Seismic analysis of links of various lengths in eccentrically braced frames

1991 ◽  
Vol 18 (1) ◽  
pp. 140-148 ◽  
Author(s):  
A. Ghobarah ◽  
T. Ramadan
Keyword(s):  
Seismic Analysis ◽  
Element Model ◽  
Elastic Stiffness ◽  
Lateral Loads ◽  
Braced Frames ◽  
Link Length ◽  
Eccentrically Braced Frames ◽  
Braced Frame ◽  
Shear Link ◽  
Inelastic Behaviour

Eccentrically braced steel frames have excellent elastic stiffness under moderate lateral loads and good ductility when subjected to severe seismic loading conditions. Under extreme loading, the inelastic behaviour is designed to be confined to a ductile link element. The behaviour of links of various lengths in eccentrically braced frames is evaluated using a finite element model. The link is subjected to extreme cyclic loading simulating a severe earthquake. The effect of the link length on its performance, capacity for energy dissipation, plastic mechanisms, and mode of failure are investigated. Measures for improving the performance of long links are examined. It was found that the most efficient link is the short shear link. However, the short link deformation is characterized by large angles of deformation, which may cause substantial damage to the nonstructural elements. On the other hand, long links were found to have smaller angles of deformation than short links, but with reduced ductility levels. An effective approach to improve the performance of long links is by increasing the flange thickness of the link section with the appropriate adjustment to the stiffener design. This technique can be applied to links of length up to 1.4 times the critical shear link length. Key words: steel, eccentric, braced, frame, link, seismic, ductility, design.

Seismic Performance of Eccentrically Braced Frames with Shear Link

2020 ◽  
Vol 35 ◽  
pp. 55-68
Author(s):  
Sara Ansari ◽  
Javad Tashakori ◽  
Javad Razzaghi
Keyword(s):  
Plastic Deformation ◽  
Seismic Performance ◽  
Braced Frames ◽  
Eccentrically Braced Frames ◽  
Braced Frame ◽  
Shear Link ◽  
Plastic Rotation ◽  
Eccentrically Braced Frame ◽  
Shear Links ◽  
Ultimate Limit

The push-over nonlinear evaluation of four eccentrically braced frame performance was conducted to assess the plastic deformation and location of plastic hinges in buildings with six, nine, twelve and fifteen stories. The excessive plastification of out-of-beam members is revealed in the majority of these buildings while the AISC design provision allows the moderate plastification in these members. Therefore, the beams out of link might be in danger of fracture of web and flange. Likewise, this was controversial evidence in Chrischurch earthquakes. In order to modify this problem either using fixed connection of braced members or using the very short shear links which have less end moment force than out-of-link beams moment strength are recommended. By this modification, the response modification coefficients are calculated for these buildings which are almost equal to the provision value. The maximum plastic rotation of shear links recommended by provisions (0.08 radian) is the upper ultimate limit to prevent emerging of out-of-link member`s instability.

Seismic Response of Composite Eccentrically Braced Frames with Short Dissipative Element

2018 ◽  
Vol 763 ◽  
pp. 846-853
Author(s):  
Adina Vătăman ◽  
Adrian Ciutina ◽  
Daniel Grecea
Keyword(s):  
Structural Integrity ◽  
Concrete Slab ◽  
Plastic Hinge ◽  
Bending Moment ◽  
Eurocode 8 ◽  
Lateral Loads ◽  
Braced Frames ◽  
Link Length ◽  
Eccentrically Braced Frames ◽  
Good Energy

Eccentrically braced frames (EBF) in steel and composite solution are very well suited structural assemblies for buildings in areas with high seismicity. Due to their good energy dissipation capacity, they can undergo important lateral deformations by plastic hinge formation in the dissipative element (link element) without impacting the structural integrity of the system. The dissipative link elements can be short, medium or long (according to modern design norms, such as Eurocode 8), based on the ratio between shear force and bending moment. If the dissipative element length is smaller than 1.6(Mpl/Vpl) [mm], it is considered to be a short element and is predominantly subjected to shear. The links can be realized on steel solutions or composite with the concrete slab. However, the steel behavior is assumed for composite link. The current article presents the results of extensive numerical testing based on experimental results on the behavior of composite EBF with short link elements subjected to seismic-like lateral loads. The results will present the main differences in strength, stiffness and ductility between the responses of steel and composite EBFs. Finally, a parametrical study will show the influence of link length, influence of number of stiffeners and of the web slenderness.

