Torsion reinforcement

Principles for the definition of torsion reinforcement

For torsion reinforcement, a closed property set boundary line is defined in principle, which represents the center line of the thin-walled, closed cross-section or the equivalent thin-walled cross-section ("equivalent box girder") for solid cross-sections.

In addition to the manual definition, it is also possible to generate the property set boundary line automatically for single-cell box girder cross-sections (option Automatic geometry in the property set properties), as well as for solid cross-sections with additional input of the edge offset (options Automatic geometry + edge offset).

Note: The automatically generated property set boundary line can be displayed in the cross-section in the 3D model (if the corresponding view option is activated).

Necessary steps/inputs for defining torsion reinforcement:

1. Creating a property set in the “torsion reinforcement” type (for each center line/(equivalent) box girder)
2. If necessary, activate/select the property set in the navigation tree (is automatically active immediately after creation) and draw a closed property set (boundary) line that represents the center line of the thin-walled, closed cross-section or the equivalent thin-walled cross-section. If applying the Automatic geometry option then this step is omitted.
3. Definition of the following properties in the properties window of the defined property set:

   Note: It is essential to enter the bar diameter, the number of reinforcement bars, the stirrup offset and the material (as well as the bar size for AASHTO LRFD).

Bar diameter

Bar diameter of the stirrup reinforcement

Bar size [for AASHTO LRFD only]

Selection of bar size according to AASHTO LRFD

Number of reinforcement bars

Number of reinforcement bars in the section through the property set per intersected line (e.g. box girder cross-section with one stirrup per web: number = 2, rectangular cross-section with a stirrup: number = 1)

Material

Material of the reinforcing bar (selection after definition or import in the Analysis/Material menu)

Stirrup offset

Spacing of the reinforcement stirrups in longitudinal direction

Effective in shear

Selection of whether the property set should also be used for the shear reinforcement

Effective area due to a stirrup

By default, the effective area is determined on the basis of the distribution of unit shear stresses. In special cases, this option can be used to determine the effective area along the property set line.

Automatic geometry

Automatically creates the geometry of the property set line automatically (only applicable for single-cell box girder and solid cross-sections)

For box girders, the property set line is calculated along the center line of the box girder if the edge offset is set to zero, for solid cross-sections along the cross-section circumference at the distance defined by the edge offset. With box girders, if an edge offset is defined then this is handled in the same way as solid cross-sections (one application, for example, is a solid cross-section with a smaller cutaway).

Note: Regarding solid cross-sections, this option is only useful for cross-sections such as rectangles or circles and not, for example, for T-shaped or more complex cross-sections.

Edge offset

[This is generally only for full cross-sections (for box girders, see above) and the Geometry automatic option]

Distance of the center line of the equivalent thin-walled cross-section from the edge of the cross-section