4. Set the title to “2 Storey Single Bay Frame” with a sub title of “Example 6.2” using the Date |Titles menu option and put your initials in the Calculations by: field.
5. In the Structure navigation window click on the button and select 2D Sub Model from the selection list. This will create an entry in the navigation tree and open the 2D Sub Model Plane form.
6. We wish to define this frame in the XZ plane, so click on the button and you will notice the axes change in the graphics. Close the Sub Model Plane form with the “OK” button.
7. To create the structural members open the Sub Model Members form by clicking on the element in the Structure tree.
8. To create a member we simply draw it in the graphics window making use of an appropriate snap mode. Initially click on the
icon in the graphics toolbar.
9. Then click on the origin of the graphics screen followed by another click 8m in the vertical direction (Count the grid points as the Snap: mode should be set to grid).
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10. If the member is drawn wrongly, simply click on the Edit Members item in the Member Tasks list and change the coordinates in the displayed form before closing this form with the “OK” button.
11. To draw the second column we use the Copy Member(s) item in the Member Task list and enter a translation vector of (10,0) before clicking on the “Apply” button.
12. Now draw the transverse beam between the top two nodes of the column by following the same procedure as in 8 above, but setting the Snap: mode on the graphics toolbar to Node in Plane.
13. We now need to split the two columns into 10 segments each. This is done by using Split Beam Element... in the Member task list.
14. In the Split Beam Element form set Split specified beam element by/ specified division by clicking on the appropriate radio button controls. And then set the Number of new elements to “10”.
15. Click on the leftmost column in the graphics (turns red) and then click on the “Apply” button to see the 10 segments generated in the graphics window. 16. Repeat 14 for the rightmost column.
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17. Now click on the beam, but set Number of new elements to “3” (hit enter to update the table) and change the segment lengths in the table to “0.15m”, “9.7m” and “0.15m”. Click on the “Apply” button to split the beam
18. Now click on the middle segment of the beam and split this into 8 equal length segments using the “Apply” button. Close the Split Beam Element form with the “OK” button. Use the Fit View icon on the graphics toolbar to fill the graphics screen with the structure.
Section Properties
We are now going to define and assign some section properties to the structure so far.
19. Close the Define Sub Model Members form with the “OK” button and change the Navigation window to Section Properties by clicking on at the bottom of the window.
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20. Click on the button and choose Design Section from the list of options. This will display the Import file form in which the “Browse...” button should be clicked. Select the file called “AU Example 6_2 Beam Section.sam” in the file browser and “Open” this file. 21. The graphics will now have two parts to the window –
the first part the structure and the second part the section.
22. Using the right mouse button in the graphics area, a number of tab and tile options can be selected to customise the layout of the window panes. Set it to Tile Vertically.
23. In the structure graphics, use the toolbar button to obtain a view on the xz plane and then window round the horizontal beam elements (using a left mouse click at the top left hand corner , releasing the button and moving the cursor to the bottom right corner and clicking again) taking care not to select any of the column members. The selected members will turn red.
24. Before closing the Import Beam File form with the “OK” button, change the description to “Beam section 700WB150” by selecting it from the drop down list.
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25. Repeat 20 & 24 but import the file called “AU Example 6_2 Column Section.sam” and change the Description: to be “Column section 310UC158 ”. 26. To select the column members, window round the whole structure and when the Confirm window asks whether the beam elements should be overwritten answer “No to All”. Close the Import File form in the normal way.
Modify Section Properties
As described in the outline we now need to enhance the stiffness of the short elements at the ends of the beam. To do this we copy the standard beam property, increase the elastic and shear modulus and then overwrite the property of these elements with the new property.
27. Right mouse click over the beam section property in the navigation window and select “copy” from the popup menu. This will create a new property and open the data form (Import data file form) allowing changes to be made. Change both elastic modulus and shear modulus by increasing them by a factor of 1000 and then changing the Description to “Stiff”.
28. To assign this property to the two short beam elements it is necessary to switch on the node markers and zoom in to each of the top corners. To switch on node markers use the orange “General” button at the right of the graphics window and tick the Show Nodes option.
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29. To zoom in, place the cursor over one of the corners and either use the mouse scroll wheel or click on the graphics toolbar button several times. When the short beam element is clear, click on it to assign the stiff property (agreeing to overwrite the existing property).
30. Repeat this for the other corner and then close the Import File form. Local Axes
The section properties defined are related to a certain set of axes and these must be consistent with the local axes of the beam elements. The YY axis of the sections is the horizontal axis parallel to the flanges, so the local y axis of all the beam and column members must be perpendicular to the plane of the frame. To check this we can turn on the local axis display using the orange “General” button on the graphics window and tick the “Local Axes” box.
The red axis is the YY axis so, it can be seen that the column members are orientated in the wrong way. Additionally, if we want the bending moment diagrams to show sagging moments always on the inside of the frame then the local Z axis should always be pointing to the outside of the frame. This means the local axis system of the members should be rotated to correct this.
31. To do this the leftmost column members should be rotated by 90 degrees and the rightmost by -90 degrees. This can be done by changing the Navigation window to Structure and using the “Add” button to open Advanced beam Set
|Local Axes. In the resulting form, Twist: should be set to “90” degrees and
then the leftmost column selected graphically (to do this use the following procedure:
a. Select the filter toolbar button on the graphics screen b. Click on De-select all in the selection tasks
c. Set the Select By: field to “Section Property”
d. Available groups “Column Section ...” sent to selected groups using the”>” button.
e. “OK”
f. Window round the leftmost column
g. Set the name of the Advanced Beam Set to “Twist 90” h. “OK”
32. Add a second Advanced beam Set |Local but set the Twist: to -90. Change