The nominal resistance of the various bridge components, such as flexural members, webs in shear, and fasteners (bolts or welds), is given by equations in the LRFD Specification.
Each nominal resistance must be multiplied by a resistance factor, @ , which is a statistically based number that accounts for differences between calculated strength and actual strength.
The @ factor, Table 11.10, provides for inaccuracies in theory and variations in material properties and dimensions. Expressions for the nominal resistance of many types of members are given in other sections of this Handbook. The nominal resistance of slip-critical bolts is considered in the following.
Field connections in beams and girders are almost always made using high-strength bolts.
Bolts conforming to AASHTO M164 (ASTM A325) are the most used types. AASHTO M253 (ASTM A490) are another type, but are rarely used. The LRFD Specification requires that bolted connections subject to stress reversal, heavy impact loads, severe vibration or where stress and strain due to joint slippage would be detrimental to the serviceability of the structure be designed as slip-critical. Slip-critical connections must be proportioned at Service II Limit State load combinations as specified in Table 11.8. The nominal slip resistance, Rn, of each bolt is
