TutorialFD - Concrete Footings
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Transcript of TutorialFD - Concrete Footings
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Example 9: Footing Design
Example 9: Reinforced Concrete footingsThis example is conceived as a guide for the user in the design of reinforced concrete footings. The
example will be more effective if the user follows the different steps in the program. Although it onlydescribes the use of the module as astandalone program, it includes some explanations and remarksrelated to the importation of the data from the main program.
The example is an isolated footing with a reinforced concrete column submitted to the action of axial
loads and bending moments at footing-column level, as it is illustrated in the next figure:
Example of Isolated Footing
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Example 9: Footing Design
1) Starting a new structure
Select the button located in the left top corner to create a New Footing
If an opened model exists, the module will ask you if you wish to save your previous model.
Once opened the new file, you can proceed with the introduction of data in the left window,following the order that is shown next.
2) Entering Units
Select the option Units system. This action will display the following drop-down option.
Select theEnglish units system
3) Design Code
Select the design code to be used.
Select the ACI 318-05 Code.
4) Foundation and column types
Select the foundation type and then the type of column.
Select the Spread footing type and the Concrete column type
5) Entering geometry data Footing data
Next go to the Geometry option. Note that all the options are of the drop down type.
Go to theMaterialoption of the Footing Data folder. Note that you have several available materials,
for this example use C3-60.
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Example 9: Footing Design
Select material C 3-60 and press the OK button.
Enter the depth of the base
Note. - The introduced value is in the default units. If you wish to introduce the same data in different
units, you should also enter the desired unit.
The footing base geometry (length, width and height) is not required to be defined because theprogram may suggest it. Only enter values if you want to use fixed and predefined values.
When initiating the module the displayed dimensions are default initial values.
6) Entering geometry data Column Data
Go to the folderColumn Data and select the option Column position relative to footing geometrycenterto locate the column in the plane of the footing.
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Example 9: Footing Design
Choose the Centered option.
Enable the Consider column reinforcementandShow dowelsoptions that will be used to determinethe splice lengths.
Introduce the column dimensions.
The dowel reinforcement is defined by the user. Enter theDowels longitudinal reinforcement.
Next define the Dowel transversal reinforcement (stirrups).
Introduce the amount legs for each direction, the bar diameter to be used and the separationbetween stirrups.
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Example 9: Footing Design
Note. - The introduction of these data is optional. To disable it, deactivate the check box Consider
column reinforcementandShow dowels.
7) Soil Data
The first option in this folder is Calculate soil bearing capacity. By defect the program displays the
option disabled, if you activate this option the program will require other data necessary for
calculating the soil bearing capacity.
For this example, let this option disabled.
Introduce the allowable soil stress. This will define basically the footing dimensions.
Establish the soil unit weight.
Enter the modulus of subgrade reaction; this will be used to determine the base elastic settlements..
Note. Each variable or option has a sensitive help with its description and definition.
8) Generating load combinations
Before entering the loads, the load conditions and load combinations should be defined. The programhas tools to generate combinations automatically according to the used Specifications.
In order to define the load conditions press the buttonLoad conditions manager
The following window is displayed:
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Example 9: Footing Design
One load condition (dead load) and two load combinations (service and design) are defined bydefault.
In this example we will add manually the condition of live load. Click in the first empty cell of the
column ID, enter an identifier of the condition (i.e., LL). Write a brief description of the load and
finally select a category by double clicking in the cell of the column Category (chose LL).
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Example 9: Footing Design
Manually introduce the new load condition. Notice that when entering a new load condition this is
added automatically in the combinations.
Note. - Also load conditions can be added easily pressing the button , this option displays a list of
the more used load conditions.
Next define the combinations:
Enter the load factors and define the type (service or design).
To automatically generate load combinations, follow the following steps:
1.- Press button
2.- A dialog window will appear, press the button in order to open a file. Select the file for thegeneration, as it is shown in the following figure.
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Example 9: Footing Design
Select the load combination according to the code that is being used, in this case ACI 318-LoadCombos_Service.rag, and immediately it will obtain a list of service combinations.
See the load combinations to be generated. Press OK.
A message with the number of generated load combinations will appear. Press OK.
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Example 9: Footing Design
Note. - If the module is run from RAM Advanse, the generation of load combinations or conditions
will not be necessary, because the main program may export all the loads directly to the module. Inany case the loads may be edited or changed in the module.
Note. - If it requires eliminate load conditions or combinations, this can be done pressing the button
easily. A window will display where is possible to select the elements to eliminate.
9) Entering Loads
Locate the Loads folder and select the option Forcesby Loads conditions.
Click on the option
The following window will appear:
This window is used for entering the forces by load condition.Note. - In case of combined footing, the program adds a new element to the above window, in order
to define the loads by column.
Select the Load case:
Choose DL.
Enterthe forces.
Define the values for the next load case.
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Example 9: Footing Design
Press OK, after entering the forces for the different Load cases.
Note. The loads may be imported directly from the main program.
Define the localization of the horizontal forces.
10) Entering the design data
Go to the Design data folder and select the option Design criterion of the footing dimensions.
Select Long/Width Ratio (default value).
Select a ratio = 1 to design a square footing.
Select the dowels force type:
Check this option when the load is predominantly in compression.Select the Bars Size for optimization
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Example 9: Footing Design
Select the bars to be used in the optimization.
11) Entering Configuration values
This values should be eventually defined or only once.
Press the button that is in the top screen side. The following window will be displayed to theuser:
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Example 9: Footing Design
Configuration window. Leave it with the values by defect and click in accept.
With this option, the user may define general configuration values for concrete, reinforcement, soiland design.
12) Suggest dimensions
In order to obtain the suggested dimensions of the base press the button.
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Example 9: Footing Design
In the data window and in the detailing window the footing dimensions are shown.
Note. When several load conditions or combinations are used there may be a small delay in the
calculations.
13) Optimizing the reinforcement
Press . Note that the reinforcement obtained will be according to the bars selected for theoptimization (see step 10).
14) Checking the design
Once the dimensions and reinforcement is obtained, you should verify if such dimensions and
reinforcement fulfill all requirements of the Specifications. Press .
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Example 9: Footing Design
Check the traffic lights at the top right of the screen .
Note. - Remember that a yellow traffic light indicates warnings, while a red light indicates errors.
15) FEM diagram
Click in order to see the following diagram:
FEM Diagram of contact pressures. Also it is possible to see a FEM diagram of settlements.
16) Footing detailing
Once the footing is analyzed and designed, go to the detailing screen.
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Example 9: Footing Design
This screen displays a spreadsheet with the reinforcement data that may be edited or changed
according to your requirements. After modifying the reinforcement, check the design with the
button .
The spreadsheet has two labels: Longitudinal (parallel reinforcement to the length of the footing) and
Transversal (parallel reinforcement to the width one of the footing).
Whenever you change the spreadsheet data, the traffic lights will be off, in order to remind you tocheck design.
Note - If the user wants to return to the initial results of automatic design, the Optimize design
button can be used.
Note. If the type of column is pedestal the program may suggest its reinforcement, too.
17) Seeing the report
All results and data are included in the report:
Press button in order to see the report.
The report consists of 3 sections: General data, results and explanatory notes.
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Example 9: Footing Design
General data. Relative to the base geometry, the used materials, the soil foundation properties, the
provide reinforcement, etc.
Results. Relative to the footing-soil interaction and the footing strength as a reinforced concreteelement.
In order to print the report press
Note.- If you wish to edit the report, you can easily export it to Microsoft Word or Microsoft Excel.
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Example 9: Footing Design
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