Assigning joint static loads

The second level lateral earthquake loads (load cases EQX and EQY) are assigned as joint static loads. Also the static load pattern to be used in the pushover analysis, PUSHPAT is assigned as joint static loads.

Note the static load pattern for the pushover analysis could be any combination of joint, frame and shell loading.

1. Click in the window labeled X-Y Plane @ Z=24 to make sure it is active. Note when the window is active, its title bar will be highlighted.

2. Click the Down One Gridline button on the main toolbar to display the second floor plan at Z=12.

3. Click the Set Elements button on the main toolbar (or select Set Elements…

from the View menu). This displays the Set Elements Dialog box.

4. In this dialog box uncheck the Labels box in the Frames area, check the Labels box in the Joints area and click the OK button. Note we are leaving the Restraints box in the Joints area checked.

5. Click joint 14 to select it.

6. From the Assign menu select Joint Static Loads… and then Forces… from the submenu. This will display the Joint Forces dialog box.

7. In this dialog box:

• Select EQX from the Load Case Name drop-down box.

• In the Options area, select the Add to Existing Loads option.

• In the Loads area type 2.67 in the Force Global X edit box.

• Click the OK button to apply the load.

8. Click the Restore Previous Selection button on the side toolbar (or select Get Previous Selection from the Select menu).

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10. In this dialog box:

• Select EQY from the Load Case Name drop-down box.

• In the Loads area type 0 in the Force Global X edit box.

• In the Loads area type 3.83 in the Force Global Y edit box.

• Click the OK button to apply the load.

11. Click on joints 11, 13, 15 and 17 to select them.

12. From the Assign menu select Joint Static Loads… and then Forces… from the submenu. This will display the Joint Forces dialog box.

13. In this dialog box:

• Select EQX from the Load Case Name drop-down box.

• In the Options area, select the Add to Existing Loads option.

• In the Loads area type 2 in the Force Global X edit box.

• In the Loads area type 0 in the Force Global Y edit box.

• Click the OK button to apply the load.

14. Click the Restore Previous Selection button on the side toolbar (or select Get Previous Selection from the Select menu).

15. From the Assign menu select Joint Static Loads… and then Forces… from the submenu. This will display the Joint Forces dialog box.

16. In this dialog box:

• Select EQY from the Load Case Name drop-down box.

• In the Loads area type 0 in the Force Global X edit box.

• In the Loads area type 2.88 in the Force Global Y edit box.

• Click the OK button to apply the load.

17. Click on joints 10, 12, 16 and 18 to select them.

18. From the Assign menu select Joint Static Loads… and then Forces… from the submenu. This will display the Joint Forces dialog box.

19. In this dialog box:

• Select EQX from the Load Case Name drop-down box.

• In the Options area, select the Add to Existing Loads option.

• In the Loads area type 1.33 in the Force Global X edit box.

• In the Loads area type 0 in the Force Global Y edit box.

• Click the OK button to apply the load.

20. Click the Restore Previous Selection button on the side toolbar (or select Get Previous Selection from the Select menu).

21. From the Assign menu select Joint Static Loads… and then Forces… from the submenu. This will display the Joint Forces dialog box.

22. In this dialog box:

• Select EQY from the Load Case Name drop-down box.

• In the Loads area type 0 in the Force Global X edit box.

• In the Loads area type 1.92 in the Force Global Y edit box.

• Click the OK button to apply the load.

23. We will now define the PUSHPAT load pattern that will be used in the pushover analysis. It will be a triangular distribution of load over the height of the building.

From the Select menu select Select and then Groups… from the submenu. This will display the Select Groups dialog box.

Note: Our purpose here is to input an inverted triangular loading pattern over the height of the building. Thus we will put 1 kip loads at 9 second level joints (9 kips total) and 2 kip loads at 9 roof level joints (18 kips total). We

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joints on a tributary area basis, or some other basis, but we will not consider any such refinement in this example.

24. Click on the group name 2ND and then click the OK button.

25. From the Assign menu select Joint Static Loads… and then Forces… from the submenu. This will display the Joint Forces dialog box.

26. In this dialog box:

• Select PUSHPAT from the Load Case Name drop-down box.

• In the Loads area type 1 in the Force Global X edit box.

• In the Loads area type 0 in the Force Global Y edit box.

• Click the OK button to apply the load.

27. Click the Up One Gridline button on the main toolbar to display the roof level plan at Z=24.

28. From the Select menu select Select and then Groups… from the submenu. This will display the Select Groups dialog box.

29. Click on the group name ROOF and then click the OK button.

30. Click on joints 22 and 26 to deselect them.

31. From the Assign menu select Joint Static Loads… and then Forces… from the submenu. This will display the Joint Forces dialog box.

32. In this dialog box:

• Select PUSHPAT from the Load Case Name drop-down box.

• In the Loads area type 2 in the Force Global X edit box.

• Click the OK button to apply the load.

33. From the Assign menu select Clear Display of Assigns to clear the display of joint loads. Note that the joint element labels remain because they were turned on using the Set Elements command.

34. Click the Save Model button on the main toolbar, or select Save from the File menu to save the file.

This completes the assignment of joint static loads.