We consider a column with a 0.3 x 0.4 m rectangular section and a 3.10 m height. The concrete class is 25/30. The loads on the column are the following:

The workflow followed by the program to establish the reinforcement area is the following:

This calculation is done individually for X and Y directions.

The
program starts from a **minimum reinforcement** area:

This method consists of two verifications:

1. N_{Ed }≤ N_{Rd}

2.

The increment step of the iterative calculation of reinforcement bars can be defined in the Design Assumptions dialog, as Reinforcement precision.

The detailed report gives the final theoretical reinforcement that verifies the relation.

The
following example follows will use the reinforcement areas from the report
to exemplify the calculation for total external eccentricity, e_{ext}.

A_{s,x} = 1.2 cm^{2}

A_{s,y} = 1.2 cm^{2}

The
detailed calculation below is given for combination 105, giving the maximum A_{x }corresponding
to the last iteration.

This method consists of two verifications:

N_{Ed }≤ N_{Rd}

and

e_{int} ≥ e_{ext}

e_{ext} is
the total external eccentricity

e_{ext} = e_{1}_{ }+ e_{2}

e_{1} is
the 1^{st} order eccentricity

e_{2} is
the 2^{nd} order eccentricity

e_{1} = e_{0 }+ e_{i}

e_{0} is the initial eccentricity

e_{i} is the geometrical imperfections
eccentricity

ε_{c} is
the concrete strain

(Compressive strain in the concrete at the peak stress fc)

φ(∞,t_{0}) _{ }is the final
creep coefficient.

This value is displayed in the report in the Creep Coefficient chapter.

φ(∞,t_{0})
= 2.71

M_{0Eqp} is
the first-order bending moment in a quasi-permanent load combination (SLS).

M_{0Ed} is
the first-order bending moment in design load combination (ULS).

Regardless of the method used for element calculation, the geometrical imperfections should be considered only at ULS.

We consider an initial eccentricity defined by:

**M _{0Ed}**= M

**M**_{0Eqp}= M_{0Eqp,input }= **30 kNm** (in quasi-permanent load
combination 114)

ε_{s} =
3.19‰ (the value for which the section is balanced)

(the bottom concrete strain value for which the section is balanced)

Since, in the design phase, the real d’ is not known, the program will use in calculation the concrete cover from the Concrete cover dialog:

In the initial stage, the calculation will be done using the value from the Viewport. After a certain number of iterations, a longitudinal reinforcement area and a transversal reinforcement area with specific diameters will result.

In the final stage, the calculation is done again with the real d’ obtained as:

The report will reflect the final stage, with the real value of d’.

The value for l_{0} is
automatically calculated. It is displayed in the Buckling
Length dialog and the Geometry chapter of the report.