# Global Analysis of Adjustable Pallet Rack Down-Aisle Frames Using the Generalised Beam Theory
## 8 Advantages of GBT in the Modelling of Down-Aisle Rack Frames  
Before moving on to the concluding remarks of this study, it is worth highlighting the main advantages encountered during the analyses of the rack frame with GBT when compared to standard beam and shell finite element analyses:  
1. The model of the structure is easily created in a similar manner to that of any model using conventional beams.
2. The warping degree of freedom is inherently incorporated in the beam element formulation.
3. The effect of local and distortional deformations on the global behaviour of the structure can be accounted for without requiring a shell finite element model, which usually involves higher modelling costs. Additionally, the use of the reduction stiffness factors typically applied in beam models to consider such effects is unnecessary. If material nonlinearity had been incorporated into the analysis, the effect of local plasticity could also be addressed.
4. Similarly, the effect of perforations is considered through a rigorous formulation. There is no need to use equivalent reduced thicknesses or properties of the cross-section.
5. GBT enables the individual activation of each deformation mode and its corresponding imperfection. Consequently, (i) the effect of each individual, or type of, deformation mode can be independently investigated. For instance, it can be known the contribution of a deformation mode to the total stress at a specific point of a structure; (ii) GBT facilitates the introduction of pure imperfection shapes, such as pure torsional or distortional imperfections. This can be performed in a straightforward manner, without the need for indirect strategies.  
Figure 24: Longitudinal membrane stress distribution (S/T-/AD1-/Perf member imperfection) of the (**a**) axial, (**b**) chamber, (**c**) bow, (**d**) twist, (**e**) distortional modes, and (**f**) with all deformation modes involved in the analysis.  
* Torsional warping (as well as other warping deformations) can be independently and easily constrained, or left unconstrained, at the connections. This is more difficult in shell finite element models.
* The simplicity of the beam-to-column and floor joint models can be similar to that of beam finite element models. As a consequence, the moment-rotation curve derived from experimental tests can be directly implemented in the global analysis using rotational linear or nonlinear springs. Modelling rack joints with shell finite elements is significantly more complex.
* In GBT, the same model can be used to easily derive both beam type results, such as internal forces, and shell-type results, such as stresses. Consequently, it can be used, for instance, in both a design based on GNIA with checks against standard formulations, and a \"direct\" design based in GMNIA.  
It should be noted that material nonlinearity is not considered in the present investigation. As a consequence, the authors have not verified the advantages mentioned above concerning the plasticity effects and GMNIA, nor are they aware of the potential computational costs that may be associated. Contrarily, they can confirm that the computational cost of the GBT analyses presented throughout this work is similar to that of beam models.