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4.9  Advanced connection models

• Screw models
• Physical point with rotations

4.9.1  Screw models

Proper representation of screws is a classical difficulty that can be much alleviated using automated procedures. The models used here consider the screw as a circular beam with diameter equal to that of the hole.

Rigid screw models use rings of rigid connections. One only takes a few nodes on the screw to be masters, and big lumps of model nodes are forced to follow the associated rigid body motion.

Flexible screw models assume that the responses of the nodes on the beam are dependent on the response of a number of other nodes in the model. This dependency is represented as a weighted sum, which in terms of loads corresponds to a distribution of loads on a number of nodes.

4.9.2  Physical point with rotations

This type of connection finds the element a given node is connected to (see feutilb match) and uses shape functions of underlying element to estimate motion at the node. Rotations are determined using local derivatives of the shape functions at the physical point.