Create and manage load patterns

Tekla Structural Designer
2021
Tekla Structural Designer

Create and manage load patterns

Having live/imposed loads applied only to a portion of the structure can produce a more unfavorable loading than the "fully loaded" condition. More unfavorable loading conditions can be considered in Tekla Structural Designer by the use of load patterns.

Overview of load patterns

Note: When you apply pattern loading to live/imposed loads, the factors of the loaded and unloaded spans are specific to the design code that you are using.

The basic steps of applying pattern loads

  1. Set individual live/imposed loadcases to be patterned according to your needs.

    These loadcases are referred to as fully loaded pattern loadcases.

  2. Set the gravity combinations that contain live/imposed loadcases to be patterned according to your needs.

    These gravity combinations are referred to as base case pattern combinations.

After load decomposition, the building analysis automatically sets up the pattern cases for continuous concrete beams, (cases are also set up for continuous steel beams if the 'Use load patterning for steel beams' option is selected in Model Settings> Loading > General). Patterns are set up in Dir1 and Dir2 directions as follows:

  • 10 pattern cases for each pattern gravity combination

  • 5 pattern cases for beams along Dir1 and 5 for beams along Dir2

Note: By default, patterns are only applied to beam loads, and slab loads that have been decomposed on to beams. Loads applied to meshed slabs should be manually patterned using engineering judgement.

Pattern loadcases

A pattern combination containing patterned live/imposed loadcases results in 11 combinations: the base case combination, and 10 pattern combinations derived from the base combination.

If you later modify the building geometry, you must run Update Patterns to ensure the load patterns reflect the changes.
Note: Tekla Structural Designer contains a set of 10 pattern combinations associated with each fully loaded pattern combination. The pattern combinations are the same for beams and slabs.

The rules of applying load patterns to slabs and beams

Slab load patterning only applies where two-way slabs have been meshed in the solver model:
  • in FE chasedown analysis

  • in 3D analysis where two-way slabs are set as meshed

Therefore, the slab load pattern setting has no affect on:
  • one-way spanning slabs

  • two-way slabs not meshed in 3D analysis, as the slab loads are being decomposed to beams and walls prior to creation of the solver model

  • two-way slab in Grillage chasedown analysis, as the slab loads are being decomposed to beams and walls prior to creation of the solver model

Therefore, in 3D analysis and Grillage chasedown analysis:
  • When a beam is set to Full Load, it receives the full decomposed load from adjacent unmeshed two-way slabs, irrespective of whether the slabs themselves are set to Full Load or Min Load.

  • When a beam is set to Min Load, it receives the min decomposed load from adjacent unmeshed two-way slabs, irrespective of whether the slabs themselves are set to Full Load or Min Load.

Apply patterning to live/imposed loadcases

If necessary, you can apply load patterning to live/imposed loadcases in a combination. In order to do so, see the following instructions.

  1. On the Load tab, click Loadcases.

    The Loading dialog box opens on the Loadcases page. On this page, you can see all currently existing loadcases.

  2. Click the live/imposed loadcase to which you want to apply patterning.
  3. Select the Pattern Load option.
  4. Click OK.

Apply patterning to load combinations

You can only apply load combinations to gravity combinations, as lateral and seismic combinations do not consider pattern loading. For detailed information on how to apply pattern loading to load combinations, see the following instructions.

  1. On the Load tab, click Combination.

    The Loading dialog box opens on the Combinations page. On this page, you can see all currently existing load combinations.

  2. On the left side pane of the Loading dialog box, select the name of the load combination.
  3. In Parameters, ensure that the Pattern option is selected.
  4. Click OK.
    Note: If you wish, you can use pattern loading for every gravity combination in your model. However, doing so may create many additional combinations.

Update load patterns

Tekla Structural Designer applies patterning to beam loads automatically. However, if you need to apply patterning to slab loads for slab design or other purposes, you must update the load patterns manually.

  1. On the Load tab, click Update Patterns.
  2. In the Properties window, select each pattern in order to review the loading status of the existing beams and slabs.
  3. To switch the loading status of a slab in the current pattern, click, or box around the slab(s) in the model.
The pattern that has been defined is applied to every imposed/live loadcase that is set to be patterned.
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