Assessing the Merit of F14T Super High Strength Structural Bolts

Abstract

Steel buildings and bridge structures across the United States currently utilize two main types of high strength structural bolts to transfer the forces developed in the connections between structural members. These bolts are designated by the American Society for Testing and Materials (ASTM) as A325 and A490, which can hold up to 120ksi and 150ksi respectively. Several countries across the globe have recently introduced new grades of high strength bolts to cope with increasing material strength and to enhance design options. The recently developed Japanese Industrial Standard (JIS) F14T bolt has an ultimate tensile strength of roughly 200ksi, 33% stronger than the A490, the strongest ASTM bolt. Although the F14T is considerably stronger than the A490, that does not necessarily mean the connection will be stronger. There are many ways a connection can fail besides bolt failure. The type of failure depends on many factors such as what kind of connection it is, what types of loads are being applied to the connection, and the material properties of all connection members. To determine the potential benefit of the F14T over the A325 and A490, all connection limit states must be investigated and calculated using the different bolts. Also, before this is done the standards and practices of each standardizing company (ASTM and JIS) must be researched to determine if the bolts can be directly compared or if some values must be changed for a fair representation of their differences.