Tension Indicators
Tension Indicators
(OP)
On a recent project visit, I was made aware that a client is performing structural steel erection using A325 and A490 bolted connections. These connections are being made using direct tension indicators. The client has waived any type of testing of impact devices based on a preliminary test of a representative samples of these devices.
The client also specified that these connections are not "shear". Being new to AISC specifications, I have a few questions.
DTI's are designed to "squirt" upon a certain tension being attained from an impact device. If a device has not been recently tested, how is OVER tensioning of the bolt avoided ? The client actually said that as long as the bolt does not break it's not over-tensioned .
What constitutes a shear and moment connection ?
Any and all help would be greatly appreciated from a person who has had structural steel erection thrust upon him !!





RE: Tension Indicators
The latter seems to be likely your case as I see no reason to have specific and otherwise expensive inspection procedures for establishing bolt tension. The fact that the client chooses to use load indicating washers is evidence of the nature of the connection and desire to reduce inspection costs as well assure quality.
From my perspective, the bolts/washers should be tested using the Skidmore-Wihlem apparatus (commonly used on site or in tesing labs). The SW reads bolt tension and can be used to determine when the washer activates. This will ensure that the washer is working properly. THis may have been done already and the lot of washers certified. Then the inspector need only watch to see that the ironworker doesn't needlessly sit on the bolt longer than necessary. It will otherwise be obvious that the proper load has been achieved.
Obviously, the client is wrong in stating that "as long as the bolt doesn't break its not overtensioned". We know that the bolt may yield prior to fracturing. However small.
RE: Tension Indicators
Also as QShake noted, only slip critical connections really need to be checked for proper tensioning. On bearing connections, it's nice to have all the bolts tightened consistently, but actual bolt tension is somewhat irrelevant, assuming they are reasonably tight (snug tight is the preferred industry term).
RE: Tension Indicators
RE: Tension Indicators