DESIGN CONSIDERATIONS FOR CflKGRGE EQUALIZATION OF AN

The Committee on Design of Steel Building Structures of the Committee on Metals of the Structural Division of ASCE of the Structural Engineering Institute of ASCE was formed in 1981 with the express purpose of studying prob-lems that are uniquely associated with the design of the overall structural steel building. Previous publications by this committee have been written to address specific design office problems that have not been addressed through con-certed efforts of research and development.As part of the continuing effort to bring useful informa-tion to the design community, the Committee on Design of Steel Building Structures recognized a need for a list of references covering a variety of subjects. Therefore, a com-pendium of selected, accurate, complete and available ref-erences on a wide variety of subjects regarding design of steel structures was assembled by collecting references that are used by the Committee members and their associates. The subjects were selected to cover a fairly wide range of subjects of interest to those practicing in a design office. The references were selected to be current, complete and easily available. As a general guideline, a maximum of three references were selected; hence some other very good references may not appear on the list. Therefore the absence of a reference from this list should not be taken as an unfavorable comment on that reference but rather a need to economize the listing.This list is offered to the design community as a useful reference. It is expected that publication of this list will inspire responses from the design community, including added suggestions for references. Readers of this article are invited to offer comments on this list. Future discussion will allow these comments to be brought forth. Comments should be addressed to:The Committee on Design of Steel Building Structures, Structural Engineering Institute, 1801 Alexander Bell Dr., Reston, VA 20191-4400 (email:sei@).Anchor Rods and Embedments•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 2, “Connections,”American Institute of Steel Construction (AISC), pp. 8-88,Chicago, Illinois, (1994).•Fisher, J. M., “Industrial Buildings: Roofs to Column Anchorage,” American Institute of Steel Construction(AISC) Steel Design Guide Series, No. 7, American Institute of Steel Construction (AISC), Chicago, Illinois, (1993).•DeWolf, J. T., and Ricker, D. T., “Column Base Plates,”American Institute of Steel Construction (AISC) SteelDesign Guide Series, No. 1, American Institute of SteelConstruction (AISC), Chicago, Illinois, (1990).Base Plates•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 2, “Connections,”American Institute of Steel Construction (AISC), pp. 11-54, Chicago, Illinois, (1994).•Manual of Steel Construction - Allowable Stress Design (ASD), Ninth Edition, American Institute of SteelConstruction (AISC), pp. 3-106 to 3-110, Chicago, Illinois, (1989).•DeWolf, J. T., and Ricker, D. T., “Column Base Plates,”American Institute of Steel Construction (AISC) SteelDesign Guide Series, No. 1, American Institute of SteelConstruction (AISC), Chicago, Illinois, (1990).Beams•Salmon, C. G., and Johnson, J. E., Steel Structures: Design and Behavior, Fourth Edition, Chapters 7-10, HarperCollins College Publishers, New York, New York, (1996).•Geschwindner, L. F., Disque, R. O., and Bjorhovde, R., Load and Resistance Factor Design of Steel Structures,Chapter 7, Prentice-Hall, Englewood Cliffs, New Jersey,(1994).Beam-Columns•Galambos, T. V., Ed., Guide to Stability Design Criteria for Metal Structures, Fourth Edition, Wiley-Interscience, NewYork, New York, (1988).Bearing Plates•Salmon, C. G., and Johnson, J. E., Steel Structures: Design and Behavior, Fourth Edition, Chapters 11 and 13, Harper Collins College Publishers, New York, New York, (1996). Bolts•“LRFD Specification for Structural Joints Using ASTM A325 and A490 Bolts,” Research Council on StructuralConnections, American Institute of Steel Construction(AISC), Chicago, Illinois, (1994).•Kulak, G. L., Fisher, J. W., and Struik, J. H. A., Guide toResource GuidesA Compendium of Steel References for the Design OfficeDesign Criteria for Bolted and Riveted Joints, SecondEdition, Wiley-Interscience, New York, New York, (1987).•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 2, “Connections,”American Institute of Steel Construction (AISC), Chicago,Illinois, (1994).Bracing•“Is Your Structure Suitably Braced?,” Structural Stability Research Council (SSRC), Lehigh University, Bethlehem,Pennsylvania, (1993).•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 2, “Connections,”American Institute of Steel Construction (AISC), Chapter7, (1994).•Nair, R. S., “Forces on Bracing Systems,” Engineering Journal, American Institute of Steel Construction (AISC),Vol. 29, No. 1, pp. 45, First Quarter, (1992). •Fisher, J. M., “The Importance of Tension Chord Bracing,” Engineering Journal, American Institute of Steel Construction (AISC), Vol. 20, No. 3, pp. 103-106, ThirdQuarter, (1983).•Lutz, L. A., and Fisher, J. M., “A Unified Approach For Stability Bracing Requirements,” Engineering Journal,American Institute of Steel Construction (AISC), Vol. 22,No. 4, pp. 163-167, Fourth Quarter, (1985). •Rongoe, J., “Design Guidelines for Continuous Beams Supporting Steel Joist Roof Structures,” National SteelConstruction Conference Proceedings, Phoenix, pp. 23.1-23.44, American Institute of Steel Construction (AISC),Chicago, Illinois, (1996).Buckling•Bleich, F., Buckling Strength of Metal Structures, McGraw-Hill Book Company, New York, (1952). •Galambos, T. V., Ed., Guide to Stability Design Criteria for Metal Structures, Fourth Edition, Wiley-Interscience, New York, New York, (1988).Cambering•Larson, J. W., and Huzzard, R. K., “Economical Use of Cambered Steel Beams,” National Steel ConstructionConference Proceedings, Kansas City, American Institute of Steel Construction (AISC), Chicago, Illinois, (1990).•Ricker, D. T., “Cambering Steel Beams,” Engineering Journal, American Institute of Steel Construction (AISC),Vol. 26, No. 4, pp. 136-142, Fourth Quarter, (1989). Cladding Supports•Fisher, J. M., and West, M. A., “Serviceability Design Considerations for Low Rise Buildings,” AmericanInstitute of Steel Construction (AISC) Steel Design GuideSeries, No. 3, American Institute of Steel Construction(AISC), Chicago, Illinois, (1990).Columns•Galambos, T. V., Ed., Guide to Stability Design Criteria for Metal Structure, Fourth Edition, Wiley-Interscience, NewYork, New York, (1988).•Geschwindner, L. F., Disque, R. O., and Bjorhovde, R., Load and Resistance Factor Design of Steel Structures,Chapter 6, Prentice-Hall, Englewood Cliffs, New Jersey,(1994).Cold Formed Steel Structures•Load and Resistance Factor Design (LRFD) Cold-Formed Steel Design Manual, American Iron and Steel Institute(AISI), Washington, D.C., (1991).•Yu, W. W., Cold-Formed Steel Design, Second Edition, Wiley-Interscience, New York, New York, (1991). Composite Construction•Salmon, C. G., and Johnson, J. E., Steel Structures, Design and Behavior, Fourth Edition, Chapter 16, Harper CollinsCollege Publishers, New York, New York, (1996). •Viest, I. M., Editor-in-Chief, Composite Construction Design for Buildings, McGraw-Hill/ASCE, New York, NewYork, (1997).•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 2, “Connections,”American Institute of Steel Construction (AISC), Chicago,Illinois, (1994).•Thornton, W. A., and Kane, T., “Connections,” Structural Steel Designers Handbook, Section 5, Brockenbrough, R.L. and Merritt, F. S., Eds., Second Edition, McGraw Hill,New York, (1994).Coped Beams•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 2, “Connections,”American Institute of Steel Construction (AISC), Chicago,Illinois, (1994).Crane Runways•Ricker, D. T., “Tips for Avoiding Crane RunwayProblems,” Engineering Journal, American Institute ofSteel Construction (AISC), Vol. 19, No. 4, pp. 181-205,Fourth Quarter, (1982).•Fisher, J. M., “Industrial Buildings: Roofs to Column Anchorage,” American Institute of Steel Construction(AISC) Steel Design Guide Series, No. 7, American Institute of Steel Construction (AISC), Chicago, Illinois, (1993). •“Guide for the Design and Construction of Mill Buildings,”Association of Iron and Steel Engineers (AISE) TechnicalReport, No. 13, Pittsburgh, Pennsylvania, (1991). Deflections•Fisher, J. M., and West, M. A., “Serviceability Design Considerations for Low Rise Buildings,” AmericanInstitute of Steel Construction (AISC)Steel Design GuideSeries, No. 3, American Institute of Steel Construction(AISC), Chicago, Illinois, (1990).•Ruddy, J. L., “Ponding of Concrete Floor Decks,”Engineering Journal, American Institute of SteelConstruction (AISC), Vol. 23, No. 3, pp. 107-115, ThirdQuarter, (1986).Diaphragms•Lutrell, L. D., Steel Deck Institute (SDI) Diaphragm Design Manual, Second Edition, Steel Deck Institute(SDI), (1990).Drift•“Wind Drift Design of Steel-Framed Buildings: State of the Art Report,” Task Committee on Drift Control of SteelBuilding Structures,Journal of Structural Engineering,American Society of Civil Engineers (ASCE), Vol. 114, No.9, pp. 2085-2108, September, (1988).•Fisher, J. M., and West, M. A., “Serviceability Design Considerations for Low Rise Buildings,” AmericanInstitute of Steel Construction (AISC) Steel Design GuideSeries, No. 3, American Institute of Steel Construction(AISC), Chicago, Illinois, (1990).Elevator Beams•Safety Code for Elevators and Escalators, ANSI/ASME A17.1, American National Standards Institute (ANSI) andAmerican Society of Mechanical Engineers (ASME), NewYork, New York, (1987).•“Compendium of Design Office Problems,” Committee on Design of Steel Building Structures, Journal of StructuralEngineering, American Society of Civil Engineers (ASCE),Vol. 118, No. 12, pp. 3444-3465, December, (1992). Erection•“Code of Standard Practice for Steel Buildings and Bridges,” American Institute of Steel Construction (AISC),Chicago, Illinois, (1992).•Fisher, J. M., and West, M. A., “Erection Bracing of Structural Steel Frames,” 1995 National EngineeringConference Proceedings, San Antonio, pp. 34.1-34.24,American Institute of Steel Construction (AISC), Chicago,Illinois, (1995).Expansion Joints•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 1, 1-13 to 1-14,American Institute of Steel Construction (AISC), Chicago,Illinois, (1994).•“Expansion Joints in Buildings”, Federal Construction Council Technical Report, No. 65, National Academy ofSciences, National Research Council, Washington, D.C.,(1974).Fatigue•Fisher J. W., Fatigue & Fracture in Steel Bridges, Wiley, New York, (1984).•Barsom, J. M., and Rolfe, S. T., Fracture and Fatigue Control in Structures, Second Edition, Prentice Hall,Englewood Cliffs, New Jersey, (1987).Fire Protection•Lie, T. T., “Structural Fire Protection,” American Society of Civil Engineers (ASCE) Practice Manual, No. 78, NewYork, New York, (1992).•Designing Fire Protection for Steel Beams, Subcommittee on Fire Technology of the Committee on ConstructionCodes and Standards, American Iron and Steel Institute(AISI), Washington, D.C., (1984).•Designing Fire Protection for Steel Columns, Subcommittee on Fire Technology of the Committee on ConstructionCodes and Standards, American Iron and Steel Institute(AISI), Third Edition, Washington, D.C.•Designing Fire Protection for Steel Trusses, Subcommittee on Fire Technology of the Committee on ConstructionCodes and Standards, American Iron and Steel Institute(AISI), Second Edition, Washington, D.C., (1981). Fracture Mechanics/Brittle Fracture•Barsom, J. M., and Rolfe, S. T., Fracture and Fatigue Control in Structures, Second Edition, Prentice Hall,Englewood Cliffs, New Jersey, (1987).Frame Stability•Timoshenko, S. P., and Gere, J. M., Theory of Elastic Stability, Second Edition, McGraw-Hill Book Company,Inc., New York, New York, (1961).•Galambos, T. V., Ed., Guide to Stability Design Criteria for Metal Structures, Fourth Edition, Wiley-Interscience, NewYork, New York, (1988).•Chen, W. F., and Toma, S., Advanced Analysis of SteelFrames Theory, Software and Applications, CRC Press,Boca Raton, Florida, (1994).Framing Systems•Fisher, J. M., West, M. A., and Van de Pas, J. P., Designing with Steel Joists,Joist Girders, Steel Deck, NUCORCorporation, Charlotte, North Carolina, (1991). •Englekirk, R., Steel Structures, Controlling Behavior Through Design, John Wiley & Sons, New York, New York, (1994).Grid Beam System•Elleby, H. A., “Automated Analysis of Grid Beam Systems.” Engineering Journal, American Institute of Steel Construction (AISC), Vol. 5, No. 3, pp. 123-127, ThirdQuarter, (1968).•Vukov, V., “Limit Analysis and Plastic Design of Grid Systems,” Engineering Journal, American Institute of Steel Construction (AISC), Vol. 23, No. 2, pp. 77-83, SecondQuarter, (1986)Heat Straightening•Avent, R. R., “Engineered Heat Straightening Comes of Age,” Modern Steel Construction, American Institute ofSteel Construction (AISC), Vol. 35, No. 2, pp. 32-39,February, (1995).•Avent, R. R., “Engineered Heat Straightening,” 1995 National Steel Construction Conference Proceedings, SanAntonio, pp. 2-1 to 2-18, American Institute of SteelConstruction (AISC), Chicago, Illinois, (1995). •Avent, R. R., “Heat Straightening: Fact and Fable,”Journal of Structural Engineering, American Society ofCivil Engineers (ASCE), Vol. 115, No. 11, pp. 2773-2793,November, (1989).Horizontally Curved Beams•Guide Specifications for Horizontally Curved Highway Bridges, American Association of State Highway andTransportation Officials, (AASHTO), Washington, D.C.,(1993).•Brookhart, G. C., “Circular-Arc I-Type Girders,”Journal of the Structural Division, American Society of CivilEngineers (ASCE), Vol. 93, ST6, pp. 133-159, December,(1967).Human Response to Floor Vibrations•Murray, T. M., “Building Floor Vibrations,”Engineering Journal, American Institute of Steel Construction (AISC),Vol. 28, No. 3, pp. 102-109, Third Quarter, (1991). Industrial Buildings•“Roof Framing with Cantilever Girders and Open Web Joists,” Canadian Institute of Steel Construction,Willowdale, Ontario, Canada, (1989).•Fisher, J. M., “Industrial Buildings: Roof to Column Anchorage,” American Institute of Steel Construction(AISC)Steel Design Guide Series, No. 7, (1993). •Guide for the Design and Construction of Mill Buildings, Association of Iron and Steel Engineers (AISE) TechnicalReport, No. 13, Pittsburgh, Pennsylvania, (1991). Inspection• A Guide to Engineering and Quality Criteria for Steel Structures, Fourth Edition, American Institute of SteelConstruction (AISC), Chicago, Illinois, (1997). •“Suggested Procedure for Inspecting and Upgrading Existing Structures,” Guide for the Design andConstruction of Mill Buildings, Association of Iron andSteel Engineers (AISE) Technical Report, No. 13,Supplement II, Pittsburgh, Pennsylvania, (1991). •Brock, D. S., and Sutcliffe, L. L., Jr., Field Inspection Handbook, McGraw-Hill, New York, (1986). Instantaneous Center of Rotation•Crawford, S. F., and Kulak, G. L., “Eccentrically Loaded Bolted Connections,” Journal of the Structural Division,American Society of Civil Engineers (ASCE), Vol. 97, No.ST3, pp. 765-784, March, (1971).Jumbo Shapes•Bjorhovde, R., “Solutions for the Use of Jumbo Shapes,”1988 National Steel Construction Conference Proceedings,Miami Beach, pp. 2.1-2.20, American Institute of SteelConstruction (AISC), Chicago, Illinois, (1988). •Fisher, J. W., and Pense, A. W., “Experience with Use of Heavy W-Shapes in Tension,” Engineering Journal,American Institute of Steel Construction (AISC), Vol. 24,No. 2, pp. 63-77, Second Quarter, (1987). •Barsom, J. M., “Material Considerations in Structural Steel Design,” Engineering Journal, American Institute of SteelConstruction (AISC), Vol. 24, No. 3, pp. 127-139, ThirdQuarter, (1987).Knee Braces•Vilas, H. K., and Surtees, J. O., “Analysis of Knee-Braced Portal Frames For Vertical Loading,” Engineering Journal, American Institute of Steel Construction (AISC), Vol. 20,No, 4, pp. 181-184, Fourth Quarter, (1983).