The graphical display of story forces shows the distribution of lateral forces coming into/ out of each level, typically at points where the members of the lateral force resisting system (LFRS) – be it braced bays, moment frames or shear walls – are attached. Note that story forces are only depicted at levels and not in between levels.

For an example of story forces, consider the following Dir 1 frame, in which:

• the first and third bays are braced
• the fifth bay is a moment frame
• the last bay is a meshed shear wall
• lateral loads are applied as shown

By selecting Story Forces Dir 1 the following results are displayed:

• Red arrows show the story forces at each level at those points where the LFRS is attached, (where the change in shear takes place).
• Each arrow indicates the direction of force. The value is positive if the arrow acts in the selected building direction and negative if it acts against the selected building direction.
• In the meshed shear wall a single total value is displayed at each level, which considers all the nodes in the panel at that level.
• Blue arrows drawn outside the structure show the summations at each level of lateral forces applied at that level, lateral forces applied between levels are not considered in these summations.

Story force calculations

As previously stated, story force is the net horizontal force acting on a node when considering the internal forces of all elements that connect to that node just above and just below the level in which it lies. So by considering the axial forces in the diagonal braces in the first bay we can see how the story forces have been calculated.

For the meshed wall, in order to determine the net horizontal forces we would need to the display the Shear Major forces in the Wall Lines:

• At the 3rd level there is only a wall connecting from below, so the horizontal force = -11
• At the 2nd level, walls connect from above and below. The net horizontal force is 11+20 = 31
• At the 1st level, walls connect from above and below. The net horizontal force is -20+74 = 54

Tabular display of story forces

The summation of story forces in each direction can also be shown in a Solver Model Data view, (by following these instructions).

Story shear is the shear load that has to be resisted by the structure immediately below the level by the lateral force resisting system (LFRS) – be it braced bays, moment frames or shear walls.

The graphical display of Dir 1 and Dir 2 story shears shows the cumulative horizontal shear resulting from all loads applied above and at each level in the selected building direction. Note that these shears are only depicted at levels and not in between levels.

For example, consider the frame from the previous section:

By selecting Story Shears Dir 1 the following results are displayed:

Story shears are shown immediately below the level to which they relate.

• Red arrows show the individual cumulative shears. (The value at each node being the sum of shears from elements connected below the node.)
• Each arrow indicates the direction of force. The value is positive if the arrow acts in the selected building direction and negative if it acts against the selected building direction.
• Blue arrows drawn outside the structure show the total shear load to be resisted by the structure immediately below each level.

Tabular display of story shears

The summation of story shears in each direction can also be shown in a Solver Model Data view, (by following these instructions).

The graphical display of Dir 1 and Dir 2 wall/braced bay story shears shows the cumulative horizontal shear resulting from all loads applied above and at each level in the selected building direction that is resisted in a vertical plane by braced bays or shear walls only – columns that are not attached to braces, and moment frames do not have any values shown.

For example, consider the frame from the previous sections:

By selecting Wall/Braced Bay Story Shears Dir 1 the following results are displayed:

• Blue arrows show the cumulative shears at each level in each braced bay or shear wall.
• Each arrow indicates the direction of force. The value is positive if the arrow acts in the selected building direction and negative if it acts against the selected building direction.

This diagram is easier to work with than the “Story Shears Dir 1" and "Story Shears Dir 2” diagrams because:

• a single shear value is displayed at each level in each bay
• moment frame values are hidden
• values on columns not attached to braced bays are hidden.

Tabular display of wall/braced bay story shears

Wall/braced bay story shears can also be shown in a Solver Model Data view, (by following these instructions). This view shows the values in each direction as well as the in-plane values.

The in-plane values are described in the next section.

The graphical display of in-plane wall/frame story shears shows the cumulative horizontal shear resulting from all loads applied above and at each level that is resisted by braced bays or shear walls in the plane in which they are aligned – columns that are not attached to braces (e.g. columns in moment frames) do not have any values shown.

For example, consider the frame from the previous sections:

By selecting Wall/Braced Bay Story Shears In-Plane the following results are displayed:

Because the braced bays and shear walls in this example are aligned to Dir 1 they are identical to the Wall/Braced Bay Story Shears Dir 1 in the previous section.

The main advantage of the “Wall/Braced Bay Story Shears In-Plane” graphical display when compared to the “Wall/Braced Bay Story Shears Dir 1, Dir 2” displays is that it shows the values of interest irrespective of how braced bays and walls are aligned, and the view isn't cluttered by out-of-plane values that could be ignored.

By selecting Wall/Braced Bay Story Shears In-Plane you can immediately see (below right) the forces to be resisted by each lateral force resisting system (LFRS).

The arrows show the direction of force. The sign convention applied to values is:

• if the vertical plane in which an arrow lies is more closely aligned with Dir 1 (within +-45 deg of Dir 1), the value is positive if the arrow acts towards Dir 1 and negative if it acts against Dir 1
• otherwise the arrow will be more closely aligned with Dir 2, in which case the value is positive if the arrow acts towards Dir 2 and negative if it acts against Dir 2.

Applying this convention to the above example:

Tabular display of wall/braced bay story shears

The above wall/braced bay story shears can also be shown in a Solver Model Data view, (which can be displayed by following these instructions).