Concrete Frame Design Manual
®
ETABS
Integrated Building Design Software
Concrete Frame Design Manual
Computers and Structures, Inc.Version 8 Berkeley, California, USA
January 2002
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.
1995 University Avenue
Berkeley, California 94704 USA
Phone: (510) 845-2177
FAX: (510) 845-4096
e-mail: info@csiberkeley.com (for general questions)
e-mail: support@csiberkeley.com (for technical support questions)
web: www.csiberkeley.com
Copyright Computers and Structures, Inc., 1978-2002. 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
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
THIS PROGRAM IS A VERY PRACTICAL TOOL FOR THE DESIGN/CHECK OF
CONCRETE STRUCTURES. HOWEVER, THE USER MUST THOROUGHLY READ
©C OMPUTERS AND S TRUCTURES , I NC ., B ERKELEY , C ALIFORNIA D ECEMBER 2001
C ONCRETE F RAME D ESIGN Contents General Concrete Frame Design Information
Design Codes 1-1
Units 1-1
Overwriting the Frame Design Procedure for a Con- crete Frame 1-1
Design Load Combinations 1-2 Design of Beams 1-2 Design of Columns 1-3 Beam/Column Flexural Capacity Ratios 1-4 Second Order P-Delta Effects 1-4 Element Unsupported Lengths 1-6 Analysis Sections and Design Sections 1-7
2 Concrete Frame Design Process
Concrete Frame Design Procedure 2-1
1 General Design Information
General 3-1
Concrete Design Information Form 3-1
4 Output Data Plotted Directly on the Model
Overview 4-1
Using the Print Design Tables Form 4-1 Design Input
4-2 Design Output
4-2
3 Interactive Concrete Frame Design
Concrete Frame Design Manual Concrete Frame Design Specific to UBC97
5 General and Notation
Introduction to the UBC 97 Series of Technical Notes 5-1 Notation
5-2
6 Preferences
General 6-1
Using the Preferences Form 6-1 Preferences
6-2
7 Overwrites
General 7-1
Overwrites 7-1
Making Changes in the Overwrites Form 7-3 Resetting Concrete Frame Overwrites to Default 7-4
Values
8 Design Load Combinations
9 Strength Reduction Factors
10 Column Design
Overview 10-1
Generation of Biaxial Interaction Surfaces 10-2 Calculate Column Capacity Ratio 10-5
Determine Factored Moments and Forces 10-6 Determine Moment Magnification Factors 10-6 Determine Capacity Ratio 10-8
Required Reinforcing Area 10-10 Design Column Shear Reinforcement 10-10
Determine Required Shear Reinforcement 10-14 Reference
10-15
11 Beam Design
Overview 11-1
Design Beam Flexural Reinforcement 11-1 Determine Factored Moments 11-2 Determine Required Flexural Reinforcement 11-2
Contents
Design Beam Shear Reinforcement 11-10
12 Joint Design
Overview 12-1
Determine the Panel Zone Shear Force 12-1 Determine the Effective Area of Joint 12-5 Check Panel Zone Shear Stress 12-5 Beam/Column Flexural Capacity Ratios 12-6
13 Input Data
Input data 13-1
Using the Print Design Tables Form 13-3
14 Output Details
Using the Print Design Tables Form 14-3
Concrete Frame Design Specific to ACI-318-99
15 General and Notation
Introduction to the ACI318-99 Series of Technical 15-1 Notes
Notation 15-2
16 Preferences
General 16-1
Using the Preferences Form 16-1 Preferences
16-2
17 Overwrites
General 17-1
Overwrites 17-1
Making Changes in the Overwrites Form 17-3 Resetting Concrete Frame Overwrites to Default 17-4
Values
18 Design Load Combinations
19 Strength Reduction Factors
Concrete Frame Design Manual
Design Beam Shear Reinforcement 21-9 Determine Shear Force and Moment 21-11 Determine Concrete Shear Capacity 21-12 Determine Required Shear Reinforcement 21-13
Using the Print Design Tables Form 23-3
Input Data 23-1
23 Input Data
Check Panel Zone Shear Stress 22-4 Beam/Column Flexural Capacity Ratios 22-6
Determine the Panel Zone Shear Force 22-1 Determine the Effective Area of Joint 22-4
Overview 22-1
22 Joint Design
20 Column Design
Overview 20-1
Overview 21-1
21 Beam Design
References 20-15
Determine Section Forces 20-11 Determine Concrete Shear Capacity 20-12 Determine Required Shear Reinforcement 20-13
Required Reinforcing Area 20-10 Design Column Shear Reinforcement 20-10
Determine Factored Moments and Forces 20-6 Determine Moment Magnification Factors 20-6 Determine Capacity Ratio 20-9
Generation of Biaxial Interaction Surfaces 20-2 Calculate Column Capacity Ratio 20-5
Design Beam Flexural Reinforcement 21-1 Determine Factored Moments 21-2 Determine Required Flexural Reinforcement 21-2 Design for T-Beam 21-5 Minimum Tensile Reinforcement 21-8 Special Consideration for Seismic Design 21-8
Contents
Using the Print Design Tables Form 24-3
©C S , I ., B , C J 2002 C ONCRETE F RAME D ESIGN
Technical Note 1 General Design Information
This Technical Note presents some basic information and concepts helpful when performing concrete frame design using this program.
