bolt tightening

By Lawrence (*****)

Date 09-25-2009 14:27

Diddn't the non-conformance report site the text portion (reference) of the of code that he thinks you did not comply with?

By jwright650 (*****)

Date 09-25-2009 15:14

I'd review the report like Lawrence pointed out.

By bert lee (**)

Date 09-25-2009 16:05

no nothing, it only say the bolts are not in snug tight condition.

he claimed that once you erected the components, it should be final.
no more tightening and the final inspection shall be done on the ground not after erection.

By Joseph P. Kane (****)

Date 09-25-2009 16:06 Edited 09-25-2009 16:08

Bert

Were you supposed to have made the connections "Snug Tight" as described in the RCSC, or just bolt to ship? I have seen contractors misinterpret what was meant by the contract specification, and just tighten the bolts so the end connection angles and splice plates remained in place during shipment. One thing that gave one of the contractors away was that the faying surfaces of the connected elements were not drawn up in intimate contact. Many people do not read the tight contact requirement, and think they just have to hand tighten the bolts.

Joe Kane

By jwright650 (*****)

Date 09-25-2009 17:24

Me too Joe...scary to see clips and bolts laying on the bed of the truck when the steel arrives at the jobsite.

By eekpod

Date 09-25-2009 17:47

At a minimum we always have the bolts "snug tight". But we aware, snug tight means "the full effort of an ironworker using and ordinary spud wrench or a few hits of an impact gun to brings the plies into firm contact". Snug tight does NOT mean snug tight, run the nut up by hand.
I have to explain this to all our new guys because at home in the garage snug tight means just that, nothing too tight, but in the steel industry, its different. The full effort of an iron worker using a 14" spud wrench can get a bolt/ nut pretty dam tight.
Even our bolt to ship parts get "snug tight" just for the situation you had, so they don't rattle loose on the road and go through someones windshield.
In my opinion, I'd say your shop didn't do what was required, but that's just my opinion, good luck.
Chris

By 803056

Date 09-25-2009 21:57 Edited 09-26-2009 05:01

Eekpod said it all very nicely.

As for the inspector, it sounds like he gets around on the steel like a squirrel, a ground squirrel that is.

Connections that are assembled and tightened in the shop are not routinely inspected in the field unless there is something suspect. Shop bolts should be checked in the shop before the connections are painted. Routine observation is all that is required for snug tight, but again, the fabricator has to understand the terminology.

Where is the shop QC during the assembly and snugging of the shop bolts? Does QC understand the difference between the classes of tighness, i.e., snug tight, pretensioned, and slip critical, does he have a copy of the appropriate AISC Steel Construction Manual with information about the use of washers, which nuts are to be used with different types of bolts, etc.?

Here it comes, hold it, hold it; Does the shop QC have the AWS bolting endorsement? Sorry, I couldn't resist throwing that out into the ring.

Best regards - Al

By bert lee (**)

Date 09-26-2009 00:11

the steel components were secured and the bolts were tightened during shipment,
but in our mind, the bolts tightness of the parts members will have a final check after erection.

is it a common practice to perform the final inspection of bolt tightness after erection?

By rfieldbuilds (**)

Date 09-26-2009 02:10 Edited 09-26-2009 02:18

From a TPI inspection perspective, An engineers perspective when issueing a directive that all bolts be snug tight, I would INTERPRET this to meen that his calculations are meant to be based on all HS bolts being snug tight after completed erection. He would want to see the HS bolts being in a snug tight condition after erection. Any condition such as seismic loading or possibly during application of live loads. As a TPI, I feel that my job is to insure that that requirement is met. If you need clarification, the engineer is the responsible party to contact. That being said, I cannot see an engineer requiring anything less than a snug tight condition on site after erection practices have leveled and plumbed a building.
I often times have to qwell an owners concerns on plumbness of erected structures, and tell them that sometimes, bolts are loosened to allow play in the connections so that they can be brought into proper alignment. My experience is that after these onsite conditions meet the AISC requirments, snug tight conditions can be checked to insure they meet contract specifications.

