Masonry basement - vertical tie problem

[n3jc]

Hi, not long ago i was asking about modeling concrete horizontal/vertical ties for masonry basement.
I modeled it as pinned top/bottom for vertical ties and pinned in corners for horizontal tie.

Now im dealing with actual basement.

Because of geometry of the walls I have problem with marked vertical tie.
The problem is eccentric loading + supporting wall at the edge of the tie- there will be torsion in vertical tie because of it + biaxial bending...

I think it would be better to make dilatation and two vertical ties instead of one.

What do you think? Vertical tie dimensions are 59/30 cm...

 

[StrEng007]

What is the elevation of your horizontal ties in relation to your floor system above the basement? Can you use your floor as a diaphragm to brace this location?

 

[EngineeringEric]

I feel like this may be more complicated than it should be.... your walls can span vertically alone (foundation to floor) you resists soils at Ko. you have tension on the inside face of wall. loading profile is triangular with bottom reaction more than top (66% vs 33%).

then you provide the horizontal as required and give yourself bond beams at the top. Design first floor attachment for the top reaction.

if you have center walls that are also masonry they can be used if needed, but they also can just be suspenders. it all depends on the height of the wall. Masonry begs for simplicity IMHO.

 

[n3jc]

What is the elevation of your horizontal ties in relation to your floor system above the basement? Can you use your floor as a diaphragm to brace this location?

Basement height is 300 cm.
Horizontal tie is located little less than 1/2 of basement wall height.
Above the basement is concrete slab (15 cm thick) which can be a diaphragm.

 

[OldBldgGuy]

Listen to EEric. It's a house, and not very big at that. You can do this under prescriptive requirements for unreinforced masonry that have worked since concrete block were invented. Don't overthink it.

 

[KootK]

I'd be inclined to go the other way: more concrete. That way, you've got a stiff, vertical spanning member that will shield the original column from soil pressure loading.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[n3jc]

Alright guys. thanks for help. I might be overthinking, but I do this for the first time.

Regards

 

[concretemasonry]

+10 clarity points to OBG -

It is always fun to see some fellow engineers over-analyze a simple masonry structure.

At least no one looked a the needed mortar strength as a so-called structural criteria.

ACI 530 would handle everything easily using the simpler and cleaner methods of analysis. Standard assumed minimums for materials would be adequate as long as recommended steel and placement.

When we first developed ACI 530, we were always concerned that many engineers would get lost and try to over-complicate the design and analysis because of the options presented for more specialized specialized conditions.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.