The beam elements are designed for static and dynamic, linear and nonlinear analysis. For nonlinear analysis, finite strains are supported.
Beam elements may contain an initial strain, stress, or force and eccentricities. Special means for computing the crosssection constants are available.
The following element types are available:
Table 15. ReissnerSimo Beam Elements for Stress Analysis
Element type  Remarks 

B2.S.RS  A twonode linear prismatic Timoshenko beam
element with selective underintegration, according to
the Reissner/Simo formulation. The shape functions are
compatible with the R2.S rod/cable
element and with the element edges of linear shell and
continuum elements. This element may not be very
accurate for pure bending if only a single element is
being used to discretize a thin beam.

B3.S.RS  A threenode quadratic prismatic Timoshenko
beam element with selective underintegration,
according to the Reissner/Simo formulation. The shape
functions are compatible with the
R3.S rod/cable element and with the
element edges of quadratic shell and continuum
elements.

Table 16. Cubic Beam Elements for Stress Analysis
Element type  Remarks 

B2.S.E2  A twonode cubic Timoshenko beam element with
2*6 elementinternal degreesoffreedom. The shape
functions are not compatible with those of shell or
solid elements, except at the beam ends. A straight
beam is assumed for the initial configuration. Full
integration is conducted with 5point
GaussLegendreLobatto quadrature. Thus, stresses are
calculated also at the beam ends. This element is
accurate for pure bending. The behaviour of a cubic
EulerBernoulli beam element can be achieved by
setting the shear_correction_factors
in the beam property to a high value.

B4.S  A fournode cubic Timoshenko beam element. The
shape functions are compatible with the
R4.S rod/cable element and with the
element edges of cubic shell and continuum
elements. Full integration is conducted with 5point
GaussLegendreLobatto quadrature. Thus, stresses are
calculated also at the beam ends. This element is
accurate for purebending if it is not curved in the
initial configuration and if the nodes are
equidistant. The behaviour of a cubic EulerBernoulli
beam element can be achieved by setting the
shear_correction_factors in the beam
property to a high value.

beam_orientation
x y z

Defines the beam orientation vector in the beamlocal xy plane. The same definition will be used for all elements defined hereafter, until a new beam_orientation option is encountered or until the
eltype
command is specified. beam_orientation refnode
nodeid

Defines the beam reference node
(external node identifier). For the definition, see generic beam elements. The reference node defines a vector in the beam local xy plane. The same definition will be used for all elements defined hereafter, until a new beam_orientation option is encountered or until thenodeid
eltype
command is specified. pid
id

Specifies the beam property identifier
pointing to the beam property table. The same definition will be used for all elements defined hereafter, until a newid
pid
option is encountered or until a new element type is specified.
beam_offsets
x1 y1 z1 x2 y2 z2 ...

Defines the beam eccentricities (or offsets) for all nodes defining the beam, for subsequently defined beam elements (for the definition, see generic beam elements).
,x
, andy
are defined with respect to the branch reference frame. The same definition will be used for all elements defined hereafter, until a newz
beam_offsets
option is encountered or until theeltype
command is specified. beam_dof_release1
dofs
clear

Release part of the element's connections to the degreesoffreedom at the first node. The degreesoffreedom to be released are specified w.r.t. the beamlocal coordinate system.
dofs
is a concatenated string containing the degrees of freedom (1, 2, 3, 4, 5, or 6) to be released. clear removes all releases (i.e., nothing is released). The same definition will be used for all elements defined hereafter, until a newbeam_dof_release1
option is encountered or until theeltype
command is specified.Example: beam_dof_release1
456
releases all rotational degrees of freedom. beam_dof_release2
dofs
clear

Release part of the element's connections to the degreesoffreedom at the second node. The degreesoffreedom to be released are specified w.r.t. the beamlocal coordinate system.
dofs
is a concatenated string containing the degrees of freedom (1, 2, 3, 4, 5, or 6) to be released. clear removes all releases (i.e., nothing is released). The same definition will be used for all elements defined hereafter, until a newbeam_dof_release2
option is encountered or until theeltype
command is specified.Example: beam_dof_release2
4
releases the rotational degreeoffreedom of the beam end node around the beamlocal xdirection (the beam axis). initial_strain_xx
e
 initial_stress_xxs
 initial_force_xf

initial_strain_xx defines an initial strain
for subsequently defined beam elements. The initial strain is assumed constant along the element xaxis. The same definition will be used for all elements defined hereafter, until a newe
initial_strain_xx
option is encountered or until theeltype
command is specified.initial_stress_xx defines an initial stress
for subsequently defined beam elements. The initial stress is assumed constant along the element xaxis. The same definition will be used for all elements defined hereafter, until a news
initial_stress_xx
option is encountered or until theeltype
command is specified.initial_force_x defines an initial force
acting at the centroid for subsequently defined beam elements. The initial force is assumed constant along the element xaxis. The same definition will be used for all elements defined hereafter, until a newf
initial_force_x
option is encountered or until theeltype
command is specified. group
eid

Defines the element group number
gid
(a nonnegative integer number). The default group number is 0. The same definition will be used for all elements defined hereafter, until a new group option is encountered or until theeltype
command is specified. non_structural_mass
v

Defines the nonstructural mass per unit length. Default is 0. The same definition will be used for all elements defined hereafter, until a new
non_structural_mass
option is encountered or until theeltype
command is specified.
Forces, moments, stresses, and strains are stored on database are all expressed in the elementlocal coordinate system. For linear analysis, the strains and stresses stored on the database are the "engineering" stresses and strains. For nonlinear analysis, the strain is the GreenLagrange strain, while the stress is the Cauchy stress.
Stresses and strains are evaluated at the Gauss integration points and may be extrapolated to the nodes defining the beam.