Shear Deformation!!

I am just a fresher in the practical field.For my upcoming project i would be working on analysis and design of a steel building whose majority of beams are I sections.Since from the basic study on strength of materials shear deformation in I sections would be considerate.
Would the software(STAAD in our office) take into account these shear deformations or account for deflections due to bending alone?

 

[DaveAtkins]

Shear deformation in steel wide flange sections is typically ignored, since it is such a small part of the deflection.

 

Thanks DaveAtkins :
But, for certain cases say I section ISLB400
max def= 5/384 wl4(10.12h2/l2)
which means for l=3m. deflection due to shear will be 18% than that due to bending.Should it be neglected??
sugg

 

[lippie]

STAAD does take shear deformation into consideration for any cross section. If you don't want shear deformation to be taken into effect, you can use a primsatic section with the properties equivalent to a wide flange, channel, etc.

 

[austim]

sugg,

I can only recall one occasion in the past 40+ years when I have needed to worry about shear deflection in a steel beam.

Having said that, your example is very unusual. The span is remarkaby short for a beam 400mm deep, with span/depth = 7.5.

Just to satisfy myself I ran a quick check on your values (I don't have access to Indian section properties, so my results are only approximate, but they do confirm yours).

For a UDL of 400 kN, (40 tonnes) I get a flexural deflection of 3.7mm, shear deflection of 0.6 mm. If the maximum deflection is critical to your application, then yes, you should include the shear effect.

This size of beam would more commonly be used for spans of 10 metres or so. For the same maximum bending moment on a 10 metre span, I get flexural deflection in excess of 40mm, while the shear deflection remains the same at 0.6 mm. That is, for the more common case, shear is 'negligible'

 

[butelja]

Shear deformation is usually only a problem in short span/depth ratio beams. In equipment frame design for large presses, it is very important.