ETABS. Integrated Building Design Software. Composite Floor Frame Design Manual. Computers and Structures, Inc. Berkeley, California, USA

Transcription

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2 ETABS Integrated Building Design Software Composite Floor Frame Design Manual Computers and Structures, Inc. Berkeley, California, USA Version 8 January 2002

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4 Copyright The computer program ETABS and all associated documentation are proprietary and copyrighted products. Worldwide rights of ownership rest with Computers and Structures, Inc. Unlicensed use of the program or reproduction of the documentation in any form, without prior written authorization from Computers and Structures, Inc., is explicitly prohibited. Further information and copies of this documentation may be obtained from: Computers and Structures, Inc University Avenue Berkeley, California USA Phone: (510) FAX: (510) (for general questions) (for technical support questions) web: Copyright Computers and Structures, Inc., The CSI Logo is a trademark of Computers and Structures, Inc. ETABS is a trademark of Computers and Structures, Inc. Windows is a registered trademark of Microsoft Corporation. Adobe and Acrobat are registered trademarks of Adobe Systems Incorporated

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6 DISCLAIMER CONSIDERABLE TIME, EFFORT AND EXPENSE HAVE GONE INTO THE DEVELOPMENT AND DOCUMENTATION OF ETABS. THE PROGRAM HAS BEEN THOROUGHLY TESTED AND USED. IN USING THE PROGRAM, HOWEVER, THE USER ACCEPTS AND UNDERSTANDS THAT NO WARRANTY IS EXPRESSED OR IMPLIED BY THE DEVELOPERS OR THE DISTRIBUTORS ON THE ACCURACY OR THE RELIABILITY OF THE PROGRAM. THIS PROGRAM IS A VERY PRACTICAL TOOL FOR THE DESIGN/CHECK OF STEEL STRUCTURES. HOWEVER, THE USER MUST THOROUGHLY READ THE MANUAL AND CLEARLY RECOGNIZE THE ASPECTS OF COMPOSITE DESIGN THAT THE PROGRAM ALGORITHMS DO NOT ADDRESS. THE USER MUST EXPLICITLY UNDERSTAND THE ASSUMPTIONS OF THE PROGRAM AND MUST INDEPENDENTLY VERIFY THE RESULTS.

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8 COMPUTERS AND STRUCTURES, INC., BERKELEY, CALIFORNIA DECEMBER 2001 COMPOSITE BEAM DESIGN Contents General Composite Beam Design Information 1 General Design Information Design Codes 1-1 Units 1-1 Beams Designed as Composite Beams 1-1 Material Property Requirements for Composite Beams 1-2 Other Requirements for Composite Beams 1-2 Frame Elements Designed by Default as Composite Beams 1-3 Overwriting the Frame Design Procedure for a Composite Beam 1-3 How the Program Optimizes Design Groups 1-5 Using Price to Select Optimum Beam Sections 1-6 Design Load Combinations 1-8 Analysis Sections and Design Sections 1-8 Output Stations Composite Beam Design Process Design Process for a New Building 2-1 Check Process for an Existing Building Interactive Composite Beam Design Member Identification 3-1 Section Information 3-2 Acceptable Sections List 3-3 ReDefine 3-4 i

9 Composite Beam Design Manual Temporary 3-5 Show Details Output Data Plotted Directly on the Model Overview 4-1 Labels Displayed on the Model 4-2 Design Data 4-3 Stress Ratios 4-4 Deflection Ratios Input Data General 5-1 Using the Print Composite Beam Design Tables Form 5-1 Material Properties Input Data 5-2 Section Properties Input Data 5-3 Deck Properties Input Data 5-4 Design Preferences Input Data 5-6 Beam Overwrites Input Data Output Data Overview 6-1 Using the Print Composite Beam Design Tables Form 6-1 Summary of Composite Beam Output Composite Beam Properties Beam Properties 7-1 Metal Deck and Slab Properties 7-3 Shear Stud Properties 7-5 Cover Plates Effective Width of Concrete Slab Location Where Effective Slab Width is Checked 8-1 Multiple Deck Types or Directions Along the Beam Length 8-2 Effect of Diagonal Beams on Effective Slab Width 8-6 ii

10 Contents Effect of Openings on Effective Slab Width 8-8 Effective Slab Width and Transformed Section Properties Beam Unbraced Length Overview 9-1 Determination of the Braced Points of a Beam 9-2 User-Defined Unbraced Length of a Beam Overview 9-3 User-Specified Uniform and Point Bracing 9-4 Design Check Locations Design Load Combinations Overview 10-1 Special Live Load Patterning for Cantilever Back Spans 10-2 Special Live Load Patterning for Continuous Spans Beam Deflection and Camber Deflection 11-1 Camber Beam Vibration Overview 12-1 Vibration Frequency 12-1 Murray's Minimum Damping Requirement 12-4 Initial Displacement Amplitude 12-4 Effective Number of Beams Resisting Heel Drop Impact 12-6 References Distribution of Shear Studs on a Composite Beam Overview 13-1 Composite Beam Segments 13-1 iii

