# D5.D.3.8 Clause 6.33 – Uniform members in bending and axial compression

The D-NA recommends the use of the method in Annex B of EC-3 to determine the values of kyy, kyz, kzy and kzz to be used  in 6.3.3 ( EC-3) checks. STAAD.Pro uses the method in Annex B.

## Clause 12.3.1.2.3 (NEN 6770): Rotation/bending capacity

The Dutch NA also requires additional checks as per clause 12.3.1.2.3 of NEN 6770.

The checks given in this clause deals with additional checks for columns that form part of a buttressed or non-butressed framework.  The program uses the ESTIFF parameter with two different values to identify the framework type:

Table 1. Framework parameter ESTIFF values for the Dutch NA
ESTIFF value Description
0 (default) Column part of a buttressed framework. Selecting this value will internally perform the checks as per section 1 of clause 12.3.1.2.3
1 Column is not part of a buttressed framework. Selecting this value will internally perform the checks as per section 2 of clause 12.3.1.2.3

These checks are described below:

1. For columns in buttressed frameworks the buckling length is to be taken based on either

• the system length or
• the distance between adjacent lateral supports

The following conditions should also be satisfied:

If Nc;s;d/ Npl;d < 0.15, no additional checks are required

If Nc;s;d/ Npl;d ≥ 0.15  and the steel grade is S235 or S 275 then

$N c ; s ; d N p l ; d + λ y 120 ≤ 1$

Where:

• Nc;s;d is the axial load in the section
• Npl;d = Axial capacity of section = A·fy;d
• λy = Slenderness of the section about the major axis ( Y-axis)

If Nc;s;d/ Npl;d ≥ 0.15  and the steel grade is S355 then

$N c ; s ; d N p l ; d + λ y 100 ≤ 1$

Where:

• Nc;s;d = the axial load in the section
• Npl;d = Axial capacity of section = A·fy;d
• λy = Slenderness of the section about the major axis ( Y-axis)
2. For columns that are not part of buttressed frameworks the following additional checks need to be done:

If Nc;s;d/ Npl;d < 0.15, no additional checks are required

If Nc;s;d/ Npl;d ≥ 0.15  and the steel grade is S235 or S 275 then

$N c ; s ; d N p l ; d + λ y 100 ≤ 1$

Where:

• Nc;s;d = the axial load in the section and
• Npl;d = Axial capacity of section = A·fy;d
• λy = Slenderness of the section about the major axis ( Y-axis)

If Nc;s;d/ Npl;d ≥ 0.15  and the steel grade is S355 then

$N c ; s ; d N p l ; d + λ y 80 ≤ 1$