11. Concrete Base check

A. General

The final stage in order to conclude the example is to design the concrete base of the specified structure. In INSTANT steel a user can design a “Footing” and a “Strip Footing”. More specifically, INSTANT steel performs certain verification checks on single foundation foot, centric or eccentric, with rectangular sectional plan and prismatic or cone shaped. The participation of foundation beams is ignored. All the checks are based on the ΕKOS/EAK2003 (Greek regulations) or the Eurocodes (EC2/EC7) and include the following:

  1. Load eccentricities check.
  2. Bearing capacity (ultimate axial force).
  3. Design in Bending (Bending reinforcement).
  4. Design in Shear (Check of concrete resistance without reinforcement/stirrups).
  5. Design in Drilling.
  6. Normative limits for minimum/maximum reinforcement values and other geometric restrictions.

In addition, INSTANT steel performs a complete dimensioning procedure on strip foundations of inverted Tau section with the web centered in the flange. The dimensioning takes into account checks which are based on the NKOS and EAK2003 and includes the following:

  1. Bearing capacity.
  2. Strip foundation failure (Bending, shear of web/flange).
  3. Normative limits for minimum/maximum reinforcement values and other geometric restrictions (par. 18.6 EKOS).

The longitudinal reinforcement calculated is symmetrical (same percentage of bars in tension and compression) and the contribution of the reinforcement in compression is taken into account in the section’s capacity and equilibrium.

Material safety factors:

Concrete γc = 1,50

Steel γs = 1,15

B. Concrete Base environment

In order to enter at the Concrete Base program, the following procedure is taking place:

From the general window INSTANT steel – Linear 3D, by selecting: Design Checks > Concrete Base rolled Members as shown below.


The main window for Concrete Base application has the following look:


After the completion of the above selection a new window will open called “Cbase”. Select the “New” instant-wiki-08-04 icon and from the “New File” dialog window that will open give the appropriate “Job Info”.


Select as “File Name” Concrete Base and also as a “Job Name” Base1. By clicking on “Search” button the following dialog window will open.


From this window, the user selects the appropriate TOP file from the relevant “Projects” file. After the above procedure is finished the “New File” window will have the following look.


Press the OK button and the “Concrete Base” screen will upload the linear topology from the specified folder.


Remember at this point to save the “Concrete Base” job, simply by clicking on the “Save” instant-wiki-05-02 icon on the top toolbar. This selection will have as a result to open the following window.


Set as file name “Concrete Base” as shown above. The file name will be saved at the relevant “Project” file.

After we have saved the Concrete Base file, we set the “General Foundation Elements” by selecting from the main toolbar Footing > General Foundation Elements.


After this selection is complete a dialog window will open called “General Parameters of Foundations”. There select the values for the different type parameters as shown below.


From the above selection, the “Design norm” is set to EC2 and the “Seismic area” is set to “I”. Press the OK button on the top corner of the dialog window and then you will return to the main “Concrete Base” screen.

Note: The units at Concrete Base are set to the current units of the project.

By clicking from the main toolbar Footing > New Footing, a “Footing” dialog window will open.


There set the following values in order to describe the “Footing” topology.


After, the above values are set press the OK button and you will return on the Concrete Base screen. There on the left hand-side there is a toolbar as shown below. From the toolbar select the “Add new footing” instant-wiki-10-12 icon and click on the support nodes on the model topology that is on the right hand-side of the Concrete Base screen.


When you have finished your selections the main screen will be as following:


Then we are ready for “Analysis” by clicking on the “Analysis” instant-wiki-10-15 icon on the top toolbar. This selection will open the following “Solve” dialog window. Press the OK button and the design of the “Footings” will take place.


By clicking on the “Results view” instant-wiki-10-17 icon, a “Footing design results” window will open as shown below.


The user can have a quick look on the various verifications that are taking place and decide whether the “Footing” is sufficient or not in order to alter any geometrical data of the footing.

By clicking on the “Report” instant-wiki-10-19 icon, a “Select Nodes” window will open as shown below. Here the user selects the base footings that he wishes to include on the report that will be created. In addition, the user selects the “Report language” from the right hand-side of the dialog window.


By pressing the OK button the report is created in a text format as shown below.

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