Creating the element
When creating a beam from the Wizard you have the option to make it simply supported or leave out any supports. Since it is always easier to start from a predefined template and just add another support it is recommended to have this option enabled.
This will leave the user with elements that are simply supported in all phases/stages.
Adding the support/supports
In order to make an extra support, select the Load combination in the list that you want to add a support in. If you make it in one combination, it will be considered temporary only and will be removed in the next stage, but the effects of it may live on and affect all of the following load combinations.
In the menu, select Input > Geometry
This window will show all the nodes in the element. Joint 1 and 2 are the left and right ends of the element, while the blue joint 3 and 4 are the standard supports. (Joints may also be known as nodes in some cases)
Select the Unsupported joints-button to the right of the upper node-list.
In the following window it is possible to create joints (that will be converted into supports soon) with relative or absolute distances from the end joints (1 - Left or 2 - Right).
- Give the new joint a unique name (or number).
- Select the beam-element to add it in - there should only be one available.
- And the distance from the joint in [m]. In the Relative-tab you select the percentage of the beam length from the end (1/5th of the distance will be the same as 20% so enter the 0.20). If you use joint 2 as a reference point, do not enter a negative value, the program will convert the distance into a value according to its own coordinate system.
- Press [dd] in order to add the joint to the list.
When you have added all the joints you want in this combination, press [OK]
Select the joint in the Geometry - numerical input-window, and then select in what direction it should be supported. x is horizontal and y is vertical, if you have selected any of them m will light up giving the user the possibility to have a fixed support.
Giving the look of this load combination, if any other combinations needs this support, repeat the process for those particular load combinations.
Add loads as any other element
There are a few questions why the moment curve might look strange with these kinds of supports. And the answer is quite simple. The major contribution is the effect of the prestressing strands, but also take into account that the effects of creep and shrinkage, maybe a better concrete grade, and the optional effect of a topping, changing the stiffness will contribute to a change in the deflection of the element.
If the beam would only have normal reinforcement, not prestressing strands the curve would look different:
The difference is basically the prestressing force times the distance between the center of gravity and center of prestressing force.