11 Composite Beam Design Manual Physical End of the Beam Top Flange 13-2 Distribution of Shear Studs Within a Composite Beam Segment 13-5 How the Program Distributes Shear Studs on a Beam 13-5 Equations Used When the Program Works from Left to Right 13-8 Equations Used When the Program Works from Right to Left 13-9 Minimum and Maximum Number of Shear Studs in a Composite Beam Segment A Note About Multiple Design Load Combinations The Number of Shear Studs that Fit in a Composite Beam Segment General 14-1 Solid Slab or Deck Ribs Oriented Parallel to Beam Span 14-2 Deck Ribs Oriented Perpendicular to Beam Span 14-6 Different Deck Type or Orientation on Beam Sides User-Defined Shear Stud Patterns Specifying a User-Defined Shear Connector Pattern 15-1 Uniformly Spaced Shear Studs Over the Length of the Beam 15-2 Additional Shear Studs in Specified Sections of Beam 15-4 Defining Additional Beam Sections 15-4 Example of a User-Defined Shear Stud Pattern 15-8 How the Program Checks a Beam with User- Defined Shear Studs 15-9 iv

12 Contents Composite Beam Design Specific to AISC-ASD89 16 General and Notation Introduction to the AISC-ASD89 Series of Technical Notes 16-1 Notation Preferences General 17-1 Using the Preferences Form 17-1 Preferences 17-2 Factors Tab 17-3 Beam Tab 17-3 Deflection Tab 17-4 Vibration Tab 17-5 Price Tab Overwrites General 18-1 Using the Composite Beam Overwrites Form 18-2 Overwrites 18-3 Beam Tab 18-4 Bracing (C) Tab and Bracing Tab 18-6 Deck Tab 18-9 Shear Studs Tab Deflection Tab Vibration Tab Miscellaneous Tab EQ Factor Width-to-Thickness Checks Overview 19-1 Limiting Width-to-Thickness Ratios for Flanges 19-2 Compact Section Limits for Flanges 19-2 Noncompact Section Limits for Flanges 19-2 v

13 Composite Beam Design Manual Limiting Width-to-Thickness Ratios for Webs 19-3 Compact Section Limits for Webs 19-3 Noncompact Section Limits for Webs 19-3 Limiting Width-to-Thickness Ratios for Cover Plates 19-4 Compact Section Limits for Cover Plates 19-5 Noncompact Section Limits for Cover Plates Transformed Section Moment of Inertia Background 20-2 Properties of Steel Beam (Plus Cover Plate) Alone 20-4 Properties of the Composite Section General Calculation Method 20-7 Equivalent Hand Calculation Method to Calculate the Distance y e Background Equations Hand Calculation Process for y e Equivalent Hand Calculation Method to Calculate the Composite Properties Elastic Stresses with Partial Composite Connection Effective Moment of Inertia for Partial Composite Connection 21-1 Effective Section Modulus Referred to the Extreme Tension Fiber 21-2 Location of the ENA for Partial Composite Connection 21-3 Steel Section Stresses for Partial Composite Connection 21-5 Concrete Slab Stresses for Partial Composite Connection Allowable Bending Stresses General 22-1 vi

14 Contents Allowable Bending Stress for Steel Beam Alone 22-2 Allowable Bending Stresses for Positive Bending in the Composite Beam Bending Stress Checks Bending Stress Checks Without Composite Action 23-1 Positive Moment in a Composite Beam 23-2 Important Notes Regarding Unshored Composite Beams 23-5 Steel Stress Checks 23-5 Concrete Stress Checks Beam Shear Checks Shear Stress Check 24-1 Typical Case 24-1 Slender Web 24-2 Copes 24-3 Shear Rupture Check 24-4 Limitations of Shear Check Shear Studs Overview 25-1 Shear Stud Connectors 25-1 Reduction Factor when Metal Deck is Perpendicular to Beam 25-2 Reduction Factor when Metal Deck is Parallel to Beam 25-3 Horizontal Shear for Full Composite Connection 25-4 Number of Shear Studs 25-5 Between the Output Station with Maximum Moment and the Point of Zero Moment 25-6 Between Other Output Stations and Points of Zero Moment 25-6 vii

15 Composite Beam Design Manual 26 Calculation of the Number of Shear Studs Basic Equations 26-1 Shear Stud Distribution Example Shear Stud Distribution Example Shear Stud Distribution Example Detailed Calculations Input Data Beam Overwrites Input Data Output Details Short Form Output Details 28-1 Composite Beam Design Specific to AISC-LRFD93 29 General and Notation AISC-LRFD93 Design Methodology 29-1 Notation Preferences General 30-1 Using the Preferences Form 30-1 Preferences 30-2 Factors Tab 30-3 Beam Tab 30-4 Deflection Tab 30-5 Vibration Tab 30-5 Price Tab Overwrites General 31-1 Using the Composite Beam Overwrites Form 31-2 Resetting Composite Beam Overwrites to Default Values 31-3 Overwrites 31-3 Beam Tab 31-4 Brace (C) Tab and Bracing Tab 31-6 viii

