Shear strength of slab wall connection

[hetgen]

How do you guys calculate critical section of a flat slab for shear strength around uncoupled shear wall?

If the lateral resisting system is not relaying on coupling composite effect of shear wall - flat slab (no load reversal) . Do I still have to use a stringent critical section similar to attached picture?
How about shear distribution due to an unbalanced moment at a slab-
wall connection? can this be treated as edge column?

Thanks.

 

[hokie66]

Flat slabs are rarely considered to be part of the lateral load resistance. They deliver loads to the shear walls by diaphragm action, but are not considered to work as coupling beams. Beam shear needs to be checked at wall supports, and punching shear at columns, due to gravity loads, not lateral. Yes, unbalanced moments, whether at internal or external columns, result in nonuniform shear distribution.

 

[ajk1]

Hmmm. If the shear is there at the face of the wall, as I believe it is, I would have thought that you should check it as per Hetgen's diagram.

 

[slickdeals]

There have been a few papers that I have read in the past.

http://nees.ucla.edu/wallace/Abstracts and Presentations/Kang, Thomas/Conference-8NCEE-000258.pdf

I will look for others and post them.

 

[slickdeals]

http://images2.wikia.nocookie.net/_...sign_Criteria_for_Slab-Column_Connections.pdf

 

[slickdeals]

You may also want to see this paper.

Design of Floor Slabs Coupling Shear Walls
J. Struct. Engrg. 109, 109 (1983); doi:10.1061/(ASCE)0733-9445(1983)109:1(109) (17 pages)

 

[hokie66]

hetgen said that the shear walls are not coupled, so the shear walls are stiff enough to resist lateral forces on their own. His sketch then shows the action of coupling members. Which is it?

 

[hetgen]

Thanks for the response guys. I should have been clearer on my question…
The structure that I’m dealing with is in non-seismic area and as hokie stated above the shear walls are sized to resist all lateral forces without coupling effect.

My question is how to deal with the concentration of shear stress at edge of shear wall due to unbalanced load?

Hokie66,
If you say that only beam shear due to gravity load is to be checked at wall support. How do you deal with the variation of shear stress along the length of shear wall? (see attached picture) Shear stress at the inner edge of the wall will be higher as compare to the outer edge.
So do we consider edge of the wall as column and check punching shear? If so what is the critical section?

Slickdeal, thanks

 

[hokie66]

Yes, it is appropriate to consider the end of the shear wall as a column and check for punching shear. Critical section at d/2, but the length of your assumed column is susceptible to your engineering judgement. Maybe two or three times the wall thickness.

 

[hetgen]

Thanks hokie66, but I was hoping to hear more than ‘engineering judgement’ about this from you. Monday’s could be boring, please share your guru knowledge as you always do when you get a chance.

“When I hear the words ‘engineering judgement’, I know they are just going to make up numbers” (Feynman, 1993)...

 

[hokie66]

Feynman is an idiot. If you want a cookbook for everything, talk to someone else.

 

[hetgen]

Sorry hokie, don’t mean to be disrespectful. I was just pulling your leg. Seriously i have learned so much from all your post in engtips I have to thank you for that.

Yes Feynman, could be an idiot, after all he help formulate a nuclear bomb.

 

[hokie66]

Then he may be able to blow up a building, but I doubt he could design one. Back to your picture, I wouldn't be concerned about punching shear at the end of the walls. You have two way action, so beam shear perpendicular to the walls is on your load path. Punching shear at those columns on the other side is where you need to concentrate your design efforts.