rsj help

[tony1851]

yes your right on the plasterboard 0.35 is high but the tiles are 9,47kg sq mt his calculation is 0.7
how much does that improve the deflection?

9.47kg sq m. is way too low for tiles. Most of the interlocking concrete tiles are around 45 to 50kg sq m, which equates to around 0.5 kN sq m.

If you want to work out the deflection of any steel beam yourself, for a uniform load, the equation is;

0.0063 *W * L^3 / I (answer in m.)

L = span
I = second moment of area on the x-x axis, which is read from steel tables
by looking up the section size you are using.
W = total dead + live load

 

[happyman1010]

ah but i found some called envirotile interlocking roof tile and they are 9,47 kg sq mt, thanks for all your help

 

[happyman1010]

they weigh 630grams and approx 13 to the sq mt

 

[tony1851]

ah but i found some called envirotile interlocking roof tile and they are 9,47 kg sq mt, thanks for all your help

In that case the dead load of the tiles will be around 0.1kN/m^2, which makes a big reduction to your total dead load.

 

[happyman1010]

thought so, when i looked at the values did tell him at the time what i was using, but now he passed away

 

[happyman1010]

hi am i being thick but using the formula just making sure i read it right ?
for uc 203/203/52
0.0063*1.87*6^3/5259
im getting
0.0004838745
must be doing something wrong ?
steel tables say 5259
but what about area of roof?
ie 24 sq mts come in to this ?

 

[jeds]

a lean to roof 3.89 wide by 7.3 mts long ay 18 degs
has a loading of
LL 0.6
DL 1.27

Where do you get 0.6 LL from?

A standard roof at 0.85DL and 0.75LL would give you a 203x133x25UB at 6m span with 5.3mm deflection.

 

[happyman1010]

from his calculations, just testing i am reading the formula right
rob

 

[happyman1010]

are you using
0.0063*1.6*6^3/2348?

 

[jeds]

Tony might put me right but it's not a figure I recognise. Live loads are prescribed by building regulations rather than calculated. In your area it would be 0.75kN/m² below altitudes of 100m - 1.00kN/m² above.

 

[happyman1010]

well looking at some SE calculations its done by calculation
and thats where the prob is
vaules a high 1.27 DL AND 0.6 LL

 

[jeds]

You can comfortably use 0.85kN/m² for the dead load unless you are using unusual tiles like stone or some dense concrete types. Live load is 0.75. Remember that only half the roof goes to the beam - the other half goes to the house wall plate. So your roof span should be divided by 2.

 

[happyman1010]

ah forgot about that divide by two plus its light weight tiles only 9.47kg sq mt think thats 0.1 kn

 

[tony1851]

Tony might put me right but it's not a figure I recognise. Live loads are prescribed by building regulations rather than calculated. In your area it would be 0.75kN/m² below altitudes of 100m - 1.00kN/m² above.

hi jeds,

this is how I arrived at that odd-looking equation for deflection - just my attempt to simplify the numerical bit!

Agree about the live load. Initially I thought it was because the SE had measured it horizontally(?) but that wouldn't have reduced it by so much - yes, should be 0.75.

Untitled

• tony1851
• 28 May 2014
• 1

 

[happyman1010]

well thanks guys looks like i need to get a set of SE calculations look a bit over the top the set i have
using a LL 0.75
and a DL 0.47 with what i have but take it up to 0.85
instead of the 1.27 he used