# Geometry (Concrete Beam)

The Geometry dialog box contains the following tabs:

Span geometry

A number of spans, with belonging lengths and end connections are being defined in the Span geometry dialog box.

Cross-section

The current type of section and its dimensions are defined in the Cross-section dialog box. The types that can be chosen are shown in the picture below:

It is possible to vary the cross-section height that however must remain constant within the span.

Support

The length of the supports, as well as column connection (if there is any) from columns that connect to the beam from under and/or above, are being defined in the Support dialog box. The effect of possible columns is only considered in the elastic but not in the plastic calculation. (Only Danish Annex). If the support lengths have been defined the moment of supporting points will be rounded according to these.

Permissible values for column stiffness:

Stiffness (K-values):

0 to 1 x 1050 kNm²

Column stiffness (K-values) are calculated as:
4 Ep Ip / Lp (the far end of the column is fixed)
3 Ep Ip / Lp (the far end of the column is hinged)

where for the column:
Ep = the modulus of elasticity,
Ip = the moment of inertia,
Lp = the length.

If relative values have been used for the EI-values of the spans, then the values for the column-stiffness must also be relatively stated.

The formulas will then be:
3 E' I' / Lp respectively 4 E' I' / Lp
where E' I' = Ep Ip / (Eb Ib) and:
Ep = the modulus of elasticity for the base span,
Ip = the moment of inertia for the base span.

For constant E the formula is reduced as to:
4 Ip / (Lp Ib) respectively 3 Ip / (Lp Ib)