Structural Bolts Feb2609 DONE Fastenal（结构螺栓Feb2609 .完成）.pdf

Structural Bolting ASTM A325 and ASTM A490 are the two U.S. standard structural bolts. When looking at the mechanical requirements of bolts it appears that an ASTM A325 and SAE J429 Grade 5 are identical as do the ASTM A490 and the SAE J429 Grade 8. This begs the question, “Can an SAE J429 Grade 5 be used when an ASTM A325 is specified?” The answer is definitely no. This is also the case for substituting a Grade 8 when A490 is specified, and here are some reasons why: First, A325 and A490 bolts are produced with a heavy hex head configuration which provides a wider bearing surface over which to distribute the load. Grade 5 and 8 bolts are produced to standard hex cap screw configuration and therefore cannot distribute the load as much as is needed for structural applications. Second, the shank length (non-threaded portion of the body) on the A325 and A490 bolts is designed to be greater (shorter thread lengths) than your standard hex bolt or hex cap screw. Remember, the weakest section of standard carbon steel fasteners is through the threaded region. Minute design changes such as this can create a stronger tensile connection. Third, the difference in thread length is also likely to result in a change in shear strength. The following two diagrams Notice the Grade 5 has a much smaller head demonstrate this difference: configuration and a shorter shank then the A325 structural bolt. If both bolts are ¾-10 x 4, Bolt X has the shear plane acting through the body of the bolt, while Bolt N has its shear plane acting through the threaded portion. Assuming that both fasteners have an ultimate shear capacity of 72,000 PSI, just how many pounds would each fastener be capable of handling? To determine the load in pounds, one must first calculate