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4. Why does the deformation at time infinite differ from the deformation calculated in time?

# Why does the deformation at time infinite differ from the deformation calculated in time?

Contents

## Overview of the differences

If you would compare the cracked deflection  to the cracked deflection at time t = ∞, they’re not equal if you use default settings. This is why:

The deformation at time infinite  The deformation over time
The result of this calculation is on deformation at time t = ∞. The result of this calculation is the deformation at different times and at time t = ∞.
The cracked stiffness is determined using a SLS RC enveloppe. The cracked stiffness is determined using the combinations imposed by the user.

• Some clients use a SLS QP for dead loads and a SLS RC for variable loads.
• Some clients use an SLS RC 1 for both dead loads and variable loads.
Non-linearities (no tension at top walls, support that cannot bear tension, …) are taken into account. Non-linearities are neglected.
It is supposed that all loads cause creep. It is supposed that all permanent loads (self-weight and dead loads) + the quasi permanent part of the variable loads cause creep.

The deformation at time t = ∞ calculated with , is usally larger then the deformation at time t = ∞ calcualted with .

## How to obtain approximately the same result for both calculation methods

The settings for this  calculation cannot be changed by the user, so will change the setting of this  calculation so the results approach those of this calculation.

1. Remove all non-linearities from the model.
2. Select SLS RC 1 (we cannot select and SLS RC enveloppe, so we select the next best thing: SLS RC 1) as the combination for cracking for all load groups .
3. Add an additional combination (named ‘New combination in the image below’) to .
Make sure to set the factor Cc(t) to 1 for all load groups. Meaning that all load groups cause creep for the full 100%.
4. Compare the cracked deformation of this new combination with the cracked deformation obtained with thiscalculation.