A devilish grin amongst the details?

Some of the facts of life on this planet (commercial construction in the USA) :
• You are governed by lots of documents (contracts, plan, specs, ASI’s …)
• Plans often have conflicts, improbabilities, or impossibilities within them.
• Specs are almost always flawed, in serious or minor ways.
• The plans and specs are often in conflict.

When first going through the documents you cannot always know if the architect is serious or pulled an “oops”. Sometimes this is true on second pass. Sometimes resolution of a tiny detail can be prolonged. We have a job to supply pieces of precast concrete that hold plates that somehow help diffuse air through sewage during treatment. Or something like that: truth is I do not fully understand the system of which these pieces are but one part.

Section through precast diffuser plate holder

Section through precast diffuser plate holder

Full section  (Link is for those who want to see the section so big that they can read it)

One end has a special metal casting for the air inlet. This we embed in the precast concrete;  the metal piece is supplied to us by the GC (for my comments on that casting see https://planetcommercialconstruction.wordpress.com/2013/01/23/minor-mentoring-is-a-pleasure/ ). The other end has a lifting insert that we buy. Normally no big deal, but this one is unlike any ever seen by me or by the 3 other gray-haired buddies I consulted with.

Also unusual is the mention of bolting to forms – makes no obvious sense in the context. And the capacity of a 1” bolt is an order of magnitude more than the piece weighs. Why use a 1” lifter? Maybe there is a reason. Maybe not.

This being a very large (=bureaucratic) owner, I over-communicated to avoid rejected submittals. So both on the shop drawing and in a separate substitution request, I stated my assumptions, questioned the insert, and proposed something more appropriate. All in a manner both crisp and thorough. That was Feb 18 (this year). Since then I received a formal approval on everything but the substitution of the insert – it was stated it had to be for a 1” bolt. Normal, readily available inserts don’t look like this one and vaguely similar ones are deeper (because bigger bolts mean more capacity means more embedment in the concrete) and there is not room for a deeper insert where the insert goes in the piece. So I made a formal request for a vendor and part # for this now-elusive insert. I also again asked what this 1” bolt does. Yesterday (March 14) the GC called; he was still trying to get answers and said he would call an engineer at the agency.

Today, I still don’t know if there is a function for the 1″ bolt (GC may not even use the insert for lifting) , or if this is an insert that exists in another realm or on a different planet (we looked at plumbing catalogs but nothing matched) or if the reviewer who rejected it just is a stickler for enforcing whatever someone else once wrote down . Or maybe someone is “just kidding” about the 1”. Time may tell. I’ll let you know. Those of you who live on other planets may find this story bizarre, but anyone  living on planetcommercialconstruction will find it quite normal.  While this uncertainty about simple things can be annoying, it keeps this business from being predictable, routine, and boring.

Advertisements

About Leo Schlosberg

Graybeard with experience in commercial construction and IT, and an interest in information flow and process. Aware and respectful of the enormous complexity, technical, legal, and other, embedded in every structure that is part of the built environment.
This entry was posted in knowledge. Bookmark the permalink.

One Response to A devilish grin amongst the details?

  1. Where does one comes up with wire fabric that is bent and hooked, let alone in a 6″ wide section? After designing precast for many years (some gray hairs), I have seen very oddly proposed sections, which are not typically done as shown. If I were designing it, I would probably just use the fabric flat (6′-4″) long and probably 4 vertical bars similar to that shown on the diagram.

    If you are going to call out a lifting insert, then I would show a realistically used lifting insert. This appears to be the air inlet casting insert scaled down. Also, if this is a precast piece, lifting inserts preferences vary depending on the precast contractor used. The precaster would probably prefer to pick it at 1/5 points, and not at the ends, but again, this depends on the stripping, shipping and erecting methods, and precaster used for the production of the piece.

    You say a 1″ diameter bolt, inserts will project outside the piece, typical rules of thumb are to have the same engagement depth as bolt diameter. Also see links below. If you only have 1/4″ of thread interlock, depending on strength of bolt and nut material and pitch of threads, a reduction of capacity should be calculated. I would not count on the first couple threads, especially if they are tapered.

    http://www.gizmology.net/nutsbolts.htm
    http://www.fastenal.com/content/feds/pdf/Article%20-%20Screw%20Threads%20Design.pdf

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s