Long Cantilever Beam Questions 2

[DevinTheStudent]

Hello all, this is my first time posting here so apologies if this is formatted wrong.

I had a couple questions about a beam I am currently analyzing that has a large cantilever section and had a few questions

*UDL of 0.31 kip/ft is a snow load
*UDL of 0.35 kip/ft is a LL/DL
*Point load of 1.42 kips from joists running parallel
All loads are factored

1) I am worried about the resulting uplift of force on the left support from the total load on the beam causing some sort of teeter totter effect , am I correct in assuming this is a concern?

2) What can be done to ensure this left support does not fail from the resulting uplift?

3) Can cantilevered sections operate safely at this span length?

 

[dik]

Your backspan is short, but it's doable... as long as everything can take the loads. Any chance for vibration (wind)? or impact loads? bottom flange bracing for LTB? Camber? With no camber, you don't have to worry about drainage.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[DevinTheStudent]

little to no exposure to wind and does not govern, my worry is a full loading on the right span (where master bath is) and say little to no LL on left span causing a large uplift force on left support

 

[1503-44]

Exactly. I was going to say the same. There is no control aver how snow load is placed. You must make conservative judgements. LL to the right, none to the left and, if that result is marginal, maybe consider a 10% reduction in Left dead load.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[EdStainless]

What is the actual defection at the outside?
Could make that wall connection tricky.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[1503-44]

Says in the fine print it is 0,80 in.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[Ron247]

Did you check Dead Load on everything with only Live Load on the cantilever?
I guess you put DL and LL together. It is best to separate them.

 

[DevinTheStudent]

Yes I have the new beam with DL on left only (0.9 factor) and a live/dead point load from bathroom (factored) only.
see attached

as you can see there is about 800lbs of uplift force on the beam in this worst case scenario.

 

[Ron247]

I disagree that the deflection of .66" is L/520. To me, you should use the 12'-11" = 155" as your "L". Anyone standing near the left support and looking to the right will see a gradual uphill followed by a sharp downhill.

Is there no distributed LL across the 12'-11" span?

 

[DevinTheStudent]

Ron247 the 12'-11'' span has the joists running parallel therefore not picking up a UDL and instead picking up a point load from another beam at the end (1.68 kips).

 

[1503-44]

If there was a tile floor on that beam, L for deflection limits should be the whole length of 29'

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[Ron247]

1503-44, why would the absence or presence of a tile floor determine the magnitude of L?

 

[1503-44]

Maybe I didn't say that right. Flexure cracking and distortion considerations for the finish above. Assuming that the cantilever is not always at full load that might be significant. Like in measuring the maximum deflection on a perpendicular from a line drawn from each end of the beam.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[dik]

You don't want a brittle finish on whatever is over the cantilever...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik