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Ductility criteria for steel structures
J. Construct. Steel Res. Vol. 46, Nos. 1-3. pp. 4434, paper number 220 1998 01998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0143-974X/98 $19.00 + 0.00 PII: SO143-974X(98)00142-9 ELSEVIER
Ductility Criteria for Steel Structures V. Gioncu Department of Architecture, Politechnica University Timisoara, str. Traian Lalescu 2, 1900 Timisoara, Romania Paper Number 220 Full paper on enclosed CD-ROM
The application of capacity design principles in seismic analysis is based on the occurrence of a global plastic mechanism, characterized by the presence of a sufficient number of plastic hinges to assure the dissipation of a required quantity of seismic energy. The assurance of a good structural behaviour requires the verification of ductility capacity of these plastic hinges which must be greater than the required ductility:
D, - L
D,
Ym
where D, is the available ductility, determined from the local ductility of plastic hinges, D,, the required ductility, determined from the global ductility of full structure, Ye, partial safety factor. The purpose of this paper is to review the factor influencing the required and available ductilities, and the correlation between these two behaviour parameters. Global ductility depends on ground motions (source characteristics, distance from source, site characteristics), and on structure response (foundations, structure systems, non-structural elements). From the analysis of these factors the required ductility results. Local ductility is function on elements (material properties, cross-sections, members) and joints (panel zones, column flanges, connections). The available ductility results. The influence of all these parameters on the ductility demands is discussed in the paper. Relation between local and global ductilities, exact and simplified methods for determining these ductilities are also presented in the paper. The present codes for structural design are based on linear analysis, using the design spectra. Only direct checking for strength and stiffness is required, the ductility demands being ensured only by detailing rules. The paper shows that additional comprehensive and transparent methodology for direct control 443
444
V. Gioncu
of ductility must be developed, taking into account all the above parameters. This is an urgent task of specialists involved in the preparation of the new design codes for steel structures. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Available ductility, required ductility, global ductility, local ductility, earthquake, near and far field, global plastic mechanism, local plastic mechanism, joint plastic mechanism.
Ductility Criteria for Steel Structures V. Gioncu Department of Architecture, Politechnica University Timisoara, str. Traian Lalescu 2, 1900 Timisoara, Romania Paper Number 220 Full paper on enclosed CD-ROM
The application of capacity design principles in seismic analysis is based on the occurrence of a global plastic mechanism, characterized by the presence of a sufficient number of plastic hinges to assure the dissipation of a required quantity of seismic energy. The assurance of a good structural behaviour requires the verification of ductility capacity of these plastic hinges which must be greater than the required ductility:
D, - L
D,
Ym
where D, is the available ductility, determined from the local ductility of plastic hinges, D,, the required ductility, determined from the global ductility of full structure, Ye, partial safety factor. The purpose of this paper is to review the factor influencing the required and available ductilities, and the correlation between these two behaviour parameters. Global ductility depends on ground motions (source characteristics, distance from source, site characteristics), and on structure response (foundations, structure systems, non-structural elements). From the analysis of these factors the required ductility results. Local ductility is function on elements (material properties, cross-sections, members) and joints (panel zones, column flanges, connections). The available ductility results. The influence of all these parameters on the ductility demands is discussed in the paper. Relation between local and global ductilities, exact and simplified methods for determining these ductilities are also presented in the paper. The present codes for structural design are based on linear analysis, using the design spectra. Only direct checking for strength and stiffness is required, the ductility demands being ensured only by detailing rules. The paper shows that additional comprehensive and transparent methodology for direct control 443
444
V. Gioncu
of ductility must be developed, taking into account all the above parameters. This is an urgent task of specialists involved in the preparation of the new design codes for steel structures. 0 1998 Elsevier Science Ltd. All rights reserved
KEYWORDS
Available ductility, required ductility, global ductility, local ductility, earthquake, near and far field, global plastic mechanism, local plastic mechanism, joint plastic mechanism.