Load Event Sequences dialog box

Tekla Structural Designer
2023
Tekla Structural Designer

Load Event Sequences dialog box

The Load Event Sequences dialog box is used to define all the construction stage events that slabs in a sub model will go through starting from the day the slabs are cast.

To display the dialog box:

  • On the Slab Deflection toolbar, click Event Sequences

The dialog box content is described below.

1. Event sequences and submodels pane

Event Sequences

Select Event Sequences to show a summary of the model event sequence and any custom event sequences that have been defined.

When this page is active you can:
  • Add a Custom Load Event Sequence.
  • Remove a selected Custom Load Event Sequence.
  • Review which Event Sequences are used in submodels

Model Event Sequence

Select Model Event Sequence to display the various event sequence parameters for editing.

When this page is active you can:
  • Review the existing Load Events and edit all the quantities (except included loadcases)
  • Add an event to the end of the sequence
  • Insert an event above the selected event in the sequence
  • Remove events
  • Move Up or Move Down events to re-order the sequence
  • Reset the Model Event Sequence to the default Event Sequence in the active Settings Set

Custom Event Sequences

Pages for custom event sequences are only displayed if they have been added from the Event Sequences page.

When a custom event sequence page is active you can:
  • Review the existing Load Events and edit all the quantities (except included loadcases)
  • Add an event to the end of the sequence
  • Insert an event above the selected event in the sequence
  • Remove events
  • Move Up or Move Down events to re-order the sequence
  • Reset the custom event sequence to be the same as the Model Event Sequence
Note: Model Event Sequences and Custom Event Sequences do not behave differently - they are both just Event Sequences.

Load Event subpages

Load Event subpages are displayed under the Model Event Sequence, and any custom Event Sequences pages. Each Load Event has a separate subpage which is used to define the loadcases included in the Load Event.

The [>>] and [<<] buttons are used to add or remove loadcases from the Included Loadcases list.

On submodel specifies the percentage of each included loadcase on the submodel.

From chasedown specifies the percentage of each included loadcase from the chasedown.
Note: For propping loadcases - “From Chasedown” should be 0%.

Submodels

Select Submodels to assign a custom event sequence to a submodel if required.

  • With this row selected you can edit the section size and grade for all stacks simultaneously.

2a. Event sequence parameters table (Eurocode)

The input parameters required for each event are:

  • Event Number - Automatic

  • Event Name - A user defined name to help explain the event

  • Load Start time - The time at which the event takes place

  • Beta - a coefficient to take account of the influence of the duration of loading. (See: EC2 Clause 7.4.3) This coefficient is used to account for the fact that tension stiffening effects reduce over time.

    Tension stiffening is the phenomenon that when the concrete is not fully cracked, there is still concrete in the tension zone that transfers some tensile forces, so the stiffness is greater than that of the fully cracked stiffness (and less than the uncracked stiffness). Since this effect reduces over time, to model loads with a longer duration, you want to model a lower stiffness, which means setting beta = 0.5.

    In Tekla Structural Designer, Beta defaults to 1.0 where the start event time is ≤ 30 days and 0.5 if >30 days, but may be changed for any event.

    Tension stiffening reduces over time because of increased cracking and bond failure between the steel reinforcement and concrete.

    These phenomena cannot be reversed, so reduced tension stiffening cannot be recovered.

    For this reason, if Beta is set to 0.5, and then in a later event set to 1.0, a warning flag is shown.

  • Temperature - Used in the calculation of the Composite Modulus. The effective age of concrete is adjusted to account for the defined temperature.

  • Relative Humidity - Used in the calculation of creep.

  • Number of Exposed Faces - Used for the calculation of creep.

  • Construction load - The construction load you wish to allow for at the chosen load event.

  • Loadcase - You select the loadcases you wish to be included in the event.

  • On submodel - The % of load to apply to the slab, applied directly to the sub-model.

  • From chasedown - The % of load to apply to the slab, from the reactions established in analysis of the sub-models above.

2b. Event sequence parameters table (ACI)

The input parameters required for each event are:

  • Event Number - Automatic

  • Event Name - A user defined name to help explain the event

  • Load Start time - The time at which the event takes place

  • Ultimate Creep Coefficient

  • Aging Coefficient

  • Number of Exposed Faces - Used for the calculation of creep.

  • Construction load - The construction load you wish to allow for at the chosen load event.

  • Loadcase - You select the loadcases you wish to be included in the event.

  • On submodel - The % of load to apply to the slab, applied directly to the sub-model.

  • From chasedown - The % of load to apply to the slab, from the reactions established in analysis of the sub-models above.

3. Update custom event sequences

If you select the Update custom event sequences option, changes made to the Event in the Model Event Sequence are also replicated in custom event sequences.

4. Buttons

Button Description

OK

Saves the current reinforcement and closes the dialog box.

Cancel

Closes the dialog box without saving changes.

Add

Depends on the page selected in the Event sequences and submodels pane.
Insert Depends on the page selected in the Event sequences and submodels pane.

Remove

Depends on the page selected in the Event sequences and submodels pane.

Move Up

Depends on the page selected in the Event sequences and submodels pane.

Move Down

Depends on the page selected in the Event sequences and submodels pane.

Reset

Depends on the page selected in the Event sequences and submodels pane.
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