Columns for braced isolated elements

15.6 Analysis Of structures Of fixed

In structures of fixed nodes the design can consider each single element as a bar connected at their extremities to other structural elements, where the internal forces and moments obtained through analysis of the structure, according to the first order theory, are applied.

The analysis of second order local effects should be carried out in accordance with 15.8.

Whenever the structure is under horizontal forces it is designed as displaceable. The fact that structures are classified as having fixed nodes exempts only the consideration of second order global internal forces and moments.

The equivalent length l_e of the compressed element (column), supposed to be connected at both extremities, should be the lower of the following values:

l_e = l₀ + h

l_e = l

where:

l₀ is the distance between the internal faces of the structural elements, supposed horizontal, that connects the column;

h is the depth of the column transversal section measured in the structure plan being studied;

l is the distance between the axis of the structural elements in which the column is connected.

Ref: NBR6118/2014.

15.4.4 Isolated elements

Isolated elements considered as following :

a) isostatic structural elements;

b) braced elements;

c) elements of bracing having fixed nodes;

d) elements of bracing substructures having nodes whenever to the internal forces and moments obtained in a first order analysis are added those determined by a second order global analysis.

Ref: NBR6118/2014.