Packing out a steel column with washers - is this OK ? 1

[threeReefs]

I'm having a forestry building put up, and the contractors have done this to compensate for slight variations in slab height. The building is steel-frame, 14m x 13m, 4m high. You're looking at the foot of a cold-rolled steel pillar - one of 10 structural pillars forming the main frame of the building - bolted to an L-plate which is in turn bolted to the slab.

I am an electrical rather than a structural engineer, but this looks wrong to me : the columns do not touch the slab, so the L-plate isn't just locating them, it's carrying the load, and that load will now go only through the washers - point load, and no stability in the forward/backward direction and not a whole lot in the other. OK, the building is rigid so it's not trying to hinge forward or backward, but I still don't like the look. Can someone tell me whether I should worry or is this fairly normal practice ?

Thoughts much appreciated.
Richard

 

[KootK]

It looks suspicious to me as well.

Do the drawings call for a grout bed beneath the post? Are the bolt holes oversized or slotted?

Even when there is no grout bed, one normally accomplishes something similar using nuts and washers above and below that get properly pre-tensioned.

These don't look like real structural use washers to me.

 

[Heaviside1925]

These look like wedge or sleeve anchors in a slab. It appears to be a light gauge pre-engineered building. Is this one of those cases where its "foundation by others" with no connection details? As KootK noted, these are typically grouted afterwards but I'd be concerned with uplift if no connection details were considered.

 

[Eng16080]

Without knowing fastener dimensions, column loads, etc. it’s perhaps unfair to form a strong opinion, but it certainly looks like somebody grabbed a bunch of bolts from the local hardware store to put together their building. Most projects I’m involved in use 3/4” diameter galvanized anchor bolts, which those do not look like. The washers look sketchy too, but I wouldn’t be too worried if the space is packed with grout.

 

[hokie66]

The 'anchor bolts' look like drilled in 'dynabolts' or the like. Cadmium plated, not galvanized. And the whole column is supported on two bolts in shear. The whole thing looks 'jerry rigged'.

 

[LittleInch]

Just so we all understand this can you sketch out the cross section of this rather odd looking joint.

You would normally expect the L plate would be bolted down first then drill the connecting holes.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cliff234]

A couple things look odd about this detail. First, the bolts appear to be post-installed expansion anchors. Second, the column flanges appear to overhang the baseplate. I wonder if this is a soldier column (resisting lateral loads only). I’ve never seen a column baseplate stop short of the column flanges. I hope the baseplate will eventually be grouted.

 

[dvd]

The bolts on the web make it look like this is a clip angle foot. Wondering what the opposite side looks like - is there a slotted vertical hole that is bottomed out?

 

[human909]

This is exactly the sort of thing I expect for what is often called down here in AS land as 'kit sheds'. All members are cold formed steel members from about 1.2-2.4mm thick. The base plate is a angle bracket hot rolled but pretty much everything else is cold formed.

Many are absolutely rubbish signed off by questionable engineers. Some are certainly fit for purpose, but plenty aren't. And those putting them together aren't exactly the good installers either.

In North America these might be classified as PEMB. But from my perspective North America PEMB's are less cowboy than Australian kit sheds. (On the other hand most industrial structures here that might be PEMBs in North America are engineered for the specific needs and location of the structure.)


Regarding the question at hand. The washers packing things out might actually be far more suitable than other parts of the structure!

 

[threeReefs]

Thanks for the replies, everyone - much appreciated.

This is (probably in the context of most of the members here) a small building, with all parts pre-cut / drilled and delivered to site for assembly by bolting together. The main structure is hot-rolled galvanised, about 3mm. Here's the whole thing :

For scale, the roof ridge is 4m and the eaves 3.5m.

The slab is drilled and then anchor bolts dropped in, the L-plate is put over the top of those and then nuts/washers (M18) to secure it - it's at this stage that the packing washers appear to be added, presumably to achieve a levelled set of mountings for the columns. Here's an anchor bolt :

The plates and columns are pre-drilled (everything is pre-drilled) so there's no scope to adjust here. I can see that a good approach would be mounting the plates, aligning the columns alongside and then drilling through & bolting, but that doesn't seem to be the approach here. None of the holes are slotted.

And yes, I notice that some of the anchor bolts have not been put in vertical.

I am really not happy about the way the frame has been erected - it looks like it was done in a hurry. Although it's all being done by one company - who have been helpful and professional in most areas - erection has been the classic series of fitters coming on site (Groundworks, then Steel, then Cladding etc) with no-one overall project-managing or QA checking on handoff. So I'm doing a snagging list and have a senior guy coming down later this week. Hence wanting some outside/expert input on the washer thing. If I'm reading the room right, the consensus seems to be that packing out with grout would be an effective solution here. Would you back off the nuts on the anchor bolts before pushing it into the gap and then tighten after ? Or just do it as-is.

