The model shows the effect of an axial force on the torsion of a member. Three identical members are subjected to a torsional moment of 1.2 kNm; in addition, a tensile force of 500 kN, no axial force, or a compressive force of 500 kN acts on them. The calculation is performed using second-order analysis with the “Torsional Warping” add-on (7 DOF).
The tensile force acts as a stiffening force and reduces rotation, while the compressive force significantly increases it. The axial force-induced component M_xN is reported as the secondary torsional moment Mt,sec—positive for tension and negative for compression. In all three cases, the sum of Mt,pri and Mt,sec yields the applied torsional moment of 1.2 kNm. For the compressed member, this causes Mt,pri to increase by over 60%.
Torsion Induced by Axial Force – Effect of Tension and Compressive Forces on Mt,pri and Mt,sec
| Number of Nodes | 6 |
| Number of Lines | 3 |
| Number of Members | 3 |
| Number of Surfaces | 0 |
| Number of Solids | 0 |
| Number of Load Cases | 2 |
| Number of Load Combinations | 0 |
| Number of Result Combinations | 0 |
| Total Weight | 0.619 t |
| Dimensions (Metric) | 3.000 x 0.000 x 4.000 m |
| Dimensions (Imperial) | 9.84 x 0 x 13.12 feet |
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