scholarly journals Advances in design of eccentrically braced frames

1987 ◽  
Vol 20 (1) ◽  
pp. 22-29 ◽  
Author(s):  
Egor P. Popov ◽  
Kazuhiko Kasai ◽  
Michael D. Engelhardt
Keyword(s):  
Design Procedure ◽  
Preliminary Design ◽  
Braced Frames ◽  
Link Length ◽  
Eccentrically Braced Frames ◽  
Short Beam ◽  
Different Types ◽  
Proper Design ◽  
Seismic Forces ◽  
The University

Eccentrically Braced Frames (EBFs) have attained recognized status as a viable structural steel system for resisting lateral seismic forces. Sustained research at the University of California, Berkeley, since 1977 and numerous field applications provide a
good database for their proper design. In this paper the different types of EBF are critically evaluated, and the kinematics of their inelastic deformation are examined with particular reference to the behaviour of isolated short beam segments or links. Desirable link length and web stiffening are recommended. A preliminary design procedure for hand-calculation of EBFs is described and some suggestions for brace connection details are advanced.

scholarly journals An Alternative System for Eccentrically Braced Frames Resisting Lateral Loads

2019 ◽  
Vol 9 (3) ◽  
pp. 4281-4286
Author(s):  
N. W. Bishay-Girges
Keyword(s):  
Energy Dissipation ◽  
Steel Frames ◽  
Structural Safety ◽  
Lateral Loads ◽  
Braced Frames ◽  
Moment Frames ◽  
Lateral Control ◽  
Eccentrically Braced Frames ◽  
Architectural Features ◽  
Control Devices

Eccentrically braced steel frames are structures used to resist lateral loads as they combine the ductility that is characteristic of moment frames and the stiffness associated with braced frames. Damper devices can be used as the main source of energy dissipation and have become more popular lately for the lateral control of structures. Control devices generally reduce damage by increasing structural safety, serviceability and preventing the building from collapse during vibration. This study focused on improving the performance of the structures with a proposed damping system, which has more advantages than eccentrically braced frames (EBFs). It can accommodate many architectural features and make construction and complementarity in the structures easier. The purpose of this study is to evaluate the performance of the structure with the proposed damping system and its construction in the building.

On Design of Eccentrically Braced Frames

1989 ◽  
Vol 5 (3) ◽  
pp. 495-511 ◽  
Author(s):  
Michael D. Engelhardt ◽  
Egor P. Popov
Keyword(s):  
Current Practice ◽  
Specific Reference ◽  
Braced Frames ◽  
Steel Buildings ◽  
Capacity Design ◽  
Link Length ◽  
Eccentrically Braced Frames ◽  
Overall Design ◽  
Design Requirements ◽  
Code Format

Seismic-resistant Eccentrically Braced Frames (EBFs) are becoming a widely used lateral resisting system for steel buildings, with even wider application anticipated as design requirements are put into building code format. This paper addresses a number of EBF design issues, which in the opinion of the authors are inadequately considered either in current practice or in the emerging code provisions. The overall design philosophy for EBFs is reviewed, with specific reference to the concept of “Capacity Design”. Application of capacity design principles assures that yielding will be restricted primarily to the ductile link elements, an important goal of EBF design. Further, through careful choice of frame geometry and link length at the preliminary stages, many potential design difficulties can be avoided. The paper also presents some important observations from experimental work currently underway on EBFs with long, flexural yielding links.

scholarly journals Validation of a Design Procedure for Failure Mode Control of EB-Frames: Push-Over and IDA Analyses

2013 ◽  
Vol 7 (1) ◽  
pp. 193-207 ◽  
Author(s):  
Luigi Mastrandrea ◽  
Elide Nastri ◽  
Vincenzo Piluso
Keyword(s):  
Seismic Response ◽  
Failure Mode ◽  
Design Procedure ◽  
High Energy ◽  
Collapse Mechanism ◽  
Braced Frames ◽  
Link Length ◽  
Eccentrically Braced Frames ◽  
Ductility Demand ◽  
Global Type

