Tension flange restraint

[mobe]

Has anyone any references (or thoughts about) the effect on the slenderness ratio if the tension flange only of a beam is restrained? This seems to be largely ignored in UK codes but is quite a common situation in lightweight structures. The only reference I have seen has been in the Canadian code for aluminium.

 

[Lutfi]

I fail to see why any one would restrain the tension flange? What am I missing? You need to restrain the compression flange because it becomes a column of sorts and hence the lateral bucking will take place once maximum compressive loads are reached.

I do not think restraining the tension flange will increase neither the compressive strength of the beam element nor the flexural strength.

One of the best steel design text books is written by William "Bill" McGuire. This text is tremendous and covers the steel design from A to Z.

Good luck.

 

[IFRs]

Restraining the tension flange makes sense if the shape is unbalanced like a tall channel - it will prevent the shape from rolling or twisting. Of course, compression flange bracing is usually more important but often the compression flange is braced by the rest of the structure. I think tension flange bracing is often overlooked and can be the primary mode of failure in some special cases.

 

[hernma]

Lutfi:

Please, can you give me more information about the book by McGuire (editorial, year...).

Thank you.

 

[Lutfi]

The book is in my office. I would be delighted to pass the all relevant data. I may be able to do so this afternoon.

 

[Lutfi]

The book title is Structural Analysis and Design Series, Steel Structures. The author is William McGuire and the book is published by Prentice-Hall. I bought my copy when I was in graduate school back in 1984 (shows my age). I am sure it is still out there and if not, libraries would have a copy of it.

In my humble opinion, this book is the best and most comprehensive steel design book out there. It is full of theories and examples. I am not a big fan of theory only and a bunch of integrals and differentiations and no practical aspects.

Good luck.

 

[dlew]

mobe,

The restraint of the tension flange provides some restraint to the compression flange through the bending strength of the web. This approach is commonly used in light-gage shapes as channels and Zees that support siding or roofing subject to reversal of wind loads.

The book "Cold-Formed Structures" by Wei-Wen Yu shows a method to calculate the equivalent restraint to the compression flange of a light-gage section. I think the same method could be applied to structural steel shapes.

Regards

AEF

 

[mobe]

Perhaps I should have explained this better. The elements in question are vertical cladding/curtain wall aluminium sections which have to be designed for both negative & positive wind loads. Unfortunately the largest force is often negative wind pressure which puts the unrestrained flange into compression.
dlew, I think the your reference is exactly what I'm looking for.
Thanks all
Regards
Mobe