The feature is fully automatic and requires no additional modeling or loading. To activate it, as shown in the pictures below, simply:
Check on the new “Use patterning of eccentricity moments…” option ( in Home > Settings > Loading > General for Global Settings and new models, and the same location in Home > Model Settings for an existing open model)
Check on the “Pattern Eccentricity Moments” for the Imposed (Live) Load case(s) in the Loading dialog (no other load types can be patterned)
(Note that the default for both settings is Off)
Key aspects of this new feature are:
The inferred ecc. moment profile assumes the same pattern at the top and bottom of a stack e.g. it is not possible to have P1 at the top and P4 at the bottom of a stack.
Patterned ecc. moments are combined with ‘real’ moments in the same way as in previous releases (which essentially considered only P0).
Axial force; this is reduced (by patterns P1-4) at the current level while that from floors above is from P0 (which is a conservative assumption)
All design checks apart from ‘Shear’ can be affected by patterning
Note that, in this and all previous releases, there is no rigorous implementation of ‘Simple Construction’ in which load patterning is explicitly ignored (per BS 5950 Clause 4.7.7)
Eccentricity moments are determined by a post-analysis process which applies to all Head Codes.
The Load Analysis View is also enhanced to enable the viewing of results for patterns to see how they affect the major and minor moments, and axial force. The picture below shows the effect on the major axis moment. A pattern number drop-down list is added allowing the results of a specific pattern to be selected (the eccentricity moments are denoted by a dashed line).
The eccentricity moments are considered by the steel column design process for the Eurocode (all country NA’s) and US Head Codes.
To keep the design details to a manageable level, results for every pattern are not listed; the pattern which produces the governing design forces is listed in the check combination and location tree and details heading, as shown in the picture below.