•Vilas, H. K., and Surtees, J. O., “Analysis of Knee-braced Portal Frames For Vertical Loading: Part 2 - Columns ofUnequal Stiffness,” Engineering Journal, AmericanInstitute of Steel Construction (AISC), Vol. 21, No. 4, pp.223-226, Fourth Quarter, (1984).Lamellar Tearing•“Commentary on Highly Restrained Welded Connections,”Engineering Journal, American Institute of SteelConstruction (AISC), Vol. 10, No. 3, pp. 61-73, ThirdQuarter, (1973).•Thornton, C. H., “Quality Control in Design andSupervision Combine to Eliminate Lamellar Tearing,”Engineering Journal, American Institute of SteelConstruction (AISC), Vol. 10, No. 4, pp. 112-116, FourthQuarter, (1973).•Kloiber, L. A., “The Fabrication and Erection ofMinneapolis Convention Center,” Proceedings of theSessions Related to Steel Structures, Structures Congress?89, San Francisco, pp. 165-174, American Society of Civil Engineers (ASCE), Washington, D.C., (1989).Low Rise Buildings•Fisher, J. M., and West, M. A., “Serviceability Design Considerations for Low Rise Buildings,” AmericanInstitute of Steel Construction (AISC) Steel Design GuideSeries, No. 3, American Institute of Steel Construction(AISC), Chicago, Illinois, (1990).•Allison, H., “Low and Medium Rise Steel Buildings,”American Institute of Steel Construction (AISC) SteelDesign Guide Series, No. 5, (1991).Material Properties•Barsom, J. M., “Material Considerations in Structural Steel Design,” Engineering Journal, American Institute of SteelConstruction (AISC), Vol. 24, No. 3, pp. 127-139, ThirdQuarter, (1987).•Barsom, J. M., “Properties of Bridge Steels,” Highway Structural Design Handbook, Vol. 1, Chapter 3, AmericanInstitute of Steel Construction Marketing (AISCM),Chicago, Illinois, May, (1991).•Lankford, W. T., Samways, N. L., Craven, R. F., and McGannon, H. E., The Making, Shaping and Treating ofSteel, Tenth Edition, Association of Iron and SteelEngineers (AISE), Pittsburgh, Pennsylvania, (1985). •Geschwindner, L. F., Disque, R. O., and Bjorhovde, R., Load and Resistance Factor Design of Steel Structures,Chapter 4, Prentice-Hall, Englewood Cliffs, New Jersey,(1994).•Brockenbrough, R. L.,Material Properties, Chapter 1.2 in Constructional Steel Design - An International Guide,Dowling, P.J., Harding, J. E., and Bjorhovde, R., Eds.,Elsevier Applied Science, London, England, (1992). Metric Conversion•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Metric Conversion of the Second Edition,Vols. I and II, American Institute of Steel Construction(AISC), Chicago, Illinois, (1999).Mill Practices•Brockenbrough, R. L., Material Properties, Chapter 1.2 in Constructional Steel Design - An International Guide,Dowling, P.J., Harding, J. E., and Bjorhovde, R., Eds.,Elsevier Applied Science, London, England, (1992). •Manual of Steel Construction - Load and Resistance Factor Design (LRFD), Second Edition, American Institute ofSteel Construction (AISC), Chicago, Illinois, (1994).Old Steel Shapes•Ferris, H. W.,Iron and Steel Beams, 1873 - 1952, American Institute of Steel Construction (AISC), Chicago,Illinois, (1985).Painting•Volume 1, Good Painting Practice, Second Edition, Steel Structures Painting Council, Pittsburgh, Pennsylvania,(1982).•Volume 2, Systems & Specifications, Sixth Edition, Steel Structures Painting Council, Pittsburgh, Pennsylvania,(1991).Parking Garages•Troup, E. W. J., “Steel Frame Car Parks - New England Style,” Steel Construction Annual, New HampshireBusiness Review, Manchester, New Hampshire, (1989). Plastic Design•Plastic Design in Steel: A Guide and Commentary, Second Edition, American Society of Civil Engineers (ASCE) -Welding Research Council (WRC), New York, New York,(1971).•Disque, R. O., Applied Plastic Design in Steel, Van Nostrand Reinhold Company, New York, (1971). •Specification for Structural Steel Buildings - Allowable Stress Design and Plastic Design, American Institute ofSteel Construction (AISC), Chicago, Illinois, (1989). Plate Girders•Geschwindner, L. F., Disque, R. O., and Bjorhovde, R., Load and Resistance Factor Design of Steel Structures,Chapter 8, Prentice-Hall, Englewood Cliffs, New Jersey,(1994).•Salmon, C. G., and Johnson, J. E., Steel Structures: Design and Behavior, Fourth Edition, Chapter 11, Harper CollinsCollege Publishers, New York, New York, (1996). •Galambos, T. V., Lin, F. J., and Johnston, B. G., Basic Steel Design with Load and Resistance Factor Design(LRFD),Chapter 7, Prentice-Hall, Upper Saddle River, New Jersey, (1996).•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, Vol. 1, American Institute of Steel Construction (AISC), Chicago, Il, 1994. •Zahn, C. J., “Plate Girder Design Using Load and Resistance Factor Design (LRFD),” Engineering Journal,American Institute of Steel Construction (AISC), Vol. 24,No. 1, pp. 11-20, First Quarter, (1987).Plate Structures•“Design of Plate Structures,” Committee of Steel Plate Producers, American Iron and Steel Institute (AISI) withcooperation of Steel Plate Fabricators Association,Downers Grove, Illinois, (1979).Pre-engineered Metal Buildings•1996 Low Rise Building Systems Manual, Metal Building Manufacturers Association (MBMA), Cleveland, Ohio,(1996).•Guide Specifications for Producer Engineered Steel Building Systems, Metal Building ManufacturersAssociation (MBMA), Cleveland, Ohio, June, (1996). Prying Action•Thornton, W. A., “Prying Action - A General Treatment,”Engineering Journal, American Institute of SteelConstruction (AISC), Vol. 22, No. 2, pp. 67-76, SecondQuarter, (1985).•Kulak, G. L., Fisher, J. W., and Struik, J. H. A., Guide to Design Criteria for Bolted and Riveted Joints, SecondEdition, Wiley-Interscience, New York, New York, (1987). •Thornton, W. A., “Strength and Serviceability of Hanger Connections” Engineering Journal, American Institute ofSteel Construction (AISC), Vol. 29, No. 4, pp. 145-149,Fourth Quarter, (1992).•Manual of Steel Construction - Load and Resistance Factor Design(LRFD), Second Edition, American Institute ofSteel Construction (AISC), Chicago, Illinois, (1994). Riveted Joints•Kulak, G. L., Fisher, J. W., and Struik, J. H. A., Guide to Design Criteria for Bolted and Riveted Joints, SecondEdition, Wiley-Interscience, New York, New York, (1987). Repair, Rehabilitationand Restoration•Ricker, D. T., “Field Welding to Existing Steel Structures,”Engineering Journal, American Institute of SteelConstruction (AISC), Vol. 25, No. 1, pp. 1-16, FirstQuarter, (1988).Residual Stress•Galambos, T. V., Ed., Guide to Stability Design Criteria for Metal Structures, Fourth Edition, Wiley-Interscience, NewYork, New York, (1988).•Geschwindner, L. F., Disque, R. O., and Bjorhovde, R., Load and Resistance Factor Design of Steel Structures,Chapter 6, Prentice-Hall, Englewood Cliffs, New Jersey,(1994).Rivets•Kulak, G. L., Fisher, J. W., and Struik, J. H. A., Guide toDesign Criteria for Bolted and Riveted Joints, SecondEdition, Wiley-Interscience, New York, New York, (1987). Second Order Analysis•Chen, W. F., and Toma, S., Advanced Analysis of Steel Frames Theory Software & Application, CRC Press, BocaRaton, Florida, (1994).•Chen, W. F., and Sohal, I., Plastic Design and Second-Order Analysis of Steel Frames, Springer Verlag, NewYork, (1995).•Galambos, T. V., Ed., Guide to Stability Design Criteria for Metal Structures, Fourth Edition, Wiley-Interscience, NewYork, New York, (1988).Seismic Design•Recommended Lateral Force Requirements andCommentary, Structural Engineers Association ofCalifornia (SEAC), Sacramento, California, (1996). •Seismic Provisions for Structural Steel Buildings, American Institute of Steel Construction (AISC), Chicago, Illinois,(1992), with Supplement No. 1(1999).•NEHRP Recommended Provisions for Seismic Regulations for New Buildings, Federal Emergency ManagementAgency, Washington, D.C., (1994).•Popov, E. P., “U. S. Seismic Steel Codes,” Engineering Journal, American Institute of Steel Construction (AISC),Vol. 28, No. 3, pp. 119-128, Third Quarter, (1991). •Englekirk, R., Steel Structures Controlling Behavior Through Design, John Wiley & Sons, New York, New York, (1994).•Naeim, F., Ed.,The Seismic Design Handbook, Van Nostrand Reinhold Company, New York, New York,(1989).•Becker, R., Naeim, F., and Teal E. J., Seismic Design Practice for Steel Buildings, Structural Steel EducationCouncil, Moraga, California, (1988).Semi-Rigid Frames and Connections•Chen, W. F., and Toma S., Advanced Analysis of Steel Frames, CRC Press, Boca Raton, Florida, (1994). •Chen, W. F., Goto, Y., and Liew, J. Y. R., Stability Design of Semi-Rigid Frames, John Wiley & Sons, New York, NewYork, (1996).•Bjorhovde, R., Brozzetti, J., and Colson, A., Connections in Steel Structures, Elsevier Applied Science, London, (1988). •Bjorhovde, R., Colson, A., Haaijer, G. and Stark, J. W. B., Connections in Steel Structures II, American Institute ofSteel Construction (AISC), Chicago, Illinois, (1992). •Bjorhovde, R., Colson, A., and Zandonini, R., Connections in Steel Structures III, Pergamon/Elsevier Science, Oxford,England, (1996).Serviceability•Leon, R. T., “Serviceability Criteria for Load and Resistance Factor Design (LRFD) Composite Floors,” 1990 National Steel Construction Conference Proceedings,Kansas City, American Institute of Steel Construction(AISC), Chicago, Illinois, (1990).•Ellingwood, B. R., “Serviceability Guidelines for Steel Structures,” 1988 National Steel Construction ConferenceProceedings, Miami Beach, American Institute of SteelConstruction (AISC), Chicago, Illinois, (1988). •Fisher, J. M., and West, M. A., “Serviceability Design Considerations for Low Rise Buildings,” AmericanInstitute of Steel Construction (AISC) Steel Design Guide,No. 3, American Institute of Steel Construction (AISC),Chicago, Illinois, (1990).Stability•Nair, R. S., “Simple Solutions to Stability Problems in the Design Office,” 1988 National Steel ConstructionConference Proceedings, Miami Beach, American Instituteof Steel Construction (AISC), Chicago, Illinois, (1988). •Galambos, T. V., Ed., Guide to Stability Design Criteria for Metal Structures, Fourth Edition, Wiley-Interscience, New York, New York, (1988).•Timoshenko, S. P., and Gere, J. M., Theory of Elastic Stability, Second Edition, McGraw-Hill Book Company,New York, (1961).•Chen, W. F., and Lui, E. M., Structural Stability Theory and Implementation, Elsevier Applied Science, London,(1987).Staggered Truss Systems•“Staggered Truss Framing Systems For High Rise Buildings,” United States Steel (USS) Technical ReportADUSS 27-5227-02, Pittsburgh, Pennsylvania, (1972). Stainless Steel•ASCE Specification for the Design of Stainless Steel Cold-Formed Structural Members, American Society of CivilEngineers (ASCE) Standard No. ASCE-8-90. •Pickering, F. B., Ed., The Metallurgical Evolution of Stainless Steels, American Society for Metals, Metals Park, Ohio, (1979).Stairs•Metal Stairs Manual, Fifth Edition, National Association of Architectural Metal Manufacturers, Chicago, Illinois,(1992)•Stock Components for Architectural Metal Work, Catalog 16, Julius Blum & Company, Carlstadt, New Jersey, (1995-1999).•Code of Federal Regulation, Title 29, Part 1926,Paragraphs 1926.500, 1926.1052, 1926.1053, U.S.Government Printing Office, Washington D.C., (1994). Steel Deck•Design Manual for Composite Decks, Form Decks Roof Decks, and Cellular Metal Floor Deck with ElectricalDistribution, Publication No. 27, Steel Deck Institute,Canton, Ohio, (1995).•Standard for the Structural Design of Composite Slabs ANSI/ASCE 3-91, American Society of Civil Engineers(ASCE), New York, New York, December, (1992). Steel Joists•Fisher, J. M., West, M. A., and Van De Pas, J. P., Designing with Steel Joists, Joist Girders and Steel Deck, NucorCorporation, Charlotte, North Carolina, (1991).•Steel Joist Institute 60-Year Manual, Steel Joist Institute, Myrtle Beach, South Carolina, (1992).•Standard Specifications, Load Tables, and Weight Tables for Steel Joists and Joist Girders, Steel Joist Institute,Myrtle Beach, South Carolina, (1994). •Brockenbrough, R. L., Material Properties, Chapter 1.2 in Constructional Steel Design - An International Guide,Dowling, P.J., Harding, J. E., and Bjorhovde, R., Eds.,Elsevier Applied Science, London, England, (1992). Steel Materials•Brockenbrough, R. L., and Barsom, J. M., Metallurgy, Chapter 1.1 in Constructional Steel Design - AnInternational Guide, Dowling, P. J., Harding, J. E., andBjorhovde, R., Eds., Elsevier Applied Science, London,England, (1992).•Geschwindner, L. F., Disque, R. O., and Bjorhovde, R., Load and Resistance Factor Design of Steel Structures,Chapter 4, Prentice-Hall, Englewood Cliffs, New Jersey,(1994).•Barsom, J. M., “Properties of Bridge Steels,”Highway Structures Design Handbook, Vol. 1, American Institute ofSteel Construction (AISC), Chicago, Illinois, (1991). •Dieter, G., Mechanical Metallurgy,Third Edition, McGraw-Hill, New York, (1986).Stepped Columns•Lui, E. M., and Sun, M., “Effective Length of Uniform and Stepped Crane Columns,” Engineering Journal, AmericanInstitute of Steel Construction (AISC), Vol. 32, No. 3, pp.98-106, Third Quarter, (1995).•Agrawal, K. M., and Stafiej, A. P., “Calculation of Effective Length of Stepped Columns,” Engineering Journal,American Institute of Steel Construction (AISC), Vol. 17,No. 4, pp. 96-105, Fourth Quarter, (1980).•“Guide for the Design and Construction of Mill Buildings,”Association of Iron and Steel Engineers (AISE) TechnicalReport, No. 13, Pittsburgh, Pennsylvania, (1991). Stress Corrosion Cracking•Barsom, J. M., and Rolfe, S. T., Fracture and Fatigue Control in Structures, Second Edition, Prentice-Hall,Englewood Cliffs, New Jersey, (1987).Tapered Members•Lee, G. C., Ketter, R. L., and Hsu,Design of Single Story Rigid Frames,Metal Buildings Manufacturers Association(MBMA), Cleveland, Ohio, (1981).Tension Members•McGuire, W.,Steel Structures, Prentice-Hall, Englewood Cliffs, New Jersey, (1968).•Geschwindner, L. F., Disque, R. O., and Bjorhovde, R., Load and Resistance Factor Design of Steel Structures,Chapter 5, Prentice-Hall, Englewood Cliffs, New Jersey,(1994).Thermal Movement•“Expansion Joints in Buildings,” Federal Construction Council Technical Report, No. 65, National Academy ofSciences - National Research Council, Washington, D.C.,(1974).Tolerances•“Standard Specifications for General Requirements for Rolled Steel Plates, Shapes, Sheet Piling, and Bars forStructural Use,” ASTM A6, American Society for Testingand Materials (ASTM), Philadelphia, Pennsylvania, (1992). •Code of Standard Practice for Steel Buildings and Bridges, American Institute of Steel Construction (AISC), Chicago,Illinois, (1992).Torsional Design•Seaburg, P. A., and Carter, C. J., “Torsional Analysis of Structural Steel Members,” American Institute of SteelConstruction (AISC) Steel Design Guide Series, No. 9,American Institute of Steel Construction (AISC), Chicago,Illinois, (1997).•Salmon, C. G., and Johnson, J. E., Steel Structures: Design and Behavior, Fourth Edition, Chapter 8, Harper CollinsCollege Publishers, New York, New York, (1996).。

