Seismic Performance of Buckling Restrained Braced Frame Systems PDF Download

Author: Stephen A. Mahin
Publisher:
ISBN:
Category : Buckling (Mechanics)
Languages : en
Pages : 14

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Author: Adam S. Christopulos
Publisher:
ISBN:
Category : Buildings
Languages : en
Pages : 612

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Author: Yousef Bozorgnia
Publisher: CRC Press
ISBN: 0203486242
Category : Technology & Engineering
Languages : en
Pages : 958

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Book Description
This multi-contributor book provides comprehensive coverage of earthquake engineering problems, an overview of traditional methods, and the scientific background on recent developments. It discusses computer methods on structural analysis and provides access to the recent design methodologies and serves as a reference for both professionals and res

Author: Subhash Chandra Goel
Publisher:
ISBN: 9781580017145
Category : Building, Iron and steel
Languages : en
Pages : 261

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Author: Keith D. Palmer
Publisher:
ISBN:
Category : Earthquake resistant design
Languages : en
Pages : 638

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Book Description
This dissertation describes a research program on special concentrically braced frame (SCBF) and buckling-restrained braced frame (BRBF) systems. The study builds upon previous work performed as part of a research program supported by the George E. Brown Network for Earthquake Engineering Simulation (NEES) entitled "International Hybrid Simulation of Tomorrow's Braced Frame." This program was initiated due to practical and experimental evidence that SCBFs were not performing as intended by current seismic design provisions. The current study includes a comprehensive experimental and analytical program which included two first-of-its-kind, two-story, one-bay by one-bay SCBF and BRBFs experiments. The experiments were performed at the University of Minnesota NEES laboratory to take advantage of its ability to apply large-displacement bi-directional loading. The two specimens were configured with braces in two orthogonal bays framing into a ``shared'' column with a floor system designed and constructed to simulate realistic conditions. The first specimen, the SCBF, employed HSS3x3x1/4 braces in a single-story X-configuration with one continuous brace and a pair of spliced braces in the opposing direction. The second test specimen, the BRBF, employed pin-ended, collared BRBs in a single-diagonal configuration. The analytical study consisted of a large suite of finite element simulations aimed at identifying the main parameters that influence the damage at the beam-column-gusset connection region in BRBFs and to make recommendations for the design and detailing of this connection region. This research has resulted in a number of findings including the observation that out-of-plane loading and deformation had little impact on the drift and ductility capacity of the system when compared to planar frame test results. In fact, the drift capacity of the SCBF test frame was only 6% less than that of comparable planar frames while the ductility and cumulative ductility capacities of the BRBF exceeded that of many of the planar BRBF system tests. Based on the experimental and analytical findings, design and detailing recommendations were developed for the connection at the brace splice point in the single-story, X-configured system. Design and detailing recommendations were also made for the corner gusset plate connection region in BRBFs.

Author: Fokruddin Ahmad
Publisher:
ISBN:
Category : Earthquake engineering
Languages : en
Pages : 0

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Book Description
The use of Buckling Restrained Brace Frames (BRBFs) has been increasing in recent decades due to their ability to provide superior seismic performance and enhance the resilience of buildings against earthquakes. However, not many studies have extensively and thoroughly investigated the response and resiliency of prescriptively designed BRBF buildings to varying types of earthquake hazards. This study fills that research gap by investigating the seismic performance of two code-designed BRBFs prototype buildings subjected to far-field, near field with pulse and without pulse, and long-duration ground motion sets. The first phase of the study investigated the seismic resiliency of the prescriptively designed BRBF buildings and compared them to identical prototypes designed with mass timber PT-CLT rocking walls using the FEMA P-58 methodology to compare seismic losses. The seismic loss investigation was part of a larger study evaluating the two types of structural systems using multiple criteria decision analysis across four performance categories of seismic resiliency, global warming potential, superstructure cost, and durability. The global warming potential and superstructure cost estimate was completed by others, but this study completed the seismic resiliency assessment and multiple criteria decision analysis.The second phase of this dissertation work analyzed the structural response of the two BRBF prototype buildings across four sets of ground motions representing different hazard levels in Seattle, WA. The two prototype buildings were modeled in 3D using OpenSeesPy to understand the effect of different ground motion types on the structural responses. The analysis results showed that near-field motions increase the deformation demands, such as inter-story drift and maximum ductility in the pulse direction. Though BRBFs are not a self-centering systems, only the upper two floors of the mid-rise building experienced residual drift higher than 0.2%, which is the threshold for expecting minor repair and structural realignment. None of the stories had residual inter-story drift exceeding 0.5% drift for any motion sets. Overall, the code minimum based BRBF buildings showed excellent performance across all the different hazard types. However, the one caveat of this analysis was that long-duration motions had significantly higher cumulative ductility demand than other motion sets.Therefore, the final phase of this dissertation works further investigated the cumulative deformation demand on BRBF braces under long-duration motions. It is important to verify the ductility of the braces through analysis or testing because they act as the primary structural fuse to dissipate the earthquake energy. The final study compared different loading protocols from different countries to the nonlinear modeling results of long-duration motions. It was determined that the long duration motions had over 80% probability of exceeding the current AISC 341 required testing protocol. To rectify these issues, a new loading protocol appropriate for long-duration earthquakes was proposed that accounts for the increased plastic deformation demand and matches the cyclic content of the nonlinear dynamic analyses.In conclusion, these studies have demonstrated that prescriptively designed BRBFs that meet code minimum requirements are a high performing lateral force resisting system to a range of earthquake hazards. They have excellent seismic resiliency, even when not optimized during design through nonlinear time history analysis, as is common in performance-based earthquake engineering. Additionally, the code-designed BRBF buildings were not predicted to have high residual inter-story drifts, which means they are highly likely to be repairable with minor adjustments and re-alignment. However, it was identified that long-duration earthquakes will increase the ductility demand on the braces significantly compared to far-field and near-field earthquakes and that current minimum testing requirements do not account for this increase. A new protocol was proposed to rectify this one challenge with BRBFs.