Design Codes
The design code is set using the Options menu > Preferences > Concrete
Frame Design command. You can choose to design for any one design code
in any one design run. You cannot design some elements 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 concrete frame design in this program, any set of consistent units can be used for input. You can change the system of units at any time. Typically, de- sign codes are based on one specific set of units.
Overwriting the Frame Design Procedure for a Concrete
FrameThe two design procedures possible for concrete beam design are:
Concrete frame design
No design If a line object is assigned a frame section property that has a concrete ma- terial property, its default design procedure is Concrete Frame Design. A con- crete frame element can be switched between the Concrete Frame Design and the "None" design procedure. Assign a concrete frame element the "None" design procedure if you do not want it designed by the Concrete Frame De- sign postprocessor. General Design Information Concrete Frame Design
Change the default design procedure used for concrete frame elements by selecting the element(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 a concrete element and attempt to change the design procedure to Steel Frame Design, the program will not allow the change because a concrete element cannot be changed to a steel frame element.
Design Load Combinations
The program creates a number of default design load combinations for con- crete frame design. You can add in your own design load combinations. You can also modify or delete the program default load combinations. An unlim- ited number of design load combinations can be specified.
To define a design load combination, simply specify one or more load cases, each with its own scale factor. For more information see Concrete Frame De- sign UBC97 Technical Note 8 Design Load Combination and Concrete Frame Design ACI 318-99 Technical Note 18 Design Load Combination.
Design of Beams
The program designs all concrete frame elements designated as beam sec- tions in their Frame Section Properties as beams (see Define menu >Frame
Sections command and click the Reinforcement button). In the design of
concrete beams, in general, the program calculates and reports the required areas of steel for flexure and shear based on the beam moments, shears, load combination factors, and other criteria, which are described in detail in Con- crete Frame UBC97 Technical Note Beam Design 11 and Concrete Frame ACI 318-99 Technical Note 21 Beam Design. The reinforcement requirements are calculated at each output station along the beam span.
All the beams are designed for major direction flexure and shear only.
Effects resulting from any axial forces, minor direction bending, and
torsion that may exist in the beams must be investigated independ-
ently by the user.In designing the flexural reinforcement for the major moment at a particular section of a particular beam, the steps involve the determination of the maximum factored moments and the determination of the reinforcing steel.
Concrete Frame Design General Design Information
The beam section is designed for the maximum positive and maximum nega- tive factored moment envelopes obtained from all of the load combinations. Negative beam moments produce top steel. In such cases, the beam is al- ways designed as a rectangular section. Positive beam moments produce bottom steel. In such cases, the beam may be designed as a rectangular- or T-beam. For the design of flexural reinforcement, the beam is first designed as a singly reinforced beam. If the beam section is not adequate, the required compression reinforcement is calculated. In designing the shear reinforcement for a particular beam for a particular set of loading combinations at a particular station resulting from the beam major shear, the steps involve the determination of the factored shear force, the determination of the shear force that can be resisted by concrete, and the determination of the reinforcement steel required to carry the balance.
Design of Columns
The program designs all concrete frame elements designated as column sec- tions in their Frame Section Properties as columns (see Define menu
>Frame Sections command and click the Reinforcement button). In the
design of the columns, the program calculates the required longitudinal steel, or if the longitudinal steel is specified, the column stress condition is reported in terms of a column capacity ratio. The capacity ratio is a factor that gives an indication of the stress condition of the column with respect to the capacity of the column. The design procedure for reinforced concrete columns involves the following steps:
Generate axial force-biaxial moment interaction surfaces for all of the dif-
ferent concrete section types of the model. Check the capacity of each column for the factored axial force and bending
moments obtained from each load combination at each end of the column.This step is also used to calculate the required reinforcement (if none was specified) that will produce a capacity ratio of 1.0.
