## 2. Generic beam (B) elements

Bx elements define one-dimensional elements with linear (B2) or higher order (B3, ...) representation of the beam geometry.

Beam element data are defined with respect to the beam local orthogonal coordinate system, the local x-axis being tangential to the beam axis, adn the local y-axis and z-axis in a plane normal to the x-axis. The orientation of the local y- and z-axes are defined as follows:

• By an orientation vector o defining the element local x-y plane with respect to the global coordinate system. The orientation vector must be specified by the MDL elements attributes beam_orientation.

• By a node nref which defines the beam orientation vector o = n1o, where n1 is the coordinate vector of the first node defining the beam element. n1o must be defined by the MDL coordinates command.

The figures below illustrate the beam element node connectivities. Note that node indices are positive integers and all node indices defining the element must belong to the same branch.