This app calculates the internal forces diagrams for frame elements. It can be used for determinate and indeterminate frames or beams. The analysis is based on the Opensees finite element package.

Before starting make sure your structure is stable and have enough supports.

Step 1:

Insert node coordinates and corresponding loads or restraints.

When inserting nodes, care for the nodes arrangement per each member (see step 2). 

Step 2:

Add as many elements as you need.

For horizontal elements (beams), always make Node 1 the left node. This will give you the proper orientation for the local axis (explained below)

Choose any node orientation you want for vertical (columns) or inclined elements, but be aware that this will impact your uniform load direction and moments plots. Preferable to define vertical elements starting from the bottom nodes.

Opensees has a default local axes system. Along the element length, the local x-axis goes from the start node to the end node. The local z-axis always goes out of the screen towards you, while the local y-axis is defined based on the right-hand rule. Ash shown below. 

Example 1

Element 2 is subjected to a uniform load of 5 kN/m (downward). 

Case 1 (note element 3 orientation and the moment value is -ve)

Case 2 (note element 3 orientation and the moment value is +ve)

Note that despite the moment sign being flipped, the moment plot will always be on the side of the moment semi-circular arrow tail.

Note that because of the orientation element two, the uniform load was inserted -5 kN/m as it is in the opposite direction of the element local axis y for both cases. 

Example 2

Element 2 is subjected to a uniform load of 5 kN/m (downward), and element 3 is subjected to 10 kN/m (right to left)

Case 1 (note element 3 orientation and the moment value is +ve)

Case 2 (note element 3 orientation and the moment value is -ve)

Note that because of the orientation element 2, the uniform load was inserted -5 kN/m as it is in the opposite direction of the element local axis y for both cases. However, for element 3, -10 kN/m was used as the load was in the opposite direction of element local axis 3. On the other hand, 10 kN/m was used for case 2 as the load was in the same direction as the local axis y. 

Finally hover over the plots to see the values of the internal forces at various locations