Live Load Reduction for Continuous Beam

[jayson34]

Hi Everyone,

To apply the live load reduction factor for a continuous beam, can the tributary area be based on the entire length of the beam? Or do different factors need to be applied to each beam segment based on its corresponding span length? Do you know any code languages that address this?

Please take a look at the sketch for illustration, assuming we need to design the orange beam.

Thanks,
Jayson

 

[dik]

I wouldn't... If you had several of them 'stacked' like in a highrise, I would use LL reduction.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

My experience is, the economy is determined by the structural system you choose, not in minimising loading... I'd put a splice in about 4.5' into the middle span, use 2 beams and design them plastically. Just a guess...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[RobertHale]

Personally, I take the LLR segment by segment. I think the commentary diagram in ASCE 7 that deals with the KLL factor kind of implies that approach, but that is a big reach and assumption on my part. It feels like the conservative answer. I don't know of any white papers or commentaries that deal with this question specifically, but I haven't searched.

 

[JLNJ]

I would probably use the 30' width with a KLL of 2 and then use patterned loading variants to check the beam.

 

[dik]

That's one of the advantages of plastic design. Alternate loading 'nearly disappears'.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[bobbyboucher]

I think you can, but probably controlled by pattern loading anyway, and I think the pattern loading wouldn't have sufficient tributary area to allow for any LL reduction.