Load Combination Generator
The Load Combination Generator in the PRE-Stress software allows you to see all the different stages of the life cycle of the prestressed element, see all load cases and combine them into any load combinations in each stage.
The self-weight of modelled precast elements (precast element + optional topping) is automatically added as a dead load in each stage in which they are present.
Depending on the type selected for the load, the program will automatically add the correct factors according to the national annex used. Safety factors can also be manually modified if we want to work with different load factors.
Load Combination Generator Logic
No load combination is automatically generated unless you choose to activate automatic generation of load combinations based on dead load at the initial creation of the element. These initially generated load combinations will thus only contain dead load.
PRE-Stress uses a feature called “dependency” to model the effects of preceding load combinations, such as transfer losses and remaining displacement due to creep, shrinkage and cracking.
A given load combination can be set to depend on a previous load combination. Dependency on an ultimate limit state (ULS) load combination cannot be set (and is not a meaningful concept), whereas dependency on a serviceability limit state (SLS) load combination is always possible. Thus, a ULS can depend on an SLS, but never the reverse.
Load combinations are calculated in the order given in the load combination list, meaning a load combination can only depend on earlier load combinations. Chains of dependency (depending on a load combination which in turn depends on a load combination, and so on) are permitted and indeed common.
For the current load combination, start values such as remaining deformation after release, cracking etc., are inherited from the load combination it is dependant on.
For more technical information and theory on the Load Combination Generator please visit the PRE-Stress Wiki by clicking here.