**Some basic concepts as used in
the program**

**- Types of
calculations**

In addition to linear static calculations,
geometric non-linear calculations (incl. 2nd order effects) are also possible.

In linear calculations, the various base load
cases can be calculated in one operation; for
geometrically non-linear calculations this must be done separately (the
superposition principle is then not valid).

Furthermore, the calculation of Eigen
frequencies is supported.

**- Base load cases**

A base load case is a collection of
associated member and/or node loads.

The geometry, member properties, prescribed
displacements, eccentric beam connections and spring-supported nodes remain
unchanged.

In a calculation, the following equation is solved: __k__ = [S].__v__

with

** k** is the load vector, containing the load
present on the nodes

** [S]** is the
stiffness matrix of the total structure

__v____ __is the displacement
vector, containing the displacements occurring at the nodes (degrees of
freedom)

__k__** **and

In a linear calculation, the superposition
principle applies, which makes it possible to calculate several base load cases
in one step.

__k __*= k_{i} ..….k_{n}*

with

__v__* = v _{i}
..….v_{n} *as associated unknown displacements.

*[S]* is then equal in all
base load cases

**- Load combinations**

A load combination is a collection of associated base load cases . Each base load case is multiplied
by a multiplication factor to be entered.

This is a form of post-processing and is performed
after * v* from

**- Nodes**

A framework consists of straight beams that together form the geometry of the framework. Both ends of a beam are called nodes.

The location of these nodes is determined by the nodal coordinates to be entered.

Several beams can be connected to a node.

Degrees of freedom are present at the nodes: translations and rotations.

**- Beams**

A beam forms the straight connection between 2
nodes; No more and no less. The length of the beam is determined from the
distance between the two connecting nodes.

In principle a beam can transfer normal forces,
shear forces and moments. Some tines called *‘beam-column’*
elements in literature.

By arranging hinges on both sides of a beam, a beam can possibly be
limited to the transfer of normal forces only.

In the case of trusses, however, this is a somewhat dated method of
schematization.

**- Beam properties**

In *[S]* the beam properties are
included. This concerns quantities such as E-modulus (E), area (A), moment of
inertia, etc.

If the stresses also have to be calculated
during post-processing, additional properties such as e.g. moments of
resistance are entered.

A database with steel sections is available.

The relevant Eurocodes are
also supported.

**- Prescribed displacements **(including supports)

Equation * k = [S].v* can be solved if there is a connection
with the outside world only.

This means that displacements at some of the nodes must
be prescribed.

If the magnitude of this prescribed displacement is equal to zero, then
the relevant degree of freedom is fixed (support).

If the magnitude of this prescribed displacement is unequal to zero,
then the respective degree of freedom undergoes a fixed value prescribed at the
input (a settlement).

**- Beam connections (including hinges)**

By default a beam is rigidly connected to the
two connecting nodes.

A beam can also be spring connected to one or both nodes. If the
stiffness of the bending spring is equal to zero then it functions as a hinge
(simplified input for hinges is provided).

**- Eccentric beam connections**

By default, the centreline of a beam is directly
connected to both nodes. By entering an eccentric connection, the
centreline may be shifted with respect to the nodes
(offset).

The shifted part is not part of the elastically deforming beam; is
infinitely stiff as it were.

**- Nodal loads**

Point shaped loads can be directly introduced in the direction of the
respective degrees of freedom.

Internally entered beam loads are converted to nodal loads to solve for __k__ = [S].__v__

**- Beam loads**

Different types of beam loads can be entered on
the various beams present; acting along the longitudinal direction of the
respective beams.

Internally entered beam loads are converted to nodal loads to solve for __k__ = [S].__v__

The force acting in the longitudinal direction of the beams is a form of
post-processing after solving __k__ = [S].__v__

**- Spring supported nodes**

Using this option, a node can be spring connected to the outside world.

This is a variant of the option of *'Prescribed
displacements'*

**-
Spring-supported beams**

Using
this option, a spring-supported bed acting along the beam axis can be entered.

**- Influence
Lines **(2D only)

Using
this option, the influence of a mobile load can be calculated
(principle:
Maxwell's reciprocity law; Müller-Breslau method).

This
option uses the option of 'Linked nodes' internally.

**- Tyings **(2D only)

Using
this option, dependency relationships between different nodes can be entered.

This
is a fairly advanced option.

**- 'Wizards'**

With
the help of various 'wizards', certain construction types can be entered relatively
quickly and easily using a type of template.

Such
as for continuous beams, spring supported beams, trusses, beams and columns,
grillages and space frames.

It
is not a fundamentally new option, but is intended to
aid in data entry for a particular type of construction.