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Many designers feel that it is unrealistic to model a long shear wall segment as a rigid body that rotates as a unit when subjected to an overturning force at the top. The rigid-body assumption underlies the distribution of a dead line load at the top of the wall to point loads at the bottom of the end chords, which contribute to compressive stress at one end and counteract tensile hold-down forces at the other.
The data group Dead and wind uplift load concentrated at end chords allows you to specify the distance from the end of a shear wall segment over which dead loads and/or wind uplift loads applied at the top will be concentrated at the end chords. The remainder in the middle of the wall is passed through directly as a line load to the level below.
The calculations resulting from these choices are described under Distribution of Dead And Wind Uplift Loads to End Chords.
Tension End and Compression End
There are separate inputs for what is ordinarily the end chord subject to tension and the one in compression. . For west-to-east (left-to-right) loads, the tension end is the west (left) end and the compression end is the east (right) end. Note that it is possible to have tension forces at the "compression" end, and vice versa, if for example a tension force from the level above comes in over an opening adjacent to the compression end.
Include load on
A dropdown box has the following inputs. The default value is Wall length L/2, however this can be changed via Save as default for new file.
None
All the dead or wind uplift over the half of the wall at the designated end will be passed through as a line load and none of it will be concentrated at the wall ends. Note that this does not mean that no dead force will appear at the end of the wall. If the selection at the other end is other than None then some of the load at tht end will be distributed to the far end of the wall.
Wall length L/2
All the dead or wind uplift over the half of the wall at the designated end will be concentrated at the wall ends and none will be passed through as a line load. This does not mean that all of the load is concentrated at that end, some will appear as a force at the other end of the wall.
If L/2 is selected for both ends, all of the dead or wind uplift load on the wall will be concentrated at the wall end.
Times wall height (max L/2)
Dead or wind uplift load over a specified multiple of wall heights will be concentrated at the ends, and the remainder in the middle section of the wall passed down to as a line load. The calculations for this scenario are described in Dead Load Does Not Completely Counteract Overturning.
To hold-down offset
Dead or wind uplift loads outside the moment arm for overturning calculations; i.e. the hold-down offset, will be concentrated at the end; the rest will be passed down as a line load.
Stud spacing / 2
Dead load supported by the end stud pack, i.e. half the distance to the next end stud, will be concentrated at the end; the rest will be passed down as a line load.
Wall Heights
When Times wall heights is selected as Include load on, enter the multiple of wall heights here. he default value is 1.0, however this can be changed via Save as default for new file.
Include dead load on entire wall if it completely counteracts overturning
If this is checked, and the program calculates that using all of the dead load on the wall will completely counteract overturning such that there is no tension force and no hold-down device would be necessary, then the selection is Include load on is over-ridden and sufficient dead load over the whole length of the wall is concentrated at the end supports such that there is no net force at the tension end. The calculations are described in Dead Load Completely Counteracts Overturning.
This setting defaults to "true", but this can be changed via Save as default for new file.