Design the column shear reinforcement.
The shear reinforcement design procedure for columns is very similar to that for beams, except that the effect of the axial force on the concrete shear ca- pacity needs to be considered. See Concrete Frame UBC97 Technical Note 10
General Design Information Concrete Frame Design
Column Design and Concrete Frame ACI 318-99 Technical Note 20 Column Design for more information.
Beam/Column Flexural Capacity Ratios
When the ACI 318-99 or UBC97 code is selected, the program calculates the ratio of the sum of the beam moment capacities to the sum of the column moment capacities at a particular joint for a particular column direction, ma- jor or minor. The capacities are calculated with no reinforcing overstrength factor, α, and including ϕ factors. The beam capacities are calculated for re- versed situations and the maximum summation obtained is used.
The moment capacities of beams that frame into the joint in a direction that is not parallel to the major or minor direction of the column are resolved along the direction that is being investigated and the resolved components are added to the summation.
The column capacity summation includes the column above and the column below the joint. For each load combination, the axial force, P u , in each of the columns is calculated from the program analysis load combinations. For each load combination, the moment capacity of each column under the influence of the corresponding axial load P u is then determined separately for the major and minor directions of the column, using the uniaxial column interaction dia- gram. The moment capacities of the two columns are added to give the ca- pacity summation for the corresponding load combination. The maximum ca- pacity summations obtained from all of the load combinations is used for the beam/column capacity ratio.
The beam/column flexural capacity ratios are only reported for Special Mo- ment-Resisting Frames involving seismic design load combinations. See Beam/Column Flexural Capacity Ratios in Concrete Frame UBC97 Techni- cal Note 12 Joint Design or in Concrete Frame ACI 318-99 Technical Note 22 Joint Design for more information.
Second Order P-Delta Effects
Typically, design codes require that second order P-Delta effects be consid- ered when designing concrete frames. The P-Delta effects come from two sources. They are the global lateral translation of the frame and the local de- formation of elements within the frame.
Concrete Frame Design General Design Information
∆
Original position of frame Final deflected position of element shown by vertical frame element that line includes the global lateral translation, ∆, and the
δ
local deformation of the Position of frame element element, δ as a result of global lateral translation, ∆, shown by dashed line
Figure 1: The Total Second Order P-Delta Effects on a Frame Element Caused by Both ∆ ∆ ∆ ∆ and δ δ δδ
Consider the frame element shown in Figure 1, which is extracted from a story level of a larger structure. The overall global translation of this frame element is indicated by ∆. The local deformation of the element is shown as δ. The total second order P-Delta effects on this frame element are those caused by both ∆ and δ.
The program has an option to consider P-Delta effects in the analysis. Con- trols for considering this effect are found using the Analyze menu > Set
Analysis Options command and then clicking the Set P-Delta Parameters
button. When you consider P-Delta effects in the analysis, the program does a good job of capturing the effect due to the ∆ deformation shown in Figure 1, but it does not typically capture the effect of the δ deformation (unless, in the model, the frame element is broken into multiple pieces over its length).
In design codes, consideration of the second order P-Delta effects is generally achieved by computing the flexural design capacity using a formula similar to that shown in Equation. 1.
M CAP nt lt
= aM + bM Eqn. 1 where,
M CAP
= Flexural design capacity General Design Information Concrete Frame Design
M nt = Required flexural capacity of the member assuming there is
no translation of the frame (i.e., associated with the δ defor- mation in Figure 1)
M lt
= Required flexural capacity of the member as a result of lateral translation of the frame only (i.e., associated with the ∆ de- formation in Figure 1) a = Unitless factor multiplying M nt b = Unitless factor multiplying M lt (assumed equal to 1 by the program; see below)
When the program performs concrete frame design, it assumes that the factor
b is equal to 1 and it uses code-specific formulas to calculate the factor a.
That b = 1 assumes that you have considered P-Delta effects in the analysis, as previously described. Thus, in general, if you are performing concrete frame design in this program, you should consider P-Delta effects in the analysis before running the design.