And yes, travel and other unforseeable loads can loosen a snug tight connection. That is why in most contracts, fabricators choose to use TC HS bolts. These are tightend after erection, plumbing and field welding are complete. This should be the goal of any AISC certified erector and should (as mentioned above) be a part of their written procedures.
Also, These bolts supplied in-house during fabrication are now subject to sampling, testing (skidmore) and inspection in-house, prior to shipment.

By bert lee (**)

Date 09-26-2009 03:28 Edited 09-26-2009 03:30

thanks mr rfieldbuilds and to the rest.

By 803056

Date 09-26-2009 05:00

In New England, as a general practice, shop installed bolts are shop tightened. The only time they would be checked in the field is if they had to be loosened in the field and retightened.

The fabricator has to perform verification testing before installing the bolts just as the field crew does. The installation of the snug tight shop bolts would be observed by the TPI if the owner requires it or if it is required by Special Inspections.

I cannot remember the last time I saw shop installed bolts left in the loose condition unless they were purposely left loose to keep fittings such as splice plates from being misplaced. Shop installed bolts, typical of double angle and single clip angles at the ends of a beam, do not need to be shipped loose for the purpose of plumbing the structure. The field bolts generally allow sufficient movement to plumb the structure. The field bolts are tightened once the structure is plumbed .

With the popularity of "TC" bolts, it is rare to see fabricators hand tighten snug tight HS bolts. It is usually faster to have one man tighten the connection with the electric gun than to have someone tighten them by hand with a spud. It is also an advantage to be able to visually check the "TC" bolt to see that it was tightened. As Joe mentioned, snug tight still requires the bolts to draw the iron tight, the use of the electric gun is faster and provides visual evidence the bolt was tightened. If the worker installing the HS "TC" bolts snugs the connection before "snapping the splines", it is generally accepted the connection is fully compacted as required for all conditions of tightening, i.e., snug tight, pretensioned, or slip critical.

Best regards - Al

By Mikeqc1 (****)

Date 09-26-2009 20:01

I inspected in a bridge bearing shop for 6 years and we either Drove the bolts home, or shipped the plates and hardware seperate. We were never were asked to "Hand tighten" them.
MDK

By Joseph P. Kane (****)

Date 09-27-2009 19:26

Mikeqc1

The term "Bolt to Ship" (BTS) is often used. In that case,the pieces are not usually tightened to any code. I have seen them hand tightened, impact gun tightened, and even had galvanized nuts or bolts mixed with non-galvanized nuts or bolts. (The mix of galvanized with non-galvanized fastener components often does not allow full tightening, and often the nuts cannot be unscrewed.) Since these are just shipping bolts, and they have to be replaced in the field, it is usually the fabricator's choice. It is my opinion that the better "quality" shops are more conscientious.

In my experience, usually bridge work shops fully pretension all the bolts. In NY State, bolts have to be tensioned using the "Turn of Nut" method, and TC Bolts are not generally used. If components, such as girder splice plate,s are to be shipped, the State requires them to be stamped in a defined location that specifies which face and which direction the plates were installed during progressive assembly and drill off. Some of the smaller components such a "End Connection Angles" to be installed on minor sub-assemblies are occasionally sent "Wire to Ship" or"Bolt to ship", but very rarely.

Joe Kane

By Jim Hughes (***)

Date 09-27-2009 16:13

Concerning TC bolts. We have had nothing but problems with them. From not geting the joint tight enough to iron workers cheating by breaking the ends of and then installing them and tighting them with a spud wrench.
I saw a very interesting DVD the other day showing the difference bewteen TC bolts and DTI's. They had a skidmore with a window covering the gauge so you could not see. They stuck the TC bolt in and then tightened it until it sheared. When they opened the window the bolt was to be 39 kips and the gauge only read 25. They did this 10 times and 9 times the bolt failed to reach the required kips before shearing. They did it with slightly rusty, and then with bolts taken directly out of the bolt container, and finely with bolts slightly lubed. They did the same exercisee with DTI's and 10 out of 10 times the bolt was tensioned corectly.

