One bolt ledger- quick sanity check 3

[SleeplessEngineer]

I specified one bolt ledger to support this steel stringer, since there is not enough space to add another bolt (8" min distance reqd. at brick wall).

The steel stringer is also supported on the LVL beam through bolts. GC did not want to add bent plate to bear on it since they didn't want to disturb existing floor finish. Through bolt alone fails by wood bearing stress, so I added this seat angle which would be connected to brick wall. After the supplier produced the drawing per what I specified, I start having doubts on having just one bolt. Can someone be kind enough to share their views?

 

[Eng16080]

I don't think there's anything wrong with using a single bolt provided the connection can resist the required loads. I'm assuming that you're not trying to resist any moment at this connection, only vertical load.

Through bolt alone fails by wood bearing stress

Not sure I understand what you mean by that. Normally, I wouldn't directly check wood bearing stress in a bolted connection. Maybe you mean dowel bearing strength, which is checked as part of the yield limit equations of NDS Section 12.3.

 

[XR250]

Why not use a longer clip and more bolts in the wood?
Never seen A325 bolts being used for wood to steel construction.

 

[lexpatrie]

Single bolts used to be a big no-no as I recall, but that was for structural steel.

This is a stair stringer which is specifically not structural steel, as well as having what looks like multiple load paths (if all the bolts fail the stringer can be "trapped" laterally by the supporting beam and the connection at the bottom to the floor to provide some measure of reserve strength, and all the bolts failing sounds very unlikely, unless there's a drastic design error in there somewhere.

If we are taking F_cp, bearing stress on the wood, first off, there's some implicit crushing in the "elastic" range, up to 0.73 F_cp, more crushing beyond that, but the crushing is a check to protect finishes, not a life-safety check, if you ask me.

Is this a normal stair or some sort of ornamental showcase showdown stair that 500 people will gather on to celebrate something?

 

[Eng16080]

Never seen A325 bolts being used for wood to steel construction.

Me neither, although for certain conditions, per the NDS equations, you can get much higher connection capacities using the higher strength bolts. I forget the particulars now (of course).

 

[lexpatrie]

Are you wanting to see an A307 bolt here then?

 

[XR250]

I think part of the problem is finding an A325 bolt with no threads at that length. I imagine wood bearing controls so having a higher strength bolt here will not likely yield any benefits.

 

[SWComposites]

why not just make the L be a L6x3x3/8 and add two more bolts thru the LVL? A lot simpler than adding the extra ledger L.

 

[DoubleStud]

Why not connect to the top of the beam? You still have 3" space to finish floor. Maybe make the end plate an upside down L that goes over the top of the beam?

 

[Eng16080]

I imagine wood bearing controls so having a higher strength bolt here will not likely yield any benefits.

For this connection, I think you're probably right. A double shear connection, on the other hand, can benefit quite a bit from the higher strength bolts. To be fair, I'd be afraid that the contractor wouldn't use the high strength bolts if I had specified them.

 

[XR250]

Even so, most would specify a Grade 8 bolt in lieu of A325 if higher strength is needed

 

[SleeplessEngineer]

Thanks everyone for your input.
@XR250 TBH I did not even notice the bolt specification until you pointed out. This is a steel supplier, and they specified their typical bolt type. I only specified sizes through email, and they prepared drawings. Good point, I will pay more attention next time!

@lexpatrie it is just 10' simple stair going to mezzanine level on one corner. Nothing fancy.

@doublestud yes, I wanted it to bear on the beam with bent plate too; I don't want to rely on bolt bearing. But they don't want that since the finishes not to be disturbed.

 

[Eng16080]

XR250, Yeah, that's true. If bolt strength is the limiting factor, then Gr 8 or A490 would be better.