Section IV.2 Statically Determinate Stiffened Box Beams

### Section IV.2 Statically Determinate Box Beams with Constant-Shear-Flow Webs

The box beam shown in the figure below has three stiffeners and three constant-shear-flow webs, as a result, there are 6 unknown loads (i.e., 3 shear flows qAB, qBC, qAC and 3 axial forces FA, FB, and FC).

Since for a non-concurrent, non-coplaner (general) force system we have 6 equilibrium equations, we should be able to use these equations to solve for the 6 unknown loads.

Hence, in statically determinate box beams, we do not need to use the procedure involving the general shear flow equation as described in previous section.

If we were to modify the box beam by including an additional stiffener, then the problem becomes statically indeterminate as there would be 8 unknown loads to solve for as opposed to 6 in the previous case.

Under these conditions, we rely on the procedure described in the previous section based on the general shear flow equation. The solution procedure becomes much simpler, however, as the shear flow along each web is constant.

The example below describes the method of solution for statically determinate stiffened box beams. The discussion of statically indeterminate box beams will be given in the next section.

EXAMPLE PROBLEMS

• Example 1 Shear flow distribution, axial force calculation, and shear center location in a single-cell 2-flange cantilever beam

To Section IV.3