Define Post-tensioned Tendon
Description
This form is used to apply pre-stress effects to the structure by defining tendon profiles and applying the appropriate forces along the tendon profile. It is designed for post-tensioned tendons and reference should be made to the methodology that is described here.
The table on the left of the form lists all the tendons that have been defined. The details on the right apply to a single tendon only. The particular tendon is selected by clicking in the required row of the table.
For each tendon a reference axis is required. The tendon profile is then defined relative to the reference axis. Additional required data is defined for stressing and loss parameters. The four tabbed pages on the right of the form enable entry of this data.
The analysis is performed by generating a beam member to correspond with each portion of the reference axis, and assigning eccentricities at the ends of these beam members in order to match the tendon profile. For best results therefore, the reference axis should be defined to follow the tendon profile as closely as possible.Outline Procedure
This form is accessed through Data | Prestress in the main menu.
A new tendon is generated by clicking on the + (Insert Record) button of the left hand table. The reference axis must then be defined for the first tab sheet to the right of the table as described in 'Reference Axis' below.
Alternatively an existing tendon may be copied and moved. To do this click with the right button of the mouse whilst pointing to an existing tendon in this table, and select Copy. Then click to define the start point for the reference axis of the new tendon in its required position. The new tendon will have its profile copied from the original tendon, but not necessarily its reference axis.
If the 'Active' cell at a particular row is unchecked then the tendon defined at that row will be inactive. Inactive tendons will not be included in the analysis of the structure. A warning of inactive tendons is given during analysis.
For details of the table features, and navigation, see the help topic Table Features & Navigation.
For long beams or wide sections, the graphic option under the General side bar labelled Section Scale Factor is useful for changing the horizontal scale to suit.
Tendon Name
A name that is used for identifying the tendon is generated by the program. The default name may be changed by entering an alternative name in this field.
Tendon Association
If the 'Association' cell at a particular row shows a Structure Property reference then the tendon defined at that row is associated with a Structure Property Post-tensioned Prestressed Concrete Beam. In this case the structural tendon data is in sync with the Design Beam tendon data.
On the other hand if the 'Association' cell shows 'None' then the tendon is not associated with a Design Beam and all fields on all tabs can be edited freely.
Association can be broken by clicking on the 'break association' button next to the 'Structural Property' reference.
An associated Structure Property can reference either a linked or embedded Design Beam:
- If linked then all fields on all tab pages are disabled with an exception of the 'Material Property' field. Any change to the tendon data is done in the Design Beam file. Note for data consistency reasons the 'Material Property' field refers to a material in the project rather than the linked Design Beam file.
- If embedded then all fields on all tab pages are disabled without exception. Any change to the tendon data is done directly in the Design Beam tendon definition form.
'Association' can be broken for all tendons at the same time by using the 'Disconnect all tendons associated with design beams' right click menu item. The association can only be re-established by reassigning the 'Structural Property' to the structure members.
If any association is broken for a selected beam on result transfer, a warning of non-correspondence between Design Beam and Structural Analysis tendon is given.
Action
Five different action can be made to a tendon in a construction stage:
| Action | Description |
|---|---|
| Stress | tendon is stressed to the desired level. All tendon parameters can be modified. |
| De-stress | indicates that the tendon is not stressed and does not work together with the structure. Stressing and loss of prestress parameters cannot be edited. This is the default setting for a new tendon. |
| Re-stress | if selected tendon is re-stressed to a value defined by the '% Prestress added' field. Stressing and loss of prestress parameters cannot be edited. |
| Grout | structural bond is established between tendon and concrete. Loss of prestress parameters cannot be edited. |
| No change | tendon configuration is not changed in this stage. |
Related Topics
Prestressed Analysis With Post-Tensioned Tendons
Also refer to the following topics individual tab page help