Advances in Design of Eccentrically Braced Frames

1987 ◽  
Vol 3 (1) ◽  
pp. 43-55 ◽  
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 behavior 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 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 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.

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.

Behaviour of bolted link-column joints in eccentrically braced frames

1995 ◽  
Vol 22 (4) ◽  
pp. 745-754 ◽  
Author(s):  
T. Ramadan ◽  
A. Ghobarah
Keyword(s):  
Shear Force ◽  
Design Procedure ◽  
Experimental Program ◽  
Braced Frames ◽  
Eccentrically Braced Frames ◽  
End Plate ◽  
Column Joint ◽  
Extended End Plate ◽  
Plate Connections ◽  
Plate Connection

Current seismic provisions require that shear links in eccentrically braced frames be fully welded to the column flanges at the link-column joint. Since field welding may have its disadvantages, the use of bolted extended end-plate connection is examined. An experimental program is conducted to assess the response of extended end-plate connections of link-column joints in eccentrically braced frames. Six link-column joint specimens are tested using a cyclic load that represents the severe load reversals that the frame may be subjected to during strong earthquakes. The specimens are selected on the basis of different connection designs. Measurements of forces, strains, and displacements are made. Interaction curves relating the shear force and moment acting on links with semirigid connections are developed. The slip tendency and energy dissipation capacity of the different specimens are compared. On the basis of the test results, a design procedure is developed for the bolted extended end-plate link-column connection. It is concluded that bolted extended end-plate connections can be used for link-column joints of eccentrically braced frames. In properly designed connections bolt slippage was not measured even at high shear forces that are characteristic of link-column joint. Existing guidelines for the design of extended end-plate link-column joints are modified to account for the variable shear force and moment associated with links of different lengths. Key words: steel, frame, eccentric, braced, bolted, end plate, link, connection.

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 Retrofitting of Eccentrically Braced Frames by Rocking Walls and Viscous Dampers

2018 ◽  
Vol 763 ◽  
pp. 1105-1112 ◽  
Author(s):  
Francesca Barbagallo ◽  
Melina Bosco ◽  
Aurelio Ghersi ◽  
Edoardo Michele Marino ◽  
Pier Paolo Rossi
Keyword(s):  
Damping Ratio ◽  
Design Procedure ◽  
Seismic Retrofitting ◽  
Braced Frames ◽  
Viscous Dampers ◽  
Equivalent Viscous Damping ◽  
Eccentrically Braced Frames ◽  
Displacement Ductility ◽  
Displacement Capacity ◽  
Rocking Walls

A design procedure for seismic retrofitting of eccentrically braced frames (EBFs) by rocking walls and viscous dampers is proposed. The design procedure is founded on the displacement-based approach. The top displacement capacity of the building is evaluated based on the displacement ductility capacity of links and on a rigid lateral deformed configuration of the structure promoted by the rocking walls. The equivalent viscous damping ratio capacity of the EBFs with rocking walls is calculated by semi-empirical relationships specifically calibrated for EBFs with links characterized by mechanical length lower than 2.0. Additional damping is provided by linear viscous dampers. The design internal forces of the rocking walls are evaluated based on the seismic effects of more than one mode of vibration. The effectiveness of the design procedure is verified by means of a case study.

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 A Capacity Design Procedure for Columns of Steel Structures with Diagonals Braces

2014 ◽  
Vol 8 (1) ◽  
pp. 196-207 ◽  
Author(s):  
M. Bosco ◽  
A. Ghersi ◽  
E.M. Marino ◽  
P.P. Rossi
Keyword(s):  
Design Procedure ◽  
Steel Structures ◽  
Building Structures ◽  
Axial Deformation ◽  
Braced Frames ◽  
Capacity Design ◽  
Concentrically Braced Frames ◽  
Design Spectrum ◽  
Internal Forces ◽  
Seismic Forces

According to modern seismic codes, in concentrically braced frames the seismic input energy should be dissipated by means of the hysteretic behaviour of braces while all the other members (i.e. beams and columns) have to remain elastic. Accordingly, the design internal forces of braces are determined in these codes by elastic analysis of the structure subjected to seismic forces obtained by the design spectrum. The internal forces of the non-dissipative members, instead, are calculated by means of specified rules for the application of capacity design principles. According to some recent numerical analyses, the yielding or buckling of columns may take place before braces achieve their axial deformation capacity. This paper investigates the reasons of this unsatisfactory behaviour and proposes technological suggestions and a design procedure to improve the seismic performance of columns of building structures with diagonal braces.

CONSTRUCTING A DEMONSTRATION VEGETABLE GARDEN

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 671f-671
Author(s):  
M. Marutani ◽  
R. Quitugua ◽  
C. Simpson ◽  
R. Crisostomo
Keyword(s):  
Weed Control ◽  
Cultural Practices ◽  
Irrigation System ◽  
Agricultural Science ◽  
Drip Irrigation System ◽  
Vegetable Crops ◽  
University Campus ◽  
Crop Cover ◽  
Different Types ◽  
The University

A demonstration vegetable garden was constructed for students in elementary, middle and high schools to expose them to agricultural science. On Charter Day, a University-wide celebration, students were invited to the garden on the University campus. The purpose of this project was twofold: (1) for participants to learn how to make a garden and (2) for visitors to see a variety of available crops and cultural techniques. Approximately 30 vegetable crops were grown. The garden also presented some cultural practices to improve plant development, which included weed control by solarization, mulching, a drip irrigation system, staking, shading and crop cover. Different types of compost bins were shown and various nitrogen-fixing legumes were displayed as useful hedge plants for the garden.

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