# D13.D.4 Columns

Reinforcement for columns of rectangular or circular cross section can be calculated. The flexibility of columns can be evaluated in two ways.

- In the case of linear analysis (i.e., the
`PERFORM ANALYSIS`command), the effective length is evaluated using the`ELY`and`ELZ`parameters, conforming to provisions of SP5 2.13330.2011. - If a
`P-DELTA`or`NONLINEAR`(i.e. nonlinear geometry) analysis is performed, the values of the`ELY`and`ELZ`parameters should be close to zero (e.g., ELY = ELZ = 0.01).

Longitudinal reinforcement for columns is calculated only for the strength condition. Longitudinal forces and bending moments in relation to local axes Y and Z are taken into account in longitudinal reinforcement calculations.

For rectangular columns, the following output is generated:

- column number;
- column length and cross-sectional dimensions;
- distance of centroid of each longitudinal bar from the nearest edge of the cross-section;
- concrete class;
- longitudinal reinforcement class;
- range of longitudinal reinforcement bar diameters assumed in calculation;
- diameter of longitudinal reinforcement bars obtained in calculation;
- total quantity of longitudinal bars;
- quantity of longitudinal bars at each cross-section edge, directed parallel to the local axis Y ;
- quantity of longitudinal bars at each cross-section edge, directed parallel to the local axis Z.

In nine columns of the table under the heading LONGITUDINAL REINFORCEMENT, the following output is presented:

- Section – distance of the section from the start of the column, mm;
- Astot – total cross-sectional area of longitudinal reinforcement, sq.cm;
- Asy – cross-sectional area of longitudinal reinforcement bars at each edge of section, directed parallel to the local axis Y , sq.cm;
- Asz – cross-sectional area of longitudinal reinforcement bars at each edge of section, directed parallel to the local axis Z , sq.cm;
- Percent – reinforcement percentage in the section;
- Nx, Mz, My – respective values of longitudinal force and bending moments in relation to the local axes Z and Y , determining cross-sectional area of longitudinal reinforcement;
- Load.N. – number of loading version, determining cross-sectional area of longitudinal reinforcement.