16 Contents Deck Tab 31-9 Shear Studs Tab Deflection Tab Vibration Tab Miscellaneous Tab Design Load Combinations Strength Check for Construction Loads 32-1 Strength Check for Final Loads 32-2 Deflection Check for Final Loads 32-2 Reference Compact and Noncompact Requirements Overview 33-1 Limiting Width-to-Thickness Ratios for Flanges 33-2 Compact Section Limits for Flanges 33-2 Noncompact Section Limits for Flanges 33-2 Limiting Width-to-Thickness Ratios for Webs 33-3 Compact Section Limits for Webs 33-3 Noncompact Section Limits for Webs 33-4 Limiting Width-to-Thickness Ratios for Cover Plates 33-5 Compact Section Limits for Cover Plates 33-5 Noncompact Section Limits for Cover Plates Composite Plastic Moment Capacity for Positive Bending Overview 34-1 Location of the Plastic Neutral Axis 34-2 PNA in the Concrete Slab Above the Steel Beam 34-5 PNA within the Beam Top Flange 34-8 PNA within the Beam Top Fillet 34-9 PNA within the Beam Web ix

17 Composite Beam Design Manual PNA within the Beam Bottom Fillet PNA within the Beam Bottom Flange PNA within the Cover Plate Calculating the PNA Location Plastic Moment Capacity for Positive Bending Composite Section Elastic Moment Capacity Positive Moment Capacity with an Elastic Stress Distribution Moment Capacity for Steel Section Alone Overview 36-1 Steel Beam Properties 36-1 Moment Capacity for a Doubly Symmetric Beam or a Channel Section 36-2 Lateral Unbraced Length Checks 36-3 Yielding Criteria in AISC-LRFD93 Section F Lateral Torsional Buckling Criteria in AISC-LRFD93 Section F1.2a 36-5 AISC-LFRD Appendix F1(b) Equation A-F Moment Capacity for a Singly Symmetric Beam with a Compact Web 36-7 AISC-LFRD93 Equation A-F1-1 for WLB 36-8 AISC-FLRD93 Equation A-F1-1 for FLB 36-8 AISC-FLRD93 Equation A-F1-3 for FLB 36-9 AISC-FLRD93 Equation A-F1-1 for LTB 36-9 AISC-FLRD93 Equation A-F1-2 for LTB Moment Capacity for a Singly Symmetric Beam with a Noncompact Web x

18 Contents AISC-LFRD93 Equation A-F1-3 for WLB Partial Composite Connection with a Plastic Stress Distribution Estimating the Required Percent Composite Connection 37-1 Calculating MPFconc 37-2 Location of PNA 37-3 Determining the Effective Portion of the Concrete Slab 37-4 Moment Capacity of a Partially Composite Beam with a Plastic Stress Distribution Bending and Deflection Checks Bending Check Locations 38-1 Bending Check 38-1 Deflection Check Shear Connectors Shear Stud Connectors 39-1 Horizontal Shear for Full Composite Connection 39-1 Number of Shear Connectors 39-2 Between Maximum Moment and Point of Zero Moment 39-2 Between Point Load and Point of Zero Moment Beam Shear Capacity Shear Capacity 40-1 Checking the Beam Shear 40-2 Limitations of Beam Shear Check Input Data Beam Overwrites Input 41-1 xi

19 Composite Beam Design Manual 42 Output Details Short Form Output Details 42-1 Long Form Output Details 42-8 xii

20 COMPUTERS AND STRUCTURES, INC., BERKELEY, CALIFORNIA DECEMBER 2001 COMPOSITE BEAM DESIGN Technical Note 1 General Design Information This Technical Note presents some basic information and concepts that are useful when performing composite beam design using this program. Design Codes The design code is set using the Options menu > Preferences > Composite Beam Design command. You can choose to design for any one design code in any one design run. You cannot design some beams for one code and others for a different code in the same design run. You can however perform different design runs using different design codes without rerunning the analysis. Units For composite beam design in this program, any set of consistent units can be used for input. Typically, design codes are based on one specific set of units. The documentation in the Composite Beam Design series of Technical Notes is presented in kip-inch-seconds units unless otherwise noted. Again, any system of units can be used to define and design a building in the program. You can change the system of units at any time using the pull-down menu on the Status Bar or pull-down menu on individual forms where available. Note: You can use any set of units in composite beam design and you can change the units "on the fly." Beams Designed as Composite Beams Section Requirements for Composite Beams Only I-shaped and channel-shaped beams can be designed as composite beams. The I-shaped and channel-shaped beams can be selected from the Design Codes Technical Note 1-1

21 General Design Information Composite Beam Design built-in program section database, or they can be user defined. The userdefined sections can be specified using the Define menu > Frame Sections command and clicking either the Add I/Wide Flange or the Add Channel option. Note that beam sections that are defined in Section Designer are always treated as general sections. Thus, if you define an I-type or channel-type section in Section Designer, the program will consider it as a general section, not an I-shaped or channel-shaped section, and will not allow it to be designed as a composite beam. Note: Beam sections defined in the section designer utility cannot be designed as composite beams. Material Property Requirement for Composite Beams If a beam is to be designed as a composite beam, the Type of Design associated with the Material Property Data assigned to the beam must be Steel. Use the Define menu > Material Properties > Modify/Show Materials command to check your beams. Other Requirements for Composite Beams The line type associated with the line object that represents a composite beam must be "Beam." In other words, the beam element must lie in a horizontal plane. Right click on a line object to bring up the Line Information form to check the Line Type. For composite beams, the beam local 2-axis must be vertical. The Local axis 2 Angle is displayed on the Assignments tab of the Line Information form. Note: The line object representing a composite beam should span from support to support. Composite beams should not be modeled using multiple, adjacent line objects between supports for a single composite beam. The line object representing a composite beam should span from support to support. In the case of a cantilever beam overhang, the line object should span from the overhang support to the end of the beam. The cantilever beam back span should be modeled using a separate line object. If you do not model cantilever beams in this way, the analysis results for moments and Technical Note 1-2 Beams Designed as Composite Beams

