1、Steel Design Guide SeriesLoad and Resistance Factor Design ofW-ShapesEncased in Concrete 2003 by American Institute of Steel Construction, Inc. All rights reserved.This publication or any part thereof must not be reproduced in any form without permission of the publisher.Steel Design Guide SeriesLoa
2、d and ResistanceFactor Design ofW-Shapes Encasedin ConcreteLawrence G. GriffisWalter P. Moore and Associates, Inc.Houston, TexasAMERICAN INSTITUTE OF STEEL CONSTRUCTION 2003 by American Institute of Steel Construction, Inc. All rights reserved.This publication or any part thereof must not be reprodu
3、ced in any form without permission of the publisher.Copyright 1992 by American Institute of Steel Construction.All rights reserved. No part of this publication may be reproducedwithout written permission.Published by the American Institute of Steel Construction, Inc.at One East Wacker Drive, Suite 3
4、100, Chicago, IL 60601-2001. 2003 by American Institute of Steel Construction, Inc. All rights reserved.This publication or any part thereof must not be reproduced in any form without permission of the publisher.TABLE OF CONTENTSINTRODUCTION. 1SCOPE . 1PART 1: USE AND DESIGN OFCOMPOSITE COLUMNS 1Com
5、posite Frame Construction . 1Practical Uses of Composite Columns. 2Advantages, Disadvantages, and Limitations 2Practical Design Considerations 3Fire Resistance . 3Longitudinal Reinforcing Bar Arrangement. 3Ties . 4Longitudinal Reinforcing Bar Splices 4Connection of Steel Beam to EncasedWide Flange .
6、 5Shear Connectors . 5Base Plate. 6Erection and Temporary Wind Bracing During Composite Frame Construction 1Load and Resistance Factor Design (LRFD) ofComposite Columns 7Comparison Between LRFD and Strain Compatibility Methods . 8Description of the Composite Beam-Column Load Tables 10REFERENCES . 11
7、NOMENCLATURE 12PART 2: SUGGESTED DETAILS FORCOMPOSITE COLUMNS . 13PART 3: DESIGN EXAMPLES. 18PART 4: LRFD COMPOSITE BEAM-COLUMN DESIGN TABLES. 29Instructions for Using LRFD Composite Beam- Column Design Tables . 29PART 5: COMPOSITE COLUMN PROGRAMCMPOL 310 2003 by American Institute of Steel Construc
8、tion, Inc. All rights reserved.This publication or any part thereof must not be reproduced in any form without permission of the publisher.PREFACEThis booklet was prepared under the direction of the Com-mittee on Research of the American Institute of Steel Con-struction, Inc. as part of a series of
9、publications on specialtopics related to fabricated structural steel. Its purpose is toserve as a supplemental reference to the AISC Manual of SteelConstruction to assist practicing engineers engaged in build-ing design.The design guidelines suggested by the authors that areoutside the scope of the
10、AISC Specifications or Code do notrepresent an official position of the Institute and are notintended to exclude other design methods and procedures. Itis recognized that the design of structures is within the scopeof expertise of a competent licensed structural engineer,architect, or other licensed
11、 professional for the application ofprinciples to a particular structure.The sponsorship of this publication by the American Iron andSteel Institute is gratefully acknowledged.The information presented in this publication has been prepared in accordance with recognized engineeringprinciples and is f
12、or general information only. While it is believed to be accurate, this information should not beused or relied upon for any specific application without competent professional examination and verification ofits accuracy, suitability, and applicability by a licensed professional engineer, designer, o
13、r architect. Thepublication of the material contained herein is not intended as a representation or warranty on the part of theAmerican Institute of Steel Construction, Inc. or the American Iron and Steel Institute, or of any other personnamed herein, that this information is suitable for any genera
14、l or particular use or of freedom infringement of anypatent or patents. Anyone making use of this information assumes all liability arising from such use. 2003 by American Institute of Steel Construction, Inc. All rights reserved.This publication or any part thereof must not be reproduced in any for
15、m without permission of the publisher.LOAD AND RESISTANCE FACTOR DESIGN OFW-SHAPES ENCASED IN CONCRETEINTRODUCTIONStructural members comprised of steel shapes in combinationwith plain or reinforced concrete have been utilized by engi-neers for many years. Early structures simply took advantageof the
16、 protection that the concrete afforded to the steel shapesfor resistance to fire and corrosion. But research on thestrength of such members was conducted in the early 1900s,1and design provisions were formulated by 1924.2More re-cently, with the advent of modern composite frame construc-tion in high
17、 rise buildings, engineers developed new rationalmethods to take advantage of the stiffening and strengtheningeffects of concrete and reinforcing bars on the capacity ofencased steel shapes.This Guide presents design tables for composite columns,developed under the sponsorship of the American Instit
