AISC


6.3. Verification Testing

6.3.1. What constitutes evidence of material conformity for high-strength bolts, washers, and nuts?

RCSC recommends that purchase orders require the following as evidence of conformity:

1. That the vendor provides certification that the bolts, nuts and washers furnished conform to all requirements of the referenced ASTM specification.

2. That the certified manufacturer’s mill test reports supplied that clearly show the applicable ASTM mechanical and chemical requirements together with the actual test results for the supplied fasteners.

3. That the bolt heads and the nuts of the supplied fasteners must be marked with the manufacturer’s identification mark, the strength grade and type as specified by ASTM specifications.

4. That, for projects requiring slip-critical connections, the lubricated bolt, nut and washer be preassembled to assure proper fit of the bolt and nut and the assembly tested for strength to meet 1.05 times the requirements of Table 8.1 of the Specification for Structural Joint Using ASTM A325 or A490 Bolts prior to shipment to the purchaser.

6.3.2. When must the purchaser test high-strength bolts and why must they be tested if the manufacturer has already done so?

Section 7 of the RCSC Specification requires pre-installation verification “only as indicated in Section 8.2.” In other words ,pre-installation verification is only required when the bolts are to be pre-tensioned. ASTM Specifications are adequate and appropriate for the strength and quality of the separate components, but may not be representative of the factors and conditions that determine performance of the fastener assembly during installation and service as it is used in construction. For one example, the bolt itself is tested for strength by the manufacturer by screwing the bolt into a standard testing fixture and subjecting it to pure tension. However, in usual applications, bolt tension is induced by torque on the nut and the bolt is subject to combined tension and torque, which may cause the bolt to fail at a load less than its strength in pure tension. RCSC states that pre-installation verification is necessary to:

1. Confirm the suitability of the complete fastener assembly, including lubrication, for pre-tensioned installation.

2. Confirm the procedure and proper use by the bolting crew of the pre-tensioning method to be used.