22 Composite Beam Design General Design Information shears will still be correct but the design performed by the Composite Beam Design processor probably will not be correct. Frame Elements Designed by Default as Composite Beams The program will design certain frame elements using the design procedures documented in these Technical Notes by default. Those elements must meet the following restrictions: The beam must meet the section requirements described in the subsection entitled "Section Requirements for Composite Beams" in this Technical Note. The beam must meet the material property requirement described in the subsection entitled "Material Property Requirement for Composite Beams" in this Technical Note. The beam must meet the two other requirements described in the subsection entitled "Other Requirements for Composite Beams" in this Technical Note. At least one side of the beam must support deck that is specified as a Deck section (not a Slab or Wall section). The deck section can be filled, unfilled or a solid slab. When the deck is unfilled, the beam will still go through the Composite Beam Design postprocessor and will simply be designed as a noncomposite beam. The beam must not frame continuously into a column or a brace. Both ends of the beam must be pinned for major axis bending (bending about the local 3-axis). Overwriting the Frame Design Procedure for a Composite Beam The three procedures possible for steel beam design are: Composite beam design Steel frame design No design By default, steel sections are designed using either the composite beam design procedure or the steel frame design procedure. All steel sections that Beams Designed as Composite Beams Technical Note 1-3

23 General Design Information Composite Beam Design meet the requirements described in the previous subsection entitled "Frame Elements Designed by Default as Composite Beams" are by default designed using the composite beam design procedures. All other steel frame elements are by default designed using the steel frame design procedures. Change the default design procedure used for a beam(s) by selecting the beam(s) and clicking Design menu > Overwrite Frame Design Procedure. This change is only successful if the design procedure assigned to an element is valid for that element. For example, if you select two steel beams, one an I-section and the other a tube section, and attempt to change the design procedure to Composite Beam Design, the change will be executed for the I-section, but not for the tube section because it is not a valid section for the composite beam design procedure. A section is valid for the composite beam design procedure if it meets the requirements specified in the subsections entitled "Section Requirements for Composite Beams," "Material Property Requirement for Composite Beams" and "Other Requirements for Composite Beams" earlier in this Technical Note. Note that the procedures documented for composite beam design allow for designing a beam noncompositely. One of the overwrites available for composite beam design is to specify that selected beams are either designed as composite, noncomposite but still with a minimum number of shear studs specified, or noncomposite with no shear studs. These overwrites do not affect the design procedure. Changing the overwrite to one of the noncomposite designs does not change the design procedure from Composite Beam Design to Steel Frame Design. The noncomposite design in this case is still performed from within the Composite Beam Design postprocessor. Using the composite beam design procedure, out-of-plane bending is not considered and slender sections are not designed. This is different from the Steel Frame Design postprocessor. Thus, the design results obtained for certain beams may be different, depending on the design procedure used. Finally, note that you can specify that the composite beam design procedures are to be used for a beam even if that beam does not support any deck, or for that matter, even if no slab is specified. In these cases, the beam will be designed as a noncomposite beam by the Composite Beam Design postprocessor. Technical Note 1-4 Beams Designed as Composite Beams

24 Composite Beam Design General Design Information How the Program Optimizes Design Groups This section describes the process the program uses to select the optimum section for a design group. In this description, note the distinction between the term section, which refers to a beam section in an auto select section list, and the term beam, which refers to a specific element in the design group. When considering design groups, the program first discards any beam in the design group that is not assigned an auto select section list. Next, the program looks at the auto select section list assigned to each beam in the design group and creates a new list that contains the sections that are common to all of the auto select section lists in the design group. The program sorts this new common section list in ascending order, from smallest section to largest section based on section weight (area). Note: When designing with design groups, the program attempts to quickly eliminate inadequate beams. The program then finds the beam with the largest positive design moment in the design group, or the "pseudo-critical beam." The program then checks the design of the pseudo-critical beam for all sections in the common section list. Any sections in the common section list that are not adequate for the pseudocritical beam are discarded from the common section list, making the list shorter. This new list is the shorter common section list. The shorter common section list is still in ascending order based on section weight (area). Now the program checks all beams in the design group for the first section (smallest by weight [area]) in the shorter common section list. If the optimization is being performed on the basis of beam weight and the section is adequate for all beams in the design group, the optimum section has been identified. If the section is not adequate for a beam, the next higher section in the shorter common section list is tried until a section is found that is adequate for all beams in the design group. If the optimization is based on price instead of weight, the program finds the first section in the shorter common section list (i.e., the one with the lowest weight) that is adequate for all beams. Next it calculates the cost of this first How the Program Optimizes Design Groups Technical Note 1-5