18、ute ofSteel Construction (AISC) as an aid to the practicing struc-tural engineer in the application of the AISC Load and Resis-tance Factor Design (LRFD) Specification for StructuralSteel Buildings.3The information presented supplements thatfound in the AISC LRFD Manual.4Background on the LRFDcriter
19、ia for composite columns may be found in References 5and 6. Engineers interested in Allowable Stress Design (ASD)are encouraged to consider the procedure developed pre-viously by the Structural Stability Research Council (SSRC).7The SSRC procedure is not presently included in the AISCASD Specificati
20、on.8The reader is cautioned that independent professional judg-ment must be exercised when data or recommendations setforth in this Guide are applied. The publication of the materialcontained herein is not intended as a representation or war-ranty on the part of the American Institute of Steel Const
21、ruc-tion, Inc.or any person named hereinthat this informa-tion is suitable for general or particular use, or freedom frominfringement of any patent or patents. Anyone making use ofthis information assumes all liability rising from such use.The design of structures should only be performed by or unde
22、rthe direction of a competent licensed structural engineer,architect, or other licensed professional.SCOPEThis Guide is specifically for composite columns comprisedof rolled wide flange shapes encased in reinforced structuralconcrete with vertical deformed reinforcing bars and lateralties. Composite
23、 columns are defined in Section I1 of theLRFD Specification as a “steel column fabricated from rolledor built-up steel shapes and encased in reinforced structuralconcrete or fabricated from steel pipe or tubing and filled withstructural concrete.“ Further, the Specification requires inSection I2.1 t
24、hat the cross sectional area of the steel shapecomprise at least four percent of the total composite crosssection. The Commentary to the Specification states thatwhen the steel shape area is less, the column should bedesigned under the rules for conventional reinforced concretecolumns.Part 1 of this
25、 Guide includes a discussion of compositeframe construction, practical uses of composite columns,their advantages and limitations, and a review of importantpractical design considerations. A summary of the pertinentLRFD rules is presented and compared to other methods. Aset of suggested design detai
26、ls is given in Part 2, showingplacement of reinforcing bars and ties, as well as treatment ofjoints and base plates. Five design examples are given inPart 3 to illustrate how the tables were derived and how theyare applied. Finally, a comprehensive set of tables is presentedin Part 4 to assist the d
27、esigner in the rapid selection of themost economical section to resist required values of factoredload and moment.PART 1: USE AND DESIGN OFCOMPOSITE COLUMNSComposite Frame ConstructionAlthough engineers since the 1930s have encased structuralsteel shapes in concrete for fireproofing and corrosion pr
28、otec-tion, it was not until the development and popularity ofmodern composite frame construction in the 1960s that com-posite columns again became a common and viable structuralmember type. The late Dr. Fazlur Khan, in his early discus-sions of structural systems for tall buildings, first proposedth
29、e concept of a composite frame system9, 10utilizing compos-ite columns as part of the overall wind and earthquake resist-ing frame. Since that time composite frame construction hasbeen adopted for many high rise buildings all over the world.Its usage, with the composite column as the key element, is
30、well documented in the work of the Council on Tall Buildingsand numerous other publications.11-15The term “composite frame structure“ describes a buildingemploying concrete encased steel columns and a compositefloor system (structural steel and concrete filled steel deck).1 2003 by American Institut
31、e of Steel Construction, Inc. All rights reserved.This publication or any part thereof must not be reproduced in any form without permission of the publisher.The bare steel columns resist the initial gravity, construction,and lateral loads until such time as the concrete is cast aroundthem to form c
32、omposite columns capable of resisting the totalgravity and lateral loads of the completed structure. In acomposite frame building, the structural steel and reinforcedconcrete combine to produce a structure having the advan-tages of each material. Composite frames have the advantageof speed of constr
33、uction by allowing a vertical spread of theconstruction activity so that numerous trades can engagesimultaneously in the construction of the building. Inherentstiffness is obtained with the reinforced concrete to moreeasily control the building drift under lateral loads and reduceperception to motio
