Treating periodic ribbed plates with symmetric ribs as individual subsystems in Statistical Energy Analysis: Models for bending wave transmission across L-junctions in the low- and mid-frequency ranges

The inclusion of rib-stiffened plates within the framework of Statistical Energy Analysis (SEA) is a challenge in the field of engineering noise control for the low- and mid-frequency ranges. This paper focuses on periodic ribbed plates with symmetric ribs and assesses different approaches using SEA to model bending wave transmission when one or both of the rectangular plates that form an L-junction are a periodic ribbed plate. SEA is compared with measurements and Finite Element Methods (FEM) with all plate boundaries pinned to give boundary conditions that are representative of engineering structures typically used for noise control. When one or both plates are ribbed, and the ribs are parallel to the junction, the closest agreement between measurements and FEM is with SEA models that use a combination of Bloch theory and wave theory to determine the coupling loss factors. However, when both plates are ribbed plates, one with ribs orientated perpendicular to the junction and the other with ribs parallel to the junction, the available SEA models which assume an effective isotropic plate, or an equivalent isotropic plate or angle-dependent bending stiffness all underestimate the energy level difference.