Fundamental Periods of Vibration of Braced Steel Frames for Seismic Design

2005 ◽  
Vol 21 (3) ◽  
pp. 833-860 ◽  
Author(s):  
Robert Tremblay
Keyword(s):  
Lower Bound ◽  
Seismic Hazard ◽  
Seismic Design ◽  
Analytical Study ◽  
Steel Frames ◽  
Simple Expression ◽  
Soil Conditions ◽  
Concentrically Braced ◽  
Period Solution ◽  
Hazard Levels

An analytical study is performed to propose a simple expression for the fundamental period of vibration of concentrically braced steel frames. This work was carried out in the context of the development of the 2005 National Building Code of Canada (NBCC) and is mainly applicable to structures located in moderate and low seismic regions. Available field and test measurements of building periods are compared to analytical predictions. An empirical period formula is developed based on a survey of analytically computed building periods published in the literature. The influence of the 2005 NBCC design provisions on braced steel-frame periods is examined through a closed-form period solution and an extensive parametric study. Building periods are found to vary significantly with seismic hazard levels and soil conditions. An expression is tentatively proposed that provides reasonable lower-bound period estimates for most situations in Canada.

Code provisions for seismic design for concentrically braced steel frames

1992 ◽  
Vol 19 (6) ◽  
pp. 1025-1031 ◽  
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.

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

2017 ◽  
Vol 11 (1) ◽  
pp. 485-495 ◽  
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.

Up-to-Date of Seismic Design Spectrum for Offshore Platforms at the Bay of Campeche

2003 ◽  
Author(s):  
Joel A. Garci´a Vargas ◽  
Roberto Pe´rez Marti´nez
Keyword(s):  
Seismic Hazard ◽  
Seismic Design ◽  
Soil Conditions ◽  
Reserve Capacity ◽  
Seismic Action ◽  
Offshore Platforms ◽  
Local Conditions ◽  
Design Spectrum ◽  
Earthquake Sources ◽  
Local Soil

This paper presents the procedure proposed by the ISO code adapted to the local conditions in the Bay of Campeche, Mexico in order to obtain design spectrum for different seismic reserve capacity factors. A probabilistic seismic hazard analyses is used in order to determine the uniform hazard spectrum where the seismic environment, according to previous researches, is influenced by three primary types of earthquake sources: the subduction zone on the western pacific coast of Mexico, the lithospheric slab within the central portion of Mexico and the trans-mexican volcanic belt. This earthquake spatial distribution can be shown trough the historic catalog of earthquake occurrences during the period 1900–2001 used. On the one hand, in the evaluation of the characteristics and the uncertainties associated with the earthquake sources and their effects on the interest sites, are taken into account the characterization of the earthquake sources, the effect of the seismic wave propagation, the local conditions and the soil-structure interaction developed during earthquake ground motions. On the other hand, the uncertainties on the seismic hazard curve and those associated with the platform behavior (mass, stiffness, damping) in which their values are assigned to be consistent with the ISO 19901-2 and ISO 19902 seismic code suggestions. The final result consists in a seismic design spectrum for offshore platforms at the Bay of Campeche, which are consistent with the recommended ISO 19902 seismic reserve capacity factors, modified for local soil conditions, following a detailed seismic-action procedure.

scholarly journals On California Structural Steel Seismic Design

1986 ◽  
Vol 2 (4) ◽  
pp. 703-727 ◽  
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.

scholarly journals On California structural steel seismic design

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.

Experimental Study on Steel Frames Infilled with Sandwich Composite Panels

2011 ◽  
Vol 243-249 ◽  
pp. 499-505
Author(s):  
Can Xing Qiu ◽  
He Tao Hou ◽  
Wei Long Liu ◽  
Ming Lei Wu
Keyword(s):  
Seismic Design ◽  
Steel Frames ◽  
Strength Degradation ◽  
Hysteretic Behavior ◽  
Sandwich Composite ◽  
Viscous Damping ◽  
Test Results ◽  
Ductility Index ◽  
Damage Process ◽  
Seismic Behaviors

A model of full scale one-bay, one storey was tested under low cyclic loading in order to study the hysteretic behavior of steel frames with sandwich composite (SC) panels. According to the failure pattern and damage process of test specimen, seismic behaviors were evaluated. Hysterics loops, skeleton curves, curves of strength degradation, and curves of stiffness degradation, ductility index and viscous damping coefficient were analyzed. Test results show that the failures of panels mainly occurred around the embedded parts, but compared with traditional panels and walls, SC panels exhibit a better integration. The connection between panel and steel frame is vital to the mutual work of the two parts. Finally, seismic design recommendations based on the analysis of ductility index and energy dissipation of the structures are presented.

scholarly journals Seismic Hazard Assessment for the Tianshui Urban Area, Gansu Province, China

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Zhenming Wang ◽  
David T. Butler ◽  
Edward W. Woolery ◽  
Lanmin Wang
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Seismic Design ◽  
Hazard Analysis ◽  
Seismic Hazard Assessment ◽  
Gansu Province ◽  
Mitigation Measures ◽  
Peak Ground Velocity ◽  
Ground Acceleration ◽  
Acceleration Time Histories

A scenario seismic hazard analysis was performed for the city of Tianshui. The scenario hazard analysis utilized the best available geologic and seismological information as well as composite source model (i.e., ground motion simulation) to derive ground motion hazards in terms of acceleration time histories, peak values (e.g., peak ground acceleration and peak ground velocity), and response spectra. This study confirms that Tianshui is facing significant seismic hazard, and certain mitigation measures, such as better seismic design for buildings and other structures, should be developed and implemented. This study shows that PGA of 0.3 g (equivalent to Chinese intensity VIII) should be considered for seismic design of general building and PGA of 0.4 g (equivalent to Chinese intensity IX) for seismic design of critical facility in Tianshui.

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