On California Structural Steel Seismic Design

A number of new code developments, largely initiated in California, are taking place in the USA for the seismic design of steel structures. The principal ones are reviewed and commented upon in the paper. Key experimental support for some of the changes is indicated. Major attention is directed to the three main types of steel construction: moment-resisting frames, concentrically braced steel frames, and, the relatively new method for seismic design, eccentric bracing. Some of the proposed and possible practical improvements in moment-resisting connections are given; the reasons for some concern over the use of concentrically braced frames for severe seismic applications are discussed; and a brief overview on the application of eccentrically braced steel frames is presented. The paper concludes with a few remarks on future trends and needs in structural steel seismic design.

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On California structural steel seismic design

Bulletin of the New Zealand Society for Earthquake Engineering ◽

10.5459/bnzsee.20.1.7-21 ◽

1987 ◽

Vol 20 (1) ◽

pp. 7-21

Author(s):

Egor P. Popov

Keyword(s):

Structural Steel ◽

Seismic Design ◽

Steel Frames ◽

Steel Structures ◽

Concentrically Braced Frames ◽

Concentrically Braced ◽

Moment Resisting ◽

The Usa ◽

Major Attention ◽

Eccentric Bracing

A number of new code developments, largely initiated in California, are taking place in the USA for the seismic design of steel structures.  The principal ones are reviewed and commented upon in the paper. Key experimental support for some of the changes is indicated. Major attention is directed to the three main types of steel construction: moment resisting frames, concentrically braced steel frames, and, the relatively new method for seismic design, eccentric bracing. Some of the proposed and possible practical improvements in moment-resisting connections are given: the reasons for some concern over the use of concentrically braced frames for severe seismic applications are discussed; and a brief overview on the application of eccentrically braced steel frames is presented. The paper concludes with a few remarks on future trends and needs in structural steel seismic design.

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Seismic design of steel buildings: lessons from the 1995 Hyogo-ken Nanbu earthquake

Canadian Journal of Civil Engineering ◽

10.1139/l96-885 ◽

1996 ◽

Vol 23 (3) ◽

pp. 727-756 ◽

Cited By ~ 69

Author(s):

Robert Tremblay ◽

Andre Filiatrault ◽

Michel Bruneau ◽

Masayoshi Nakashima ◽

Helmut G. L. Prion ◽

...

Keyword(s):

Seismic Design ◽

Steel Structures ◽

Structural Systems ◽

Braced Frames ◽

Steel Buildings ◽

Concentrically Braced Frames ◽

Framed Structures ◽

Concentrically Braced ◽

Moment Resisting ◽

Column Bases

Past and current seismic design provisions for steel structures in Japan are presented and compared with Canadian requirements. The performance of steel framed structures during the January 17, 1995, Hyogo-ken Nanbu earthquake is described. Numerous failures and examples of inadequate behaviour could be observed in buildings of various ages, sizes, and heights, and braced with different structural systems. In moment resisting frames, the damage included failures of beams, columns, beam-to-column connections, and column bases. Fracture of bracing members or their connections was found in concentrically braced frames. The adequacy of the current Canadian seismic design provisions is examined in view of the observations made. Key words: earthquake, seismic design, steel structures.

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Performance of steel structures during the 1994 Northridge earthquake

Canadian Journal of Civil Engineering ◽

10.1139/l95-046 ◽

1995 ◽

Vol 22 (2) ◽

pp. 338-360 ◽

Cited By ~ 113

Author(s):

Robert Tremblay ◽

André Filiatrault ◽

Peter Timler ◽

Michel Bruneau

Keyword(s):

