Innovative Stainless Steel Applications in transport ... - Euro Inox

Defining the loading case is a basic problem in panel design. Key load information
includes location, type and magnitude. Apart from loads, boundary conditions are
essential factors in structural behaviour – in design these may be either free edge, free
support or stiff support. In practice, boundary conditions will be either free edge or
something between free and stiff support. Apart from boundary conditions, it is also
essential to define whether the structure will behave in a beam or plate-type manner.
The strength criteria indicate the usability of the chosen structure with the chosen
boundary conditions and loading cases (Romanoff & Kujala 2002, Kujala et al. 2003).
The stiffness properties of a panel are defined on the basis of the design starting/source
data. Once this is established, panel response can be defined by elastic structural
analysis. Elastic structural analysis will determine both panel stress and deformation
state. Once the panel cross-section is known, the critical stresses and forces can be
defined for the structure. The set strength and displacement criteria and the stresses and
displacements in the structure can then be compared (Romanoff & Kujala 2002, Kujala
et al. 2003).
3.2.2 Panel cross-section
As described earlier, there are several types of all-steel sandwich panel. The most
common are so-called prismatic panels, where the core is formed by parallel elements
stiffening the panel in a longitudinal direction (Figure 49). Cross-section variables
include surface (front and back), sheet thickness, core sheet thickness, core width and
height, distance between core elements, core flange width(s) and web angle. The
benefits of prismatic panels include fast production and high stiffness-to-weight ratio,
especially in the core (longitudinal) direction. In the direction transverse to the core,
shear stiffness is relatively low. Because of this inhomogeneity, the panel works best as
a beam, with its longitudinal axis coinciding with the beam axis (Kujala et al. 2003).
3.2.3 Elastic response
The procedure for calculating a panel’s elastic response depends on whether the
structure is more like a beam or a plate in nature. Furthermore, whether beam analysis
or 2D or 3D finite element analysis is used also has an effect. In practice, choice of
method is governed by the required speed and accuracy of the analysis. Beam analysis
is the fastest but least accurate method and 3D finite element analysis the slowest and
most accurate. An exhaustive and detailed description of the design process can be
found in Romanoff & Kujala (2002), but it usually consists of the following steps:
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