D5.C.5.2 Members Subject to Bending Moments
The cross section capacity of a member subject to bending is checked as per Cl .6.2.5 of the code. The condition to be satisfied is:
Where Mc,Rd is the is the design resistance given by:
- for class 1 and 2 cross-sections
- for class 3 cross-sections
- for class 4 cross-sections
Cross sectional bending capacity checks will be done for both major and minor axis bending moments.
Members subject to major axis bending will also be checked for Lateral Torsional Buckling resistance as per Section 6.3.2 of the code. The design buckling resistance moment Mb,Rd will be calculated as:
χLT is the reduction factor for lateral torsional buckling. This reduction factor is evaluated per Cl. 188.8.131.52 or Cl 184.108.40.206 of the EN 1993 code depending on the section type. For I sections, the program will by default use Cl. 220.127.116.11 to evalute χLT and for all other sections the program will resort to Cl 18.104.22.168. However, if a particular National Annex has been specified, the program will check if the National Annex expands on Cl.22.214.171.124 (Table 6.5) to include sections other than I sections. If so, the program will use Cl. 126.96.36.199 for the cross-section(s) included in Cl. 188.8.131.52 (or Table 6.5). For all other cases the program will use Cl. 184.108.40.206.
When using Cl. 220.127.116.11 to calculate χLT, the program will consider the correction factor kc (Table 6.6 of EN 1993-1-1:2006) based on the value of the KC parameter in the design input. By default the value of KC will be taken as 1.0. If you want the program to calculate kc, you must explicitly set the value of the KC parameter to zero.
The non-dimensional slenderness λ LT (used to evaluate χLT) for both the above cases is evaluated as:
Mcr is the elastic critical moment for lateral torsional buckling. EN 1993-1-1 does not however specify a method to evaluate Mcr. Hence, the program will make use of the method specified in Annex F of DD ENV 1993-1-1 to evaluate Mcr by default.