25 General Design Information Composite Beam Design adequate section and then determines the theoretical heaviest section that could still have a cost equal to the adequate section by dividing the total price of the beam with the adequate section (steel plus camber plus shear connectors) by the unit price of the steel. This assumes that when the cost of the steel section alone is equal to or greater than the total cost of the adequate section, the section could not have a total cost less than the adequate section. The program then checks any other sections in the shorter common section list that have a weight less than or equal to the calculated maximum weight. If any of the other sections are also adequate, a cost is calculated for them. Finally, the section with the lowest associated cost is selected as the optimum section for the design group. Regardless of whether the optimization is based on weight or cost, if all sections in the shorter common section list are tried and none of them are adequate for all of the beams in the design group, the program proceeds to design each beam in the design group individually based on its own auto section list and ignores the rest of the design group. If for a particular beam none of the sections in the auto select section list are adequate, the program displays results for the section in the auto select list with the smallest controlling ratio in a red font. Note that the controlling ratio may be based on stress or deflection. Note: By default, the program selects the optimum composite beam size based on weight, not price. Using Price to Select Optimum Beam Sections By default, when auto select section lists are assigned to beams, the program compares alternate acceptable composite beam designs based on the weight of the steel beam (not including the cover plate, if it exists) to determine the optimum section. The beam with the least weight is considered the optimum section. The choice of optimum section does not consider the number of shear connectors required or if beam camber is required. Technical Note 1-6 Using Price to Select Optimum Beam Sections

26 Composite Beam Design General Design Information Important Note about Optimizing Beams by Weight and Price When a beam is optimized by weight, the program internally optimizes the beam based on area of steel (excluding the cover plate, if it exists). Thus, the weight density specified for the steel is irrelevant in such a case. When a beam is optimized by price, the program determines the price associated with the steel by multiplying the volume of the beam (including the cover plate, if it exists) by the weight density of the beam by the price per unit weight specified in the material properties for the steel. The price associated with camber is determined by multiplying the volume of the beam (including the cover plate, if it exists) by the weight density of the beam by the specified price per unit weight for camber defined in the composite beam preferences. The price for shear connectors is determined by multiplying the total number of shear connectors by the price per connector specified in the composite beam preferences. The total price for the beam is determined by summing the prices for the steel, camber and shear connectors. Thus, when a beam is optimized by price, the weight density for the steel is important and must be correctly specified for the price to be correctly calculated. Note that the volume of the beam is calculated by multiplying the area of the steel beam (plus the area of the cover plate, if used) by the length of the beam from center-of-support to center-of-support You can request that the program use price to determine the optimum section by clicking the Options menu > Preferences > Composite Beam Design command, selecting the Price tab and setting the "Optimize for Price" item to Yes. If you request a price analysis, the program compares alternate acceptable beam designs based on their price and selects the one with the least cost as the optimum section. For the cost comparison, specify costs for steel, shear studs and beam camber. The steel cost is specified as a part of the steel material property using the Define menu > Material Properties command. The shear stud and beam camber costs are specified in the composite beam preferences. The costs for steel and cambering are specified on a unit weight of the beam basis; for example, a cost per pound of the beam. The shear connector cost is specified on a cost per connector. By assigning different prices for steel, shear Using Price to Select Optimum Beam Sections Technical Note 1-7

27 General Design Information Composite Beam Design connectors and camber, you can influence the choice of optimum section. The cost of the cover plate is not included in the comparison (but it would be the same for all beam sections if it were included). See the previous "Important Note about Optimizing Beams by Weight and Price" for additional information. Design Load Combinations Using the Composite Beam Design postprocessor, three separate types of load combinations are considered. They are: Construction load strength design load combinations Final condition strength design load combinations Final condition deflection design load combinations You can specify as many load combinations as you want for each of these types. In addition, the program creates special live load patterns for cantilever beams. See Composite Beam Design Technical Note 20 Design Load Combinations for additional information on design load combinations for the Composite Beam Design postprocessor. Analysis Sections and Design Sections Analysis sections are those section properties used to analyze the model when you click the Analyze menu > Run Analysis command. The design section is whatever section has most currently been designed and thus designated the current design section. Tip: It is important to understand the difference between analysis sections and design sections. It is possible for the last used analysis section and the current design section to be different. For example, you may have run your analysis using a W18X35 beam and then found in the design that a W16X31 beam worked. In that case, the last used analysis section is the W18X35 and the current design section is the W16X31. Before you complete the design process, verify that the last used analysis section and the current design section are the same. Technical Note 1-8 Design Load Combinations

28 Composite Beam Design General Design Information The Design menu > Composite Beam Design > Verify Analysis vs Design Section command is useful for this task. The program keeps track of the analysis section and the design section separately. Note the following about analysis and design sections: Assigning a beam a frame section property using the Assign menu > Frame/Line > Frame Section command assigns the section as both the analysis section and the design section. Running an analysis using the Analyze menu > Run Analysis command (or its associated toolbar button) always sets the analysis section to be the same as the current design section. Assigning an auto select list to a frame section using the Assign menu > Frame/Line > Frame Section command initially sets the design section to be the beam with the median weight in the auto select list. Unlocking a model deletes the design results, but it does not delete or change the design section. Using the Design menu > Composite Beam Design > Select Design Combo command to change a design load combination deletes the design results, but it does not delete or change the design section. Using the Define menu > Load Combinations command to change a design load combination deletes the design results, but it does not delete or change the design section. Using the Options menu > Preferences > Composite Beam Design command to change any of the composite beam design preferences deletes the design results, but it does not delete or change the design section. Deleting the static nonlinear analysis results also deletes the design results for any load combination that includes static nonlinear forces. Typically, static nonlinear analysis and design results are deleted when one of the following actions is taken: Use the Define menu > Frame Nonlinear Hinge Properties command to redefine existing or define new hinges. Analysis Sections and Design Sections Technical Note 1-9