Element Unsupported Lengths
The column unsupported lengths are required to account for column slender- ness effects. The program automatically determines these unsupported lengths. They can also be overwritten by the user on an element-by-element basis, if desired, using the Design menu > Concrete Frame Design >
View/Revise Overwrites command.
There are two unsupported lengths to consider. They are L 33 and L 22, as shown in Figure 2. These are the lengths between support points of the ele- ment in the corresponding directions. The length L 33 corresponds to instability about the 3-3 axis (major axis), and L 22 corresponds to instability about the
2-2 axis (minor axis). The length L 22 is also used for lateral-torsional buckling caused by major direction bending (i.e., about the 3-3 axis). In determining the values for L 22 and L 33 of the elements, the program recog- nizes various aspects of the structure that have an effect on these lengths, such as member connectivity, diaphragm constraints and support points. The program automatically locates the element support points and evaluates the corresponding unsupported length.
Concrete Frame Design General Design Information
Figure 2: Major and Minor Axes of Bending
It is possible for the unsupported length of a frame element to be evaluated by the program as greater than the corresponding element length. For exam- ple, assume a column has a beam framing into it in one direction, but not the other, at a floor level. In this case, the column is assumed to be supported in one direction only at that story level, and its unsupported length in the other direction will exceed the story height.
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 desig- nated the current design section.
Tip:
It is important to understand the difference between analysis sections and design sec- tions.
General Design Information Concrete Frame Design
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. The Design menu > Concrete Frame Design > Verify Analysis vs De- sign 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 > Concrete Frame 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 de-
sign load combination deletes the design results, but it does not delete or change the design section.
Using the Options menu > Preferences > Concrete Frame 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, Concrete Frame Design General Design Information static nonlinear analysis and design results are deleted when one of the following actions is taken:
9 Use the Define menu > Frame Nonlinear Hinge Properties com- mand to redefine existing or define new hinges.
9 Use the Define menu > Static Nonlinear/Pushover Cases com- mand to redefine existing or define new static nonlinear load cases.
9 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.
©C S , I ., B , C D 2001 C ONCRETE F RAME D ESIGN
Technical Note 2 Concrete Frame Design Process
This Technical Note describes a basic concrete frame design process using this program. Although the exact steps you follow may vary, the basic design process should be similar to that described herein. Other Technical Notes in the Concrete Frame Design series provide additional information, including the distinction between analysis sections and design sections (see Analysis Sections and Design Sections in Concrete Frame Design Technical Note 1 General Design Information).
The concrete frame design postprocessor can design or check concrete col- umns and can design concrete beams.
Important note:
A concrete frame element is designed as a beam or a col-
umn
, depending on how its frame section property was designated when it was defined using the Define menu > Frame Sections command. Note that when using this command, after you have specified that a section has a con- crete material property, you can click on the Reinforcement button and specify whether it is a beam or a column.
Concrete Frame Design Procedure
The following sequence describes a typical concrete frame 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 > Concrete Frame Design command to choose the concrete frame design code and to review other concrete frame design preferences and revise them if necessary. Note that default values are provided for all concrete frame design prefer- ences, so it is unnecessary to define any preferences unless you want to change some of the default values. See Concrete Frame Design ACI UBC97 Technical Notes 6 Preferences and Concrete Frame Design ACI 318-99 Technical Notes 16 Preferences for more information.
Concrete Frame Design Process Concrete Frame Design 2. Create the building model.
3. Run the building analysis using the Analyze menu > Run Analysis command.
4. Assign concrete frame overwrites, if needed, using the Design menu >
Concrete Frame Design > View/Revise Overwrites command. Note
that you must select frame elements before using this command. Also note that default values are provided for all concrete frame design over- writes, so it is unnecessary to define any overwrites unless you want to change some of the default values. Note that the overwrites can be as- signed before or after the analysis is run. See Concrete Frame Design UBC97 Technical Note 7 Overwrites and Concrete Frame Design ACI 318-99 Technical Note 17 Overwrites for more information.
5. To use any design load combinations other than the defaults created by the program for your concrete frame design, click the Design menu >
Concrete Frame Design > Select Design Combo command. Note
that you must have already created your own design combos by clicking the Define menu > Load Combinations command. See Concrete Frame Design UBC97 Technical Note 8 Design Load Combinations and Concrete Frame Design ACI 318-99 Technical Note 18 Design Load Combinations for more information.