Has anyone done this exercise or seen this exercise?

Thanks
Jim Hughes

By 803056

Date 09-27-2009 17:36

I've had problems with DTI washers and TC bolts both, but the problem with the TC bolts was easily addressed.

The only problem I've had with TC bolts, other than the human kind, was when they were tightened in very cold weather. They snapped at some rather low values. The solution was to wait a couple of hours until it warmed up and they tightened without further problems.

The DTI washers were related to manufacturing issues. The entire batch of seveal kegs was bad. The 1 inch A490 bolts would snap off before the protrusions would crush. Being ever resorcefull, the workers would hammer the protrusions before installing the washers.

Best regards - Al

By swnorris (****)

Date 09-28-2009 17:57 Edited 09-28-2009 18:00

Bert,

Part of your initial post was this: “we did the bolt tightening (snug tight) of steel structural components at the workshop before delivery to site”.

Did you truly follow the RCSC requirements regarding snug tightening? 8.1 of the RCSC defines the snug tightened condition as the tightness that is attained with a few impacts of an impact wrench or the full effort of an ironworker using an ordinary spud wrench to bring the connected plies into firm contact. This is common knowledge. If you followed this for each bolt and did nothing further, that may be your problem. I say this because 8.1 requires the compacting of the joint to the snug tight condition by progressing systematically from the most rigid part of the joint, and, further states that more than one cycle through the bolt pattern may be required to achieve a snug tightened joint..... similar to how nuts are tightened on a car rim. Since you received a complaint that some of the bolts weren’t tightened properly, I have to wonder if you followed through with additional cycles during the snug tightening process to ensure that each bolt was brought to a snug tight condition. This is the only thing that would make any sense to me as to why some bolts were reportedly not tightened properly. Either that, or maybe everyone had it in their minds that all the bolts were going to be tightened after erection anyway, and didn’t really follow through properly.
Pretension is not required for the proper performance of a snug tightened joint, so no further tightening is required beyond the snug tightened condition.

As for the extent of inspection requirements for snug tightened joints in accordance with 9.1 of the RCSC, this consists of verification that (1) the proper fastener components were used, (2) the connected elements were fabricated properly, and (3) the bolted joint was drawn into firm contact.

The only other thing is that if this turns into a pissing contest, you’ll probably need some sort of QA/QC documentation showing that the requirements of 9.1 were followed in your shop, which should have been part of the in-process inspection during the fabrication of the job.

By eekpod

Date 09-28-2009 19:19

DTI's suck in my opionion. I havne't seen that video your talking about but it sounds like its from a manufacturer of DTI's.
Yes TC bolts are not perfect, and you do have to watch how they are stored and installed. Once guys understand how it works and you keep an eye on them there shouldn't be any problems. (unless their lazy and want to cheat).
The biggest thing that stinks about TC bolts is you can't re-lubricate them, so extra caution HAS to be taken in their storage containers before they are used. You can't have crews leaving pallets of kegs open w/ out covers at the site filing up with snow and rain, your just wasting money because the manufacture will only allow you to use their special sauce/ lubricant and its usually not worth the time and money at that point.
DTI's can be very particular with the gap and the miniscule gauge that is used to check the gaps. Yes the squirters make it easier, but there are even different levels/ amounts of "squirt" and some inspectors will say, "that didn't squirt enough" while your saying "look it came out, give me a break". Also since they can be artificailly flattened with a hammer, I personnally think its easier for someone if they wanted to cheat by taking a hammer to the bumps, vs snapping off the TC bolts prior to installation, but thats just my opinion.
Chris

By jwright650 (*****)

Date 09-28-2009 19:36

Cheating by breaking off the splines of a TC bolt sounds like more work than it's worth. I'd rather just let the TC gun do the work, than to go to all of that trouble.

