# D3.D.3 Structural Model

Structural slabs that are to be designed to BS8007 must be modeled using finite elements. Refer to
G.5 Finite Element Information
for information on the sign convention used in the program for defining elements

It is recommended to connect elements in such a way that the positive local z axis points outwards away, from the center of the container. In this manner the "Top" of elements will consistently fall on the outer surface and internal pressure loads will act in the positive direction of the local z axis.

An example of a rectangular tank is provided to demonstrate the above procedure.

Element properties are based on the thickness given under `ELEMENT PROPERTIES` command. The following example demonstrates the required input for a 300 mm slab modeled with ten elements.

UNIT MM ELEMENT PROPERTIES 1 TO 10 THI 300.0