6. Click the Design menu > Concrete Frame Design > Start De- sign/Check of Structure command to run the concrete frame design.
7. Review the concrete frame design results by doing one of the following:
a. Click the Design menu > Concrete Frame Design > Display De-
sign Info command to display design input and output information on
the model. See Concrete Frame Design Technical Note 4 Output Data Plotted Directly on the Model for more information.
b. Right click on a frame element while the design results are displayed on it to enter the interactive design mode and interactively design the frame element. Note that while you are in this mode, you can revise overwrites and immediately see the results of the new design. See Concrete Frame Design Technical Note 3 Interactive Concrete Frame Design for more information. Concrete Frame Design Concrete Frame Design Process If design results are not currently displayed (and the design has been run), click the Design menu > Concrete Frame Design > Interac-
tive Concrete Frame Design command and then right click a frame element to enter the interactive design mode for that element.
8. Use the File menu > Print Tables > Concrete Frame Design com- mand to print concrete frame design data. If you select frame elements before using this command, data is printed only for the selected ele- ments. See Concrete Frame Design UBC97 Technical Note 14 Output Details and Concrete Frame Design ACI 318-99 Technical Note 24 Out- put Details for more information.
9. Use the Design menu > Concrete Frame Design > Change Design
Section command to change the design section properties for selected frame elements.
10. Click the Design menu > Concrete Frame Design > Start De-
sign/Check of Structure command to rerun the concrete frame design
with the new section properties. Review the results using the procedures described in Item 7.
11. Rerun the building analysis using the Analyze menu > Run Analysis command. Note that the section properties used for the analysis are the last specified design section properties.
12. Click the Design menu > Concrete Frame Design > Start De-
sign/Check of Structure command to rerun the concrete frame design
with the new analysis results and new section properties. Review the re- sults using the procedures described above.
13. Again use the Design menu > Concrete Frame Design > Change
Design Section command to change the design section properties for selected frame elements, if necessary.
14. Repeat the processes in steps 10, 11 and 12 as many times as neces- sary.
15. Rerun the building analysis using the Analyze menu > Run Analysis command. Note that the section properties used for the analysis are the last specified design section properties.
Concrete Frame Design Process Concrete Frame Design
Note:
Concrete frame design is an iterative process. Typically, the analysis and design will be rerun multiple times to complete a design.
16. Click the Design menu > Concrete Frame Design > Start De-
sign/Check of Structure command to rerun the concrete frame design
with the new section properties. Review the results using the procedures described in Item 7.
17. Click the Design menu > Concrete Frame Design > Verify Analysis
vs Design Section command to verify that all of the final design sec- tions are the same as the last used analysis sections.
18. Use the File menu > Print Tables > Concrete Frame Design com- mand to print selected concrete frame design results, if desired. 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 frame section sizes and then run a design check using the forces obtained from that analysis. Use the Design menu > Concrete Frame Design > Verify
Analysis vs Design Section command to verify that the design sections are
the same as the analysis sections.©C S , I ., B , C D 2001 C ONCRETE F RAME D ESIGN
Technical Note 3 Interactive Concrete Frame Design
This Technical Note describes interactive concrete frame design and review, which is a powerful mode that allows the user to review the design results for any concrete frame design and interactively revise the design assumptions and immediately review the revised results.
General
Note that a design must have been run for the interactive design mode to be available. To run a design, click the Design menu > Concrete Frame De-
sign > Start Design/Check of Structure command.
Right click on a frame element while the design results are displayed on it to enter the interactive design mode and interactively design the element in the Concrete Design Information form. If design results are not currently dis- played (and a design has been run), click the Design menu > Concrete
Frame Design > Interactive Concrete Frame Design command and then
right click a frame element to enter the interactive design mode for that ele- ment.
Important note:
A concrete frame element is designed as a beam or a col-
umn
, depending on how its frame section property was designated when it was defined using the Define menu > Frame Sections command and the
Reinforcement button, which is only available if it is a concrete section.
Concrete Design Information Form
Table 1 describe the features that are included in the Concrete Design Infor- mation form.
Interactive Concrete Frame Design Concrete Frame Design
Table 1 Concrete Design Information Form Item DESCRIPTION Story This is the story level ID associated with the frame element
Beam This is the label associated with a frame element that has been assigned a concrete frame section property that is designated as a beam. See the important note previously in this Technical Note for more information.
