Working with foundation reaction axis systems

Tekla Structural Designer
2023
Tekla Structural Designer

Working with foundation reaction axis systems

The following options are available for setting the axis system that foundation reactions align to:
  • Local Support (default)
  • Building Direction
  • Angle to Global (X and Y)

The method for setting the axis system varies depending on whether you want to display the reactions in a graphical results view, a tabular data view, a report, or a drawing. Instructions for each method are provided below.

Also given below in the 'Understanding the axis system options' section are details of the sign conventions applicable along with some examples.

Set the axis system in a graphical results view

Once you have chosen the support reactions to be displayed in a graphical results view, you can select the axis system as follows:
  1. in the Reactions group on the Results tab, click Settings .
  2. In the dialog, select the required axis system.
    To find out more about the axis system choices, see Understanding the axis system options below.
  3. Click OK.
The Reactions graphical results view is reconfigured to display the reactions in the selected axis system.

Set the axis system for a tabular data view

Once you have displayed support reactions in a tabular data view, you can select the axis system as follows:
  1. On the Analyze tab, click Table Options.
  2. In the dialog, select the required axis system.
    To find out more about the axis system choices, see Understanding the axis system options below.
  3. Click OK.
The Foundation Reactions tabular data view is reconfigured to display the reactions in the selected axis system.

Set the axis system for a report

  1. On the Report tab, click Model Report....

    The Report Contents dialog box opens.

  2. Select a report configured to include Foundation Reactions in its Report Structure
  3. In Report Structure, right click Foundation Reactions > Foundation Reactions.
  4. In the context menu, select Settings...
  5. In the dialog, select the required axis system.
    To find out more about the axis system choices, see Understanding the axis system options below.
  6. Click OK.
  7. Click OK once more to close the Report Contents dialog.
When the report is generated the reactions are reported in the selected axis system.

Set the axis system for a drawing

  1. On the Draw tab, click Settings.

    The Drawing Settings dialog box opens.

  2. Click Options > Planar Drawings > Foundation Reactions
  3. On the General tab, select the required axis system.
  4. In the context menu, select Settings...
  5. In the dialog, select the required axis system.
    To find out more about the axis system choices, see Understanding the axis system options below.
  6. Click OK.
When a Foundation Reactions drawing is generated the reactions are reported in the selected axis system.

Understanding the axis system options

Local Support (default)

The sign convention for support reactions using this axis system is as shown below, with positive moments about an axis acting in a clockwise direction when viewed in the direction of the axis:

For columns and walls the support local axes are determined by the column/wall orientation.

Column Wall


  • Local x aligns to the column major axis

  • Local y aligns to the column minor axis

  • Local x aligns to the wall major axis

  • Local y aligns to the wall minor axis

Special case - intersection of two connecting walls

  • The shared support is aligned with the global axis system
  • When local reactions are output to a tabular data view or report, the values at the shared support are split equally between the walls and reported in the same local axis system as the other supports in each respective wall.

For more details, see: Case study (connecting walls) below.

Building Direction

The Building Direction arrows can be displayed by selecting Show Building Direction Arrows in the Structure Properties window. These Dir1 and Dir2 arrows indicate the orthogonal horizontal reaction directions when the Building Direction axis system for reporting reactions is selected. The third reaction direction is aligned to the Global Z axis.

The sign convention for support reactions using this axis system is as shown below, with positive moments about an axis acting in a clockwise direction when viewed in the direction of the axis:

Angle to Global (X and Y): when angle = 0 degrees

The Global Axis direction arrows are permanently displayed in 3D scene views.

The sign convention for support reactions using this axis system is as shown below, with positive moments about an axis acting in a clockwise direction when viewed in the direction of the axis:

Angle to Global (X and Y): for any other angle

While they are not actually displayed, the dir1 and dir2 arrows that apply when an angle to global has been specified are as follows:

  • dir1 is at an anticlockwise angle θ from Global X when looking down in plan.
  • dir2 is at 90 degrees to dir1
  • The third reaction direction is aligned to the Global Z axis.

