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*TO DO:* Provide example with solutions and midspan-moment checks for a 3-span continuous beam subjected to uniform and point loading.
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The *pattern live-load factor* (Pllf) is intended to account for variability in the live-load arrangement on a structure. Since live-load pattern is not automated, Pllf approximates its design effect.

When nonzero Pllf is assigned to a [frame|kb:Frame] object, positive design moments are calculated assuming a simply supported condition under live-load application. While this does affect design moments, analysis moments are not affected. Pllf enables users to specify the live-load percentage applied to a frame object for which no continuity is assumed. Negative moments are then redistributed in a manner similar to that of moment redistribution from yielding. As a result, positive midspan-moment values increase. Zero Pllf may be specified to avoid moment redistribution.

Pattern live-load factors may be assigned to individual elements using the Design > Steel Frame Design _or_ Concrete Frame Design > View/Revise Preferences command, as shown in Figure 1:

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!Pattern_live_load_factor.png|align=center,border=0!

{center-text}Figure 1 - Pattern live-load factor{center-text}


h1. Example

The maximum positive midspan design moment induced by uniform dead\- and live-load application would be calculated as follows:

!Expression 1.PNG|align=center,border=0!

where:

* *{_}f1{_}* = code-based dead-load factor (1.2)

* *{_}f2{_}* = code-based live-load factor (1.6)

* *{_}Pllf{_}* = Pattern live-load factor (0.75) specified in [SAP2000|sap2000:home] or [ETABS|etabs:Home]

* *{_}l{_}* = element length

* *{_}LL{_}* = distributed live load (force/length)

* *{_}M{_}{*}{*}{_}{~}DL{~}{_}* = positive dead-load moment with actual boundary conditions due to dead load only

* *{_}M{_}{*}{*}{_}{~}pos{~}{_}* *{~}MAX{~}* \- maximum positive midspan design moment assuming a simply-supported condition with no continuity for live load
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Given point loading, *{_}M{_}{*}{*}{_}{~}pos{~}{_}* *{~}MAX{~}* would be calculated similarly as for uniform loading, wherein which a simply supported condition is assumed and the live-load factors specified are applied.


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