I am installing some A325 bolts, and I am using direct-tension-indicator (DTI) washers. Does the DTI replace the F436 washer that I would normally use, or do I still use a standard F436 washer?

dti-washer-configurationsAccording to the Research Council on Structural Connections (RCSC December 31, 2009 edition), an F436 washer is used in addition to a DTI washer with an A325 structural bolt.  RCSC’s Specification for Structural Joints Using ASTM A325 or A490 Bolts, Section 6 Use of Washers, states that a ASTM F436 washer is always used, but the location where the washer is used depends on how the bolt is being installed and location of the DTI washer.

6.2.4 Direct-Tension-Indicator Pretensioning: When the direct–tension-indicator pretensioning method is used, an ASTM F436 washer shall be used as follows:

  1. When the nut is turned and the direct tension indicator is located under the bolt head, an ASTM F436 washer shall be used under the nut;
  2. When the nut is turned and the direct tension indicator is located under the nut, an ASTM F436 washer shall be used between the nut and the direct tension indicator;
  3. When the bolt head is turned and the direct tension indicator is located under the nut, an ASTM F436 washer shall be used under the bolt head; and,
  4. When the bolt head is turned and the direct tension indicator is located under the bolt head, an ASTM F436 washer shall be used between the bolt head and the direct tension indicator.

Essentially, the location of the F436 washer varies depending on whether the nut or the head of the bolt is being turned, and also if the DTI washer is under the head of the bolt or under the nut.  However, in all situations an ASTM F436 hard washer is used as part of the connection.

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2 comments

    Thank you for being a resource for all questions related to bolting.

    Is there ever a reason to put DTI’s under both the head of the bolt and the nut? Such a configuration does not seem logical but is being requested by an owner.

    Please advise.

    Thank you.

    Travis Konda

    @Travis- We have never heard of a DTI being used both under the head and the nut. It does not seem like it would make sense, but we are far from experts on DTIs. You might contact one of the two manufacturers of DTIs, Turnasure or Applied Bolting. They would have more insight.

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