29 General Design Information Composite Beam Design Use the Define menu > Static Nonlinear/Pushover Cases command to redefine existing or define new static nonlinear load cases. Use the Assign menu > Frame/Line > Frame Nonlinear Hinges command to add or delete hinges. Again, note that these actions delete only results for load combinations that include static nonlinear forces. Output Stations Frame output stations are designated locations along a frame element. They are used as locations to report output forces and to perform design, and as plotting points used for graphic display of force diagrams. When force diagrams are plotted, exact forces are plotted at each output station and then those points are connected by straight lines. Output stations occur at userspecified locations and at point load locations along a beam. Designate the output stations for a frame element using the Assign menu. Note: Access the display of frame element output stations using the View menu. For composite beam design, the program checks the moments, shears and deflections at each output station along the beam. No checks are made at any points along the beam that are not output stations. Technical Note 1-10 Output Stations

30 COMPUTERS AND STRUCTURES, INC., BERKELEY, CALIFORNIA DECEMBER 2001 COMPOSITE BEAM DESIGN Technical Note 2 Composite Beam Design Process This Technical Notes describes a basic composite beam design process using this program. Although the exact steps you follow may vary, the basic design process should be similar to that described herein. Separate processes are described for design of a new building and check of an existing building. Other Technical Notes in the Composite Beam Design General series provide additional information. Design Process for a New Building The following sequence describes a typical composite beam design process for a new building. Note that although the sequence of steps you follow may vary, the basic process probably will be essentially the same. 1. Use the Options menu > Preferences > Composite Beam Design command to choose the composite beam design code and to review other composite beam design preferences and revise them if necessary. Note that default values are provided for all composite beam design preferences, so it is unnecessary to define any preferences unless you want to change some of the default values. See AISC-ASD89 Composite Beam Design Technical Note 17 Preferences and AISC-LRFD93 Composite Beam Design Technical Note 30 Preferences for more information about preferences. 2. Create the building model, as described in Volumes 1 and Run the building analysis using the Analyze menu > Run Analysis command. 4. Assign composite beam overwrites, if needed, using the Design menu > Composite Beam Design > View/Revise Overwrites command. Note that you must select beams before using this command. Also note that default values are provided for all composite beam design overwrites so it is unnecessary to define overwrites unless you want to change some of Design Process for a New Building Technical Note 2-1

31 Composite Beam Design Process Composite Beam Design the default values. Note that the overwrites can be assigned before or after the analysis is run. See AISC-ASD89 Composite Beam Design Technical Note 18 Overwrites and See AISC-LRFD93 Composite Beam Design Technical Note 31 Overwrites. 5. Designate design groups, if desired, using the Design menu > Composite Beam Design > Select Design Group command. Note that you must have already created some groups by selecting objects and clicking the Assign menu > Group Names command. 6. To use design load combinations other than the defaults created by the program for composite beam design, click the Design menu > Composite Beam Design > Select Design Combo command. Note that you must have already created your own design combos by clicking the Define menu > Load Combinations command. Note that for composite beam design, you specify separate design load combinations for construction loading, final loading considering strength, and final loading considering deflection. Design load combinations for each of these three conditions are specified using the Design menu > Composite Beam Design > Select Design Combo command. See Composite Beam Design Technical Note 10 Design Load Combinations. 7. Click the Design menu > Composite Beam Design > Start Design/Check of Structure command to run the composite beam design. 8. Review the composite beam design results by doing one of the following: a. Click the Design menu > Composite Beam Design > Display Design Info command to display design input and output information on the model. See Composite Beam Design Technical Note 4 Data Plotted Directly on the Model. b. Right click on a beam while the design results are displayed on it to enter the interactive design mode and interactively design the beam. Note that while you are in this mode, you can also view diagrams (load, moment, shear and deflection) and view design details on the screen. See Composite Beam Design Technical Note 3 Interactive Composite Beam Design for more information. Technical Note 2-2 Design Process for a New Building