The sign convention for support reactions using this axis system is as shown below, with positive moments about an axis acting in a clockwise direction when viewed in the direction of the axis:

Columns example

Consider the following structure consisting of a slab supported on eight columns. The building direction has been defined at an angle of 30 degrees to the global axes. We will investigate the reactions resulting from a wind load which has been applied to one side.

The total wind load is 1.0kN/m2 * 14.5m * 3m = 43.5kN

When viewed from above you can see how the local axis system of each support is determined by the rotation angle of the column being supported.

In the Results View, Foundation Reactions can be displayed in each of the axis systems.

  • In the Local Support axis system the Fx and Fy reactions would be displayed as follows:

  • In the Building Direction axis system the Dir1 and Dir2 reactions would be displayed as follows:

  • In the Angle to Global axis system (with angle set to 0 degrees) the FX and FY reactions would be displayed as follows:

  • In the Angle to Global axis system (with angle set to 45 degrees) the F1 and F2 reactions would be displayed as follows:

The reactions can also be displayed in a Tabular Data View.

  • In the Local Support axis system the tabular reactions would be displayed as follows:


    Because the local axes are all in different directions, there is nothing to be gained from summing the above reactions.

  • In the Building Direction axis system the tabular reactions would be displayed as follows:

    When the above reactions are summed, FDir1 equates to -43.5kN, and FDir2 equates to 0kN.


  • In the Angle to Global axis system (with angle set to 0 degrees) the reactions would be displayed as follows:
    When the above reactions are summed, FX and FY equate to the Total Reaction figures given in the Project Workspace Loading Summary, (as the Total Reaction is always reported according to the Global Axis system.

Walls example

Consider the following structure consisting of a slab supported on two connected walls and a column. The building direction has been defined at an angle of 30 degrees to the global axes.


It can be seen that:
  • The Building Directions (Dir 1 and Dir 2) are not aligned to the Global Axis System.

  • Wall W1’s major axis is aligned with Building Direction Dir 1

  • Wall W2’s major axis is aligned with Building Direction Dir 2

We will investigate the reactions resulting from a wind load of 18kN is applied to the front face of the building so that it acts in Building Dir 2.


When Support > DOF is switched on in Scene Content it can be seen that they are aligned as follows:


  • Shared support at the point where the walls connect:

    • Local x is aligned to global X

    • Local y is aligned to global Y

  • Remaining supports:

    • Local x is aligned to each wall’s major axis

    • Local y is aligned to each wall’s minor axis

After analysis the total global X,Y, and Z reactions can be obtained from the Project Workspace Loading Window.


  • In the Local Support axis system the Fx and Fy reactions would be displayed in the Results View as follows:



    At the shared support the local Fx and Fy reactions align with the global axes, whereas all the other supports they align to the wall major and minor axes.

    When the same results are displayed in a tabular data view, the reaction at the shared support (Reference 28 in the table below) is split equally and then converted to the local axis system applicable to each wall.
  • In the Building Direction axis system the FDir1 and FDir2 reactions would be displayed in the Results View as follows:



    When the same results are displayed in a tabular data view, the reactions at the shared support are output in a single row. (All rows are output in the Building Direction axis system).

    In the tabular data view, the sum of the reactions (FDir1 = 0kN, FDir2 = 18kN) equate to the applied load.

  • In the Angle to Global axis system (with angle set to 0 degrees) the FX and FY reactions would be displayed in the Results View as follows:



    When the results are displayed in a tabular data view, the reactions at the shared support are output in a single row. (All rows are output in the Global Axes system).


    The sum of the reactions (FX = 9kN, FY = 16.6kN, FZ = 0kN) equate to the global reaction values in the Project Workspace Loading Window.


Was this helpful?
Previous
Next