Inelastic Behavior and Seismic Collapse Prevention Performance of Low-ductility Steel Braced Frames PDF Download

Author: Joshua G. Sizemore
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Chen Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :

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"In low and moderate seismic regions, low-ductility concentrically braced frames (CBFs) are widely used as the seismic force-resisting system for steel structures. Unlike high-ductility CBFs, the capacity-based design principle and additional seismic detailing are not required for such systems, which are referred to as conventional CBFs (CCBFs) in this study. In CCBFs, the brace-to-gusset connections are inherently weaker than the adjoining gusset plates and braces when loaded in tension. This occurs because both the gusset plates and the braces are most often selected based on their respective compressive buckling resistances, and hence, typically have a much greater resistance in tension. As such, brace connections are critical for the seismic behaviour and collapse prevention performance of CCBFs. However, brace connections have received little research attention because they are usually assumed to remain elastic in most capacity-based designs, and as such, their inelastic behaviour is not fully understood at a fundamental level. This is reflected in the different code provisions: in Canada, the seismic design force must be amplified by 1.5 for brace connections in CCBFs unless these connections are proven to be ductile as per CSA S16-19; in New Zealand, for connections in CCBFs, a structural performance factor of 1.0 is required, compared with 0.9 for structural members, which effectively increases the seismic design force demand on connections as per NZS 3404; no analogous requirements exist for CCBFs in the USA as per ANSI/AISC 341-16 or in Europe as per Eurocode 8.The inelastic behaviour of and the seismic deformation demand on CCBF brace connections were studied through a two-level numerical simulation approach, which is presented in this thesis. The bolted flange plate connection of the I-shape brace, which is a common design choice for CCBFs, was selected as the subject of this study.At the connection level, a high-fidelity finite element (FE) simulation procedure was developed for the bolted flange plate connection and validated against laboratory test results. The force transfer mechanism within the branches of the connection was characterized. Subsequently, a parametric study based on the validated numerical simulation procedure was carried out. Three key design parameters, namely, the gusset plate thickness, the flange lap plate thickness, and the web lap plate thickness, were varied to study their effects on both the compressive and tensile behaviour of the brace and the connection assembly. Various deformation mechanisms and failure modes were revealed under both compression and tension. Design recommendations are proposed with regards to attaining better deformation capacity.Based on the knowledge gained from the high-fidelity numerical simulations, a computationally efficient component-based modeling method was developed for the bolted brace connection. The connection was discretized into individual components, and modeled by means of organized springs, which each simulate the behaviour of a component. After validation against experimental test results, the component-based connection model was incorporated into a system-level numerical model for a series of prototype CCBFs. Through nonlinear static and dynamic structural analyses, the seismic behaviour and collapse prevention performance of CCBFs were studied. When loaded in tension, the brace connections deformed much more than the brace, and amplifying the design force by 1.5 was effective in reducing the seismic deformation demand on brace connections. In some cases, a secondary seismic force-resisting mechanism developed and prevented the system from collapse after the primary seismic force-resisting mechanism had failed"--

Author: American Society of Civil Engineers
Publisher: ASCE Press
ISBN: 9780784415788
Category : Buildings
Languages : en
Pages : 1046

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Standard ASCE/SEI 7-22 provides requirements for general structural design and includes means for determining various loads and their combinations, which are suitable for inclusion in building codes and other documents.

Author: Federico Mazzolani
Publisher: CRC Press
ISBN: 020311941X
Category : Technology & Engineering
Languages : en
Pages : 1147

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Behaviour of Steel Structures in Seismic Areas is a comprehensive overview of recent developments in the field of seismic resistant steel structures. It comprises a collection of papers presented at the seventh International Specialty Conference STESSA 2012 (Santiago, Chile, 9-11 January 2012), and includes the state-of-the-art in both theore

Author: Yuli Huang
Publisher:
ISBN:
Category :
Languages : en
Pages : 438

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

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Author: T. Usami
Publisher: Elsevier
ISBN: 0080541623
Category : Technology & Engineering
Languages : en
Pages : 447

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The near-field earthquake which struck the Hanshin-Awaji area of Japan before dawn on January 17, 1995, in addition to snatching away the lives of more than 6,000 people, inflicted horrendous damage on the region's infrastructure, including the transportation, communication and lifeline supply network and, of course, on buildings, too. A year earlier, the San Fernando Valley area of California had been hit by another near-field quake, the Northridge Earthquake, which dealt a similarly destructive blow to local infrastructures. Following these two disasters, structural engineers and researchers around the world have been working vigorously to develop methods of design for the kind of structure that is capable of withstanding not only the far-field tectonic earthquakes planned for hitherto, but also the full impact of near-field earthquake.Of the observed types of earthquake damage to steel structures, there are some whose causes are well understood, but many others continue to present us with unresolved problems. To overcome these, it is now urgently necessary for specialists to come together and exchange information.The contents of this volume are selected from the Nagoya Colloquium proceedings will become an important part of the world literature on structural stability and ductility, and will prove a driving force in the development of future stability and ductility related research and design.