32 Composite Beam Design Composite Beam Design Process If design results are not currently displayed (and the design has been run), click the Design menu > Composite Beam Design > Interactive Composite Beam Design command and then right click a beam to enter the interactive design mode for that beam. c. Use the File menu > Print Tables > Composite Beam Design command to print composite beam design data. If you select beams before using this command, data is printed only for the selected beams. See AISC-ASD89 Composite Beam Design Technical Note 27 Input Data, AISC-LRFD93 Composite Beam Design Technical Note 41 Input Data, AISC-ASD89 Composite Beam Design Technical Note 28 Output Details, and AISC-LRFD93 Composite Beam Design Technical Note 42 Output Details for more information. d. Use the Design menu > Composite Beam Design > Verify all Members Passed command to verify that no members are overstressed or otherwise unacceptable. 9. Use the Design menu > Composite Beam Design > Change Design Section command to change the beam design section properties for selected beams. 10. Click the Design menu > Composite Beam Design > Start Design/Check of Structure command to rerun the composite beam design with the new section properties. Review the results using the procedures described in Step Rerun the building analysis using the Analyze menu > Run Analysis command. Note that the beam section properties used for the analysis are the last specified design section properties. 12. Click the Design menu > Composite Beam Design > Start Design/Check of Structure command to rerun the composite beam design with the new analysis results and new section properties. Review the results using the procedures described in Step Again use the Design menu > Composite Beam Design > Change Design Section command to change the beam design section properties for selected beams, if necessary. Design Process for a New Building Technical Note 2-3

33 Composite Beam Design Process Composite Beam Design 14. Repeat Steps 11, 12 and 13 as many times as necessary. Note: Composite beam design in the program is an iterative process. Typically, the analysis and design will be rerun multiple times to complete a design. 15. Select all beams and click the Design menu > Composite Beam Design > Make Auto Select Section Null command. This removes any auto select section list assignments from the selected beams. 16. Rerun the building analysis using the Analyze menu > Run Analysis command. Note that the beam section properties used for the analysis are the last specified design section properties. 17. Click the Design menu > Composite Beam Design > Start Design/Check of Structure command to rerun the composite beam design with the new section properties. Review the results using the procedures described above. 18. Click the Design menu > Composite Beam Design > Verify Analysis vs Design Section command to verify that all of the final design sections are the same as the last used analysis sections. 19. Use the File menu > Print Tables > Composite Beam Design command to print selected composite beam design results if desired. See AISC-ASD89 Composite Beam Design Technical Note 28 Output Details and AISC-LRFD93 Composite Beam Design Technical Note 42 Output Details It is important to note that design is an iterative process. The sections used in the original analysis are not typically the same as those obtained at the end of the design process. Always run the building analysis using the final beam section sizes and then run a design check using the forces obtained from that analysis. Use the Design menu > Composite Beam Design > Verify Analysis vs Design Section command to verify that the design sections are the same as the analysis sections. Check Process for an Existing Building The following sequence is a typical composite beam check process for an existing building. In general, the check process is easier than the design process Technical Note 2-4 Check Process for an Existing Building

34 Composite Beam Design Composite Beam Design Process for a new building because iteration is not required. Note that although the sequence of steps you follow may vary, the basic process probably will be essentially the same. Tip: You can define your own shear stud patterns on the Shear Studs tab in the composite beam overwrites. This allows you to model existing structures with composite floor framing. 1. Use the Options menu > Preferences > Composite Beam Design command to choose the composite beam design code and to review other composite beam design preferences and revise them if necessary. Note that default values are provided for all composite beam design preferences so it is unnecessary to define preferences unless you want to change some of the default preference values. See AISC-ASD89 Composite Beam Design Technical Note 17 Preferences and AISC-LRFD93 Composite Beam Design Technical Note 30 Preferences for more information about preferences. 2. Create the building model, as explained in Volumes 1 and Run the building analysis using the Analyze menu > Run Analysis command. 4. Assign composite beam overwrites, including the user-defined shear stud patterns, using the Design menu > Composite Beam Design > View/Revise Overwrites command. Note that you must select beams first before using this command. See AISC-ASD89 Composite Beam Design Technical Note 18 Overwrites and See AISC-LRFD93 Composite Beam Design Technical Note 31 Overwrites. 5. Click the Design menu > Composite Beam Design > Start Design/Check of Structure command to run the composite beam design. 6. Review the composite beam design results by doing do one of the following: a. Click the Design menu > Composite Beam Design > Display Design Info command to display design input and output information on the model. See Composite Beam Design Technical Note 4 Data Plotted Directly on the Model. Check Process for an Existing Building Technical Note 2-5

35 Composite Beam Design Process Composite Beam Design b. Right click on a beam while the design results are displayed on it to enter the interactive design and review mode and review the beam design. Note that while you are in this mode you can also view diagrams (load, moment, shear and deflection) and view design details on the screen. See Composite Beam Design Technical Note 3 Interactive Composite Beam Design for more information. If design results are not currently displayed (and the design has been run), click the Design menu > Composite Beam Design > Interactive Composite Beam Design command and then right click a beam to enter the interactive design mode for that beam. c. Use the File menu > Print Tables > Composite Beam Design command to print composite beam design data. If you select beams before using this command, data is printed only for the selected beams. d. Use the Design menu > Composite Beam Design > Verify all Members Passed command to verify that no members are overstressed or otherwise unacceptable. See AISC-ASD89 Composite Beam Design Technical Note 27 Input Data, AISC-LRFD93 Composite Beam Design Technical Note 41 Input Data, AISC-ASD89 Composite Beam Design Technical Note 28 Output Details, and AISC-LRFD93 Composite Beam Design Technical Note 42 Output Details for more information. Technical Note 2-6 Check Process for an Existing Building

