Transfer 3 stories building wind load to block wall below

[johndeng]

I have a 3-story wood framed building on one story parking slab (steel frame). two masonry stairs and elevator walls all way up, 12" thickness below slab, 8" above slab. and a few other isolated walls below slab as my first story shear walls. No steel moment connections and bracing, so I need to transfer all wood building wind shear load to concrete slab, then transfer to steel beams around these walls. I tied slab to walls, and tied beams to wall below with studs, please see sketch. Is this good enough? or any better suggestion?

Thanks

 

[ztengguy]

Not sure if its good enough, do the calcs work out for it? Not sure about the detail of the masonry tieing to the slab like that, are you not allowing for deflection of the beam

Would a better detail be that the wall is pin connected to the bottom of the beam, and the shear is transfered thru some plates that allow vertical deflection of the beam? Then the block in front of the beam is just cosmetic, it can crack as it likes when the beam deflects. Is there siding or anything on the walls that really would allow you to leave the block out infront of the beam? or get rid of the beam and use the masonry as load bearing?

Also never seen a #9 in a wall, not sure thats the best.

 

[woodman88]

You do not show any connections for the wood shear walls to the concrete/masonry for shear or uplift. Are these not a part of your concern in the OP?

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[johndeng]

Thanks ztengguy. I feel the same. I will ask the architect to move the column off the wall. And I just updated the ties to the walls. Is this in your mind too?
to woodman88, the simpson holddown detail to connect wood to slab is not shown here.

 

[dhengr]

John:
Mightn’t you be better off in those two sections, to eliminate the steel beams and run your metal deck and slab right out onto the conc. blk. walls? Put a continuous angle with studs on it, at 45° to the legs, in the bond beam at the deck bearing elev. and weld the deck to it. This transfers both vert. and lateral loads more efficiently to the conc. blk. walls; and eliminates the differential deflection at the steel beams, and the difficult intermittent slotted shear connections. Also, your bent #4's @ 32" o/c are of dubious transfer value because they both span a void or a slip joint at the pour stops. I also agree that the #9's @ 32" o/c vert. are a pretty large bar in a typical grouted CMU wall section. Two smaller bars in the same core, or one every 16" would be better, although a bit more placement work. Then your first steel beam is far enough away from the CMU wall so its deflection is less of a problem where so much load transfer is taking place, right at the walls.

 

[SteelPE]

My question is how would you construct your details. You would need the steel to be erected, then the masonry and finally the slab would need to be poured. Seems like kind of a slow process to me.

 

[dhengr]

Some GC’s are real clever. They can have two trades working on the job site at the same time, once the foundations are done. For that matter, the conc. blk. walls might be up, and being grouted, while the steel is still being erected. Then the decking follows that, and a narrow conc. blk. might be the pour stop. John’s sections require the steel and the CMU walls to be done at about the same time anyway, or the bent #4's are difficult to place. And, you avoid the difficult details, design and placement, caused by the differential deflection btwn. the steel and the CMU walls, then you also save some steel when the CMU wall is there to take the vert. loads anyway.

 

[johndeng]

Actually the anchors can be made adjustable vertically.
Builder said they don't want wall bearing since they like to build wall independently from the building.

For the second detail, I dont think beam will deflect if beam is on top of the wall (will blocks at the beam crack? maybe not). Is that saying it's better to keep beam on top of wall rather to keep off the wall?

 

[johndeng]

Updated details, any comments?

 

[ztengguy]

I think the best detail is to get rid of the steel beam, or at least it does not need to be tied to the wall, the masonry can tie to the slab at the top. Talk the architect, and he can talk to the owner and tell him that the structural engineer said we can save money by doing load bearing masonry. (im sure he will say its your idea)

How tall is the wall?

What is the length of the columns?

Can you post a plan of the area?

 

[johndeng]

I emailed them and wish they can remove total three cols at two stairs. Top of slab is 13' from ground. Plan of the area is attached.

ztengguy, I do see many cases (like the gyms) roof spandrel beams are on top of masonry shear walls to transfer horizontal load and support the roof.

 

[ztengguy]

Do they have a gap between the beam and the wall for deflection?

Why the heavy reinforcing on a 13' wall? what is controlling?

 

[johndeng]

One beam is right off the wall, other beams cut in the walls now. I am talking them to remove those beams that are on the walls.
these stair masonry walls hold shear from top 3 stories of building.

 

[RareBugTX]

How are you transfering shear, uplift, moment from the studs above to the masonry?? That is a big question mark.Looks like it is just sitting there.

 

[johndeng]

Wood shear walls will transfer load to concrete slab with simpson holddown.