structural bolt, hex heavy bolt, ASTM A325 TYPE1
Structural Bolts are a heavy type of hex bolt intended for use in large structures, such as buildings and bridges. Usually sold with a heavy hex nut (2H) & heavy washer (F436) included.

The ASTM A325 specification covers high strength heavy hex structural bolts from 1/2" diameter through 1-1/2" diameter. These bolts are intended for use in structural connections and therefore have shorter thread lengths than standard hex bolts.