Author: Victoria R. Wigle
Publisher:
ISBN:
Category :
Languages : en
Pages : 202

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Book Description

Author: Jian Cui
Publisher:
ISBN:
Category : Buckling (Mechanics)
Languages : en
Pages : 241

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Book Description

Author: Pierre Thibault
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Contemporary seismic-resistant design of steel structures relies on the dissipation of earthquake energy through significant inelastic deformations. Buckling-restrained braced frames (BRBFs) are a type of concentrically-braced system characterized by braces that yield both in tension and in compression. Thanks to a restraining mechanism that confines a ductile steel core, buckling-restrained braces (BRBs) can take advantage of the cyclic ductility of the steel material. However, BRBs commonly display a low post-yield stiffness, causing substantial interstory drifts and large residual drifts after seismic events. Moreover, yielding of the core is often tied to only a single performance objective, thus making its response at other levels of seismicity largely unpredictable. Hybrid BRB solutions are explored as an alternative to the traditional BRB system to overcome its limitations. The hybrid concept is hinged on harnessing different characteristics from different materials that are carefully combined into one ductile design to achieve a desirable response. This numerical study has three main objectives. Potential core metals are first evaluated to determine the best combinations of two materials with complementary engineering properties. Analysis of experimental data indicates that the post-yield behavior of hybrid BRBs is improved by employing 350WT carbon steel in conjunction with another metal, which possesses a low-yield and high-strain-hardening capacity (e.g., 304L stainless steel, 5083-O aluminum alloy, A36 carbon steel, or LYP-100 low-yield-point steel). Afterwards, two new hybrid BRB systems are designed to accommodate the complex deformation pattern of three core plates connected in parallel. The first proposed option has a restraining mechanism made from concrete-filled steel tubes, while the second hybrid BRB option is fabricated exclusively from metal plate components. Lastly, multiple finite element simulations are carried out on numerical models to quantitatively validate the performance enhancement. Compared to conventional BRBs, hybrid BRBs exhibit an improved strain hardening response, a slight increase in axial stiffness, and a greater energy dissipation capability for an equivalent brace strength.

Author: Chui-Hsin Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 342

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Book Description
The special concentrically steel braced frame (SCBF) system is one of the most effective struc-tural systems to resist lateral forces. Because of its effectiveness and straightforward design, many SCBFs are incorporated in structures throughout the world. However, the highly nonlin-ear behavior associated with buckling and non-ductile fracture of braces reduces the ability of the system to dissipate energy resulting in undesirable modes of behavior. While many studies have investigated the cyclic behavior of individual braces or the behavior of subassemblies, the dynamic demands on the structural system under various seismic hazard levels needs additional study for performance-based earthquake engineering. Archetype buildings of SCBFs and buckling restrained braced frames (BRBFs) were analyzed using the computer program OpenSees (the Open System for Earthquake Engineering Simulation) to improve the understanding of the seismic behavior of braced frame systems, and to assess seismic demands for performance-based design. Numerical models were calibrated using test data determined from testing of conventional buckling braces, buckling restrained braces, and the braced frame specimens. In addition, fiber-based OpenSees models were constructed and compared with results of a sophisticated finite-element model that realistically captured local buckling and local fracture of structural elements. Because the OpenSees models are reasona-bly accurate and efficient, they were chosen to perform set of parametric computer simulations. The seismic demands of the system and structural elements were computed and interpreted for 3-, 6-, and 16-story SCBFs and BRBFs under various hazard levels. The analysis results show large seismic demands for the 3-story SCBF, which may result in unexpected damage of struc-tural and non-structural elements. The median expected probability of a brace buckling at one or more levels in a 3-story SCBF is more than 50% for an earthquake having a 50% probability of exceedance in 50 years (the service-level event). The possible need to replace braces fol-lowing such frequent events due to brace buckling should be considered in performance-based earthquake engineering assessments. In addition, brace fracture in SCBFs is likely for an earthquake having a 2% probability of exceedance in 50 years (the MCE-level event). Analy-ses show that in general, BRBF models had larger drift demands and residual drifts compared to SCBF systems, because of the BRBF's longer fundamental period. However, the tendency to form a weak story in BRBFs is less than that in SCBFs. Evaluation of seismic demand parameters were performed for 2-, 3-, 6-, 12-, and 16-story SCBFs and BRBFs, which demonstrated that short-period braced frame systems, especially SCBFs, had higher probability of collapse than longer-period braced frame systems. Substantially improved response was observed by lowering the response reduction factor of the 2-story SCBF building; this reduced the collapse risk at the hazard level of 2% probability of exceedance in 50 years. For long-period (taller) structures, although the collapse probability was lower compared to the short-period structures, weak story behavior was commonly observed in conventionally designed SCBF. A design parameter related to the ratios of story shear demand and capacity under a pushover analysis is proposed to modify member sizes to reduce weak story behavior efficiently. This is demonstrated for a 16-story SCBF building. Regarding local deformation and force demands, simple methods to estimate out-of-plane buck-ling deformation of braces and column axial force demands are proposed. The investigation of system performance and member behavior provides seismic demands to more accurately assess the socio-economic losses of SCBFs and BRBFs for performance-based earthquake engineering.