Process Results Member Forces
Following a successful analysis of one or more stories, you can select to display the Member Forces from each story's analysis.
These results can be used to independently verify the results of the analysis and duplicate the calculated beam and column design forces. Forces are only displayed on members that have significant forces for the selected load case.
The display options selected here are only visible on the screen while this window is displayed. The window can be moved and the screen printed or manipulated (zoom etc) while this window is displayed.
Click Apply to have the current selections displayed on the screen.
| Setting | Description |
|---|---|
| Story | Select the Story for which you would like to observe member forces from the analysis. When a story is selected all the analyzed load cases for that story will be available for selection in the Case drop down list. When you click Apply, only the members of the structure that were part of the analysis of the selected story will be displayed. |
| Load Case | Select the load case for which you would like to observe member forces. Refer to the Criteria - Analysis and manual for more information on how load cases are generated. Click Apply to have the member forces displayed on the screen for the current load case. The beam(s) that are loaded in the selected load case are highlighted. If no beams are highlighted then the selected load case is one in which only the columns or walls are loaded (loads from story above or user applied column point loads). Load Cases are labeled according to their type (Dead Load = DL, Live Load Reducible = LLred, Live Load Unreducible = LLunred, Live Load Storage = LLstor, and live load roof = LLroof). Where there are multiple load cases of one type, (LLred1, LLred2 etc) they represent all the different load cases in which loads of that particular type (live load reducible) was applied. |
| Beam Forces | Select this option to display beam forces on the screen for the currently selected story and load case. Forces are displayed along the length of the beam according to the Sign Convention. Beams will always be oriented from the lower to the higher numbered node (Node I is lower node number on the beam span). All end forces are displayed at the face of the beam support (i.e. not at center-line). Select the type of force (Moment, Shear or Torsion) for which you would like to observe forces. Expand the drop-down list and select the force option with (1/4 Pts) suffix to display the forces at beam ends, and three equal spaced points along the span. Click Apply to have your selection displayed on the screen. Note that forces will only be displayed on beams that have significant (above some small limit) force for the selected load case and story. |
| Column Forces | Select this option to display column forces on the screen for the currently selected story and load case. Forces are displayed at each end of the column in accordance with the Sign Convention. Columns are oriented from top to bottom (upper node to the lower node). All forces are displayed at the face of the columns where they are continuous. Select the type of force (Moment, Shear or Torsion) for which you would like to observe forces. Click Apply to have your selection displayed on the screen. Note that forces will only be displayed on columns that have significant (above some small limit) force for the selected load case and story. Note: The screen display shows only those members that were considered a part of the analysis for the current, selected story. As such, the column axial forces displayed for the columns below the story include the axial load from the columns from above, but the columns above the story will not show the axial load from the previous (level above) stories analysis. To view the final accumulated column design forces select .
|
| Wall Forces | Select this option to display wall forces on the screen for the currently selected story and load case. Forces are displayed on the face of the wall according to the Sign Convention and calculated as described in the wall force technical section. Walls are oriented from the lower to the higher numbered node. Select the type of force (Moment, Shear or Torsion) for which you would like to see results. Click Apply to have your selection displayed on the screen. Note that forces will only be displayed on walls that have significant (above some small limit) force for the selected load case and story. |
| Show Force Diagram | Select this option to display force diagram on the screen for the currently selected story, load case and members. Forces are displayed only for beams and columns along their length according to the sign convention (see Section 3.4.2 of the manual). |
| Scale Factor | Scale factor value is used to scale the member force diagram on the screen. The scale factor number is only used for representation. You may also specify a negative value of scale factor to show the diagram on the tension face of beams and columns. Note: The screen display shows only those members that were considered a part of the analysis for the current, selected story. As such, the wall axial forces displayed for the walls below the story include the axial load from the walls above, but the walls above the story will not show the axial load from the previous (level above) stories analysis. To view the final accumulated wall design forces select .
However, in the case of stacked wall panels, the walls (and attached columns) located above the story being analyzed will show axial loads. These axial forces do not represent the axial load that is carried down the wall from the level above, but rather the redistribution of the forces amongst all the shells and columns in the wall. Look for example at the following portion of a multi-level wall. For the analysis at a particular story (Analysis story) the Finite Element Model created (See FE Model) by the program is as displayed below. Only two levels of walls are modeled in the analysis of the story, and all the loads carried down the columns and walls from the previous stories analysis are applied as nodal loads to the top of the walls at the analysis story. As is evident, the walls above the story are exhibiting an axial compression force, while the columns are exhibiting a compression force. The summation of all the forces in columns and walls above the story however, is equal to 0.0. This is as would be expected given that no loads are applied to the model above the story level. The reactions also sum up to the applied loads. The axial forces in the walls and columns above the analysis story are purely due to differential displacement of the nodes at the story relative to those at the top of the walls. As illustrated by the displaced shape below the behavior in this model is that of the columns above the story being pulled down, and the walls between the columns resisting. This is the correct and expected analytical behavior. |
