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
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?
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.
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
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
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