Column This is the label associated with a frame element that has been assigned a concrete frame section property that is designated as a column. See the important note previously in this Techni- cal Note for more information.
Section Name This is the label associated with a frame element that has been assigned a concrete frame section property .
Reinforcement Information
The reinforcement information table on the Concrete Design Information form shows the output information obtained for each design load combination at each output station along the frame element. For columns that are designed by this program, the item with the largest required amount of longitudinal reinforcing is initially highlighted. For columns that are checked by this program, the item with the largest capacity ratio is initially high- lighted. For beams, the item with the largest required amount of bottom steel is initially highlighted. Following are the possible headings in the table: Combo ID This is the name of the design load combination considered.
Station location This is the location of the station considered, measured from the i-end of the frame element. Longitudinal reinforcement
This item applies to columns only. It also only applies to col- umns for which the program designs the longitudinal reinforc- ing. It is the total required area of longitudinal reinforcing steel. Capacity ratio This item applies to columns only. It also only applies to col- umns for which you have specified the location and size of re- inforcing bars and thus the program checks the design. This item is the capacity ratio. Concrete Frame Design Interactive Concrete Frame Design
Table 1 Concrete Design Information Form Item DESCRIPTION
The capacity ratio is determined by first extending a line from the origin of the PMM interaction surface to the point repre- senting the P, M2 and M3 values for the designated load com- bination. Assume the length of this first line is designated L1. Next, a second line is extended from the origin of the PMM in- teraction surface through the point representing the P, M2 and M3 values for the designated load combination until it intersects the interaction surface. Assume the length of this line from the origin to the interaction surface is designated L2. The capacity ratio is equal to L1/L2.
Major shear This item applies to columns only. It is the total required area of reinforcement shear reinforcing per unit length for shear acting in the column major direction. Minor shear This item applies to columns only. It is the total required area of reinforcement shear reinforcing per unit length for shear acting in the column minor direction. Top steel This item applies to beams only. It is the total required area of longitudinal top steel at the specified station.
Bottom steel This item applies to beams only. It is the total required area of longitudinal bottom steel at the specified station. Shear steel This item applies to beams only. It is the total required area of shear reinforcing per unit length at the specified station for loads acting in the local 2-axis direction of the beam.
Overwrites Button
Click this button to access and make revisions to the concrete frame overwrites and then immediately see the new design re- sults. If you modify some overwrites in this mode and you exit both the Concrete Frame Design Overwrites form and the Con- crete Design Information form by clicking their respective OK buttons, the changes to the overwrites are saved permanently.
When you exit the Concrete Frame Design Overwrites form by clicking the OK button the changes are temporarily saved. If you then exit the Concrete Design Information form by clicking the Cancel button the changes you made to the concrete frame overwrites are considered temporary only and are not perma- nently saved. Permanent saving of the overwrites does not ac- tually occur until you click the OK button in the Concrete Design Information form as well as the Concrete Frame Design Over- writes form. Interactive Concrete Frame Design Concrete Frame Design
Table 1 Concrete Design Information Form Item DESCRIPTION Details Button
Clicking this button displays design details for the frame ele- ment. Print this information by selecting Print from the File menu that appears at the top of the window displaying the de- sign details.
Interaction Button
Clicking this button displays the biaxial interaction curve for the concrete section at the location in the element that is high- lighted in the table.
©C S , I ., B , C D 2001 C ONCRETE F RAME D ESIGN
Technical Note 4 Output Data Plotted Directly on the Model
This Technical Note describes the input and output data that can be plotted directly on the model.
Overview
Use the Design menu > Concrete Frame Design > Display Design Info command to display on-screen output plotted directly on the program model. If desired, the screen graphics can then be printed using the File menu >
Print Graphics command. The on-screen display data presents input and
output data.Using the Print Design Tables Form
To print the concrete frame input summary directly to a printer, use the File
menu > Print Tables > Concrete Frame Design command and click the
check box on the Print Design Tables form. Click the OK button to send the print to your printer. Click the Cancel button rather than the OK button to cancel the print. Use the File menu > Print Setup command and the Setup>> button to change printers, if necessary.
To print the concrete frame input summary to a file, click the Print to File check box on the Print Design Tables form. Click the Filename>> button to change the path or filename. Use the appropriate file extension for the de- sired format (e.g., .txt, .xls, .doc). Click the OK buttons on the Open File for Printing Tables form and the Print Design Tables form to complete the re- quest.
