## SectionBuilder-Dymore interface

In many applications, beams are complex build-up structures with thin- and thick-walled cross-sections and the increasing use of laminated composite materials leads to heterogeneous, highly anisotropic structures. Based on linear, three dimensional elasticity theory, it can be shown that the analysis of complex beam structures splits into two simpler problems.

1. A linear, two-dimensional problem over the beam's cross-section. This two-dimensional analysis is carried out via the finite element method and is implemented in SectionBuilder.
2. A nonlinear, one-dimensional problem over the beam's span. These equations are the so called “Geometrically Exact Beam Equations,” which are implemented in the beam element of Dymore.

SectionBuilder provides two important pieces of information.

1. The beam's sectional stiffness characteristics in the form of a 6x6 stiffness matrix relating the six sectional deformations, three strains and three curvatures, to the sectional loads, three forces and three moments. This stiffness matrix is an input for the geometrically exact beam element.
2. The three-dimensional strain and stress fields at all points of the beam's cross-section can be recovered once the sectional strains are known.

Figure 1 depicts in a conceptual manner the relationship between Dymore and SectionBuilder. The interface between the two codes involves the following three items.

1. The SectionBuilder section data object, which transfers the sectional properties computed by SectionBuilder to Dymore. This data object, denoted @SECTION_BUILDER_SECTION_DATA, is shown in fig. 1 with the circled label “1”.
2. The SectionBuilder recovery data object, which transfers the recovery relationships computed by SectionBuilder to Dymore. This data object, denoted @SECTION_BUILDER_RECOVERY_DATA, is shown in fig. 1 with the circled label “2”.
3. The computation of local stresses and strains at any point of the beam's cross-section is performed by means of a suitably defined sensor. This last item is shown in fig. 1 with the circled label “3”.