Bridge details with complicated multiple stiffeners are modeled as equivalent shell elements using equivalent orthotropic materials, resulting in the same longitudinal and lateral stiffness in the unit width and shear stiffness in the shell plane as the original configuration.
First, the cross-ply laminated composite doubly curved shell without stiffeners is considered.
Figure 3 also shows that the fundamental frequency of both cylindrical shell panel and spherical shell panel with ring stiffeners is the highest (only for this dimension of stiffener and their material properties).
The minimum distance between stiffeners is prescribed to ease the welding of stiffeners to the base plates.
Figure 4a depicts the decrease of central deflection with increased number of stiffener for cylindrical panel and shows that the deflection of cylindrical shell panel with orthogonal stiffeners is the smallest (i.e., the stiffest).
However, the deflection of both cylindrical shell panel and spherical shell panel with orthogonal stiffeners is the smallest (the stiffest), see Fig. 6.
Since the stiffeners are often closely spaced, the plate element between the pair of parallel stiffeners is often idealized as a long plate spanning between and fixed supported by those stiffeners.
Thus, the multiple subpanels sitting between stiffeners are structurally coupled rather than isolated, and therefore can interact during flutter.
The outer bolt of multiple-bolt-per-row configurations contributes very little to the connection resistance when column web stiffeners are not considered.
Hence in this study, web stiffened cold formed steel channel columns with various types of edge stiffeners are selected.