34、n. The light weight and strength obtainedwith structural steel equates to savings in foundation costs.Traditionally in steel framed buildings or reinforced con-crete buildings, stability and resistance to lateral loads areautomatically provided as the structure is built. Welded orbolted moment conne
35、ctions are made or braces are connectedbetween columns in a steel building immediately behind theerection of the steel frame to provide stability and resistanceto lateral loads. Shear walls, or the monolithic casting ofbeams and columns, provide stability and resistance to lateralloads soon after th
36、e concrete has cured for reinforced concretebuildings. However, for composite frame structures, the finalstability and resistance to design lateral loads is not achievedtypically until concrete around the erection steel frame hascured, which typically occurs anywhere from a minimum ofsix to as much
37、as 18 floors behind the erection of the baresteel frame. This sequence of construction is shown-schemati-cally in Fig. 1. Thus, as discussed subsequently, temporaryFig. 1. Composite-frame construction sequence.lateral bracing of the uncured portion of the frame willtypically be required.Practical Us
38、es of Composite ColumnsPractical applications for the use of composite columns canbe found in both low rise and high rise structures. In low risestructures such as a covered playground area, a warehouse, atransit terminal building, a canopy, or porte cochere, it maybe necessary or desirable to encas
39、e a steel column withconcrete for aesthetic or practical reasons. For example, ar-chitectural appearance, resistance to corrosion, or protectionagainst vehicular impact may be important. In such structures,it may be structurally advantageous to take advantage of theconcrete encasement of the rolled
40、steel shape that supportsthe steel roof structure by designing the member as a compos-ite column resisting both gravity and lateral loads.In high rise structures, composite columns are frequentlyused in the perimeter of “tube“ buildings where the closelyspaced columns work in conjunction with the sp
41、andrel beams(either steel or concrete) to resist the lateral loads. In somerecent high rise buildings, giant composite columns placed ator near the corners of the building have been utilized as partof the lateral frame to maximize the resisting moment pro-vided by the buildings dead load. Composite
42、shear walls withencased steel columns to carry the floor loads have also beenutilized in the central core of high rise buildings. Frequently,in high rise structures where floor space is a valuable andincome producing commodity, the large area taken up by aconcrete column can be reduced by the use of
43、 a heavy encasedrolled shape to help resist the extreme loads encountered intall building design. Sometimes, particularly at the bottomfloors of a high rise structure where large open lobbies oratriums are planned, a heavy encased rolled shape as part ofa composite column is a necessity because of t
44、he large loadand unbraced length. A heavy rolled shape in a compositecolumn is often utilized where the column size is restrictedarchitecturally and where reinforcing steel percentages wouldotherwise exceed the maximum code allowed values.Advantages, Disadvantages, and LimitationsSome of the advanta
45、ges of composite columns are as follows:1. Smaller cross section than required for a conventionalreinforced concrete column.2. Larger load carrying capacity.3. Ductility and toughness available for use in earthquakezones.4. Speed of construction when used as part of a compositeframe.5. Fire resistan
46、ce when compared to plain steel columns.6. Higher rigidity when part of a lateral load carryingsystem.7. Higher damping characteristics for motion perception intall buildings when part of a lateral load carrying system.2 2003 by American Institute of Steel Construction, Inc. All rights reserved.This
47、 publication or any part thereof must not be reproduced in any form without permission of the publisher.8. Stiffening effect for resistance against buckling of therolled shape.There are also, of course, some disadvantages and limita-tions. In high rise composite frame construction, design en-gineers
48、 sometimes have difficulty in controlling the rate andmagnitude of column shortening of the composite columnwith respect to adjacent steel columns or shear walls. Theseproblems are exacerbated by the wide variation in construc-tion staging often experienced in the zone between the pointwhere the ste
49、el erection columns are first erected and the pointwhere concrete is placed around the steel to form the com-posite column. This variation in the number of floors betweenconstruction activities has made it difficult to calculate withaccuracy the effect of column shortening. Creep effects on thecomposite columns with respect to the all-steel core columns,or between shears walls, can also be troublesome to predictfor the designer. The net effect of these problems can be floorsthat are not level from one point to another. One solution tothese problems has been the measurement of column