Designing a school uniform is a task that requires careful consideration of several factors,including comfort,functionality,and the representation of the schools identity. Here are some key points to consider when crafting an English composition on this topic:1.Introduction to the Importance of School Uniforms:Begin by discussing the significance of school uniforms in fostering a sense of unity and pride among students.Mention how uniforms can help create a professional learning environment and reduce distractions caused by fashion trends.2.Research on Current Uniforms:Describe the process of researching existing school uniforms,including surveys of students,parents,and staff to gather their opinions and preferences.This could involve looking at the fit,materials,and design elements of current uniforms.3.Design Considerations:Discuss the various design considerations that must be taken into account.This includes the choice of colors that reflect the schools logo and values,the incorporation of school crests or emblems,and the selection of materials that are durable,comfortable,and suitable for the climate.4.Functionality and Comfort:Explain the importance of ensuring that the uniform is functional and comfortable for students.This may involve choosing breathable fabrics,designing clothes that are easy to move in,and ensuring that the uniform can accommodate the physical activities students engage in throughout the day.5.Inclusivity and Adaptability:Address the need for the uniform to be inclusive and adaptable to different body types, genders,and cultural or religious requirements.This could involve offering a range of sizes and styles to accommodate individual needs.6.Economic Factors:Acknowledge the economic aspect of designing school uniforms,ensuring that they are affordable for all families.Discuss the balance between quality and cost,and the potential for uniforms to be longlasting and easy to maintain.7.Environmental Impact:Consider the environmental impact of the materials used and the production process. Discuss the possibility of using sustainable materials and ethical manufacturing practices to minimize the ecological footprint of the uniforms.8.Prototype Development:Detail the process of creating prototypes based on the gathered research and design considerations.Describe how these prototypes are tested for fit,comfort,and functionality with a diverse group of students.9.Feedback and Iteration:Explain the importance of gathering feedback on the prototypes and using this information to make adjustments and improvements.This iterative process ensures that the final design meets the needs and preferences of the school community.10.Final Design and Implementation:Describe the finalization of the design and the steps taken to implement the new school uniform.This may include the production of the uniforms,the distribution to students, and the communication of the new uniform policy to all stakeholders.11.Conclusion:Conclude the composition by summarizing the key points and reflecting on the benefits of a welldesigned school uniform.Highlight how it contributes to the schools image,the students sense of belonging,and the overall school environment.Remember to use descriptive language and vivid examples to illustrate the points made in the composition.This will help to engage the reader and provide a clear picture of the校服design process.。

customized designsCustomized designs have become an increasingly important aspect of many businesses today. With a rise in consumer expectations, unique and individualized designs are a great way for businesses to stand out from the crowd and offer something that cannot be found elsewhere. Customized designs can be used in a range of industries including fashion, furniture, electronics, and even food.Step 1: Identify the Target AudienceThe first step in creating a customized design is to identify the target audience. This includes understanding their preferences, interests, and needs. For example, if the target audience is fashion-conscious women, the design should reflect their taste, such as using trendy colors and styles. Understanding the target audience is crucial in creating a design that resonates with them and drives engagement.Step 2: Brainstorm IdeasOnce the target audience has been identified, brainstorming ideas around the design can begin. This phase involves collecting ideas from various sources, including market trends, competitors' designs, and consumer surveys. Brainstorming should be a collaborative process involving designers, marketers, and even customers, if possible.Step 3: Create a PrototypeAfter deciding on the design concept, a prototype can be created to test it. This prototype can be in various formats such as digital, physical, or 3D renderings. The prototype should be as close to the final product as possible to ensurethat the design works well. Testing the design prototype is important to identify any issues or defects in the design before moving on to the final stages.Step 4: Implement FeedbackOnce the testing process has been completed, feedback from customers should be implemented. This feedback could bein the form of suggestions or criticisms of the design. It is vital to consider feedback to create designs that cater tothe target audience's preferences and make adjustments accordingly.Step 5: Finalize the DesignThe final step is to finalize the design after takinginto consideration feedback and making necessary changes.Once the design is finalized, it can be produced on a larger scale. The product can be marketed to the target audience, using advertising techniques that reflect their interests.In conclusion, customized designs are an essential partof businesses today. Depending on the industry, customized designs can drive engagement and create a unique brand image. Understanding the target audience, brainstorming ideas, creating a prototype, implementing feedback, and finalizingthe design are the steps required to produce a successful customized design. With the right strategy, customizeddesigns can become a significant selling point for businesses that can help them stand out and create a loyal customer base.。

FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009Design Considerations for Asymmetric Half-Bridge ConvertersHangseok ChoiAbstract — Among various kinds of soft-switching converters, asymmetric PWM half-bridge converters have drawn attention due to their simplicity, inherent zero voltage switching (ZVS) capability, and fixed-frequency operation. This paper presents an analysis and reviews practical design considerations for an asymmetric half-bridge converter. It includes designing the transformer and selecting components. A step-by-step design procedure with a design example will help engineers design an asymmetric half-bridge converter.I. INTRODUCTION The effort to obtain ever-increasing power density of switched-mode power supplies has been limited by the size of passive components. Operation at higher frequencies considerably reduces the size of passive components, such as transformers and filters; however, switching losses have hindered high-frequency operation. To reduce switching losses and allow high-frequency operation, resonant switching and soft-switching techniques have been developed [1-5]. The resonant switching method processes power in a sinusoidal manner by utilizing the resonance during the entire switching period. Generally, the output voltage is regulated by variable frequency control and the current or voltage waveform in the resonant network has a sinusoidal shape. Meanwhile, soft-switching techniques utilize the resonance operation only during the switching transition to soften the switching characteristics of the devices. When the switching transition is over, the converter reverts to Pulse-Width-Modulation (PWM) mode. Since resonant operation only occurs during the switching transition, the parameters of resonant components are not as critical as in a resonant converter. Moreover, the switching frequency is fixed and easily synchronized to the other power stages to minimize EMI.Among various kinds of soft-switching converters, the asymmetric PWM half-bridge converter has drawn attention due to its simplicity and inherent zero voltage switching (ZVS) capability. Figure 1 and 2 show the basic circuit and typical operation waveforms of the asymmetric PWM half-bridge converter. This converter has several advantages over other soft-switching topologies: low MOSFET voltage and current stress, small output capacitor and inductor, minimum component count, and simple control.Ip+ Vd Llkp Im CB VCB Lmn:1+ Vrec -+ VO -Q2 (1-D)Ids2 -RoVinQ1 (D) Ids1Fig.1. Asymmetric PWM half-bridge converter.Fig.2. Typical waveforms of an asymmetric PWM half-bridge converter.1FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009This paper presents design considerations of an asymmetric PWM half-bridge converter. It includes designing the transformer and selecting the components. The step-by-step design procedure explained with a design example will help engineers design an asymmetric PWM half-bridge converter. II. IDEALIZED OPERATION PRINCIPLE OF ASYMMETRIC PWM HALF-BRIDGE CONVERTER Figure 3 illustrates the simplified circuit diagram of an asymmetric PWM half-bridge converter and its ideal waveforms, where the leakage inductance of the transformer is ignored. The DC blocking capacitor (CB) acts not only as an energy source feeding the load while the upper switch (Q2) is conducting, but also as a blocking capacitor to prevent transformer saturation.Substituting Equations 2 into 3, the idealized output voltage in Equation 3 is simplified as:Vo = Vin ⋅ 2(1 − D ) ⋅ D n(4)Figure 4 shows the normalized gain using Equation 4. The operation shows symmetry for the two operation ranges of D from 0% to 50% and from 50% to 100%. Since the slope of the gain curve is reversed at 50% duty cycle, duty cycle should be either below or above 50% for output voltage regulation. In general, operation range from 0% to 50% is preferred since the conventional PWM controller can be used as it is. Meanwhile, operation range above a 50% duty cycle requires additional circuitry to a conventional PWM controller due to the reversed control polarity.Fig. 4. Normalized voltage gain when ignoring the duty cycle losses caused by leakage inductance.Fig. 3. Simplified circuit diagram of an asymmetric PWM half-bridge converter and its waveforms.Applying a voltage-second balance equation across the transformer primary side as:(Vin − VCB ) ⋅ D = VCB ⋅ (1 − D)Figure 5 shows simplified primary-side current waveforms. The transformer primary-side current (Ip) is the sum of the output inductor current referred to as the primary side (ILO /n) and the magnetizing current (IM).(1) (2)The voltage across CB is obtained by:VCB = Vin ⋅ Dwhere D is the duty cycle ratio of low-side MOSFET (Q1). Idealized output voltage is obtained by averaging the secondary-side rectifier voltage (Vrec) as:Vo = (Vin − VCB ) V ⋅ D + CB ⋅ (1 − D ) n n(3)Fig. 5. Primary-side current waveforms.where n is the transformer turns ratio (Np/Ns).2FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009In steady-state operation, the magnetizing current is automatically adjusted so that the average charging current of CB over one cycle is zero. The mean value of the transformer magnetizing current, IM.avg, is obtained from the condition for zero net current through the DC blocking capacitor (CB):( I M .avg + I M .avg IO I ) D = (− I M .avg + O )(1 − D) n n IO = (1 − 2 D ) ⋅ n(5) (6)where Io is the output load current. As observed, the mean value of the transformer magnetizing current is zero when duty cycles for the MOSFETs are even (50% and 50%). Meanwhile, the mean value of the magnetizing current increases as the duty cycle moves away from 50%, which should be the worst case for transformer design. In other words, minimum and maximum duty cycles are the worst cases for operation range below 50% duty cycle and above 50% duty cycle, respectively. III. STEADY-STATE ANALYSIS OF ACTUAL ASYMMETRIC PWM HALF-BRIDGE CONVERTER Figure 6 shows the schematic of an asymmetric PWM half-bridge converter and Figure 7 shows its typical waveforms. In Figure 6, Lm and Llk are the magnetizing inductance and effective leakage inductance in the transformer primary side, respectively, and CB is the DC blocking capacitor whose voltage is almost constant during one switching cycle.Fig. 7. Typical waveforms of an asymmetric PWM half-bridge converter.In general, the asymmetric PWM half-bridge converter consists of three stages, as shown in Figure 6: a square wave generator, energy transfer network, and rectifier network. The square wave generator produces a square wave voltage (Vd) by driving switches Q1 and Q2 complementarily. In order words, the lower and upper MOSFETs duty cycles should be D and 1-D, respectively. A small dead time is usually introduced between the consecutive transitions.Fig. 6. Schematic of an asymmetric PWM half-bridge converter.The energy transfer network consists of a DC blocking capacitor and transformer. The energy transfer network removes the DC offset of the3FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009square wave voltage (Vd) using the DC blocking capacitor (CB), then transfers the pure AC square wave voltage to the secondary side through the transformer. The transformer primary-side current, Ip, lags the voltage applied to the transformer primary side due to the leakage inductance, which allows the MOSFETs to be turned on with zero voltage. As seen in Figure 7, after one of the switches has been turned off, Ip charges (or discharges) the MOSFET output capacitances and eventually swings the switch voltages from one input rail to the other (from Vin to ground or from ground to Vin). Then, Ip continues to flow through the antiparallel body diode. As long as the body diode conducts, the corresponding MOSFET can be turned on with zero voltage. The rectifier network produces a DC voltage by rectifying the AC voltage with rectifier diodes and a low-pass LC filter. The rectifier network can be implemented as a full-wave bridge or center-tapped configuration. In steady-state analysis, assumptions are made: the following(a)(b)The dead time is negligible since it is very small compared to the switching cycle. The leakage inductance is much smaller than the magnetizing inductance. The DC blocking capacitor, CB, is large enough to neglect the voltage ripple across CB. The output filter inductor operates in continuous conduction mode. All circuit elements are ideal and lossless. The duty cycle for lower MOSFET, D, is limited below 50%. The capacitors C1 and C2 include not only the internal output capacitance of MOSFETs, but also the external parasitic capacitances. A. Operation Mode Analysis The asymmetric half-bridge converter has eight operation modes during one switching cycle. The equivalent circuit of each mode is illustrated in Figure 8.