechanism. Steel BRBs offer significant energy dissipation capability through nondeteriorating inelastic response of an internal ductile core. However, seismic performance of BRBs is characterized by interaction between several factors. In this experimental study, the effects of core‐restrainer interfacial condition, gap size, loading history, bolt spacing, and restraining capacity are evaluated. A simple hinge detail is introduced at the brace ends to reduce the flexural demand on the framing components. Tested specimens with bare steel contact surfaces exhibited satisfactory performance under the American Institute of Steel Construction qualification test protocol. The BRBs with friction‐control self‐adhesive polymer liners and a graphite‐based dry lubricant displayed larger cumulative inelastic ductility under large‐amplitude cyclic loading, exceeding current code minimum requirements. The BRB system is also examined under repeated fast‐rate seismic deformation history. This system showed significant ductility capacity and remarkable endurance under dynamic loading. Furthermore, performance is qualified under long‐duration loading history from subduction zone's megathrust type of earthquake. Predictable and stable performance of the proposed hinge detail was confirmed by the test results. Internally imposed normal thrust on the restrainer is measured using series of instrumented bolts. Weak‐ and strong‐axis buckling responses of the core are examined. Higher post‐yield stiffness was achieved when the latter governed, which could be advantageous to the overall seismic response of braced frames incorporating BRBs.

Performance of an innovative self-centering buckling restrained brace for mitigating seismic responses of bridge structures with double-column piers

Buckling restrained braces (BRBs) are normally incorporated in the beam-column structures to serve as energy dissipation members due to their stable hysteretic behavior. However, the structures equipped with BRBs may suffer excessive residual deformations when they are subjected to large earthquakes. To minimize the residual deformations of the structures with traditional BRBs, a novel self-centering buckling restrained brace (SC-BRB) consisting of a self-centering system and a traditional BRB system is developed in the present study. Large-scale experimental studies are carried out and the hysteretic behavior of the proposed system is compared with the traditional BRB and self-centering brace (SCB). Experimental results show that the SC-BRB exhibits flag-shaped hysteresis response with a small residual deformation and a moderate energy dissipation capability. The proposed SC-BRB is applied to a reinforced concrete (RC) double-column bridge pier for seismic retrofitting. Nonlinear dynamic analyses are carried out to examine its effect on the seismic behavior of the bridge. Numerical results demonstrate that the bridge equipped with SC-BRB system shows much smaller residual displacement compared to the ones equipped with traditional BRB and SCB systems. Numerical results also indicate that SC-BRB system tends to amplify the peak acceleration of the bridge.

Seismic performance of precast concrete rocking walls with buckling restrained braces

The application of a buckling restrained brace (BRB) to improve the energy dissipation of a precast concrete rocking wall (PCRW) was investigated. A series of quasi-static reversed cyclic loading tests was conducted for the BRB, the PCRW subassemblage and the combined PCRW–BRB system. A commonly adopted fibre model was then developed using the Ruaumoko computer program and verified using the experimental results. The results indicate that the stable elasto-plastic BRB supplies vibration energy to the nonlinear elastic responses of the PCRW. This finding confirms that the PCRW–BRB system is a suitable alternative for use in seismic-resistant structures.

Experimental testing and design of BRB with bolted and pinned connections

The recent series of damaging earthquakes in Christchurch, New Zealand has encouraged greater recognition of the post-earthquake economic impacts on New Zealand society and higher emphasis on low-damage earthquake resisting systems. Braced frames incorporating Buckling Restrained Braces (BRB) are seen as a significant contender for such a system.
 This research project focuses on the development of a reliable design procedure and detailing requirements for a generic BRB system. To gauge the performance of the designed system and to ascertain the reliability of the developed procedure, a series of static and dynamic sub-assemblage tests on the BRB frame with two different brace connection configurations were performed. The results are presented and discussed herein.
 The experimental tests generated stable and near symmetrical hysteresis loops, which is a principal characteristic of a well performing BRB system, albeit with the occurrence of slack in the connections. The experimental test results shows that several improvements need to be made to the proposed design procedure and detailing as outlined throughout the paper; especially the procedural modification to prevent slack from occurring in the two different connection systems. It is envisaged that applications will typically involve use of proprietary braces, however these need to be applied in accordance with the New Zealand design procedure; and determining the appropriate procedure was a key part of this project.