Current Knowledge ◽

Steel Frames ◽

Steel Structures ◽

Northridge Earthquake ◽

Braced Frames ◽

Concentrically Braced Frames ◽

Load Paths ◽

Concentrically Braced ◽

Moment Resisting ◽

Observed Damage

The performance of concentrically braced steel frames and moment resisting steel frames during the January 17, 1994, Northridge, California, earthquake is examined. Most of the observations made during the reconnaissance visits confirmed the current knowledge on the inelastic response of these structural systems. This permits the anticipation of proper seismic behavior for buildings designed according to the seismic provisions that have been recently introduced in the Canadian building code and standard for steel structures. In some cases, however, the observed damage raised concerns that should be addressed in future investigations or next editions of these codes. Preventing potentially hazardous nonstructural damage, avoiding premature nonductile failures anywhere along the lateral load paths, limiting structural and nonstructural damage due to brace buckling, and accounting for the vertical ground motion are among those issues. Key words: earthquake, seismic, steel, concentrically braced frames, moment resisting frames, weld.

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Code provisions for seismic design for concentrically braced steel frames

Canadian Journal of Civil Engineering ◽

10.1139/l92-122 ◽

1992 ◽

Vol 19 (6) ◽

pp. 1025-1031 ◽

Cited By ~ 4

Author(s):

R. G. Redwood ◽

A. K. Jain

Keyword(s):

Seismic Design ◽

Structural Engineering ◽

Steel Frames ◽

Braced Frames ◽

Concentrically Braced Frames ◽

Braced Frame ◽

Concentrically Braced ◽

Interstorey Drift ◽

Available Information ◽

Steel Braced Frame

Extensive research into the inelastic seismic response of concentrically braced frames and their components has been carried out in the last two decades. This knowledge has now been incorporated into seismic design practice in several countries, notably the U.S.A., Canada, and New Zealand. In this paper, design specifications from these three countries, which derive largely from the same body of research, are compared. The basic design philosophy for concentrically braced steel frames, loading, and member detailing are examined. It is concluded that, in general, the Canadian specifications are in conformity with the available information and have many similar features to codes of the other countries. Significant differences exist in the classification of braced frames, between interstorey drift requirements, in the treatment of dual structural systems, and to a lesser extent in member detailing requirements. Some features of Canadian codes meriting review are identified. Key words: structural engineering, earthquakes, standards, steel, braced frame, ductility, concentric bracing, dual system.

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Steel structures damage from the Christchurch earthquake series of 2010 and 2011

Bulletin of the New Zealand Society for Earthquake Engineering ◽

10.5459/bnzsee.44.4.297-318 ◽

2011 ◽

Vol 44 (4) ◽

pp. 297-318 ◽

Cited By ~ 34

Author(s):

Charles Clifton ◽

Michel Bruneau ◽

Greg MacRae ◽

Roberto Leon ◽

Alistair Fussell

Keyword(s):

Steel Structures ◽

Braced Frames ◽

Concentrically Braced Frames ◽

Eccentrically Braced Frames ◽

Satisfactory Performance ◽

Concentrically Braced ◽

Earthquake Series ◽

Moment Resisting ◽

Industrial Storage ◽

Storage Racks

This paper presents preliminary field observations on the performance of selected steel structures in Christchurch during the earthquake series of 2010 to 2011. This comprises 6 damaging earthquakes, on 4 September and 26 December 2010, February 22, June 6 and two on June 13, 2011. Most notable of these was the 4 September event, at Ms7.1 and MM7 (MM as observed in the Christchurch CBD) and most intense was the 22 February event at Ms6.3 and MM9-10 within the CBD. Focus is on performance of concentrically braced frames, eccentrically braced frames, moment resisting frames and industrial storage racks. With a few notable exceptions, steel structures performed well during this earthquake series, to the extent that inelastic deformations were less than what would have been expected given the severity of the recorded strong motions. Some hypotheses are formulated to explain this satisfactory performance.

