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Why do we typically use A325 bolts rather than A490 bolts? If A490 bolts are used what test procedures are followed?

DWQA QuestionsWhy do we typically use A325 bolts rather than A490 bolts? If A490 bolts are used what test procedures are followed?
Todd Grzych Staff asked 5 months ago

Why do we typically use A325 bolts rather than A490 bolts? If A490 bolts are used what test procedures are followed?

1 Answers
Best Answer
APF Expert Staff answered 5 months ago

A490 bolts are heat-treated steel structural bolts with 150 ksi minimum tensile strength and 170 ksi maximum tensile strength. Quoting from the “Guide to Design Criteria for Bolted and Riveted Joints” Second Edition, by G. Kulak, J. Fisher And J. Struik, ” The higher the strength of the steel, the more sensitive the material becomes to both stress corrosion and hydrogen stress cracking. A490 bolts are more susceptible to brittle fracture than A325 bolts which are 120/105 minimum tensile strength steel. To minimize the risk of brittle fracture A490 bolts have both a minimum and a maximum tensile strength specified.
FHWA recommends that A325 bolts be used wherever possible. The use of A490 bolts should be thoroughly evaluated prior to being included in a structure.
When A490 bolts are included in a design the following items should be included in the project specifications or inspection requirements.

  1. The certifications for the A490 bolts should be reviewed when the fasteners are received to assure the tensile strength is within the limits in the specification.
  2. The Rotational Capacity (RC) test shall be performed on all combinations of fastener assembly lots by the manufacturer or distributor and by the fabricator or contractor at the time of installation. The RC Test should follow the procedure used for A325 bolts with the appropriate A490 tension values in the tables of the procedure. During the performance of the RC Test the maximum tension values should be observed to assure they do not exceed the upper limits of the specification. In addition to the requirements of the RC test, if the bolt tensions are outside of the specified limits the fasteners shall be rejected.

In addition to the above notes, the fasteners shall be properly stored, the installation verification tests shall be performed and the standard installation procedures shall be followed.

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