Tutorial 1 Portals Steel
1.5 Creating the model using the graphical user interface (GUI)
1.5.10 Specifying loads
Three load cases should be created for this structure. Earlier in this tutorial details of individual cases are explained. Then the corresponding commands generated are listed.
UNIT KIP FEET LOADING 1 DEAD + MEMBER LIVE LOAD 2 UNI GY ‐2.5
LOADING 2 WIND FROM LEFT JOINT LOAD 2 FX 10. March 75 PERCENT LOAD COMBINATION OF (DL + LL + WL) 1 0.75 2 0.75 Procedure:
The creation and allocation of load cases involves the following two steps
I. First, we will create all the three load cases
Creating load cases 1 and 2
1. To create loads, first select the tool Load Page (Page load) on the top toolbar.
Figure 2‐42:
Alternatively, one can go to General | Load from the left side of the screen.
Figure 2‐43:
2. Before creating the first load case, we need to change our units of length in feet. This, as above, use the tool input Units "Input units" (see Section 1.5.5) Note that a
window appears titled "Load" to
right of the screen. To create the first load case, highlight details of case load (Load
Cases Details) And then click add (Add) In the dialog box.
Figure 2‐44:
3. Dialogue Add New Load Cases (r I added new load cases) it opens.
The drop-down list for type of charge is available if you want to link the case load that we are creating with any of the definitions of ACI, AISC or IBC of dead, live, ice loads, etc. This type of association must be made if we use the installation program to automatically generate load combinations according to the codes. Note that there is a checkbox called reducible by UBC / IBC. This feature becomes active only when the load case is assigned a type called Live load at the time of creation of that case.
As we do not intend to use the option of automatic generation of load combination (Auto
Load Combination), We will leave the type of load as None (Loading Type- None). Enter
DEAD + LIVE as the title for the load case 1 and click Add.
Figure 2‐45:
The newly created load case appears under the option Load Cases Details (Details of charging load cases).
To create the load member, first select input 1: DEAD + LIVE. You will notice that the dialog
Add New Load Items (Add new items to load)
now shows more options.
Figure 2‐46:
4. In the dialog box Add New Load ItemsSelect the tab Uniform Force under the loading point of the member. Specify GY as the address, type ‐2.5 as strength and click Add.
Figure 2‐47:
The next step is to create the second load case containing a common load
5. Perform step 3 again to create a second type of load. Enhancement Load Case Details, click
Add, let the type of load as None. Specify the title of the second load case as WIND FROM LEFT
(Wind from left) and click Add.
6. Then, to create the joint load, select 2: Wind From Left.
Figure 2‐49:
7. In the dialog box Add New Load ItemsSelect the tab Node Nodal point for the load. Specify
10 for Fx and click Add.
Figure 2‐50:
Creating the third load case
The Load Cases 1 and 2 were cases of main charge. Charging Case 3 was defined as a combination of load. Then the next step is to define the load case 3 and 0.75 x (1 load
Load + 2), which is a combination of load.
1. This, again, select Load Case Details (details of the case load) in the Loads dialog & Definition. In the dialog box Add New Load CasesPress
the tab Define Combinations the left side. Specify the title as the 75 Percent of [DL +
LL + WL]. Figure 2‐51:
Table define combinations, the combination type is set to predetermined load Normal
(default), Which means an algebraic combination. The other types are called combination
available SRSS ("Square root of sum of squares" - root
square of the sum of squares) and ABS (absolute). The SRSS type offers the flexibility of SRSS and algebraic part. That is, certain load cases are combined using the square root of the sum of the squares approach, and the result is combined with algebraic other cases, as in
A + SQRT (B * B + C * C)
Where A, B and C are primary individual cases.
We intend to use the type of algebraic combination default (Normal).
2. Table defined combinationsSelect both load cases in the list box on the left side (by holding down
CTRL) And click [>]. The load cases appear in the list box on the right. Then, enter 0.75 in the edit box
Factor. (These data indicate that the two cases are adding a
multiplication factor loading of 0.75 and that the results of the load combination would be obtained by the algebraic sum of the results for individual load cases). Click Add.
Figure 2‐52:
Now that we have completed the task of creating all load cases 3, click shut down.
Associating a load case with a member
Our next step is to associate the load case 1 with 2 member following steps. 1. Select the first reference load in the load dialog (UNI GY-2.5 kip / ft).
2. Select the option Use Cursor to Assign in the allocation method box. 3. Click on Assign.
The cursor will change to this form
4. Click the Member 2.
Figure 2‐53
After charging member is assigned, the pattern will be as shown below.
Figure 2‐54:
Similarly, the second assigning load case (FX 10 kip, ft) to node 2.
Figure 2‐55:
Tip: Remember to save your work or by selecting File> Save, save the tool or press CTRL + S.