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Dead Load Does Not Completely Counteract Overturning

Consider a dead load with magnitude q1 at the tension end and q2 at the compression end, which we distribute to the end chords over a distance l1 at the tension end and l2 at the compression end.

Using beam statics, the reaction to a partial load q over a distance l at the closest end is

  q  ( l  - l2 /2L  )

At the far end of the segment, it is

 q (  l2 /2L  ).  

The free-body diagram is thus shown below:

The arrows within the wall represent the centroids of the two sets of loads at top of the wall; the loads in between cancel with the reaction at the bottom.

To check that this is statically balanced, we sum moments about the left side:

M =  Fh + q1 l1 * l1  / 2  +  q2 l2 ( L -  l2  / 2 ) -  [ Fh / L  +  q2 (l2  - l22 / 2L )  + q1l12 / 2L ] * L

    =   ( Fh  –  Fh ) + ( q1 l12 / 2 - q1 l12 / 2 ) + ( q2 l22 / 2 - q2 l22 / 2 ) + ( q2 l2 L -  q2 l2 L )

    = 0 .

See Also

Distribution of Dead And Wind Uplift Loads to End Chords

Dead Load Completely Counteracts Overturning

Effects of Wind Uplift, Upper Levels, and Adjacent Openings