Hello, in this video, we are going to see how to use the applet i-Cremona to obtain, in the same way that we obtained them with the graphical statics, the internal forces in a cable subjected to a load, as well as the forces at the supports. So, we will successively see how to introduce a load, this, you have already done it, how to introduce a support, you have also already done it. Then, we will see how to activate the funicular polygon and how to control it, that is to say to give it the proper geometry. Then, we will see how to read with the applet, the internal forces which act on the structure. In this applet, we have, as background, the configuration of the cable with a centered load in the middle. We introduce both supports, one on the left, the other one on the right. Let's try to accurately place them where the real supports are and we introduce, as a force, in the middle, a load of 10 Newtons. We can place it a little bit above the chain, we can place it below the chain, we can place it in a symmetric way. Anyway, when we move a load on its line of action, it does not have any influence on the solving. We now activate the button "funicular polygon" of the applet to activate the automatic solving, by the Cremona method. By default, the resolution starts from the first support which we have introduced, it is the support here, on the left, the one which, in our case, has a small vertical line, the other support does not have any small vertical line inside. That is from this support that the slope is defined at 45 degrees by default in the applet. Obviously, this is not that slope which interests us here. So, we are going to use this button, the red ball, which has the function to define the initial tangent. We click once on this button, it stays pushed down, you can see, it has a gray tint. Then, we come here on the polygon, we click on it, we keep the button of the mouse pushed down, and we can now move the polygon, and you can see that we can move it until it is exactly superimposed on the chain that we had on the blackboard. You can see on the right, the Cremona diagram which has been materialized, we recognize the force of 10 Newtons, both internal forces of roughly 7 Newtons. If we place the cursor on the intersection of both segments, we can see, in yellow, the solving which enlightens on the right part, that is to say, the three internal forces or forces which correspond to this configuration. If, on the contrary, we place the cursor approximately in the middle of the segment between the support and the first load, we can see that, on the right, this force enlightens in yellow, and, its magnitude, which is not exactly 7, as we had it in the accurate solving, but 6.81 and 6.96 on the right. This is a small uncertainty but which is not a particular problem. We can, for example, make a parametric study, that is to say that we are going to add a second load of 10 Newtons. So, you can see that now, in the construction, there are two loads on top of each other. And, the internal force is now equal to 13, roughly 14 Newtons, which corresponds to what we have already seen. In this configuration, we have as background, the configuration of cable with an inclined and eccentric load. We introduce both supports, as usually. A load of 10 Newtons, which we position somewhere on the line of action of the force. We now have to make it rotate. If we activate the button "control" and if we grasp the tail of the force, we can rotate it without changing its magnitude and then, we line it up quite well on the line of action which we wanted to get. We now activate the funicular polygon. We must deactivate the button "control", otherwise we will have some troubles. We click on the button "funicular polygon" and on the button "initial tangent" to give to our cable, the exact shape which we were looking for. And we obtain the internal forces, on the left of 4.4, it was 4.5 before if I remember well and of 8.47 instead of 8.5. So, it also works very well, like the various other functionalities. In this video, we have seen how to use the applet i-Cremona to obtain the internal forces in a cable with a load, whether it be vertical or inclined, or whether it be centered of eccentric. We have seen how to introduce the fixed supports, how to introduce the load, how to rotate the load for it to corresponds to what we want to do and we have also seen how to activate the funicular polygon and how to control its geometry.
