Building a MultiFrame Model
MultiFrame models are built in what is known as the Frame window. Three windows appear on the screen when the program is started. Each window (Frame, Load and Plot) work with very distinct information. These windows reflect the matricies that the computer must build in order to complete an analysis. The first matrix included factors about the physical properties of the members and how they are related to each other. The second matrix includes the loading. And the third is the one which contains the results of the analaysis. Matrix mathematics demands that certain parameters are satisfied; one of those is that there cannot be null values in distinct places in a matrix. Thus, the program will ask for more information if it does not have enough in order to analyze the structure.
The Frame window is the foremost window that initially appear when the program is starteds. If it is not appearing, pull down the Window menu and choose the Frame menu. The Frame window will then appear, and it should be a blank screen. The easiest way to begin to build a structure is to allow the computer to generate it. Pull down the frame menu and choose Generate.
The small window shown appears. There are four types of structural members that can be generated with this command: straight, curved, a bent and a frame. Choosing one of these does not preclude returning to this menue in order to generate more parts to the builidng.
If the beam menu is chosen, then another window appears which allows you to define the number of segments that the continueous bema will have and the lengths of each of the segments. The word segments is used here since a single span might require that it be divided into three segments in order to allow the rest of the structrue to be built, or if there is another piece of structure that projects fro m the beam.
After the segment spans are typed into the appropriate boxes, click on the OK button. This brings us back at the Frame Window. Often the structure which you have jsut created is nowwhere to be seen. In order to "find" it, pull down the View menu and choose "size to fit." the structure which you have created will not fit onto the screen.
There is now a structure which consists of nothing more than a defined geometry. The nature of the supporting conditions and the physicalproperties of the beams must still be applied. If an attempt is made at this point to define the structure it will fail. FIRST, the program must be told which elements are going to be defined..... so click on one or more elements that are going to be defined.
notice that the chosen element(s) is now thicker than the other elements and that when the Frame menu is pulled down that all of the menue choices are now active.
The program already has a library of elements that have been loaded with the program. Choose an appropriate section and click OK. The section can be changed at any time!!! It is often the case that after an analysis a section will be determined to be inadequete and that it must be a larger section. Simply return to this menu and choose a new section for the chosen member.
Now the program must be told how the structure is supported. Return to the Frame window and select a joint or node.
Pull down the Frame menu and choose Joint Restraint. This provides a box with a number of options......
Choose the appropriate joint symbol and double click on it. This will return to the Frame menu and the support type will now appear in the window.
Ths structure is now defined. The program assumes that all of the members that are defined are solidly attached to each other. IF a joint, or pin, connection should be placed between two elements, then select the member in the Frame Window that should have the pin.
I have found it easiest to generate a structure using the small frame. In choosing to begin with the small frame, members can be deleted, moved or subdivided at will.
to be continued
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