ESDU 73013 gives curves of the fundamental natural frequency of initially unstressed rectangular plates in a panel with flexible stiffeners (not necessarily of the same material as the skin). The mode of vibration is one in which the stiffeners are free to bend in a plane normal to the plate but are fixed in rotation. The plates are assumed to have the flexible stiffeners along their longer sides and to be clamped on the shorter sides. Comparison is made with experimental data for built-up and integrally-machined panels. ESDU 73014 gives a Fortran program for the calculation method.
ESDU 73013 B-1999 history
1999ESDU 73013 B-1999 Reference frequency of panel with flexible stiffeners.