Steel Joist Seat Shear Transfer
Steel Joist Seat Shear Transfer
(OP)
Is a joist seat capable of transferring shear perpendicular to the span of the joist on to a wall it bears on.
I have a condition where I have a joist bearing on top of masonry wall with an extended top chord. In between, the joists I put in an inverted U shaped plate (or a HSS tube) to transfer the diaphragm shears into the wall (masonry) below. The steel deck will be welded to the this plate or tube here. Another plate runs across the wall below the tube (or U plate) that is attached to the masonry with embed anchors.
Another engineer, in the office is telling me that I can rely just on the joist seat to transfer these shears. I do not need to add anything in between the joists.
I just wanted to know if my approach was incorrect.
I am in 90 mph wind zone with almost no seismic.
I have a condition where I have a joist bearing on top of masonry wall with an extended top chord. In between, the joists I put in an inverted U shaped plate (or a HSS tube) to transfer the diaphragm shears into the wall (masonry) below. The steel deck will be welded to the this plate or tube here. Another plate runs across the wall below the tube (or U plate) that is attached to the masonry with embed anchors.
Another engineer, in the office is telling me that I can rely just on the joist seat to transfer these shears. I do not need to add anything in between the joists.
I just wanted to know if my approach was incorrect.
I am in 90 mph wind zone with almost no seismic.






RE: Steel Joist Seat Shear Transfer
JOIST MANUFACTURER SHALL DESIGN JOIST SEATS TO RESIST X KIPS OF LATERAL WIND LOAD, PERPENDICULAR TO EACH SEAT
I have never done this as I always use a steel tube between joists and inter-connect the edge angle collector with the beam below.
RE: Steel Joist Seat Shear Transfer
RE: Steel Joist Seat Shear Transfer
All these projects were in Midwest, so no seismic issue with 90 mph wind.
But I can see JAE's logic and I think I would consider it if the shear was too high.
RE: Steel Joist Seat Shear Transfer
RE: Steel Joist Seat Shear Transfer
He told me that they use to it a few years ago but it lead to intense warping when actually designed. He recommends the use of blocking in between.
Thank you guys.
RE: Steel Joist Seat Shear Transfer
I don't recall where I read the information, so use it with a grain of salt, but I have written in my "Designing with Vulcraft.. " manual that the standard rollover capacity of a 2 1/2" seat is 1000 lbs. and for a 5" seat it's 500 lb.
RE: Steel Joist Seat Shear Transfer
So then the seat would see gravity, lateral shear, and induced torsion. Interesting.
I'll go as I always have with the edge angles too for the diaphragm shear.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Steel Joist Seat Shear Transfer
RE: Steel Joist Seat Shear Transfer
They also give the results from some testing they performed on actual seats (getting failure greater than 8,000#).
If in doubt, indicate it on your drawings and then have the Joist Company design appropriately.
RE: Steel Joist Seat Shear Transfer
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Steel Joist Seat Shear Transfer
They performed 4 tests on 8H3 joists (8940#), 4 tests on 24H6 joists (13,500#) and 2 tests on 26H8 joists (15,360#). The values given are the average failure load. Not a large variety of tests but tests on multiple joist seats of varying size none the less.
RE: Steel Joist Seat Shear Transfer
RE: Steel Joist Seat Shear Transfer
The tests were done on the seats only not considering the weld of the deck to the joist seat. Also, as stated above, they reduced the allowable capacity considerably due to serviceability concerns.
RE: Steel Joist Seat Shear Transfer
Wouldn't the edge distances for the anchors also govern the total force that can be allowed into the wall below?
RE: Steel Joist Seat Shear Transfer
"Designing with Vulcraft" as mentioned gives some guidance perpendicular to the joist. The load gets to the joist thru the angle used as a chord for the diaphragm not deck welds to the joist only.
RE: Steel Joist Seat Shear Transfer
Angles and bolts aren't expensive, which is why I always use them. Then the joist seats are my redundancy.
Unrelated but related- I have found this is often overlooked in wood trusses, ie, blocking vs no blocking.
RE: Steel Joist Seat Shear Transfer
Although I have framed a few houses during my college summer vacations I have not really designed many wood structures. The one garage I did I used a Simpson truss connector that had a given lateral capacity our to the plane of the truss. The contractor b*****d about it as he had never had to use the connectors before in the 500 houses they had built prior.
I imagine that using blocking to transfer the lateral forces would interfere with the venting of the roof and therefore undesirable.