Eriksson Wall supports automatic load patterning. This algorithm takes a given load combination and creates a set of sub load combinations for it to check. For example, a load combination containing wind would not apply both pressure and suction at the same time, but instead apply all the loads with both pressure followed by all the loads with suction.
Mandatory Patterns
Wind, Seismic, and Earth all have mandatory load patterning that the user cannot disable.
Load Type | Description |
|---|---|
Wind | Splits the load combination into one with pressure, and one with suction. |
Seismic | Due to not knowing the direction of the acceleration from the seismic event, the seismic loads are all reversed in direction and run again. |
Earth | Typically fill soil can be removed and can potentially be a resisting force. Because of this a second combination is run replacing all earth loads with a minimum earth load factor instead of the load combinations factor, typically 0. |
Live Load Patterning
Live load patterning checks 5 different conditions for flexure, and 2 conditions for torsion. If any of these conditions result in the same loads as a previous condition it is not checked. Any point moments added the member will be included in all patterns. The live load patterns are as follows:
Horizontal Members
All live loads are applied to the member
All loads whose magnitude is pointing down.
All loads whose magnitude is pointing up.
Alternates loads between spans to be down - up - down - up and so on.
Alternates loads between spans to be up - down - up - down and so on.
All loads that create positive torsion, or no torsion.
All loads that create negative torsion, or no torsion.
Vertical Members
All live loads are applied to the member
All loads with a positive eccentricity.
All loads with a negative eccentricity.
Alternates loads between spans based on eccentricities to be + - + - + and so on.
Alternates loads between spans based on eccentricities to be - + - + - and so on.
Note that this does not guarantee the controlling case is found. For a typical simply supported structure under uniform smooth loading with a continuous moment diagram this would be the typical way to pattern the loading. Because point moments cause discontinuities in the moment curve and can reverse the sign of the moment diagram instantaneously, they are difficult to categorize in this way. For cases where this is a concern the user should manually pattern loads.