(c)(d)(e)4FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009side. Then, the output inductor current, ILO, begins to freewheel in the secondary side through the rectifiers while C2 continues to be discharged. Since the secondary-side inductor (Lo) is disconnected from the primary side, C2 is discharged using the energy stored in the leakage inductance only. After C2 is fully discharged, the body diode of Q2 begins conducting before t3.(f)(g)Mode IV (t3~t4): The body diode of Q2 is conducting and the voltage across the switch Q2 is clamped at zero. By turning on Q2 while the body diode is conducting, zero voltage switching (ZVS) is achieved. During this mode, a voltage of -VCB is applied across the leakage inductance and the primary-side current (Ip) decreases. This mode continues until Ip, plus the magnetizing current (IM), becomes -ILO/n. During this mode, the transformer secondary-side voltage remains zero, which causes duty cycle losses of as much as:DL1 = t 4 − t3 2 I o Llk = Ts TS ⋅ n ⋅ Vin ⋅ D(7)where Ts is the switching period. Mode V (t4~t5): The upper switch (Q2) is conducting and -VCB is applied to the transformer primary side (Vpr). The transformer primary-side current (Ip) is the sum of the output inductor current referred to as the primary side (-ILO/n) and the magnetizing current (IM). This mode is similar to the power transferring mode of a conventional halfbridge converter. Mode VI (t5~t6): The upper switch (Q2) is turned off at t5 and the primary-side current Ip charges C2 and discharges C1. This mode continues until the primary-side voltage becomes zero (until C1 is discharged to Vin-VCB) at t6. Since the secondaryside inductor (Lo) is connected to the primary side, C1 is discharged using the energy stored in the leakage inductance and output inductor. Mode VII (t6~t7): At t6, the transformer primaryside and secondary-side voltages become zero and the secondary side is decoupled from the primary side. Then, the output inductor current, ILO, begins to freewheel in the secondary side and C1 continues to be discharged. Since the secondary side is disconnected from the primary side, C1 is discharged using the energy stored in the leakage5(h) Fig. 8. Operation modes of an asymmetric PWM half-bridge converter.Mode I (to~t1): The lower switch (Q1) is conducting and a voltage of (Vin-VCB) is applied to the transformer primary side (Vpr). The transformer primary-side current (Ip) is the sum of the output inductor current referred to as the primary side (ILO/n) and the magnetizing current (IM). This mode is similar to the power transferring mode of a conventional half-bridge converter. Mode II (t1~t2): The lower switch (Q1) is turned off at t1 and the primary side current, Ip, charges C1 and discharges C2. This mode continues until the primary-side voltage drops to zero (until C2 is discharged to VCB) at t2. Since the secondary side is connected to the primary side, C2 is discharged using the energy stored in the leakage inductance and output inductor. Mode III (t2~t3): At t2, the transformer primaryside and secondary-side voltages become zero and the secondary side is decoupled from the primaryFAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009inductance only. After C1 is fully discharged, the body diode of Q1 begins conducting before t7.Since Ip(t2) is always larger than |Ip(t6)| and DVin is always smaller than (1-D)Vin for duty cycles smaller than 50%, the ZVS condition of Equation 9 is Mode VIII (t7~t8): The body diode of Q1 is satisfied more easily than that of Equation 11. Thus, conducting and the voltage across the switch Q1 is the condition given by Equation 11 should be clamped at zero voltage. By turning on Q1 while the satisfied to achieve ZVS for both MOSFETs. It is body diode is conducting, zero voltage switching required to increase the leakage inductance (Llk) or (ZVS) is achieved. During this mode, a voltage of increase the value of |Ip(t6)| to guarantee ZVS for (Vin-VCB) is applied across the leakage inductance both switches over wide load range. Too large a and the primary side current (Ip) increases. This leakage inductance increases the voltage overshoot mode continues until Ip minus the magnetizing and ringing in the rectifier diodes, which results in current becomes ILO /n. During this mode, the using higher voltage rated rectifiers and power transformer secondary side voltage remains zero, dissipation in the snubber circuit to clamp the which causes duty cycle losses of as much as voltage overshoot. Another way to guarantee ZVS over a wide load range is to increase the value of t −t 2 I o Llk (8) DL 2 = 8 7 = |Ip(t6)| by reducing the magnetizing inductance. Ts TS ⋅ n ⋅ Vin ⋅ (1 − D) Even though this method increases conduction losses on the primary side, it is more effective than B. Zero-Voltage Switching Condition increasing the leakage inductance for high input As discussed in the explanation of operation mode, voltage applications where the conduction losses in after Q1 is turned off at t1, C2 is discharged from Vin the primary side are negligible. to VCB by the energy stored in the leakage D 1-D inductance and output inductor. Then C2 is fully V V V discharged by the energy stored in the leakage inductance only. Therefore, the ZVS condition for Vds1 V switch Q2 is given as:gs1 gs2 gs1inLlk [ I p (t2 )]2 > (C1 + C2 )[ DVin ]2(9) Vds2VprVinwhere Llk is the effective leakage inductance in the transformer primary side and Ip(t2) is the primary side current at t2, given as:I p (t2 ) = Io V (1 − D) DTS + I M .avg + in n 2 LmVin-VCBVCB(10)IPAfter Q2 is turned off at t5, C1 is discharged from VIN to VIN-VCB by the energy stored in the leakage inductance and output inductor. Then C1 is fully discharged by the energy stored in the leakage inductance only. Therefore, the ZVS condition for switch Q1 is given as:Llk [ I p (t6 )]2 > (C1 + C2 )[(1 − D )Vin ]2Vgs1Vgs2Vgs2Vgs1VprVin-VCBVCB(11)Vds2Vin-VCB VCB VCB t1 t2 mode II and III t3 t5 t6Vds1Vin-VCB t7where Ip(t6) is the primary-side current at t6, given as:I V (1 − D ) DTS I p (t6 ) = − o + I M .avg − in n 2 Lm(12)mode VI and VIIFig. 9. Detailed waveforms during the switching transient.6FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009C. DC Characteristics Considering Duty Cycle Losses In the input to output voltage relationship of Equation 4, the duty cycle losses caused by leakage inductance is ignored. In practical design, however, duty cycle losses take a considerable amount of the switching cycle and should be considered to obtain the correct output voltage equation. As observed in Figure 7, duty cycle losses take place not only during the Q1 conduction period (DL1), but also during the Q2 conduction period (DL2). Considering the duty cycle losses from Equations 7 and 8, the output voltage of Equation 4 is modified as:Vo = (Vin − VCB ) V ⋅ ( D − DL 2 ) + CB ⋅ (1 − D − DL1 ) n n(13)Substituting Equations 2, 7, and 8 into 13, the output voltage in Equation 13 is simplified as:Vo = 2Vin 2 I L ⋅ D (1 − D ) − ( ) 2 o lk n n TS(14)IV. DESIGN PROCEDURE In this section, a design procedure is presented using the schematic of Figure 10 as a reference. A center tapped transformer is used in the rectifier stage and the input voltage is assumed to be supplied from power factor correction (PFC) preregulator. A DC-DC converter with a 192W/24V output has been selected as a design example. As a major device, FSFA-series Fairchild Power Switch (FPSTM) is employed, which is an integrated Pulse Width Modulation (PWM) controller and MOSFETs specifically designed for Zero Voltage Switching (ZVS) half-bridge converters with minimal external components. Compared with a discrete MOSFET and PWM controller solution, the FSFA-series can reduce total cost, component count, size, and weight, while simultaneously increasing efficiency, productivity, and system reliability. The design specifications are as follows: Nominal Input Voltage: 400VDC (output of PFC stage) Output: 24V/8A (192W) Hold-up Time Requirement: 20ms (50Hz Line Frequency) DC Link Capacitor of PFC Output: 330µF Switching Frequency: 100kHz Maximum Duty Cycle of PWM Controller: 50%CBAs observed in Equation 14, duty cycle losses increase as the leakage inductance increases. Even though large leakage inductance increases ZVS load range and alleviates the reverse-recovery problem by reducing di/dt, it results in reduced transformer turns ratio, which causes more voltage stress on the rectifier diodes and increased conduction losses due to duty cycle losses. Considering the overall efficiency, leakage inductance resulting in 5~10% duty cycle losses (DL1+DL2) is proper.VccLVccVin (PFC output)Np NsDR1 LO COVoVDL HVccRTDR2FB Cin CSNs Control ICVCTRFSFA2100U3 KA431SGPGRsenseFig. 10. Reference circuit of an asymmetric PWM half-bridge converter for the design example.7FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009[STEP-1] Define the System Specifications The following specification should be defined. Estimated Efficiency (Eff): The power conversion efficiency must be estimated to calculate the maximum input power with a given maximum output power. If no reference data is available, use Eff = 0.88~0.92 for low-voltage output applications and Eff = 0.92~0.96 for high-voltage output applications. With the estimated efficiency, the maximum input power is:Pin = Po E ff2 2 I L Vo + VF = Vin D (1 − D ) − ( ) 2 o LK n n TS(18)where VF is the secondary-side rectifier diode voltage drop. There are three design parameters in Equation 18: duty cycle (D), transformer turns ratio (n), and leakage inductance. It is necessary to determine the leakage inductance prior to the transformer turns ratio and duty cycle. Rather than choosing the leakage inductance arbitrarily, it is reasonable to determine the leakage inductance by considering the duty cycle losses. The duty cycle losses are approximately:DLoss = DL1 + DL 2 ≅ 16 ⋅ Pin ⋅ Llk (Vin max ) 2 ⋅ TS(15)Input Voltage Range (Vinmin and Vinmax): The maximum input voltage would be the nominal PFC output voltage:Vinmax(19)= VO. PFC(16)Though the input voltage is regulated as a constant by the PFC pre-regulator, it drops during the hold-up time. The minimum input voltage, considering the hold-up time requirement, is given as:VinminIt is typical to set the duty cycle losses as 5~10% of the switching cycle. Once the leakage inductance is determined, the transformer turns ratio is calculated by solving Equation 18 for n with a given D as:n= Vin D (1 − D ) + (Vin ⋅ D ⋅ (1 − D )) 2 − 4(Vo + VF ) I o Llk f s (20) (Vo + VF )= VO. PFC22P T − in HU Cin(17)where VO.PFC is the nominal PFC output voltage, THU is the hold-up time, and Cin is the DC link bulk capacitor on the input side.(Design Example) Assuming the efficiency is 92%, P 192 Pin = o = = 209W E ff 0.92Vin max = VO.PFC = 400VVin min = VO. PFC 2 − 2 PinTHU 2 ⋅ 209 ⋅ 20 ×10−3 = 4002 − = 367V Cin 330 ×10−6When calculating the transformer turns ratio with minimum input voltage and maximum duty cycle condition, there should be some margin on the maximum duty cycle of the PWM controller to guarantee output voltage regulation.(Design Example) By choosing duty cycle losses as 9% of the switching cycle, the leakage inductance is obtained as:Llk = = DLoss ⋅ (Vin max ) 2 ⋅ TS 16 ⋅ Pin 0.09 ⋅ 4002 ⋅ 10 × 10−6 = 43µ H 16 ⋅ 209[STEP-2] Determine the Transformer Turns Ratio (n=Np/Ns) As observed in Equation 14, leakage inductance of the transformer results in duty cycle losses and affects the input to output voltage ratio. Considering the forward voltage drop in the rectifier diode, Equation 14 is modified as:Considering 5% margin on the maximum duty cycle of the PWM controller (50±3%), the worst-case maximum duty cycle to calculate the transformer turns ratio is chosen as 42%. Assuming the forward voltage drop of the rectifier is 1.2V, the turns ratio is given as:8FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009 (Design Example — Continued)n= Vin min Dmax ⋅ (1 − Dmax ) (Vo + VF ) + = (Vin min ⋅ Dmax ⋅ (1 − Dmax )) 2 − 4(Vo + VF ) I o Llk f s (Vo + VF )(Design Example) By choosing the current ripple of the output inductor as 20% of the rated output current, the output inductance is given from Equation 23 as:367 ⋅ 0.42 ⋅ (1 − 0.42) (24 + 1.2) + (367 ⋅ 0.42 ⋅ (1 − 0.42)) − 4(24 + 1.2) ⋅ 8 ⋅ 43 × 10 ⋅100 × 10 (Vo + VF )2 −6 3V (1− D) ( in −Vo −VF ) 2IOLlk n Lo = ] ×[DTS − ∆IL n ⋅Vin (1− D) 400⋅ (1− 0.34) − 25.2) 2 ⋅ 8⋅ 43×10−6 6.2 = ×[0.34⋅10×10−6 − ] 8× 0.2 6.2⋅ 400 ⋅ (1− 0.34) = 32.3µH ( The output inductor is smaller than the forward converter with the same current ripple and output power.= 6.2[STEP-3] Calculate the Nominal Duty Cycle for Maximum Input Voltage and Full-Load Condition Since the turns ratio is determined in STEP-2, the nominal duty cycle for maximum input voltage and full load condition is obtained by solving:2 2 I L Vo + VF = Vin max ⋅ Dnom (1 − Dnom )( ) − ( ) 2 o lk n n TS[STEP-5] Determine the Magnetizing Inductance As observed in Equations 10 and 12, the magnetizing inductance value is closely related to the ZVS condition, since it determines the peak current level during the switching transition. Of the two ZVS conditions in Equations 9 and 11, Equations 11 is the worst case for operation with a duty cycle below 50%. Thus, The ZVS condition for both MOSFETs is given as:Llk [ Io V (1 − D ) DTS 2 − I M .avg + in ] n 2 Lm > (C1 + C2 ) ⋅ [(1 − D )Vin ]2(21)The nominal duty cycle is given as:1 − 1 − 4[ Dnom = n(Vo + VF ) 2 I o Llk + ] max 2Vin nVin maxTS 2(22)(24)(Design Example)1 − 1 − 4[ Dnom = 1 − 1 − 4[ = n(Vo + VF ) 2 I o Llk + ] 2Vin max nVin maxTS 2where C1 and C2 are the effective output capacitances (parasitic and external capacitance) for Q1 and Q2, respectively.6.2 ⋅ 25.2 2 ⋅ 8 ⋅ 43 × 10−6 + ] 2 ⋅ 400 6.2 ⋅ 400 ⋅ 10 × 10−6 = 0.34 2[STEP-4] Output Inductor Design The current ripple of the output filter inductor is given as:V (1 − D ) ( in − Vo − VF ) 2 I O Llk n ∆I L = × [ DTS − ] Lo n ⋅ Vin (1 − D )(Design Example) Here, it is designed to guarantee ZVS from full load to 20% load. First, the duty cycle for 20% load condition is obtained as:1 − 1 − 4[ D@ 20% = 1 − 1 − 4[ n(Vo + VF ) 2 I o Llk + ] 2Vin max nVin maxTS 2 6.2 ⋅ 25.2 2 ⋅ (8 × 0.2) ⋅ 43 × 10−6 + ] 2 ⋅ 400 6.2 ⋅ 400 ⋅ 10 × 10−6 = 0.28 2(23)=where Lo is the output inductor. It is typical to set the ripple as 10~20% of the rated output current.With the duty cycle at 20% load condition, the maximum magnetizing inductance value to guarantee ZVS is obtained by solving (24) for Lm as:9FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009Io V (1 − D) DTS + I M .avg − in n 2 Lm Io Vin (1 − D) DTS I P 3 = + I M .avg + n 2 Lm I V (1 − D) DTS I P 4 = − o + I M .avg + in n 2 Lm I V (1 − D) DTS I P 7 = − o + I M .avg − in n 2 Lm I P0 =IP3 IP0 IP(29) (30) (31) (32)Lm <Vin max (1 − D) DTS 2Coss I 2[ (1 − D)Vin − o 2 D] Llk n 400 ⋅ (1 − 0.28) ⋅ 0.28 ⋅ 10 × 10 2[−62 ⋅ 150 × 10−12 8 × 0.2 (1 − 0.28) ⋅ 400 − ⋅ 2 ⋅ 0.28] 43 × 10−6 6.2 = 654µ H=The magnetizing inductance is determined as 630µH.