| 
                     The shell elements used in the truck model are either
                      quadrilaterals with four corner nodes, or triangles with
                      three corner nodes having six degrees of freedom (three
                      translations and three rotations) per node. The connection
                      between constituent nodes is defined with the *ELEMENT_SHELL
                      keyword, while nodal locations are defined with the *NODE
                      keyword. The *SECTION_SHELL keyword is used to assign section
                      properties and choose element formulation. The shell elements
                      in this truck model use one of the following three formulations:
                      Belytschko-Tsay (elform=2), S/R co-rotational Hughes-Liu
                    (elform=7), and the fully integrated shell element (elform=16). 
                   | 
                    |