Out-Of-Plane stress intensification factor for Miter Bends

[shaswin]

Hello,

There is some confusion in the attached PDF document. Most important part is given below:

[attachment=543]

According to this document the out-of-plane stress intensification factor ix for miter bends (0.75) is lower then smooth bends (0.9) according to the NEN 3650-1-2003/2012. The document of R&K says says also PLE uses the value for smooth bends which is conservative when the out-of-plane SWEIGH reduction is not used.

The ratio in the out-of-plane stress weighing factors between miter bends and smooth bends is nothing more then the ratio:
SIXcorr_factorr = ix_out_of_plane_miterbends / ix_smooth_bends = 0.75/0.9=0.8333...
According there is a relation between iy and ix, the same corrections should also be applied SIFcorr.

The formulas given in the document for SIXcorr. and SIFcorr. gives some confusion. It is better to say that SXUBH, SFIOSH and SXIOSH should be multiplied with 0.8333... (or =1/1.2).
The user should manually implemend this value in the SWEIGH input table.

Can you confirm this conclusion and if true update this in the helpfile of the upcoming Ple4Win version 4.3.0. So an user can easily search this knowledge in the (online+offline) helpfile.

Thank you.

[ir KW Radder]

Shaswin,

Your conclusion is not quite correct. In general the bending of the mitre bend will not be completely out-of-plane but a mixture between in-plane and out-of-plane. In that case applying an additional factor 0.8333 (1/1.2) is too favourable. This is justified only in case of a pure out-of plane bending. The user can check the bending direction of a bend in table CSLOAD, but it may be a tedious work to investigate if it concerns an out-of-plane bending, especially for sleeping bends.

[shaswin]

Shaswin,

Your conclusion is not quite correct. In general the bending of the mitre bend will not be completely out-of-plane but a mixture between in-plane and out-of-plane. In that case applying an additional factor 0.8333 (1/1.2) is too favourable. This is justified only in case of a pure out-of plane bending. The user can check the bending direction of a bend in table CSLOAD, but it may be a tedious work to investigate if it concerns an out-of-plane bending, especially for sleeping bends.

Rien,
The NEN 3650-1:2012 article D.6.4 doesn't say that the out of plane stress intensification factor i_x can be different for sleeping miter bends. I thought it was general for all miter bends.

[ir KW Radder]

Shaswin,

I did not say that the stress intensification factors for sleeping (mitre) bends are different. Only that it may be not so easy to check in Ple4Win whether the bending of a sleeping bend is out-of-plane.

[shaswin]

OK thanks for the clarification.