[STEP-6] Design the Transformer The peak magnetizing current is given as:I M . pk V max D(1 − D )TS I o = in + (1 − 2 D) 2 Lm nD 1-DIP4 IP7(25)Fig. 11. Primary-side current waveforms.During transient or startup, the duty cycle can be almost zero. Thus, the magnetizing current should be calculated for the worst case of zero duty cycle. The minimum turns for the transformer primary side is given as:Ae Bmax where Ae is the core cross-sectional area in mm2 and Bmax is the maximum flux density in Tesla. N p min = Lm I M . pk(26)The rms current for secondary windings are uneven for duty cycles smaller than 50%. The current in the winding for diode DF1 in normal operation is:I DF 1rms ≅ I o D(33)Meanwhile, the current in winding for DF2 diode in normal operation is:I DF 2 rms ≅ I o (1 − D)(34)Then, choose the proper number of turns for the secondary side that results in primary side turns larger than Npmin as:N p = n ⋅ N s > N p min(27)The wire diameter should be chosen based on the current density. The current density is typically 5A/mm2 when the wire is long (>1m). When the wire is short with a small number of turns, a current density of 6-10 A/mm2 is also acceptable. Avoid using wire with a diameter larger than 0.4 mm to avoid skin-effect losses as well as to make winding easier. For a high-current output, it is better to use parallel windings with multiple strands of thinner wire to minimize the skin effect. Figure 11 shows the primary-side current waveforms. The rms value of the primary side current is approximately given as:I p rms = ( I P 0 2 + I P 0 I P3 + I P 32 ) (I 2 + I P 4 I P7 + I P7 2 ) D + P4 (1 − D) 3 3(Design Example) For worst case zero duty cycle (D=0), the maximum magnetizing current is: V max D(1 − D)TS I o I M . pk = in + (1 − 2 D ) 2 Lm n 8 = (1 − 2 ⋅ 0) = 1.29 A 6.2 Since the primary-side current equals the magnetizing current plus the output current referred to the primary, magnetizing current can reach the pulse-by-pulse current limit level given by PWM controller during transient. There should be enough margin in transformer design, however, Bmax=0.15T is used to guarantee non-saturation of the transformer during transient (EER3542, Ae=109mm2). The maximum flux density in the worst case scenario will be checked in STEP-8 after current limit level is determined. The minimum number of turns for the primary winding is given as:N p min = Lm I M . pk Ae Bmax = 630 ×10−6 ⋅1.29 = 49.7turns 109 ×10−6 ⋅ 0.15(28)The primary and secondary-side turns are determined as 50 turns and 8 turns, respectively. The rms value of the primary-side current is given by:10FAIRCHILD SEMICONDUTOR POWER SEMINAR 2008 - 2009I P0 = 8 400 ⋅ (1 − 0.34) ⋅ 0.34 ⋅ 10 × 10−6 + 0.41 − = 0.99 A 6.2 2 ⋅ 630 × 10−6 8 400 ⋅ (1 − 0.34) ⋅ 0.34 ⋅ 10 × 10−6 = + 0.41 + = 2.42 A 6.2 2 ⋅ 630 × 10−6 8 400 ⋅ (1 − 0.34) ⋅ 0.34 ⋅ 10 × 10−6 =− + 0.41 + = −0.17 A 6.2 2 ⋅ 630 × 10−6 8 400 ⋅ (1 − 0.34) ⋅ 0.34 ⋅ 10 × 10−6 =− + 0.41 − = −1.59 A 6.2 2 ⋅ 630 × 10−6I P3I P4I P7Another important factor to consider when selecting the capacitor is the current rating. Since the primary-side current of 1.27A calculated in STEP-6 flows through the capacitor, a low-ESR capacitor should be chosen. Thus, a 220nF/275VAC film capacitor is selected.I p rms = 1.29 A The current in the winding for DF1 diode in normal operation isIrms DF 1[STEP-8] Current Sensing To determine the pulse-by-pulse current limit level, the peak current in the primary side should be obtained first as:I p pk = Io V D (1 − Dnom )TS (2 − 2 Dnom ) + in nom n 2 Lm≅ I o D = 8 ⋅ 0.34 = 4.7 AMeanwhile, the current in the winding for DF2 diode in normal operation is:I DF 2 rms ≅ I o (1 − D) = 8 ⋅ (1 − 0.34) = 6.5 AFor the primary winding, 0.12φ×30 (Litz wire) is selected and the current density is 3.8A/mm2. In the case of the secondary winding, 0.1φ×100 (Litz wire) is selected and the current densities are 5.9A/mm2 and 8.2A/mm2 for DF1 and DF2, respectively.(36)(Design Example) The peak current is obtained as:I p pk = = Io V D (1 − Dnom )TS (2 − 2 Dnom ) + in nom n 2 Lm[STEP-7] DC Blocking Capacitor Selection Even though it has been assumed that the DC blocking capacitor CB is large enough to neglect the voltage ripple across CB, too large a capacitor results in slow dynamic response. Thus, it is typical to select the capacitor so that the ripple is 5~10% of the input voltage. The voltage ripple of DC blocking capacitor is given as: DT 1 S 1 Io Io (35) ∆VCB ≅ i p dt = [ + (1 − 2 D)] ∫ CB 0 CB n n(Design Example) To set the voltage ripple below 30V, the minimum DC blocking capacitor value is obtained from1 CBDTS8 400 ⋅ 0.34 ⋅ (1 − 0.34) ⋅ 10 × 10 −6 (2 − 2 ⋅ 0.34) + 6.2 2 ⋅ 630 × 10−6 = 2.41ACurrent limit level is determined as 3A, using 0.2Ω resistor since the current limit threshold voltage is 0.6V. As mentioned in STEP-6, the transformer magnetizing current can reach the pulse-by-pulse current limit level given by the PWM controller during transient. Therefore, the maximum flux density of transformer should be checked as. L I 630 ×10−6 ⋅ 3 Bmax worst = m LIM = = 0.35T Ae N p min 109 ×10−6 ⋅ 50∫ i dt = Cp 01 Io Io [ + (1 − 2 Dnom )] < 30V n B n[STEP-9] Diode Selection The voltage stress for each rectifier diode (DF1 and DF2) is given as:VDF 1 = Vin ⋅ D ⋅ 2 n 2 n(37) (38)1 Io Io CB > [ + (1 − 2 Dnom )]DnomTS 30V n n 1 8 8 CB > [ + (1 − 2 ⋅ 0.34)] ⋅ 0.34 ⋅ 10 × 10−6 = 193nF 30V 6.2 6.2The voltage of CB is given as VIN×D by (2) and the maximum capacitor voltage is theoretically half of the input voltage. However, it can reach the input voltage while the converter is not operating if the leakage currents of the MOSFETs are unbalanced. Thus, voltage rating should be higher than maximum input voltage (400V).VDF 2 = Vin ⋅ (1 − D ) ⋅11。

post-disciplinary design Postdisciplinary design refers to an approach in design thinking that goes beyond the traditional disciplinary boundaries and embraces cross-disciplinary collaboration. It encourages designers to explore new ways of problem-solving and promotes innovation through the integration of various knowledge areas. In this article, we will delve into the concept of postdisciplinary design and discuss its significance in today's complex and interconnected world.First and foremost, it is essential to understand the context in which postdisciplinary design emerges. We are living in an era of rapid change and increasing complexity, with global challenges requiring multifaceted solutions. The traditional disciplinary approach has its merits, but it often falls short in addressing complex problems that require a comprehensive understanding of multiple perspectives. Therefore, postdisciplinary design offers an alternative framework that encourages designers to collaborate across disciplines, building on each other's expertise to tackle these challenges effectively.The key principle of postdisciplinary design is the integration ofdiverse knowledge areas. By involving individuals from different backgrounds, such as design, engineering, anthropology, psychology, and sociology, a broader range of expertise and perspectives can be brought to the table. This collaborative approach helps in generating innovative solutions that are not limited by a single discipline's conventional thinking. For example, when designing a new product, a postdisciplinary design team may include engineers for technical expertise, designers for aesthetics, anthropologists for understanding cultural context, and psychologists for user experience considerations. By combining these various perspectives, the team can create a product that is both functional and meaningful to its intended users.Another significant aspect of postdisciplinary design is the breaking down of silos and fostering interdisciplinary communication. Traditionally, disciplines have operated independently with limited interaction with other fields. Postdisciplinary design challenges this conventional approach by encouraging a free flow of ideas and knowledge exchange between disciplines. Through open dialogue and collaboration, designers can gain a deeper understanding of the interconnectedness of different knowledge areas and their potential for synergy. Thiscollaborative environment allows for creativity and innovation to flourish as diverse perspectives come together to explore new possibilities.Furthermore, postdisciplinary design promotes a holistic view of problem-solving. By considering the broader context and systems in which a problem exists, designers can identify and address underlying causes rather than merely treating symptoms. This holistic approach aims to create lasting and sustainable solutions that go beyond surface-level fixes. For instance, a postdisciplinary design team working on urban planning may consider not only the physical infrastructure but also sociocultural factors, environmental impact, and economic considerations to develop a comprehensive and integrated plan for urban development.Additionally, postdisciplinary design enables designers to navigate the complexity of the modern world. The interconnected nature of today's challenges necessitates a multidimensional understanding that cannot be achieved through isolated disciplinary approaches. Postdisciplinary design equips designers with a broader perspective, enabling them to identify patterns, connections, and interdependencies that may have otherwise been overlooked. Thiscomprehensive understanding allows for the development of innovative and effective solutions that address the root causes of complex problems.In conclusion, postdisciplinary design offers a fresh and innovative approach to problem-solving in an increasingly complex world. By embracing cross-disciplinary collaboration, integrating diverse knowledge areas, fostering interdisciplinary communication, promoting holistic thinking, and navigating complexity, postdisciplinary design enables designers to overcome the limitations of traditional disciplinary boundaries. In doing so, designers can develop more comprehensive, sustainable, and impactful solutions that address the interconnected challenges we face today. Embracing postdisciplinary design is essential for driving meaningful innovation and tackling the complex problems of our time.。

Journal of Geographic Information and Decision Analysis, vol.1, no.1, pp. 1-9, 1997 Design Considerations for Space and Time Distributed Collaborative Spatial Decision MakingPiotr JankowskiDepartment of Geography, University of Idaho, Idaho, USApiotrj@Milosz StasikDepartment of Geography, University of Idaho, Idaho, USAABSTRACT The idea of GIS used by citizens in exercising democracy, dubbed public GIS, involves the use of GIS tools to help laypeople understand the spatial consequences of proposed projects and actions effecting their communities. The widening use of the Internet creates the opportunity of elevating GIS to a truly public decision making tool by making it accessible regardless of spatial and temporal constraints restricting its use. Before public GIS becomes a reality, however, empirical studies are needed to determine the feasibility of this idea. This paper presents the design of a prototype called Spatial Understanding and Decision Support System (SUDSS) that is a step towards implementing public GIS. SUDSS will be used in a series of controlled experiments in which groups of participants will collaborate on the Internet in a realistic land use zoning decision making problem in Idaho. The paper discusses system's interface design, functionality, and architectural arrangements.KEYWORDS: GIS, collaborative spatial decision makingContents1. Introduction2. Design Requirements for the Internet-based SUDSS2.1. Design Guidelines3. Design of SUDSS Prototype4. Architectural Considerations for SUDSS5. ConclusionReferences1. IntroductionThe idea of public participation in decision making concerning important societal issues has been around as long as democracy. But only recently, one can witness the rise of new and innovative methods of public participation in policy decisions affecting communities and society. One such method called the consensus conference was pioneered in Europe in the late 1980s. Introduced by the Danish Board of Technology, consensus conference is intended to stimulate the participation of citizens in understanding, intelligent social debate, and evaluation of technological issues affecting the society (Sclove 1996). The participation of laypeople in the decision making process is achieved through a carefully designed program of reading and discussion preparing citizens to render judgment during an open forum.How to facilitate public participation in decision making concerning spatial issues (e.g. noxious facility siting, environmental restoration, multiple use of natural resources) has also become a vibrant research problem in geographic information science (Couclelis and Monmonier 1995). The idea of GIS used by citizens in exercising democracy, dubbed public GIS, involves the use of GIS tools to help laypeople understand the spatial consequences of proposed projects, evaluate alternatives, and create new solutions. Since public GIS requires the collaboration of multiple participants, it has also been considered in the category of collaborative spatial decision making (CSDM) (Armstrong et al. 1996). Four different arrangements of CSDM are possible: (1) the same location and time (collaborative work using a conferencing room with a local area computer network), (2) the same location and different time (collaborative work using leave behind word processing supported by a local, or wide area computer network), (3) different locations and same time (collaborative work using interactive desktop audio and video, supported by a wide area network, a dedicated wide band-width telephone line, or a satellite link), and (4) different locations and different times (collaborative work using e-mail, wide area network, and network-resident multimedia tools). The design of a spatial decision support system for CSDM focused on the first organizational arrangement, the same location and time, was discussed in Jankowski et al.(1997). This paper explores the design considerations for collaborative spatial decision making that would enable public participation under distributed space and time (fourth arrangement).2. Design Requirements for the Internet-based SUDSSThe main purpose of designing the Internet-based SUDSS has been the development of a software prototype for a series of experiments in space and time distributed collaborative work environment. Theoretical foundations to guide such empirical research have been laid in Nyerges and Jankowski (1997). The space and time distributed environment may provide not only a public exchange forum during the exploratory stage of the decision making process but also an alternative venue to community (town) meeting. The possible advantages of the space and time distributed arrangement for CSDM over the other arrangements (especially the meeting arrangement) include the flexibility of choosing the place and time of participation and the increased sense of participation equality. During the experiments the groups of participants will use the SUDSS software prototype to work on a real world problem of land use zoning. The problem is representative of many spatial decision problems combining the issues of resource management and policy development.Based on the characteristics of the land use zoning problem and experiment participants (group members may range from advanced to novices in using spatial decision support tools and in collaborative problem solving) the following design requirements were specified:•The system should offer sufficient functionality allowing users to: (1) study and explore information about the problem, (2) generate problem solution alternatives,(3) share and discuss problem solution ideas, (4) evaluate the alternatives, (5)negotiate the alternatives, and (6) vote on the alternatives.