How much Sag in 80 mm Angle?

[awemawson]

I'm supporting a 6 metre length of 80 mm x 80 mm x 6 mm rolled angle iron pretty much at the ends - (actually at one end and 500 mm from the other) and I'd like a rough idea of how much sag to expect (Brundles yet to deliver the angle so I can't measure it)

This is to hold upright some 70 mm thick sandwich construction sound deadening partition boards a metre wide, the lower end will be fixed to another angle on the floor, and when they are fixed will themselves stop the sag but while constructing I'm expecting to have to put an intermediate temporary support.

 

[Jay1st]

you can use this online calulator:

https://www.easycalculation.com/engineering/mechanical/angle-iron-deflection.php


It's loaded with usefull stuff

 

[awemawson]

mmm .. doesn't seem to like an unloaded beam, gives zero deflection

 

[Jay1st]

try with what ever load you are going to put on it ?

 

[steviec_lj]

From what I’m reading they won’t be supporting a load as such. So the calculator linked to is pretty useless.

Other than that I can help with how much a length of 80x80x6 angle will deflect under its own weight.

 

[Brad93]

Probably 6-12mm of sag. I’m just trying to visualise the last lot of angle that size we had.

 

[Brad93]

Bear in mind angle really just wants to twist rather than deflect in one direction.

 

[atomant48]

Brundle’s site should give the weight/m which should
Give you the overall weight for your length. At a rough estimate you could plug half that into one of those calculations as a point load in the middle which would give you a starting point?

 

[Maker]

mmm .. doesn't seem to like an unloaded beam, gives zero deflection

It's the wrong calculator, it models a single, point load in the centre of a massless beam, you need a uniform, distributed load to represent the weight of the beam.

Here's one.

The "Line pressure load" is the weight per unit length, I make the beam about 45kg so this is 73N/m.
Young's modulus for steel is about 210 GPa
Area moment of inertia, easiest to just get that from another calculator, is 5.7*10^-7 m^4
Distance to extreme fibres would be 40mm but that doesn't actually come into this calculation.

Comes out at -10mm, Brad was right on the money; can't beat experience.

 

[Brad93]

https://www.google.co.uk/amp/s/www.engineeringtoolbox.com/amp/steel-angles-d_1324.html

80x80x6mm Angle
Cross sectional area is 9.25cm^2

Moment Of Inertia is 55.8 cm^4

Weight is 7.34kg/m

 

[Brad93]

It's the wrong calculator, it models a single, point load in the centre of a massless beam, you need a uniform, distributed load to represent the weight of the beam.

Here's one.

The "Line pressure load" is the weight per unit length, I make the beam about 45kg so this is 73N/m.
Young's modulus for steel is about 210 GPa
Area moment of inertia, easiest to just get that from another calculator, is 5.7*10^-7 m^4
Distance to extreme fibres would be 40mm but that doesn't actually come into this calculation.

Comes out at -10mm, Brad was right on the money; can't beat experience.

nice calculator better than any I found as it lets you select the units.

bit beyond me these calculations

 

[Agroshield]

...when they are fixed will themselves stop the sag but while constructing I'm expecting to have to put an intermediate temporary support.

If it has its legs downwards and horizontal, you could pre-camber it upwards by the calculated sag (heat shrink or JCB bucket) so it is horizontal when placed in position.

 

[awemawson]

Yes that's sort of the idea - I'll probably cut a bit of timber to prop the middle while attaching panels, and as I work towards the prop remove it as the panels can easily support and stiffen it - I just wanted a guesstimate as if it was (say) a foot I'd have to think again !

Thanks for all the useful constructive suggestions

 

[mtt.tr]

It's the wrong calculator, it models a single, point load in the centre of a massless beam, you need a uniform, distributed load to represent the weight of the beam.

Here's one.

The "Line pressure load" is the weight per unit length, I make the beam about 45kg so this is 73N/m.
Young's modulus for steel is about 210 GPa
Area moment of inertia, easiest to just get that from another calculator, is 5.7*10^-7 m^4
Distance to extreme fibres would be 40mm but that doesn't actually come into this calculation.

Comes out at -10mm, Brad was right on the money; can't beat experience.

My calculator came up with 12mm

 

[mtt.tr]

I use beam deflector cost about £5 on playstore crazy amount of common sections. Beats long hand and calculator.