Mullion deflection under wind pressure

[Ali76J]

Hi All,

This is my first post here!

I work in doors and windows industry. One of the tests we often do is structural testing.
For those who want to have an idea about it, the aim is to measure the maximum deflection of the mullion(middle vertical member of a window) under certain wind pressures according to the standard.

My aim is to find the best way to calculate this deflection without participating the actual test to save some money for the company.
There are charts and graphs available but I am very curious to find the right formula for this calculation.

for example on the following website they have developed a calculation but they haven't mentioned the method of their calculations.

http://www.aluconengineering.com/mullion-deflection--twin-span-.html

Please see attached and share your thoughts.

Cheers
Ali

 

[hokie66]

Your formula is for a simple span, loaded uniformly over the entire length. If you want to use just the trapezoidal part, there is another formula, a bit more complex. But I would stick with what you have, as it is slightly conservative.

 

[robyengIT]

comparison with your own system has to be done with mullion deflection (simply supported)of the website listed by you and not with mullion deflection (twin span) as shown with your link.
In fact, with same data, simply supported deflection is the double of the twin span deflection (using formulas of website)because the span is double

 

[hokie66]

robyengIT,

Not sure what you mean by your last statement. But doubling the span gives a lot more than double the deflection.

 

[robyengIT]

Hokie, You are right. I should have said "approx the double" (in fact 4.6/1.9 = 2.4) from comparison as per attached file

 

[XR250]

Without going thru the literature, it maybe saying that a 2-span continuous condition has about 1/2 the deflection of a simple span condition. (I think it was 2.2 last time I calc'ed it)

 

[Ali76J]

Thanks guys,

Can someone help me out with the formula of max deflection under spread trapezium load?

 

[robyengIT]

case 23 (If I well understood)

 

[Ali76J]

Many thanks case 23,

May I trouble you to run the formula on my example. The formula is not 100% clear specially the powers on "c" and "l" I am getting funny results.

 

[robyengIT]

Pay attention to the units, that is :

for steel E= 2'100'000 kg/cm2
deflection f= cm
load Q= metric tons
span l=meter
Inertia J=cm4

PS : attached a better scan