The paper is devoted to the investigation of the seismic response of eccentrically braced frames characterised by links having different length. In addition, the analysed structures have been designed according to a methodology, already proposed by the authors, aiming to guarantee a collapse mechanism of global type. Therefore, the results of the nonlinear analyses herein presented provide the validation of the proposed design procedure, by testifying that all the designed structures exhibit a global failure mode where all the links are yielded while all the columns remain in elastic range with the exception of the base section of first storey columns, leading to high energy dissipation capacity and global ductility. Furthermore, two different distributions of the link lengths are examined. The first one is characterised by short links with uniform lengths along the height of the structure. The second one is characterised by the use of link elements having different length at the different storeys which are selected to assure the same value of the non-dimensional link length. The seismic response of EB-Frames with such distributions of the link length is investigated by means of both push-over analyses and dynamic non-linear analyses. The comparison of the performances is mainly carried out in terms of plastic hinges distribution, local ductility demand and frame lateral stiffness.

Resisting Seismic Behavior Study of an Adding Cover-Plate Protocol Used For D-Type Eccentrically Braced Steel Frames

2010 ◽  
Vol 163-167 ◽  
pp. 567-575 ◽  
Author(s):  
Xiu Zhen Pan ◽  
Ji Ping Hao ◽  
Jie Gao
Keyword(s):  
Seismic Behavior ◽  
Cover Plate ◽  
Lateral Loads ◽  
Braced Frames ◽  
Eccentrically Braced Frames ◽  
Earthquake Energy ◽  
Behavior Study ◽  
Scale Ratio ◽  
New Type ◽  
Rare Earthquake

This paper suggests a new connection protocol, adding cover-plate between shear links and column, which was used to enhance moment and shear carrying capacity of beam, relax the restriction and assure the sufficiency development of plastic deformation of the link, and dissipate more earthquake energy. Considering the scale ratio of 1:3, the experimental data was achieved by a specimen under cyclic loading, which was verified by nonlinear finite element analyses. Results indicate that the new type of eccentrically braced steel frame have enough stiffness and deformation capacity, draw link away from flange of column, and dissipate more earthquake energy. The single diagonal eccentrically braced frames adopted adding cover-plate protocol will ensure sufficient lateral stiffness under ordinary circumstances, including lateral loads due to wind and moderate seismic disturbances, have preferable resisting seismic behavior under rare earthquake, and be so practical and costly that it can be easily applied in present project.

Experimental Testing and Design of High Performance Shear Links for Eccentrically Braced Frames

2018 ◽  
Vol 763 ◽  
pp. 384-393 ◽  
Author(s):  
Dimitry Volynkin-Ewens ◽  
George Charles Clifton ◽  
Peter Dusicka
Keyword(s):  
Cross Sections ◽  
High Performance ◽  
Experimental Testing ◽  
Past Research ◽  
Braced Frames ◽  
Eccentrically Braced Frames ◽  
Shear Link ◽  
Aspect Ratios ◽  
Shear Links ◽  
Incoming Energy

Steel links inside Eccentrically Braced Frames (EBFs) can be classified as either short, intermediate or long. The more commonly used short links yield primarily in shear and dissipate incoming energy inside the web of the link. Advances in shear link research and industry practice, particularly the increased use of bolted links, have allowed greater freedom in the design of the link section, as the section used can be decoupled from the collector beam section. Seven shear link specimens were tested inside a full scale EBF set up, and were subjected to AISC’s 2005 shear link loading protocol. Increasing levels of rotation were applied to links of varied cross-sections and intermediate stiffener spacings. Links with low web aspect ratios performed to a higher rotation than past research would have suggested, and when intermediate stiffeners were removed, they performed to an even higher rotation. Recommendations for design are presented, including a relaxation of the stiffener spacing equations when web aspect ratio criteria are met. A provision is also included to allow greater rotational ductilities in EBF frames with low web aspect shear links.

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