36 COMPUTERS AND STRUCTURES, INC., BERKELEY, CALIFORNIA DECEMBER 2001 COMPOSITE BEAM DESIGN Technical Note 3 Interactive Composite Beam Design Interactive composite beam design is a powerful feature that allows the user to review the design results for any composite beam and interactively revise the design assumptions and immediately review the revised results. Note that a design must have been run for the interactive design mode to be available. To enter the interactive design mode and interactively design the beam, right click on a beam while the design results are displayed in the active window. If design results are not displayed (and the design has been run), click the Design menu > Composite Beam Design > Interactive Composite Beam Design command and then right click a beam. The following sections describe the features that are included in the Interactive Composite Beam Design and Review form. Member Identification Story ID This is the story level ID associated with the composite beam. Beam Label This is the label associated with the composite beam. Design Group This list box displays the name of the design group that the beam is assigned to if that design group was considered in the design of the beam. If the beam is part of a design group but the design group was not considered in the design, N/A is displayed. If the beam is not assigned to any design group, "NONE" is displayed. If a beam is redesigned as a result of a change made in the Interactive Composite Beam Design and Review form, the design group is ignored and only the single beam is considered. Thus, as soon as you design a beam in the Member Identification Technical Note 3-1

37 Interactive Composite Beam Design Composite Beam Design Interactive Composite Beam Design and Review form, the Design Group box either displays N/A or None. You cannot directly edit the contents of this list box. Section Information Auto Select List This drop-down box displays the name of the auto select section list assigned to the beam. If no auto select list has been assigned to the beam, NONE is displayed. You can change this item to another auto select list or to NONE while in the form and the design results will be updated immediately. If you change this item to NONE, the design is performed for the Current Design/Next Analysis section property. Optimal If an auto select section list is assigned to the beam, this list box displays the optimal section as determined by beam weight or price, depending on what has been specified in the composite beam preferences. If no auto select list is assigned to the beam, N/A is displayed for this item. You cannot directly edit the contents of this list box. Last Analysis This list box displays the name of the section that was used for this beam in the last analysis. Thus, the beam forces are based on a beam of this section property. For the final design iteration, the Current Design/Next Analysis section property and the Last Analysis section property should be the same. You cannot directly edit the contents of this list box. Current Design/Next Analysis This list box displays the name of the current design section property. If the beam is assigned an auto select list, the section displayed in this form initially defaults to the optimal section. Tip: The section property displayed for the Current Design/Next Analysis item is used by the program as the section property for the next analysis run. Technical Note 3-2 Section Information

38 Composite Beam Design Interactive Composite Beam Design If no auto select list has been assigned to the beam, the beam design is performed for the section property specified in this edit box. It is important to note that subsequent analyses use the section property specified in this list box for the next analysis section for the beam. Thus, the forces and moments obtained in the next analysis are based on this beam size. The Current Design/Next Analysis section property can be changed by clicking the Sections button that is described later in this Technical Note. Important note: Changes made to the Current Design/Next Analysis section property are permanently saved (until you revise them again) if you click the OK button to exit the Interactive Composite Beam Design and Review form. If you exit the form by clicking the Cancel button, these changes are considered temporary and are not permanently saved. Acceptable Sections List The Acceptable Sections List includes the following information for each beam section that is acceptable for all considered design load combinations. Section name Steel yield stress, Fy Connector layout Camber Ratio Tip: A single beam displayed in a red font in the Acceptable Sections List means that none of the sections considered were acceptable. Typically, the ratio displayed is the largest ratio obtained considering the stress ratios for positive moment, negative moment and shear for both construction loads and final loads, as well as the stud ratio(s), deflection ratios, and if they are specified to be considered when determining if a beam section is acceptable, the vibration ratios. Acceptable Sections List Technical Note 3-3

39 Interactive Composite Beam Design Composite Beam Design If the beam is assigned an auto select list, many beam sections may be listed in the Acceptable Sections List. If necessary, use the scroll bar to scroll through the acceptable sections. The optimal section is initially highlighted in the list. If the beam is not assigned an auto select list, only one beam section will be listed in the Acceptable Sections List. It is the same section as specified in the Current Design/Next Analysis edit box. At least one beam will always be shown in the Acceptable Sections List, even if none of the beams considered are acceptable. When no beams are acceptable, the program displays the section with the smallest maximum ratio in a red font. Thus, a single beam displayed in a red font in the Acceptable Sections List means that none of the sections considered were acceptable. ReDefine Sections Button Use the Sections button to change the Current Design/Next Analysis section property. This button can designate a new section property whether the section property is or is not displayed in the Acceptable Sections List. When you click on the Sections button, the Select Sections form appears. Assign any frame section property to the beam by clicking on the desired property and clicking OK. Note that if an auto select list is assigned to the beam, using the Sections button sets the auto select list assignment to NONE. Overwrites Button Click the overwrites button to access and make revisions to the composite beam overwrites and then immediately see the new design results. Modifying some overwrites in this mode and exiting both the Composite Beam Overwrites form and the Interactive Composite Beam Design and Review form by clicking their respective OK buttons permanently saves changes made to the overwrites. Exiting the Composite Beam Overwrites form by clicking the OK button temporarily saves changes. Subsequently exiting the Interactive Composite Beam Design and Review form by clicking the Cancel button cancels the changes made. Permanent saving of the overwrites does not occur until the OK but- Technical Note 3-4 ReDefine