Design of Connections for Steel Members - Design of Modern Steel Railway Bridges - page 378

TABLE 9.4
Minimum Required Bolt Pretension for High-Strength Steel Bolts
in Slip-Resistant Connections

Minimum Required Bolt Pretension, T bP (kips)

Bolt Diameter, d b , (in.) A325 Bolts A490 Bolts

1/2 12 16 (AREMA uses 15)

5/8 19 24

3/4 28 35

7/8 38 (AREMA uses 39) 48 (AREMA uses 49)

1 50 (AREMA uses 51) 62 (AREMA uses 64)

1 2

98 (AREMA uses 103) 140 (AREMA uses 148)

be subjected to eccentric loads. Figure 9.10c shows a beam splice arrangement using
bolted lap joints. Figure 9.10d shows a type of lap joint used to connect attachments
such as stiffeners to girder web plates.
Bolted “T” and corner joints (Figure 9.10e and f ) are rarely used to connect web
plates and flange plates of plate and box girder bending members in modern steel
railwaysuperstructures.However,“T”andcornerjointsmaybeusedinthefabrication
of built-up axial members.
Bolted butt joints (Figure 9.10g) are typically used in join plate ends in a similar
fashion to the flange splice joints shown in Figure 9.10c.

9.3.4 B OLTED J OINT D ESIGN

9.3.4.1 Allowable Bolt Stresses

Forces in a connection are transmitted through the effective shear, bearing, and tensile
strength of the bolts. Bearing-type and slip-resistant connections exhibit different
behavior in effective shear, but similar bolt bearing and tension behavior.

9.3.4.1.1 Allowable Effective Shear Stress
The allowable effective shear force on bearing-type connections is based on the allow-
able shear strength of the bolt shanks in the joint. Slip-resistant connections have an
effective shear strength based on the magnitude of the prestress force and the shear
slip coefficient of the steel connection elements. Following the failure of slip-resistant
connections, the connection will behave as a bearing-type connection.

9.3.4.1.1.1 Allowable Effective Shear Stress in Bearing-Type Connections
Figure 9.11 illustrates that the behavior of a bolt under shear load is inelastic and
without a well-defined yield stress. Therefore, bolt strength is determined based on
ultimate shear strength. Experimentation has shown that the ultimate shear strength,
F bv , is in direct proportion to the ultimate tensile strength, P bU , and is not affected
by bolt prestress (Kulak et al., 1987). Therefore, the allowable shear stress of a bolt