A couple problems that I've seen with TC bolts was in regards to furnishing the correct length so that the gun would engage the splines correctly and not strip the splines off before shearing off the end.

and.....We had some problems with a few galvanized TC bolts and not being able to get the gun to engage the splines due to the extra thickness of the coating on the bolt splines.

By waynekoe (**)

Date 09-28-2009 21:56 Edited 09-28-2009 22:03

In over eight years, I've only had to reject one lot ot TC bolts during the pre install verification test, and had only one real problem with the tensiong sequece prior to pre tensioning, these were two inch thick truss splice plates and were pretty much due to the ironworkers laziness. If there was that much of a failure rate in the skidmore test in the DVD, I would be pretty suspect. It just depends on who's telling the story like was mentioned above. Each type of pre tensioning method have their drawbacks and their advantages.
Personally, I can't see where if the specs call for the shop bolts to snug tight, that would could expect them to be tight when they arrive at the jobsite. All that jostling around during transport is going to looosen snugged connections. I would go back and revisit the the specs for the structural steel-shop bolted connections. But, I could be wrong

By Joey

Date 09-29-2009 05:00

Bert,

Obviously there is some variation in the degrees of tightness obtained under the snug tight conditions. If the choice is to use spud wrench and the bolt tightening is to be witnessed by your client, you get an ironworker having an arm size bigger than the client :)

It is essential to have the agreed ITP (Inspection & Test Plan) prior to the start of work, this will guide you on test frequency and requirement... whether shop test or after erection. But it will be good to confirm the bolt tightness after the structures have been erected (provided accessible). Anyway, light hammer taps can be used to test the tightness of bolts., which I think will give you a quick result.

Regards
Joey

By Jim Hughes (***)

Date 10-01-2009 12:18

Just like a lot of issues with the inspection world there are a lot of opionions out there with concern to TC and DTI's bolting. To answer eekpod about who produced the DVD, in the spirit of full disclosure it was produced by a bolt manufacture who sell both DTI's and other type of bolts. They don't sell squirters.

I threw that question out there because we have had problems with TC bolts and it's easy to say "once guys understand how it works and you keep an eys on them there shouldn't be a problem". From the replys it sounds like people have had issues with both.

Thanks
Jim Hughes

By Atorroja Date 10-03-2009 10:56

Ok, the NCR was issued. Then the problem is how to close this item. Is a post mortem activity. I have not idea what's the way to close this NCR. May be, you need to prepare a tightness procedure for the next delivery?

By eekpod

Date 10-05-2009 10:33

That's what I would do to clear out this situation if I had it. Basically you identified the problem (loose bolts in the field) , wrote an NCR, now you have to find a way to keep this situation from happening again in the future, and one answer is to create/ implement a shop bolting minimum requirement procedure. This is assuming you are the shop fabricator.
Write a proceure, make "snug tight" the mimimum requirement, train your fitters and welders on the official defintion of snug tight, make sure they do it with periodic inspections, and you should be ok.
I would actually consider this an CAR because it's a procedural issue. Iv'e had NRC's create CAR's because of the severity of the issue, if this were my shop I would write an CAR refrencing the NCR, but if your not an AISC certified shop, disregard this statment, it won't apply to you. Good Luck, Chris

By bert lee (**)

Date 10-05-2009 14:45 Edited 10-05-2009 14:51

we've closed the ncr by retightening the bolts in the presence of inspector hired by the client. this was done on the ground before erection.
after tightening of bolts in snug tight condition, inspection report was generated which is signed by client's inspector.

for the next bolt tightening, our shop manager has decided to invite the client for witnessing, this work becomes a "hold point" before delivery of items to erection site.
although i still believe that bolt tightening after erection is necessary, which should be considered as final.

this ncr helps us by removing our responsibilities on bolt tightening after erection, this new arrangement is favourable to us (bolt tightening at fabrication shop is much easier).

i think the ncr was issued in a careless manner.

bert