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