How Minimum Design Forces are used

The following topics illustrate how Minimum Design Forces are applied in different areas of Tekla Structural Designer.

Member end force reports/drawings

Tekla Structural Designer reports member end forces (Beam end forces/Bracing forces) based on analysis results.

The ‘Minimum Design Forces’ inputs under Brace Force/Beam End Forces allow the user to specify minimum values for the reported forces, and also apply rounding increments to them.

Note: While minimum design values and rounding increments are applied to the member end force reports/drawings, they have no impact on steel and concrete member design in Tekla Structural Designer, or timber and precast design using Tekla Tedds.

Consider a fixed beam with axial force + major/minor shear + torsion + major/minor moment.

Forces/moments are reported in the Beam End Force report.

The user wants the forces rounded to the nearest 5kN and moments to the nearest 10kNm so inputs 5kN in the ‘Rounding Increment for Force’ and 10kNm in the ‘Rounding Increment for Moment’ under Beam End Forces.

The Beam End Forces report displays rounded value of forces and moments.

Note: The rounding increment for moment applies to major axis and minor axis moments, but does not apply to torsional moments (M_x).

The user might want the forces reported to be not less than minimum values, for example they might enter 200kN in the ‘Major Axis Shear Force’ under ‘Beam End Forces.

This results in the report being updated as follows.

The changes to the rounding increments and mimimum force are also reflected in the Beam End Forces drawing.

Foundation reaction reports/drawings

Tekla Structural Designer reports foundation reactions based on analysis results.

The ‘Minimum Design Forces’ inputs under Foundation Reactions allow the user to specify minimum values for the reactions, and also apply rounding increments to them.

Note: Changed force/moment values are for reporting purposes only.

Consider a fixed end support.

Forces/moments are reported in the Foundation Reactions report.

The user wants these reported values to be not less than certain minimum values, so inputs the required minimums under Foundation Reactions.

The Foundation Reactions report shows minimum design forces/moments specified by the user.

The user also wants the forces rounded to the nearest 5kN and moments to the nearest 10kNm so inputs 5kN in the ‘Rounding Increment for Force’ and 10kNm in the ‘Rounding Increment for Moment’ under Foundation Reactions.

When the report is updated, any values exceeding the minimums are rounded up accordingly.

The changes are also reflected in the Foundation Reactions drawing, which now shows the same minimum values of design force and moment.

Connection resistance checks

Tekla Structural Designer performs connection resistance checks for simple beams and braces which use design forces from the analysis results.

The ‘Minimum Design Forces’ inputs under Brace Force/Beam End Forces allow the user to specify minimum values for these forces, and also apply rounding increments to them.

Consider a simple beam connection.

Review Data of Connection Resistance shows the following details.

The user wants the forces rounded to the nearest 5kN so inputs 5kN in the ‘Rounding Increment for Force’ under Beam End Forces.

By closing and re-opening the Connection Resistance Review Data, the connection resistance check is updated and now uses the rounded value.

The user also wants a minimum design force of 75 kN for connection resistance check so inputs 75 kN in the ‘Major Axis Shear Force’ under Beam End Forces.

By closing and re-opening the Connection Resistance Review Data once again, the connection resistance check is updated to use the specified minimum design force.

Because the minimum design force is being used this is indicated in the table under the 'Note' column.

Exported connection forces

Forces exported to Tekla Connection Designer or IDEA StatiCa from Tekla Structural Designer are based on analysis results.

The ‘Minimum Design Forces’ inputs allow the user to specify minimum values for the exported forces, and also apply rounding increments to them.

Consider a base plate connection exported to Tekla Connection Designer and designed for axial load and major shear.

The user wants to design the base plate connection for a minimum shear of 50 kN and for a minimum axial load of 500 kN, so inputs these values under Foundation Reactions.

Note: For other connection types the values under Brace Forces/Beam End Forces would be edited instead.

Rounding increments could also be applied if required. These would only apply to forces and moments exceeding the above minimums.

To apply the new minimums to the existing connections, it is necessary to click Update Connections from the Project Workspace.

The base plate connection is now designed for the minimum shear of 50 kN and for the minimum axial load of 500 kN specified by the user.