Following manufacturer specification 1

[Mixtli]

Hi everyone,
I have been asked to stamp an assembly drawing for a precast culvert, for which I have no issue, after I review a number of things. But the concern is that the specified lifting pins don't pass when I do my calculations. I have been told by my manager that they will run the issue by the pin manufacturer and if they deem it good to go I should stamp the drawings just as they are with the specified pins; He says that I should be covered with the email or letter from the manufacturer approving the pins for the intended use.

The questions are:
a) am I really covered?
b) should I have the word "by others" right after the spec of the pins?
c) should we eliminate any reference of the pins on the drawing I stamp and issue another drawing only to spec the lifting pins?
d) Is the manufacturer's responsibility to stamp their approval of the pins? or their name is enough for taking responsibility for them?

Thanks a lot.

M.

 

[JedClampett]

This doesn't sound acceptable to me. Unless you're happy with the whole drawing, don't seal it.
Once you seal it, you own the whole thing.

 

[IRstuff]

It's your license on the line, not theirs, assuming they even have a license. They need to, and should be able to, convince you that their approach or calculation is correct.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //

http://www.engineering.com/AskForum/aff/32.aspx

faq731-376 forum1529

 

[thaidavid40]

"Lifting pins specified by others, and shown for reference only. Verify with manufacturer for the loads given in the drawings."
Dave

Thaidavid

 

[RHTPE]

Mixtli - What does not pass - the pins, or the effect of the lifting pins on the precast element?

If the concrete can handle the forces exerted on it by the pins, I would go with thaidavid40's disclaimer on the sealed drawing and move on. If the pins are to be supplied by the same entity producing the precast and are an integral part of the product, then you need to resolve it.

The lifting pin is a "below the hook" lifting apparatus that has a number of OSHA requirements associated with it. If it were me, I would avoid getting into it if that is possible.


Ralph
Structures Consulting
Northeast USA

 

[Mixtli]

Thanks all,
Hi Ralph,
As per Appendix D of A23.3 (Canada) it doesn't pass neither, concrete and pin, for tension and shear individually and of course it doesn't pass at the interaction of both; so do you think Thaidavid's note wouldn't be enough?

I am checking on WSIB (Canadian) if there is anything like OSHA's requirements; does anyone know about it?

Cheers and thanks again

M.

 

[RHTPE]

Mixtli - If your review is only for the precast element, and if you find that the means to lift that element will damage it, then no, I do not think that the note suggested by thaidavid40 will cover you.

Is this intended to be a 4-point pick?


Ralph
Structures Consulting
Northeast USA

 

[Mixtli]

Yes it is a box culvert with 4 point lifting, so there is Tension and shear combined.
Also, when removing from the mold, the pick up is in flower pot position, so there is shear in two directions.

 

[TehMightyEngineer]

We moved all our engineering house (aka, I got hired by the precast company I currently work for) as so much about our work was specified as "design by others". However, if the precaster you're working for doesn't have an in-house engineer then it sounds like they've hired you to do this engineering. If that's the case, then taking part of the design and giving it back to the precaster as "lifting pin design by others" would be poor practice in my mind because you are the "others".

I'd work with the precaster to find a solution that works for both you and them. The cost of the lifting inserts are going to not be huge cost to them and is much cheaper than breaking a box culvert (or worse; hurting someone).

In our shop we use Patterson or Dayton Superior "dog bone" lifting pins, they have very large capacities and often give more than enough strength for all but our largest of box culverts. They're dirt easy to design with and in a box culvert you should have plenty of room to avoid edge distance effects.

But, regardless, it's your stamp on the plans. Don't let them push you into something you're not comfortable with, this should be something that you can both find a solution on. The only thing I would add is most precasters will have a good idea of what works and what doesn't as far as lifting point layout and design. Even if they've never looked at appendix D they will do a lot of work with overhead cranes and lifting precast pieces; and should likely be quite knowledgeable about how to safely install lifting inserts.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[RHTPE]

Mixtli - Attached is my impression of the yard operations leading to the field install of the culvert section. When you say "Flower pot" I'm assuming you mean that the open ends of the culvert are top & bottom.

What I see done in my area for handling catch basin sumps & sections are 2-4 holes cast into the concrete. Smooth eye-bolts are slipped into those holes and the rigging attaches to the eye-bolts. Precast septic tanks have notches cast into the 4 corners and a different sort of rigging is used to lift the box.

The culvert section has to be rotated from its mold position to a transport and/or setting position. The operations are shown in 5 steps on each page of the attached.

AS I see it, you really only have to deal with the shear forces in both the eye-bolt and the concrete. If they are using proprietary lifting inserts as TehMightyEngineer suggests, then you should research the inserts and lifting attachments provided by the manufacturer (i.e. Dayton or an equivalent).

Ralph
Structures Consulting
Northeast USA

 

[Mixtli]

Hey guys, sorry it took me a couple of days to respond.

They finally went by my calculations and we installed the pins I suggested. Now I am pushing for the construction of a table that would allow them to choose the the lifting pin depending of weight of the culvert and position of the pins.

Cheers and thanks

M.

 

[Mixtli]

Hi guys,
The matter is not closed yet......

With further research I learnt that the pin manufacturer do their calcs based on ASD design to determine their capacity.
Here is what happens: when they have a special structure they can't find a solution on the manuals, say Dayton's (Canada), they email the vendor the structure's drawings to be handled and the vendor do their calculations and recommend the pin to be used.
Now, these calculations are done following the ASD method. They requested calculations from Dayton once and they also follow ASD.

The codes I utilize is A23.3 and CHBDC, which both are LRFD. Under these codes the pins don't pass.

So can you guys comment on the implications of stamping some out of jurisdiction calcs? or stamping a design done under ASD, that is not covered by Canadian codes?

Can we consider ASD not "legal" in Canada?

Going a bit farther, if something happens, knock on wood, would insurance pay even when the ASD is not "legal" in Canada?

All these underground structures are sold and installed in Ontario, Canada

Thanks a lot for your input.

M.

 

[TehMightyEngineer]

I don't know about Canada but in the US the only requirement I'm aware of for lifting of precast pieces is a safety factor of 3 for the lifting hardware cast into the precast piece. How you determine the safety factor is left up to the designer but is typically done through ACI 318 Appendix D, which uses LRFD. As OSHA asks for a safety factor you could argue that an ASD approach is the only valid approach.

As for your situation, it really depends on what the actual requirements governing the lifting pins is. If you have similar laws as the US does, then I don't think ASD is "illegal" if appropriately applied. Though, theoretically both ASD and LRFD approaches should result in the same design.

If it were me, I'd make sure the calculations were rational and passed a reasonable double check. If so, then I'd say it's acceptable (but still the precasters responsibility for safe design). Sounds like you have an issue with your calculations not matching theirs, in that case I'd see if there's any conservative aspects you can more accurately calculate. Otherwise you're in the position of either approving it despite your numbers not matching (not what I would do) or requiring them to revise their design and resubmit.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com