Stressing
Tendon stressing – load type TEND0
| Load Type | Description |
|---|---|
| TEND0 | Applying the prestressing, defining the tendons to be stressed. |
This load type specifies the tendons to be stressed in the current load case. The scheduled stressing scheme must have been specified prior to calculating this load case. Details on how to model pre-stressing in the schedule are given in the User Guide, chapter 7.5.4 and 11.5.3.
The options Increment-Force and Total-Force refer to tendons partially stressed in different construction stages, indicating whether the current stressing force is an initial load fully acting on the structural elements (Total-Force), or whether it is the final state after re-stressing previously stressed tendons (Increment-Force).
When tendons are stressed in two or more steps in different stages, this is considered by assigning different Stress-labels to the stressing sequences applied at different times. The action Stress with the Stress-label of the first stressing sequence must in this case be called before the Calc action for the related pre-stressing load case, then the action Stress with the Stress-label of the next sequence before Calc for the next related pre-stressing load, and so on.
Example
Construction stage 1: First stressing to the tendon force state "A"
The selection of the switch has no influence on the results. The stress state "A" is applied to a tendon in the first construction state. Selecting Total-Force or Increment-Force is irrelevant, because no previous tendon forces exist.
Construction Stage 2: Re-stressing of the tendon to the tendon force state "B"
The stressing force state "B" is assigned to this tendon in the 2nd construction stage. The total tendon force "B" is used if Total-Force is selected. If the results are summed up in a super-position file, then the sum "A+B" will be as result in the superposition file, instead of the correct state "B". If Increment-Force is selected, then the force state "B-A" will be used as loading. The sum of the 1st and 2nd construction state will now be the state due to the tendon force state "B".
Cable/external tendon stressing – load type FCAB
| Load Type | Description |
|---|---|
| FCAB | The specified pre-stressing force Fx is directly assigned to the specified elements of type cable or to external pre-stressing elements (see external prestressing). Exactly this normal force will be in the cable element after the load case calculation. |
The load type FCAB simulates the physical process "Cable tensioning" fully force related. The results will be exact for simple linear analyses.
The stressed elements are separated from the system and the force Fx is applied instead of it on the remaining structural system (direction = undeformed cable direction). The resulting internal forces and deformations of the remaining system are computed, then the element is again installed in the un-deformed structural system and the normal force in the element is set to Fx. No displacements are assigned to the element.
This load type can be used to stress the force directly into the system, if the cable force at the end of the stressing process is known,. Other than in the case of using e.g. FX0, the normal force in the stressed element will be exactly the applied force.