Table of Contents

## How do you find the torsional constant of a rectangular section?

The torsion constant is a geometrical property of a bar’s cross-section which is involved in the relationship between angle of twist and applied torque along the axis of the bar, for a homogeneous linear-elastic bar….Rectangle.

a/b | |
---|---|

2.0 | 0.229 |

2.5 | 0.249 |

3.0 | 0.263 |

4.0 | 0.281 |

**What is St Venant torsion?**

Saint-Venant’s theorem states that the simply connected cross section with maximal torsional rigidity is a circle. It is named after the French mathematician Adhémar Jean Claude Barré de Saint-Venant.

**What is the best cross section for torsion?**

Comparing Section Torsional Properties

- Round closed sections are the best for resisting torsion.
- Square closed sections are the next best, followed by rectangular closed sections.
- Open sections are no good in torsion!

### What is torsion of members with thin open sections?

BASIC THEORY If a member of open cross section is twisted by couples applied at the ends in the plane perpendicular to the axis of the bar and the ends are free to warp, we have the case of unrestrained torsion (Fig. B8. 4.1-1).

**What is torsional constant formula?**

The torsion constant K of a rod is defined by the equation. θ τ = K . in which a torque τ causes one end of a rod to rotate through an angle θ, measured in radians, while the other end of the rod is fixed.

**How is torsional section modulus calculated?**

The polar section modulus (also called section modulus of torsion), Zp, for circular sections may be found by dividing the polar moment of inertia, J, by the distance c from the center of gravity to the most remote fiber.

#### What is warping in torsion?

In addition to shear stresses, some members carry torque by axial stresses. This is called warping torsion. This happens when the cross-section wants to warp, i.e., displace axially, but is prevented from doing so during twisting of the beam.

**What is torsional rigidity?**

Torsional rigidity is the object’s torsional resistance to twisting as a torque is applied to the component and is dependent on a components geometry. As torsional rigidity increases, the torque required to produce a twist of one-unit angular measurement per one unit length of the shaft, increases.

**What shape is best for torsion?**

hollow tubes

Consequently, hollow tubes are the most efficient shapes for carrying torsional loads because nearly uniform shear stress exists on the material cross section of a large-radius thin-walled, hollow tube.

## What is the St Venant torsional constant used for?

The St. Venant torsional constant, J, measures the resistance of a structural member to pure or uniform torsion. It is used in calculating the buckling moment resistance of laterally unsupported beams and torsional-flexural buckling of compression members in accordance with CSA Standard S16.1-94 (CSA 1994).

**What type of torsion does cross-section produce?**

Some cross-sections produce only uniform St. Venant torsion. For these, only tangent stress τ t occur. Other, open cross-section might produce also normal stress as a result of torsion load: it depends whether there are constraints against warping torsion.

**Do all cross sections of beams produce torsion stress?**

Some cross-sections produce only uniform St. Venant torsion. For these, only tangent stress τ t occur. Other, open cross-section might produce also normal stress as a result of torsion load: it depends whether there are constraints against warping torsion. It depends what kind of supports restraint a beam.

### What is the warping torsion constant for hollow structural sections?

For hollow structural sections (HSS), warping deformations are small, and the warping torsional constant is generally taken as zero. Shear Centre. The shear centre, or torsion centre, is the point in the plane of the cross section about which twisting takes place.