- [Instructor] In this chapter we're going
to look at the second type of special element
which is the beam element.
And as a reminder, a beam element is
another type of one dimensional element
in the same family as the truss element.
And just like the truss, the beam has no representation
of space around its one dimensional axis.
Parametrically, it just knows the Area, Moments
of Inertia and the Torsional Constant.
The beam can carry end loads, like the truss,
but in addition it can carry moments,
shear forces and torsion.
Each end of the beam has six degrees of freedom
so it can carry these loads internally.
Applications of the beam element include
pipe-like assemblies where the joints are very stiff,
like in the oil rig jacket here,
in the construction industry
where many girder-like assemblies are used,
and there are many cases where shaft, legs,
and stanchions can all be modeled as beams.
For example, in the heavy section shown here.
The conrod shown here could be greatly simplified
just down to its axial bending
and torsional stiffness characteristics.
The beam requires a constant or prismatic section
through the geometry.
Suitable geometry would include those bodies created
through Boss-Extrude operations or Loft operations.
Using weldments is another very
useful way to create beam elements.
When the FEA mesh is created there are
an arbitrary number of elements per body.
We can increase or decrease that number of elements.
We can also control the behavior of the joints
between the geometry sections.
We can make the rigid or we can make them hinged.
The constraints or fixtures can only be applied
at the joints, but we have to be careful
because there are six degrees of freedom available
to make sure we control all those degrees of freedom.
Loads can be applied at the joints,
but in addition,
they can be applied at defined points
along the length of the beam.
We can also apply distributed loads along the beam length.
One thing to keep an eye on is the stress
or force and moment sign convention.
This is dependent again on the element orientation
and it may conflict with the conventional bending
moment shear force diagrams.
Again, it's up to us to look at the sense of that,
applying engineering judgment
to check the results from SOLIDWORKS.
We also need to keep an eye
on the parent geometry length to depth ratio.
So, for example, in here the span of the overall beam
compared to depth the sheer width is a critical value,
and that value should be great than 10.
SOLIDWORKS will issue a warning if it thinks
this parameter is being violated.
One thing to note though is for tapered beams
there is no warning issued.
The reason for the warning is that the beam elements
follow standard beam theory and if they have a ratio
of less than about 10 then it starts
to break down the theory