 

[GeorgeTheCivilEngineer]

Build a timber shutter and use pourable non-shrink grout is the usual method here.

 

[thomastheman]

In general, I would say providing shim plates, covering more or less the entire surface area of the L-profile, should be provided when correcting for height deviations when grouting is not used. This will ensure the correct contact surface to the concrete. Doing it with washers like it's done here, the contact pressure on the concrete will be very high since the vertical loads are now transferred through a very small area. You should ask the contractor if they have done any reinforcement, like cast-in steel plates (doesn't seem like it from the pictures) to accommodate the high stresses that might occur in the concrete below the washers.

 

[dvd]

For a conveyor leg, I would swap vertical slots on vertical leg of angle and weld to column after adjustment. Not sure who makes that call at this point.

 

[human909]

Mate, you get what you pay for and unless you have totally been taken to the cleaners you didn't pay a fortune for a structure that size.

This is (probably in the context of most of the members here) a small building, with all parts pre-cut / drilled and delivered to site for assembly by bolting together. The main structure is hot-rolled galvanised, about 3mm. Here's the whole thing

A slight correction if I may. It is cold-rolled steel. The girts can be seen to be 150C1.5 aka nominally 150 deep and 1.5mm thick. From that scale the columns and likely the rafters are 250C24, 250 wide deep and 2.4mm thick.

It isn't a robust structure but may be fine for your purposes assuming they put it all together correctly. I did an audit on one of these recently and fly bracing and wind bracing was missing in many places, it had no hope of surviving ultimate wind loads even if it was constructed correctly.

On the plus side yours looks a little bit more suitably proportioned for the member sizes used.

I am really not happy about the way the frame has been erected - it looks like it was done in a hurry. Although it's all being done by one company - who have been helpful and professional in most areas

Real Estate agents and car salesmen can helpful and seem professional, but that is just sales. This is a 'kit' shed. They are often under designed and built by the cheapest labour available.

So I'm doing a snagging list and have a senior guy coming down later this week. Hence wanting some outside/expert input on the washer thing. If I'm reading the room right, the consensus seems to be that packing out with grout would be an effective solution here. Would you back off the nuts on the anchor bolts before pushing it into the gap and then tighten after ? Or just do it as-is.

There quite likely is a bigger list than just the anchor bolts, but getting a proper engineer to have a look at it probably isn't worth the cost to you unless this is a critical structure. If this is a non-habitable structure in area sheltered from wind then it probably will work for your purposes.

 

[EngDM]

Those trees blocking the wind are now structural trees.

 

[Brad805]

It looks like a fine shed, but it is just a shed. Look at the documents to see what they said they would supply. In the time of this thread you could have dry packed the base plates with grout.

 

[DoubleStud]

I don't think those expansion anchors are strong enough to resist the uplift. Did someone engineer the foundation?

 

[dvd]

I don't think those expansion anchors are strong enough to resist the uplift. Did someone engineer the foundation?

I asked myself if the slab was too thin those anchors look set mighty high. Maybe the anchors are set high to keep them in the slab.

 

[human909]

You guys keep acting as though you expect a proper engineer to have designed this and signed off on this. Nah MATE, the kangaroo down in the back paddock signed off on this. This is an Aussie 'kit' shed renowned for being under designed and under built!

I am assuming this is Australian. The first photo was a big clue. The second shows what seem very much like Eucalyptus tree in the background which all but confirms it.

I don't think those expansion anchors are strong enough to resist the uplift. Did someone engineer the foundation?

There might be some engineer involved somewhere. But that doesn't mean much for one of these.

I agree the foundation would likely not withstand uplift and ULS. And if this is in a cyclonic (Wind Zone C & D) or semi-cyclonic region (B zone) then that is even more funny for everybody but the owner.

 

[Heaviside1925]

human909 I appreciate your Aussie vernacular and fully agree with your sentiment. Plenty of these kits floating around the US and contractors more than happy to install them.

OP,
I doubt you will make much headway talking to a "senior guy" or whatnot. They will likely "do some stuff" to make you feel better, like grouting the bases but will do nothing to address what human909 is saying. So now comes the question, how do you make the best of a not great situation. You could hire an engineer but the cost of the repairs to bring the building to a fully code compliant structural state will likely be more than the building itself cost. My only other though would be, consider better anchoring. At least then, if a windstorm comes, you might have a collapsed building, but I would think that would be better than part or the whole thing going airborne. But maybe not because then you would have a clean pad to build the next one on.