A typical model event sequence

Tekla Structural Designer
Tekla Structural Designer

A typical model event sequence

Let us consider a multistory building where the slab layout is the same on each level.

If we think about the slab model event sequence that occurs for the slab at level 1 it could be something like this:

  1. Strike and backprop slab (slab carries it's own weight)

  2. Cast Slab above (slab carries a proportion of the weight of slab above - the proportion is dependent on the number of levels of backpropping and there is also some debate about the efficiency of load sharing between the supporting levels. In this example we will assume 2 levels of propping and that the level directly below supports 60% and level 2 below supports 40%.)

  3. Strike and backprop slab above (slab above now carries its own weight)

  4. Cast slab 2 above (slab carries a proportion of the weight of the slab 2 above)

  5. Strike and backprop slab 2 above (slab 2 above now carries its own weight)

  6. If propping extends through 3 levels then there can be events for casting and striking the slab 3 above. In this example, the propping is removed and used two levels above.

  7. Additional load from finishes (in particular from sensitive finishes)

  8. Start of occupation.
  9. Final Load Event

A special note about the Final load event - It is perfectly ok to have multiple events at the same final time, you should not separate these events by a small number of days.

The view shown below is a graphical representation of the above but in this case is recognizing 3 levels of backpropping

Extract from How to design reinforced concrete flat slabs using Finite Element Analysis, The Concrete Centre - Figure 2

This sort of event sequence can be described within the Event Sequences dialog as shown below.
Note: Some of the event parameters vary between head codes, so both the ACI and Eurocode versions of the dialog are shown.

Model Event Sequence ACI (US Imperial units)

Model Event Sequence Eurocode (metric)

Note the increased slab self weight when casting slab 1 above and slab 2 above where an additional 60% and 40% of the slab weight is being supported respectively. This is defined in the On submodel % column.

A slab model event loading sequence for any other internal slab i.e. level 2 would be identical to that described above.

If we now consider the uppermost slab - the roof.

  • Is the slab event sequence for the roof any different?
  • Can we use the slab model event sequence above for the roof?

The event sequences for casting any slabs above are not required, since there is no need to make an allowance for additional propping loads. This means that a different event sequence is necessary to deal with the roof. In Tekla Structural Designer differences in event sequences are dealt with using a Custom Event Sequence.

Technically, we could deal with the propping events in one of two ways.

  1. Delete the event
  2. Keep the event, but adjust the included slab self weight to allow only for the roof load as the previous event. i.e the event has no change in load to that of the previous load event.

In Tekla Structural Designer, we must deal with the change using method 2 above. This is due to the way Tekla Structural Designer deals with Custom event sequences.

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