Longitudinal reinforcement

Principles for the definition of longitudinal reinforcement

The defined property sets of the longitudinal reinforcement type are generally used for all verifications that determine longitudinal reinforcement. This means, for example, that a separate property set does not have to be created for bending reinforcement and crack reinforcement. To use the property set for longitudinal shear reinforcement or longitudinal torsional reinforcement (or the interaction between shear force and torsion), the options Effective in shear or Effective in torsion must be set accordingly in the properties window of the property set.

A property set line corresponds to a reinforcement layer (the center of gravity line).

The reinforcing bars are assumed to be evenly distributed within a reinforcement layer. The distances of the first or last bar from the start or end point of the property set line can be defined in the properties window of the property set, as can the bar diameter.

It is possible to define several reinforcement layers using several property sets.

The program determines the plane of strain of the cross-section during the design and always uses the reinforcement layer that is furthest into the tension zone when adding the reinforcement quantity. This means that reinforcement is first added in the reinforcement layer furthest into the tension zone until the limit is reached based on the standard specifications (minimum bar spacing). The process is then continued for the next free reinforcement layer furthest into the tension zone.

It should be noted that only those areas of the defined property set line that are within the tension zone are taken into account in the calculation. When the results are output, the reinforcement determined for the area of the property set line lying in the tension zone is extrapolated to the area of the property set line lying outside the tension zone using the defined bar diameters and determined bar spacings for reasons of consistency.

Similarly, when calculating the longitudinal reinforcement defined as acting in torsion, only those areas of the defined property set line that lie in the torsionally effective area of the cross-section are taken into account. The reinforcement determined for this area is extrapolated to the areas outside the property set lines.

Necessary steps/inputs for defining longitudinal reinforcement:

1. Creating a property set in the “longitudinal reinforcement” category (for each reinforcement layer)
2. If necessary, activate/select the property set in the navigation tree (is automatically active immediately after creation) and draw a property set (boundary) line for this reinforcement layer, which represents its center of gravity line
3. Definition of the following properties in the properties window of the defined property set:

   Note: It is essential to enter the bar diameter and the material (and the bar size for AASHTO LRFD).

Bar diameter

Longitudinal reinforcement bar diameter

Bar size [for AASHTO LRFD only]

Selection of bar size according to AASHTO LRFD

Material

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

Effective in shear / in torsion

Use checkboxes to select whether the property set should also be used for longitudinal shear reinforcement or longitudinal torsional reinforcement (or longitudinal reinforcement according to the interaction between shear force and torsion).

As rebar area

Input of a user-defined (existing) reinforcement (optionally via a variable of the reinforcement area type)

Position of first reinforcement

Distance of the center point of the first reinforcement bar from the starting point of the defined property set line

Position of last reinforcement

Distance of the center point of the last reinforcement bar from the end point of the defined property set line

Automatic geometry

Selection of whether the property set line should be created automatically.

Note: This function is only intended for completely symmetrically reinforced cross-sections, such as square or circular columns

A continuous property set line is created along the circumference of the cross-section, at a defined distance for solid cross-sections (see below) and at the automatically calculated center line for hollow cross-sections.

Note: The automatically generated property set lines are displayed in the 3D model after the calculation (if the view option is activated to that effect).

Distance to the edge

Distance of the automatically determined property set line (see above) from the edge of the cross-section for full cross-sections. This input is ignored for hollow cross-sections. The definition can optionally be made via a variable of length type.