Torsion on WF lintels

[kaisersoze]

As the topic suggests my question is in regards to eccentric loads on beams. Say I have a 12" cmu sitting on a W30. Technically if the lintel is 2" off of center line, I would consider e=2" on my beam but from a practical point of view, wouldn't the load coming down into the cmu re-align to some extent to be closer to the stiffest part of the beam i.e. beam center line?

Assume that the joists bearing elevation (on cmu) to be about 8' above the top of WF lintel.


Kaiser

 

[Lion06]

It looks like both sides of the wall are inside, so any out-of-plane load would be the nominal 5 psf interior LL.

How much load do you have coming down on that wall that you need a W30 to span 22'?

 

[BAretired]

If it is not too late, perhaps you can extend the column up to the roof, through the beam. If the masonry is in place, then it is too late.

BA

 

[slickdeals]

Are you creating an opening in an existing building?

 

[RFreund]

my bad thought it was an exterior wall

EIT

 

[kaisersoze]

This is renovation to an existing building, the opening is new.
Load coming down on the beam is quite high = 5.1 klf
W30 was designed as unbraced entire length ti limit deflection to 0.3".
HSS columns are 7x7x5/8 and when I ran them in RISA with e=1", the deflection or drift @ top came out to be about 0.4", a little high for my taste but basically I am dealing with something thats already in the field.
The torsion and flexural check on the beam is less then unity.
I am going to ask for welded plates at T&B flanges to the column to create a torsional connection.
I did a quick check of anchor bolts (have to do it again to be sure) but basically there was no uplift or tension with e=1" just because there is like 56k of reaction coming down.
The existing structure under the base plate has already been checked with much higher loads by last engineer, so I am not worried about that.


So I guess now folks can see my point in asking the question. As one old bosses once told me "design the components but ignore the building envelope".....I am checking the beam as if the wall is free standing without some lateral support provided by the two roofs above, and I wanted to see peoples take on this approach.

Kaiser

 

[kaisersoze]

Some more load info BTW:

Low roof trib is about 32'.
High roof trib is 12', but its a 8" conc slab.
Roof LL=30

Kaiser

 

[Lion06]

FWIW:
ACI 530 took out the 0.3" limit on deflection and allows L/600 in 530-08

 

[slickdeals]

@kaiser:
Check out pages 4,5 and figure 2.6 in the AISC Design Guide for Torsion. It concludes what BA was alluding to. The bending stiffness of the wall (if properly attached to the W beam) can take out the torsion.

http://cobweb.ecn.purdue.edu/~ahvarma/CE 579/References/AISC_Torsion_Guide.pdf