•The system should not be restrictive, allowing the users to select tools and procedures in any order.•The interface should be both process-oriented and data-oriented allowing an equally easy access to task-oriented analytical tools as well as maps and data visualization tools.•The system should be capable of supporting both facilitated and nonfacilitated collaborative problem solving.•The system should allow work both in private and in public mode.2.1. Design GuidelinesThe design of the Internet-based spatial understanding and decision support system can be guided by holistic attributes, interface, and functionality (Silver 1991; DeSanctis 1993). Holistic attributes represented by restrictiveness, comprehensiveness, and decisional guidance describe the range of intended uses and interactions among the participants and between the software server and participants. Restrictiveness describes the level of structure embedded in the software and imposed on the problem exploration and decision making process. A more restrictive system requires the group to follow the pre-specified sequence of steps while a less restrictive system leaves the group more freedom in customizing the use of software to match a specific decision making process. Comprehensiveness expresses the richness of functions offered by the system. A more comprehensive system will be suitable for a larger number of tasks but it may also require the guidance of a facilitator. Decisional guidance is the degree to which the system directs the users to invoke the system operations. It ranges from a total lack of guidance where the users pick and choose the software options as they see fit, to a wizard-driven software providing suggestions on the next possible step.Interface can be characterized in terms of representations used by group members when interacting with the software, information exchange among group members, and the location of function controls. Representations can be process-oriented and data-oriented. The process-oriented interface emphasizes selections that offer tools and techniques used in problem-solving, e.g. GIS operations, weighting, scoring, and voting procedures. The data-oriented interface can present spatial and attribute data in the form of interactive maps, drawings, images, graphs, and attribute data tables. The information exchange can include communication between individual members (one-to-one), within the newsgroup (many-to-many), the system server and group members (one-to-many) and vice-versa (many-to-one). The object of the exchange may be restricted only to task-related information, but it may also include the expressions of group emotions, moods, and social dynamics. The location of function controls relates to the availability of controls. The function controls can be available equally to every group member or they can be restricted depending on the intended mode of system operation. If the system isintended to be used without the facilitator, the limited allocation of controls to every group member is a reasonable solution. In the context of collaborative work distributed in space and time, the limited allocation means that there are time constraints imposed on group members regarding the access to system functions. These time constraints can be used to keep collaborative work process on track. If the system requires facilitation and technical assistance, the functional controls may be allocated among group members and facilitator.Functionality of SUDSS can include basic and advanced tools for problem exploration and collaborative work. The basic tools should include the support for problem understanding, alternative generation, and alternative evaluation. These tools may be comprised of WWW pages with interactive 2-D and 3-D maps, hypertext, virtual imagery, e-mail access to problem experts to support problem understanding and learning, idea generation via mapping and text processing tools, idea organization via editing tools, evaluation of alternatives by scoring, representation of preferences by weights, and voting tools. Additionally, the basic tools should provide individual and shared map displays that support the visualization of alternative plans, background information, and spatial distributions of attributes associated with alternatives. The advanced tools should provide analytical capabilities including spatial analysis functions and sensitivity analysis.3. Design of SUDSS PrototypeIn the SUDSS prototype, similar to other decision support systems, the graphical user interface is the sole access point to communication with other group members, database, problem exploration tools, modeling tools, and generated problem solutions. Since it is our intent to create a simple to use and intuitive user interface, it is important to use publicly accepted and widely used tools. Communication tools include Hypertext Markup Language (HTML) documents as well as Simple Mail Transfer Protocol (SMTP) mail tools supporting Multipurpose Internet Mail Extension (MIME) formats. In the current prototype users are unable to use other data than those verified by the server. Also, the access to communication tools is somewhat limited. The usage of certain words suggesting out-of-subject discussion results in automatic exclusion from the discussion. The purpose of these measures is to create a controlled experiment environment. The interface design considerations were focused on the fact that predominant users of the SUDSS prototype are inexperienced in GIS modeling. Moreover, the assumption has been that some users may even have limited experience with working with the Windows environment, necessitating simplified interface design. Excess common elements such as controls, long lists of choices or options, and a nested hierarchy of windows may be a major obstacle to a new user. The user is provided with a two-level interface promising a logical, intuitive flow of system use. At the main-level the user has the ability to control the activation of more advanced modeless windows of the second level offering a full set of tools responsible for completing a specific part of the task.Figure 1 SUDSS Main-Level WindowAll major tools are assigned to six self-explanatory system functions represented by the corresponding six buttons (see Figure 1): file operation, request, communication, explore, evaluate and vote. The latter three buttons allow the user to work on the project, create problem solution alternatives, evaluate alternatives proposed by other users, and finally vote on feasible alternatives. The three buttons top-row allow the user to participate in collaborative work by providing a means of expressing opinion (communication button) and changing session constraints (request button). Users have the ability to increase the time needed to complete a task by submitting a request to the server (see Figure 2).An important issue has been how many and how advanced the second-level controls should be. The guiding design principle in this regard has been the striving for a balance between the utmost simplicity and robustness of the SUDSS prototype. The only functions where a beginner may find help necessary are in the evaluation and exploration panels. There is a certain minimum of functions that have to be implemented in the software to assure its functionality. In the case of the exploration window these are: drawing tools (simple graphical utilities), spatial analysis tools (implementation of ESRI's Map Objects), and commentary tools (allowing the attachment of short explanatory notes to the project). Implementation of simple support tools such as "tool tips", "tips of the day", and help files allows problems related to SUDSS use to be overcome. "Tool tips" seem to be an especially beneficial utility. Short notes are able to provide necessaryinformation without the technical jargon usually associated with help files.Figure 2 SUDSS User Request Window4. Architectural Considerations forSUDSSAn important practical question indesigning an SUDSS prototype hasbeen whether to develop a stand-alone tool, independent of WorldWide Web (WWW) browsersoftware (Figure 3, part A) or, to aimfor a wide range of users, creating atool that can become a part ofexisting WWW browser software(Figure 3, part B). Since the use ofWWW browsers has gained publicacceptance and has been growing atan exponential rate (by 341,634% a year according to the Internet Book Shop) there is a strong rationale to implement an SUDSS prototype as a part of a popular browser. New technologies including Microsoft Activex controls make such an implementation relatively easy. There is, however, a strong argument in favor of developing a stand-alone SUDSS prototype. A stand-alone software allows all restrictions related to WWW browser extensions and plug-in modulesto be bypassed. It also avoids the unnecessary software overhead resulting from the needto use browser software. For these reasons, the implementation of an SUDSS prototype as a WWW browser plug-in is less attractive at this point than creating a stand-alone software able to directly utilize capabilities of the TCP/IP protocol.The stand-alone SUDSS prototype has the ability to use not only the HTTP protocol (and consequently WWW) but also uses other protocols such as SMTP and FTP. Choosing TCP/IP as a network transport protocol opens the access to the Internet and thousands of servers with millions of potential users. The weakness of the TCP/IP protocol is its packet-switched architecture and the communication through Class C network connections (unreliable network service) with high residual error rate. However, without implementation of multimedia transmission (especially live) this datagram service is adequate for the needs of the SUDSS prototype.One of the most important concerns about the system architecture is data management in respect to the transmission media. The question is whether data should be distributed to users only once (Figure 4, part A) or whether they should be distributed gradually in response to the user's demands (Figure 4, part B). The first option allows the user to freely interact with the entire project database from the beginning, though it is often true that parts of the database are not used at all. This raises a concern about bandwidth and storage conservancy. The second option uses action-aware database management to diminish the amount of data transferred over the network during a collaborative meeting. The intended consequences of this option are the decrease of the server load and also the decrease of the demand on the availability of users' personal storage space.Figure 3Stand-alone SUDSS prototype (A) vs. SUDSS prototype as WWW plug-in software (B)Figure 4 A simple, one-step databasetransfer (A) vs. action-aware databasemanagement diminishing the amount ofdata transferredThe idea behind the action-aware database management isthat the user's action related tospecific objects (e.g. mapentities) invokes a backgroundrequest sent to the server todeliver database records relatedto these objects. If the initialcheck-up indicates that allrequired records have beenalready sent no further action isperformed. If an object is usedfor the first time, appropriaterecords are sent over to the user.Although, due to additional dataoverhead, the size of datatransmitted in this way is slightlylarger than the size of the samedata transferred with the entire database (Figure 4, part A), the action-aware database management may prove to be a more efficient way of using database resources. Unfortunately there are several obstacles that restrict implementation of this concept. Among the most important ones are: server processing time (time needed to process a query and prepare a set of relevant records), transfer time of data in the real life situation over a Public Switched Telephone Network (PSTN) using at best 28000 bps modem, and the need for an uninterrupted networkconnection throughout the problem exploration time. Considering the above, a full data transfer to the user is the solution implemented in the prototype version of SUDSS.The implementation of a timer function is a simple way to keep collaborative work on schedule, motivated, and effective. Every major step of the experiment project is going to have some initial time allocated. It is a challenge to the users to use this time as efficiently as possible. There are two principle design possibilities to regulate the use of time. Either a timer is hard-coded into the client software or it is activated, run, reset and stopped from the server. The first option assigns limited time resources to each task and does not take into account the dynamics of human-computer interaction. Even if the user is unable to complete a task within the time limits, there is no possible way to get additional work time. The timer implementation is in this solution problem-independent. The latter design is a more attractive alternative allowing the control over the decision making process to be left to the user and the server. It allows flexible time allocation, context-aware response to group needs and the implementation of objective time management. It is based on the constant monitoring by the server of users' behavior and their work progress. Such a design assumes, however, that the user stays on-line throughout the experiment time. Since an experiment session may last several days, the necessity to stay on-line may be unacceptable for many users. On the other hand, the lack of timer implementation in the software may result in a complete lack of synchronization and inability to continue work with the rest of the group. If the user's computer time used to control the work process differs from the time on the server this may result in significant time loss during every step of the task. In the case of large groups working under distributed time conditions the inability to adjust time as well as other settings would result in less effective collaboration. The need for a central time control mechanism allowing to make such adjustments is obvious. A reasonable solution in this case is that timer settings are set and checked explicitly from the server and - if necessary - adjusted during routine data exchange between a client and the server. Even sporadic, short connections with the server performed on a timely basis ought to be sufficient to verify accuracy and prevent any further problems.Unfortunately, when the user stays off-line for more than several hours some controls may be disabled if the timer runs out. At this point the client software will attempt to establish the connection with the server. If the timer reading on the server indicates that the user has still time to work on the current task, the client timer will be reset and controls enabled. If time has run out the user will be given a chance to continue work on the next task. However, if the user does not take any action for the time exceeding a given phase of the experiment the server will remove that person from the access list in order to keep the group motivated.The above elements will be implemented as an 'auto' facilitator function. Since the SUDSS prototype is designed to provide time-space distributed collaborative work capabilities, it is likely that human control over the experiment will be limited. It is then our goal to allow the server to control actions at any given step of the process.5. ConclusionThe idea of GIS empowering communities to participate in decision making about community pertinent problems has stimulated a number of interesting research issues. One of them is how groups of people, comprised of the diverse community members, cancollaborate outside the confines of the traditional public meeting environment to better understand and consequently propose feasible solution alternatives to a land use zoning problem. We will study this issue through a controlled experiment with groups of participants collaborating over the Internet in a time and space distributed computing environment. The participants will use a prototype of a spatial understanding and decision support system designed for the use on the Internet. The prototype provides tools for communication among group members, database access, problem exploration, spatial modeling, and the evaluation of proposed solution alternatives. The effectiveness of the prototype design will be tested and assessed in the course of the experiment. ReferencesArmstrong, M. P., Densham, P. J., Kemp, K. (1996) Report from the Specialist Meeting on Collaborative Spatial Decision Making, Initiative 17, National Center for Geographic Information Analysis, UC Santa Barbara, September 17-21, 1995. Couclelis, H., Monmonier, M. (1995) Using SUSS to resolve NIMBY: How Spatial Understanding Support System can help with the "not in my back yard" syndrome, Geographical Systems, 2, 83-101.DeSanctis, G. (1993) Confronting environmental dilemmas through group decision support systems, The Environmental Professional, 15, 207-218.Nyerges, T., Jankowski, P. (1997) Framing GIS-supported Collaborative Decision Making: Enhanced Adoptive Structuration Theory, Geographical Systems, in press. Jankowski, P., Nyerges, T. L., Smith, A., Moore, T. J., Horvath, E. (1997) Spatial Group Choice: A SDSS tool for collaborative spatial decision making, International Journal of Geographical Information Systems, in press.Sclove, R. E. (1996) Town Meetings on Technology. Technology Review, July 1996: 25-31.Silver, M. S. (1991) Systems that support decision makers: description and analysis. New York: John Wiley.The Internet Book Shop at:/69656999/INFOPACK/growth.htm.JGIDA vol.1, no.1JGIDA Home。

1INTRODUCTIONT raditional musical instrument amplifier productscapable of providing high output are large and not easy for a person to transport frequently.There are also small,portable amplifiers available on the market,but they are limited in their sound level capability and cannot be used for group playing or loud music styles.Amateur and prof essional musicians requireequipment that will sound excellent while playing at all levels and w hich is very reliable.It is the goal of the amplifier described here to provide good sound and suff icient output f or almost all playing situations and musical styles ,w hile remaining very compact and easy to carry.2DESIGN GOALSM odern music can sometimes place large demands on amplification systems :w ith high sound pressurelevels and long periods of continuous maximum output.Soundlevel and frequency spectrum studiesw eremade of musicians playing amplif ied guitar under many different conditions.It w as determined f rom thisresearch that an amplifier w hich can produce an continuous output of at least 120dB SPL @1M is required to meet the needs of players under most conditions.Even under these very loud conditions,additional short-term power peaks should be available,“y ”Reaching this output level w ith a relatively small loudspeaker driver requires high electrical pow er and good loudspeaker eff iciency.Listening tests indicatedthat a bass cutoff below about 200Hz w as appropriate to the sound of an electric guitar.A 165mm driverw as chosen as the best compromise betw een ef ficiency and size.T o keep the enclosure small,aggressivefiltering of deep bass frequencies is performed,andgood control of signal dynamic range is maintained.The system block diagram is show n in Figure 1.T his block diagram is generally similar to other musical instrument amplif iers ,but additional f iltering andequalization are provided at several points in the signal flow .T his filtering is carefully adapted to the loud-speaker and enclosure,and is adapted to the outputsignal level.3ENCLOSURET he system enclosure is a critical part of the soundq y y f T 文章编号:1002-8684(2008)S 1-0067-06Design Consider ations for a New Class of Compact andEfficient Musical Instrument AmplifiersKenneth Kantor(ZT Amplifiers,Inc.,2329Fourth S tre et Berkeley,CA 94710,USA)【Abstr act 】This paper describes the design considerations f or a high output ,music al instr ument amplif ier in asmall,portable enclosure.The unique goal of this design is to achieve exc ellent sound quality,with a continuous sound pressure level greater than 120dB S PL,from package dimensions of only 178mm ×203mm ×102mm.Inaddition ,the system must be highly reliable .The technical development of the preamp circuit ,signal processor ,pow er amplif ier and loudspeaker dr iver are described below .Figure 1Block D iagramSpeakerPower Amp Post-Filter Rev erbT o neDynamicsFix ed EQ Pre-Filter Preamp InputT e c h n ic a l Es s e n cE技术精粹6to give the music a d namic audible characteristic.ualit in an musical instrument ampli ier.o handle7the high pow er dissipation and to achieve the most internal volume,a metal enclosure w as chosen.Theenclosure w as developed to meet several key require-ments:(1)High strength-to-w eight ratio.(2)Impact and w ear resistance.(3)Minimum external dimensions.(4)Maximum internal volume.(5)Good heat dissipation.(6)Enough mass to avoid vibration w hen played loudly.T he assembly uses a heavy aluminum structure to support the internal electrical and acoustical compo-nents.A ttached to this inner structure is an outer skin of thin steel to provide the proper cosmetic appear-ance and durability.Great care w as taken to minimize resonance in the enclosure.The tw o layers of metalare attached together using a silicon adhesive,w hichprovides strength and vibration damping.The feel ofthe enclosure is very solid to the touch.T he rear panel of the enclosure is bare aluminum and is the main point of heat dissipation in the system.However,the entire metal structure contributes to the heatsink ef fect and provides excellent heat dissipation f rom a small package,w hile avoiding any hotspots.The loudspeaker driver is of a relatively small diameter,therefore a sealed box design w as selectedto maximiz e the low frequency output.T his avoids the cancellation of long wavelengths from the rear of the driver and controls driver excursion below the Fc resonance point.Since there are f ew er anti -phase ref lections,a sealed box also has the benefit ofy f 4INPUT STAGEIt is generally understood that a electric guitars sound the best w hen presented with a load impedance of at least 1M !.T he input stage configuration isshow n in Figure 3.T he circuit topology is selected to provide the proper loading and low noise ,w hile alsoreducing the sensitivity of the input stage to possibleRF interference.Many amplifier designers assume that the maximum output of the electric guitar is only a few hundred mV.T his is true under most conditions.How ever,w henplayed very hard,some types of guitar pickups canput out instantaneous peak voltages of over 6V pp into a load of 1M !.(1)U p to 6Vpp.(2)0.5V average level.(3)High input impedance;1M !.(4)Immune to RF interference.(5)A C-coupled.(6)L ow noise.(7)Protected against accidental overload.5SIGNAL PROCESSINGO nce the guitar signal is handled by the preamplifier circuit,it operates at a more consistent level andlow er impedance.At this point,signal processingfunctions may be applied to achieve the desired sound quality.Important features of the signal processinginclude:(1)G ain.(2)Controlled non-linear distortion.(3)Frequency response equalization.(4)Reverberation.(5)U ser T one Controls.(6)f T f q y f f Figure 2MechanicalAssembly(a )Frontage(b )SideF igure 3Input Stage100p10k10"0.0047"2M2MInputT e c h n ic a lE s s e n c e技术精粹6maintaining a more consistent response when placed close to the wall or stacked with man other ampli iers.Power protection o the loudspeaker driver.heoverall re uenc responseo the ampli ier8circuit is show n in Figure 4.T his is the nominalelectrical response of the circuit,and does not include cabinet or loudspeaker influences.Notice the boostedcharacteristic of the upper f requencies,and the sharp f iltering above and below the operating band.T heexact shape of the curve is determined by ear and by comparison to standard designs.T he filtering aboveabout 8kHz and below about 200Hz is designed toprovide good sound,and to maximize the usablepow er output.6AUDIO AMPLIFIER D uring typical use,the pow er output stage of amusical instrument amplifier is often operated above the “clipping ”point.T his is normal and expected ,and helps to generate the harmonic overtones that are part of the musical sound.How the amplifier circuitreacts to the voltage overload condition is an important part of its sound quality.A t first,a Class D sw itching amplif ier w as considered,to try and maximize theeff iciency of the system.How ever ,it w as diff icult to obtain the kind of overload response that is desirable.With an AB design it w as much easier to achieve the required output overload characteristics.In practice a Class AB output stage operated at nearly the same efficiency as a Class D,because of the very lowcrest f actor and high level of the signal.Thus,not much pow er is w asted during high volume use ,themost important condition.T he A/B design used is also very stable as the power supply varies,w ith excellent rejection ratio.T f f y ,“”T y x z voltage available across the load.The output stagecan easily deliver more than 40V p across a nominal 8O hm loudspeaker.This is more than sufficient tomeet the sound pressure level targets required.7POWER SUPP LYThe pow er supply arrangement is show n in Figure 5.Thisarrangement provides+/-24V to the pow eramplifiers with a virtual ground,thus eliminating the requirement for coupling capacitors.+/-12V rails arecreated to operate the general audio circuitry.Inaddition,there is a small, 3.3V sub-regulator to supplythe digital circuitry used.No regulation is used on the +/-24V rails,sincethe natural behavior of a linear supply is very w ell-suited to musical instrument use.T he sag behaviorintroduced by the supply supports high short -termpeaks,w hile limiting the output dissipation of theamplifier under continuous signal conditions.8LOUDSPEAKER DRIVERProper selection of the loudspeaker driver is one of the critical elements in achieving the necessary sound and reliability from a musical instrument amplifier.This is especially true when the loudspeaker must be small,and w ill be pushed to near its operating limits.A driver diameter of 165mm w as determined to be the minimum siz e for operation at the high SPL levels needed.Many engineering aspects of this driver areoptimized to give the highest possible output level.For example,compared to typical high f idelity loud-speakers,this driver is not required to have very low distortion or good bass output.Thus,it may be con-structed w ith a small Xmax,relatively high Fs,andff y O f f F igure 5Pow er S upply Configur ation+3.3V-12V-24V +12V+24V48V DCINFigure 4Electrical FrequencyResponse20k10k 5k 2k 1k 5002001005020-40-35-30-25-20-15-10-50510152025303540f /Hzd B r Te c h n ic a l Es s e n cE技术精粹6he ampli ier output is a ull balanced bridge design.his topolog ma imi es the instantaneous peakthe highest possible e icienc .ther eatures o theloudspeaker driver include9very high pow er handling,and the ability to w orkw ell in a small,sealed enclosure.T he overall near -f ield response of the amplifier system,including both the electronics and the acoustical elements ,is show nin Figure 6.Tw o slightly different response curves are plotted.The red curve indicates the response w ith the tone control set to a“minimum ,”w hile the bluecurve is the opposite setting.T his response may becompared to the electrical curve show n previously in Figure 4in order to understand the transf er function of the loudspeaker driver.9SUM MARYT he engineering design of a small guitar amplifier M y f z f pressure level and compact size.T he system is capable of very loud output and excellent sound quality in z y T f y Figure 6A coustical Frequency Response and Tone ControlRange20k10k 5k 2k 1k 5002001005020-40-35-30-25-20-15-10-50510152025303540f /Hzd B r 新型紧凑高效乐器放大器的设计思路Kenneth Kantor(ZT Amplifiers,Inc.,2329Fourth S tre et Berkeley,CA 94710,USA)【摘要】介绍了封装在体积小、便携式音箱内大功率输出乐器放大器的设计理念。

