roof beam deflection calculation

[ypzhang]

Hello everyone,

I have a question about the deflection calculation of the roof beam:

When we calculate the roof beam's deflection, should we use the snow load plus live load or snow load plus 0.5 live load?
(assume the snow load is bigger than the live load)

Thank you very much!


Best regards,


Ping

 

[youngstructural]

For all serviceability checks (including deflection) you should be using unfactored loads.

As for what snow load to apply, your code/standard should tell you this, but I would be shocked if it were anything other than:

G + Snow (at 25? 50? year return period)

The snow load will be less than ULS, which will be something like a 100 or longer return period value.

Hope that helps,
Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[Lion06]

It depends what your LL is. You typically wouldn't have any LL (or at most very little) on your roof when you have the design snow load on the roof.

 

[youngstructural]

It's a roof beam; Unless this is a roof for floor type activities, you shouldn't be considering any pedestrian live loading...

Bear in mind that snow is a live load.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[msquared48]

Other than a teenager, who in their right mind would be walking around on a sloping roof with snow on it? Ok...I'll concede to politicians and lawyers too...

Mike McCann
MMC Engineering

 

[youngstructural]

To be fair, it's also a matter of access, not just intent. And despite my personal level of detest for our hormone-fueled young'ins, I typically consider a reduced live load on top of snow if there is any possibility of a bunch of moronic teenagers getting out onto the surface...

Typically quite low; 0.25kPa range... More an access load for maintenance than a proper pedestrian live load.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[civilperson]

Canada requires snow plus rain on roof.

 

[youngstructural]

Yes, Ss and Sr are both COMPONENTS of the total snow load back home... That doesn't really change the application, just how and how much you must compute.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[msquared48]

Question here:

Do Mortuarys have live loads?

Mike McCann
MMC Engineering

 

[youngstructural]

Harsh Mike... lol

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[rheim]

Question for Mike:

Is a hearse allowed to use the car pool lane?