shear-moment diagram for actual structure

[amorrison]

This is for a self education project.
Maybe this is not a "good" question but here goes!
Most texts show how to draw shear/moment drawings given certain loads.
The actual installed structure must meet these loads where they occur - but at other locations on the beam/truss there can/will be "overbuilding" because of the size of components chosen for the actual building of the structure.
I would like to find a visual/graphical method of finding the CAPABILITY (shear/moment wise)of the final structure at any point along the length of the structure.

Any books/papers or buzz words for an Internet search?
Thanks.

 

[jhardy1]

Shouldn't be too difficult:

As you said, Shear Force and Bending Moment diagrams are easily generated for standard classical solutions for simple beams, or can be generated by a beam / frame analysis program. E.g. a simply supported beam with a uniformly distributed load has a linearly varying shear force diagram from one end to the other, and a parabolic bending moment diagram.

The shear force capacity and bending moment capacity of a section are primarily functions of the cross-section properties (area and moment of inertia), and also the strength of the material (obviously!) and the distribution and nature of intermediate restraints (which limit buckling etc). For a uniform beam, the shear force and bending moment capacity will typically be uniform along the length of the beam. For a beam with a varying cross-section, the capacities will vary along the beam, as the section varies.

If you don't have access to a full beam / frame analysis program, you could easily set up a spreadsheet to calculate and plot the shear force and bending moment diagrams and capacities along the beam. As long as the capacity is greater than the applied load effect, the beam is OK. The reserve capacity ("over design") is the difference between the capacity and the applied shear force or bending moment.

Am I missing something?