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Seismic Behavior of Concentrically Braced Steel Frames with Out-of-Plane Offset Irregularity

The Open Civil Engineering Journal ◽

10.2174/1874149501711010485 ◽

2017 ◽

Vol 11 (1) ◽

pp. 485-495 ◽

Cited By ~ 1

Author(s):

Amin Mohebkhah ◽

Marzieh Akefi

Keyword(s):

Seismic Design ◽

Seismic Behavior ◽

Steel Frames ◽

Design Parameters ◽

Braced Frames ◽

Concentrically Braced Frames ◽

Overstrength Factor ◽

Concentrically Braced ◽

Out Of Plane ◽

Story Drift

Braced steel frames are sometimes designed with out-of-plane shifted bracing members on the first story due to architectural or functional considerations. Such frames are classified and designated as frames having the Type-4 horizontal structural irregularity entitled “frames with out-of-plane offset irregularity” as per theMinimum Design Loads for Building and Other Structures(ASCE 7-10). The purpose of this study is to investigate the nonlinear seismic behavior of ordinary steel concentrically braced frames with out-of-plane offset irregularity and evaluate their seismic design parameters. To this end, two 3-story and 6-story three-dimensional ordinary concentrically braced frames (OCBFs) with and without out-of-plane offset of one of the vertical elements on the first story were considered (i.e. irregular and regular configurations). The seismic design parameters considered in this study includes: frame overall overstrength factor, column overstrength factor and the inelastic dynamic inter-story drift demands. Nonlinear time-history dynamic analysis of the frames showed that overall overstrength factor of the low- and mid-rise irregular frames studied in this research is lower than that of the regular ones. Moreover, it was found that theSeismic Provisionsprescribed overstrength factor (i.e. Ωo=2.0) to amplify columns axial seismic forces in OCBFs is not conservative for the studied regular frames’ columns as well as the columns in the vicinity of the shifted bracing members on the first story of the irregular frames. Also, it was shown that the studied low- and mid-rise regular and irregular concentrically braced frames experience greater inter-story drift demands than predicted by the amplified elastic analysis proposed in the codes.

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Accounting for overstrength in seismic design of steel structures

Canadian Journal of Civil Engineering ◽

10.1139/l97-045 ◽

1998 ◽

Vol 25 (1) ◽

pp. 1-15 ◽

Cited By ~ 18

Author(s):

M A Rahgozar ◽

J L Humar

Keyword(s):

Seismic Design ◽

Slenderness Ratio ◽

Steel Structures ◽

Building Structures ◽

Braced Frames ◽

Concentrically Braced Frames ◽

Moment Resisting Frames ◽

Moment Resisting ◽

Design Loads ◽

Reserve Strength

Observations during many earthquakes have shown that building structures are able to sustain without damage earthquake forces considerably larger than those they were designed for. This is explained by the presence in such structures of significant reserve strength not accounted for in design. Relying on such overstrength, many seismic codes permit a reduction in design loads. The possible sources of reserve strength are outlined in this paper, and it is reasoned that a more rational basis for design would be to account for such sources in assessing the capacity rather than in reducing the design loads. As an exception, one possible source of reserve strength, the redistribution of internal forces, may be used in scaling down the design forces. This is because such scaling allows the determination of design forces through an elastic analysis rather than through a limit analysis. To assess the extent of reserve strength attributable to redistribution, steel building structures having moment-resisting frames or concentrically braced frames and from 2 to 30 storeys in height are analyzed for their response to lateral loading. A static nonlinear push-over analysis is used in which the gravity loads are held constant while the earthquake forces are gradually increased until a mechanism forms or the specified limit on interstorey drift is exceeded. It is noted that in moment-resisting frames the reserve strength reduces with an increase in the number of storeys as well as in the level of design earthquake forces. The P→Δ effect causes a further reduction. In structures having braced frames the main parameter controlling the reserve strength is the slenderness ratio of the bracing members. In these structures, reserve strength is almost independent of both the height of the structure and the effect of building sway. Key words: seismic design, overstrength factor, reserve strength owing to redistribution, steel moment-resisting frames, steel-braced frames, push-over analysis.

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