Author: Federal Emergency Agency
Publisher: FEMA
ISBN:
Category :
Languages : en
Pages : 11

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This report, FEMA-350 - Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings has been developed by the SAC Joint Venture under contract to the Federal Emergency Management Agency (FEMA) to provide organizations engaged in the development of consensus design standards and building code provisions with recommended criteria for the design and construction of new buildings incorporating moment-resisting steel frame construction to resist the effects of earthquakes. It is one of a series of companion publications addressing the issue of the seismic performance of steel moment-frame buildings. The set of companion publications includes: FEMA-350 - Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings. This publication provides recommended criteria, supplemental to FEMA-302 - 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, for the design and construction of steel moment-frame buildings and provides alternative performance-based design criteria. FEMA-351 - Recommended Seismic Evaluation and Upgrade Criteria for Existing Welded Steel Moment-Frame Buildings. This publication provides recommended methods to evaluate the probable performance of existing steel moment-frame buildings in future earthquakes and to retrofit these buildings for improved performance. FEMA-352 - Recommended Postearthquake Evaluation and Repair Criteria for Welded Steel Moment-Frame Buildings. This publication provides recommendations for performing postearthquake inspections to detect damage in steel moment-frame buildings following an earthquake, evaluating the damaged buildings to determine their safety in the postearthquake environment, and repairing damaged buildings. FEMA-353 - Recommended Specifications and Quality Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications. This publication provides recommended specifications for the fabrication and erection of steel moment frames for seismic applications. The recommended design criteria contained in the other companion documents are based on the material and workmanship standards contained in this document, which also includes discussion of the basis for the quality control and quality assurance criteria contained in the recommended specifications. The information contained in these recommended design criteria, hereinafter referred to as Recommended Criteria, is presented in the form of specific design and performance evaluation procedures together with supporting commentary explaining part of the basis for these recommendations.

Author: Barbara Gwynne Simpson
Publisher:
ISBN:
Category :
Languages : en
Pages : 298

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Steel braced frames are characteristically efficient seismic force-resisting systems. However, multi-story steel braced frames tend to concentrate demands in one or a few stories in response to severe ground shaking. Brace buckling and yielding results in a reduction in story strength and/or stiffness. Unless a mechanism exists to re-distribute the inelastic demands to other stories, demands tend to concentrate in the story where the inelastic response was initiated, indicative of story mechanism behavior. Research has identified the advantages of using pivoting seismic force-resisting systems, herein termed strongback-braced frames, to mitigate story mechanism behavior. Strongback-braced frames employ an essentially elastic truss, or “strongback”, that provides an explicit mechanism of re-distributing demands to adjacent stories. Yielding and energy dissipation is provided through inelastic actions, or fuses (e.g., through brace yielding/buckling and/or beam plastic hinging). Forces and moments developed in these fuses are transferred vertically to adjacent stories by the flexural stiffness and strength of the strongback. As such, strongback-braced frames are expected to result in more uniform drift distributions, reduced peak inelastic demands, and improved design flexibility compared to conventional seismic force-resisting systems. Despite being employed successfully in both research and practice, systematic assessment of the strongback’s behavior and practical design methods have not been developed or validated. Since the behavior of strongback systems is not characterized by the formation of story mechanisms, prior studies have found it difficult to proportion the elastic members in the strongback truss and have recognized detailing issues related to large deformation demands induced in the fuses. As such, a series of investigations were aimed at understanding the dynamic behavior and seismic performance of steel strongback-braced frames. Archetype designs were numerically analyzed to characterize the seismic demands in the strongback elements. A four-story strongback-braced frame was used to benchmark the dynamic behavior observed during nonlinear dynamic analysis. Improved numerical models were calibrated to more realistically simulate the buckling-restrained brace response and to characterize the modeling parameters influencing brace buckling and low-cycle fatigue. The FEMA P695 methodology was used to assess potential design methods based on collapse performance. Extensive parametric studies were carried out on strongback geometries with a range of bracing configurations, ground motion characteristics, and design alternatives. Higher mode effects were identified as the cause of substantial force amplification in the elastic strongback truss. Unlike typical yielding systems where force demands are limited by the capacity of the fuses in every mode, force demands in the strongback are characterized by a yielding first-mode “pivoting” and elastic higher-mode “bending” force demands. Since the strongback is designed to remain elastic in all modes, it can exhibit significant strength and stiffness in higher mode bending. Under the second and higher modes, the strongback truss remains elastic and continues to accumulate force demands after the fuses have yielded and as the ground shaking intensifies. These force demands in the strongback members can be significantly larger than those estimated per traditional capacity design assuming first mode-only demands. The addition of a strongback results in improved dynamic response from typical yielding systems, including a more uniform drift profile compared to reference buckling-restrained braced frames. Based on this research, this study proposes recommendations for the design, analysis, and modeling of strongback-braced frames. Simplified static methods to estimate the dynamic demands in the strongback truss are also proposed, including modal pushover and modal enveloping analysis methods.

Author: Eric Grusenmeyer
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Braced frames are a common seismic lateral force resisting system used in steel structures. Ordinary concentric braced frames (OCBFs) and special concentric braced frames (SCBFs) are two major types of frames. Brace layouts vary for both OCBFs and SCBFs. This report examines the inverted-V brace layout which is one common arrangement. OCBFs are designed to remain in the elastic range during the design extreme seismic event. As a result, OCBFs have relatively few special requirements for design. SCBFs are designed to enter the inelastic range during the design extreme seismic event while remaining elastic during minor earthquakes and in resisting wind loads. To achieve this, SCBFs must meet a variety of stringent design and detailing requirements to ensure robust seismic performance characterized by high levels of ductility. The design of steel seismic force resisting systems must comply with the requirements of the American Institute of Steel Construction's (AISC) Seismic Provisions for Structural Steel Buildings. Seismic loads are determined in accordance with the American Society of Engineers Minimum Design Loads for Buildings and Other Structures. Seismic loads are very difficult to predict as is the behavior of structures during a large seismic event. However, a properly designed and detailed steel structure can safely withstand the effects of an earthquake. This report examines a two-story office building in a region of moderately high seismic activity. The building is designed using OCBFs and SCBFs. This report presents the designs of both systems including the calculation of loads, the design of frame members, and the design and detailing of the connections. The purpose of this report is to examine the differences in design and detailing for the two braced frame systems.