TutorialFD - Concrete Footings

8/3/2019 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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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TutorialFD - Concrete Footings

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