外文原文：Damage as a measure for earthquake-resistant design ofmasonry structuresauthor：Miha TomazˇevicAbstract:The results of lateral resistance tests of masonry walls and shaking table tests of a number of models of ma-sonry buildings of various structural configurations, built with various materials in different construction systems, havebeen analyzed to find a correlation between the occurrence of different grades of damage to structural elements, character-istic limit states, and lateral displacement capacity. On the basis of correlation between acceptable level of damage and displacement capacity, it has been shown that the range of elastic force reduction factor values used to determine the de-sign seismic loads for different masonry construction systems proposed by the recently adopted European standard Euro-code 8 EN-1998-1 for earthquake resistant design are adequate. By using the recommended design values, satisfactory performance of the masonry buildings that have been analyzed may be expected when subjected to design intensity earth-quakes with respect to both the no-collapse and damage-limitation requirements.Key words: masonry structures, seismic-resistant design, seismic performance, damage, limit states, behavior factor.1. IntroductionEarthquake-resistant design of masonry structures is a combination of tradition, experience, and modern engineer-ing principles based on experimental research. Usually, it is a two-step procedure: ( i ) the structure is conceived accord-ing to traditional requirements regarding structural configu-ration and ( ii ) the seismic resistance is verified by calculations and the dimensions and distribution of structural elements are modified, if necessary.Since no-collapse and damage-limitation requirements should be fulfilled, the ultimate state (associated with collap-se) and the serviceability limit state (associated with the oc-currence of minimum damage) also need to be verified in the case of masonrystructures. According to the recently adopted Eurocode 8 standard,Design of structures for earth-quake resistance (CEN 2004), the structure should be de-signed to withstand the design seismic action, i.e., earthquake, with a return period of 475 years and a 10% probability of exceedance in 50 years, and the no-collapse requirement defined in Eurocode 8 as ……without local or global collapse, thus retaining its structural integrity and a residual load bearing capacity after the seismic events.‟‟However, the structure should also be designed to withstand an earthquake having a larger probability of occurrence than the design earthquake, i.e., earthquake with return period of 95 years with 10% probability of exceedance in 10 years, as well as the damage-limitation requirement defined in Euro-code 8 as ……without the occurrence of damage and limita-tion of use, the costs of which would be disproportionately high in comparison with the costs of the structure itself.‟‟According to Eurocode 8, for all structural members and for the structure as a whole, the design resistance capacity Rd shall be greater than the design load Ed , which includes seismic actions if the structure is exposed to seismic haz-ard. The form in which the seismic action is used in seis-mic resistance verification depends on the importance and complexity of the structure under consideration. In the case of structures with regular structural configuration,where the response is not significantly affected by the con-tribution of higher modes of vibration, such as masonry structures, response spectra methods provide adequate re-sults. The calculations for these regular structures are fur-ther simplified by taking into account only one horizontal component of the seismic ground motion and analyzing the structure in each orthogonal direction separately. Non-linear dynamic response analysis is replaced by equivalent elastic static analysis, where the design seismic loads are evaluated on the basis of the design response spectra, con-sidering the structure as an equivalent single-degree-of-freedom system.The ordinates of the elastic response spectra are reduced by the structural behavior factor (elastic force reduction factor), q, defined by Eurocode 8 as a ……factor used for de-sign purposes to reduce the forces obtained from a linear analysis, in order to account for thenonlinear response of a structure‟‟ and it takes into account the energy dissipation and displacement capacity of the structure under considera-tion. According to Eurocode 8, ……the behavior factor q is an appr oximation of the ratio of the seismic forces that the structure would experience if its response was completely elastic with 5% viscous damping, to the minimum seismic forces that may be used in the design —with a conventional elastic analysis model —still ensuring a satisfactory re-sponse of the structure.‟‟ A ……satisfactory response,‟‟ in this case, means a ductile response; however, a response with a limited amount of damage to structural elements. Therefore,to prevent excessive damage to structural walls, the dam-age-limitation requirement should be the leading parameter when deciding upon the design ductility capacity of the structural type under consideration and, consequently, deter-mining the value of behavior factorq to be considered in the design.The amou A limited number of seismic vulnerability and other stud-ies already provide basic information regarding the damage-limitation requirements (Alcocer et al. 2004; Calvi 1999;D‟Ayala 1998) to be considered in the design and seismic esistance verification of masonry structures of different ypologies and construction systems.As a contribution to ex-isting information, experimental results obtained in the past by testing different walls and models of masonry buildings at the Slovenian National Building and Civil Engineering In-stitute (ZAG) in Ljubljana, Slovenia, have been analyzed.The results of this analysis indicate that structural damage is correlated with storey drift in anuniform way, not depending on the type of masonry under consideration. Consequently, adequate seismic performance of masonry structures may be expected if, besides ductility and energy dissipation capacity of the structure, damage-limitation requirements in terms of.maximum acceptable storey drift are taken into account when determining the design seismic loads and respective values of the elastic force reduction factor q2. Seismic resistance and limit statesBasic information regarding the seismic behaviour of structures or structural elements is obtained on the basis of known relationships between lateral resistance and displace-ments. By knowing the so-called resistance curve and of damage that is associated with typical limit states defined on the curve, the seismic performance of the structure for the case of the expected seismic loads can be assessed. In the case of unreinforced and confined masonry struc-tures, the resistance curve is adequately represented by the relationship between the resistance R of the critical storey, usually the first storey of the building, and storey drift d (relative storey displacement) of the same storey (Fig. 1). Usually, the curve is presented in a nondimensional form. The resistance is given in terms of the seismic resistance co-efficient (SRC), i.e., the ratio between the resistance, R , and weight of the building, W, above the critical section (SRC = R/W ). The displacements, however, are expressed in terms of storey rotation F , which is the ratio between the storey drift, d, and storey height, h ( F = d/h). The following four main limit states, which are used in seismic resistance verification and determine the usability of buildings, are defined on the resistance curve (Fig. 1):(1) Crack (damage) limit state, where the first cracks occur in the walls causing evident changes in stiffness of the structural system. Crack limit on the resistance curve is sometimes associated with the serviceability limit state of the structure.(2) Maximum resistance.(3) Design ultimate limit state, where the resistance of the system degrades below the acceptable level. Convention-ally, 20% of degradation of the maximum resistance is acceptable. Consequently, part of the resistance curve, where the resistance degrades below 80% of the maxi-mum, is no longer considered for design purposes. Itonly provides information about additional ductility and energy dissipation capacity, i.e., additional safety of the structure. (4) Limit of collapse, defined by partial or total collapse of the structure.3. Correlation between damage, limit states and usabilityUsability of earthquake-damaged buildings is assessed on the basis of the observed damage. Different categories of damage such as light, moderate, heavy, and very heavy (severe) are attributed to different categories of usability. Fig. 2 provides examples of post-earthquake damage obser-vations of a number of typical central European masonry buildings, showing moderate, heavy, and severe damage (near collapse). A number of unreinforced and confined masonry walls have been tested in the laboratory, by subjecting them to cyclic lateral loading, and a series of models of the same types of masonry construction systems have been tested on a shaking table. An attempt has been made to correlate the resulting physical damage to the tested walls and model buildings with the limit states and, consequently, use this information for the assessment of usability of earthquake-damaged buildings. Complete (true replica) models have also been tested on the shaking table and correlation tests, carried out on prototype and model masonry walls, showed very good agreement between the model and prototype masonry with respect to the similarity of resistance curves as well as damage patterns at the characteristic limit states. Therefore, although the information was obtained on the models, it can also be considered reliable for the case of the prototype structures. As the first step of analysis, typical damage categories (grades) have been defined. Although the types of damage to masonry walls and buildings vary depending on masonry materials and construction systems, damage to structural walls can be classified and damage grades can be defined in a uniform way. The classification of damage and damage grades proposed by the European macroseismic scale (EMS-98) (Gru¨ nthal 1998) for masonry buildings has been used as a basis for the description of structural damage to masonry walls. In the case of prevailing shear behavior, typical for all masonry construction systems when subjected to seismic loads, the following characteristic damage patterns can be attributed to damage grades as defined by the EMS-98 scale:Grade 1 — no structural damage.Grade 2 —slight structural damage, cracks in many walls: formation of the first hardly visible diagonally oriented cracks in the middle part of the wall, light damage. Grade 3 — moderate structural damage, cracks in many walls: increased number of cracks with limited width (less than 0.2 mm wide), oriented diagonally in both diag-onal directions; moderate, repairable damage which maybe defined as acceptable damage at the serviceability limitstate.Grade 4 —heavy structural damage, serious failure of walls: increased number of diagonally oriented cracks that are more than 1 mm but less than 10 mm wide; crushing of individual masonry units; heavy damage, which is in most cases repairable, but sometimes repair is not economical.Grade 5 —total or near total collapse: increased crack width (more than 10 mm); crushing of units along both wall diagonals; severe strength degradation and final col-lapse.Typical damage patterns at characteristic damage grades for the case of plain masonry walls tested in the laboratory are presented in Fig. 3.Similar correlation between the observed damage, attrib-uted damage grades, andlimit states has been made for the case of the tested model buildings:Grade 2 —first structural damage, which may cause noticeable decay of the first natural vibration frequency of the building.Grade 3 — increased number of cracks, typical for the governing behavior mechanism of the structural system (diagonal cracks in the case of shear, horizontal tension cracks in the case of a flexural mechanism). As in the case of individual walls, this type of crack pattern is typi-cally observed at, or very soon after, the attained maxi-mum lateral resistance of the building. Moderate, repairable damage.Grade 4 —heavy damage to the walls, defined by crush-ing at the corners of the building, falling out of parts of the walls, and (or) crushing of individual masonry units.Damage is in most cases repairable, but sometimes the re-pair is not economical. Grade 5 — increased damage to the walls. Damage to horizontal structural elements, such as slabs and bond beams; crushing of concrete; and rupture or buckling of reinforcing bars (if reinforced). Final collapse.It is obvious that damage grades 2 and 5 define the crack limit and limit of collapse, respectively. As indicated by the analysis of experimentally obtained resistance curves, the displacement levels at which the crack limit and maximum resistance are attained are relatively close together (see Table 1). It has also been found that grade 3 damage can develop sometime after the attained maximum resistance. The analysis of the experiments has shown that such damage may generally occur at storey drift, equal to approximately three times the storey drift (rotation) at the occurrence of the first cracks in the walls.Grade 4 damage is observed near the point that is defined as the design ultimate limit state, where the actual resistance of the structure degrades to 80% of the maximum. However, as grade 4 damage is often not economical torepair, it is proposed that, in addition to the criterion of 20% degradation of resistance, the damage-limitation requirement should also be considered when deciding on the level of design ultimate limit state. As indicated by this analysis, the occurrence of grade 3 damage seems to be an adequate measure. It is, therefore, recommended that in their design, displacement and ductility capacity of masonry structures should not be usedbeyond the storey drift, which is equal to three times the displacement (rotation) at the occurrence of the first cracks in structural walls. Therefore, the design ultimate state on the idealized resistance curve may be defined by either the displacement (rotation) value, where the resistance degrades to 80% of the maximum (no-collapse requirement), or the displacement (rotation) value, which attains three times the value of the displacement (rotation) at the occurrence of cracks (damage-limitation requirement), whichever is less:Fire following an earthquake is an important factor causing damage to buildings and life-line structures. There-fore, besides satisfying structural design requirements for normal loads, such as dead and live loads including the seismichazard, buildings should also be designed to withstand the fire following earthquakes for a certain minimum duration as required for a desired level of performance. This period of time will allow occupants to evacuate the building safely and the emergency crews to cope with the fire. Also, it is essential to reduce the post-earthquake fire (PEF) ignitions and mini-mize the damage to active fire protection systems as much as possible to prevent the spread of fire. This paper presents a state-of-the-art review on the PEF hazard and discusses the causes, mitigation measures, and performance of building structures under this hazard. Mitigation measures that could be developed based on the experience from the structural engi-neering field are identified. Both local and global approaches that should be taken to mitigate the PEF hazard, including structural and nonstructural design, various urban planning aspects, and their interactive combinations, are discussed.Based on the review, it is concluded that that there is a strong need for the development of guidelines for structural firesafety design for PEF scenarios. In addition, appropriate analysis and numerical simulation techniques for the evaluationof the structural performance under earthquake-induced fire conditions need to be developed. It is also necessary to con-duct experimental studies to validate such numerical models and refine them.文献来源：Miha Tomazˇevic 《Damage as a measure for earthquake-resistantdesign of masonry structures》损害为砌体结构的抗震设计措施作者：Miha Tomazˇevic摘要：对砌体墙抗侧力测试和振动的砌体建筑模型的各种结构配置表测试的结果，在不同的建筑系统各种材料建成的，进行了分析，发现不同档次的损坏的结构元素的发生之间的相关性特征，极限状态，和侧位移量。