Note:
The File menu > Display Input/Output Text Files command is useful for displaying out- put that is printed to a text file. The Append check box allows you to add data to an existing file. The path and filename of the current file is displayed in the box near the bottom of the Print Design Tables form. Data will be added to this file. Or use the Filename
Output Data Plotted Directly on the Model Concrete Frame Design button to locate another file, and when the Open File for Printing Tables cau- tion box appears, click Yes to replace the existing file. If you select a specific concrete frame element(s) before using the File menu
> Print Tables > concrete Frame Design command, the Selection Only
check box will be checked. The print will be for the selected steel frame ele- ment(s) only.
Design Input
The following types of data can be displayed directly on the model by select- ing the data type (shown in bold type) from the drop-down list on the Display Design Results form. Display this form by selecting he Design menu > Con- crete Frame Design > Display Design Info command.
Design Sections
Design Type
Live Load Red Factors
Unbraced L_Ratios
Eff Length K-Factors
Cm Factors
DNS Factors
DS Factors Each of these items is described in the code-specific Concrete Frame Design UBC97 Technical Note 13 Input Data and Concrete Frame Design ACI 318-99 Technical Note 23 Input Data.
Design Output
The following types of data can be displayed directly on the model by select- ing the data type (shown in bold type) from the drop-down list on the Display Design Results form. Display this form by selecting he Design menu > Con- crete Frame Design > Display Design Info command.
Concrete Frame Design Output Data Plotted Directly on the Model
Longitudinal Reinforcing Shear Reinforcing Column Capacity Ratios Joint Shear Capacity Ratios Beam/Column Capacity Ratios
Each of these items is described in the code-specific Concrete Frame Design ACI 318-99 Technical Note 24 Output Details and Concrete Frame Design UBC97 Technical Note 14 Output Details.
©C OMPUTERS AND S TRUCTURES , I NC ., B ERKELEY , C ALIFORNIA D ECEMBER 2001 C ONCRETE F RAME D ESIGN UBC97
Technical Note 5 General and Notation Introduction to the UBC97 Series of Technical Notes
The Concrete Frame Design UBC97 series of Technical Notes describes in de- tail the various aspects of the concrete design procedure that is used by this program when the user selects the UBC97 Design Code (ICBO 1997). The various notations used in this series are listed herein.
The design is based on user-specified loading combinations. The program provides a set of default load combinations that should satisfy requirements for the design of most building type structures. See Concrete Frame Design UBC97 Technical Note 8 Design Load Combinations for more information.
When using the UBC 97 option, a frame is assigned to one of the following five Seismic Zones (UBC 2213, 2214):
Zone 0
Zone 1
Zone 2
Zone 3
Zone 4 By default the Seismic Zone is taken as Zone 4 in the program. However, the Seismic Zone can be overwritten in the Preference form to change the de- fault. See Concrete Frame Design UBC97 Technical Note 6 Preferences for more information. When using the UBC 97 option, the following Framing Systems are recognized and designed according to the UBC design provisions (UBC 1627, 1921):
Ordinary Moment-Resisting Frame (OMF) General and Notation Concrete Frame Design UBC97
Intermediate Moment-Resisting Frame (IMRF) Special Moment-Resisting Frame (SMRF)
The Ordinary Moment-Resisting Frame (OMF) is appropriate in minimal seis- mic risk areas, especially in Seismic Zones 0 and 1. The Intermediate Mo- ment-Resisting Frame (IMRF) is appropriate in moderate seismic risk areas, specially in Seismic Zone 2. The Special Moment-Resisting Frame (SMRF) is appropriate in high seismic risk areas, specially in Seismic Zones 3 and 4. The UBC seismic design provisions are considered in the program. The details of the design criteria used for the different framing systems are described in Concrete Frame Design UBC97 Technical Note 9 Strength Reduction Factors, Concrete Frame Design UBC97 Technical Note 10 Column Design, Concrete Frame Design UBC97 Technical Note 11 Beam Design, and Concrete Frame Design UBC97 Technical Note 12 Joint Design.
By default the frame type is taken in the program as OMRF in Seismic Zone 0 and 1, as IMRF in Seismic Zone 2, and as SMRF in Seismic Zone 3 and 4. However, the frame type can be overwritten in the Overwrites form on a member-by-member basis. See Concrete Frame Design UBC97 Technical Note