Load combinations - What do they represent

Here you find information and developement about input of loads

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StruSoft Fredrik L
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Load combinations - What do they represent

Postby StruSoft Fredrik L » 26 Feb 2017, 21:08

Here we will explain what each load combination in the preset template represent, and how to add new combinations based on the ones in the template.

Release (Serviceability Limit State - SLS)
This stage will start the simulation of the hollowcore-dependency chain. It will simulate the moment when the prestressing wires are cut and the hollowcore will deflect upwards. The concrete strength should be entered as the release strength of the hollowcore.

Loads acting on the element: Deadload of the element

Storage/Maturing (SLS)
This is the first lomg term load combination where the long term effects from the early stages can be introduced, mainly the shrinkage from the casting, but also the creep and relaxation.

Loads acting on the element: Deadload of the element

Transport (SLS)
This stage simulates either transport and lifting on the construction site. Here it might be good to model the dynamic effects according to CEN/TR 15728:2012 ("Design and Use of Inserts for Lifting and Handling of Precast Concrete - Elements")

Loads acting on the element according to CEN/TR 15728: Deadload of the element * (gamma_g + (psi_dyn - 1)*gamma_Q)

Erection (SLS)
Construction site, the loads acting on the element during the construction phase will be defined here.

Also, if the element has a topping it shold be added as wet concrete here. The topping will automatically add the dead load of the topping as a load - if it was defined to be added into the correct load case in the wizard. The topping will not have any stiffnes in this stage, but it will be considered cast in all stages dependent of this stage.

Loads acting on the element: Loads during the construction

Intermediate stage (Short term) (SLS)
Intermediate stage is a short term load case with same loading as Final Stage (Short term) (SLS). The main purpose is to make the concrete get as much cracks for normal loading as possible before the long term load combination. This will only affect the deflection and crack width calculation in the following long term load combination. Since it will have the same load, then the moment and shear force will be the same as Final Stage (Short term). Assume time about 2 years after building has been taken into service.

Loads acting on the element: EN 1990 6.15 (Frequent)

Final Stage (Long term) (SLS)
This is the last stage before the ultimate limit states that we add the long term parameters in. As for the topping this is the only combination we can add the shrinkage and creep. Note that it is the increments of the long term parameters that should be added. Should be considered as either 20y, 50y or 100 years old.

Loads acting on the element: EN 1990 6.16 (Quasi-permanent)

Final Stage (Short term) (SLS)
Assume that this short term load is applied the day after "Final Stage (Long term) (SLS)"

Loads acting on the element: EN 1990 6.15 (Same combination as intermediate stage, Frequent)

Final Stage (6.10a, ultimate) (Ultimate Limit State - ULS)

Loads acting on the element: EN 1990 6.10a

Final Stage (6.10b, ultimate) (ULS)

Loads acting on the element: EN 1990 6.10b

Final Stage (Fire) (ULS) - Optional

Loads acting on the element: EN 1990 6.11


If you want to create a new load combination based on the same settings as another combination, select the one you want to copy from, set a new name and press [Insert], If you create a ULS-combination the dependency-chain will branch out and stop at that combination.

Lets say you want to create a combination for ULS on the construction site, due to weight of topping concrete. Go to load combination list and [Insert] a new combination with new name. Change the SLS to ULS and check so the dependencies are not linked to any following combination. Enter the ULS-loadcombination and calculate.
Fredrik Lagerström
Technical Support and Developement
StruSoft AB

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