Design of Connections for Steel Members - Design of Modern Steel Railway Bridges - page 361

the thickness of the thinnest part in the joint, in which case care must be taken to
provide adequate preheating of the weld area.
The minimum connection plate thickness recommendations of AREMA (2008)
should preclude cutting of an element, plate, or component by fillet weld penetration.
Maximum filet weld size, a max , is recommended in AWS (2005) in order to avoid
excessive base metal melting and creation of potential stress concentrations. The
maximum fillet weld size is the thickness of the thinnest of the plates or elements
in a joint for elements or plates with thickness less than 1/4 in. The maximum fillet
weld size is the thickness of the thinnest plate or element less 5/64 in. for joints with
thickness of the thinnest plates or elements greater than 1/4 in.
The minimum effective length of fillet welds is generally recommended as 4 a .
AREMA (2008) recommends that fillet welds used to resist axial tension that is
eccentric to the weld line or cyclical tensile stresses must be returned continuously
around any corner for a minimum of 2 a . AREMA (2008) also recommends that
wrap-around fillet welds not be used when welding intermediate transverse stiffeners
to girder webs.
9.2.3 J OINT T YPES
Welds are used in lap, edge, “T,” corner, and butt joints. Welded lap joints are gener-
ally used only in secondary members and edge joints are used only in nonstructural
members. However, “T,” corner, and butt joints are commonly used for main girder
fabrication and splicing of steel railway superstructure elements.
Welded lap joints ( Figure 9.4a-d) are simple joints sometimes used in secondary
members of steel railway bridges. The joints in Figure 9.4a-c are typically subjected
to eccentric loads. Figure 9.4d shows a type of lap joint used to connect attachments,
such as stiffeners, to girder web plates. Lap joints typically use fillet welds.
Welded “T” and corner joints (Figure 9.4e and f ) are typically used to connect web
plates and flange plates of plate and box girder spans, respectively. “T” and corner
joints may use fillet or groove welds and are typically subjected to horizontal shear
from bending along the longitudinal weld axis.
Welded butt joints (Figure 9.4g) often join plate ends (such as at girder flange and
web plate splices) with complete penetration groove welds. Butt joints are also used in
welded splices of entire elements or sections. There is no force eccentricity in typical
butt joints, but, particularly in tension zones, butt joints require careful consideration
of residual stresses. ∗ Weld and connection element transitions for butt welded plates
of different thickness and/or width are recommended by AREMA (2008). Butt joints
should not be used to join plates with a difference in both thickness and width unless
the element resists only axial compression. † Edge preparation and careful alignment
during welding are critical for good quality butt joints.
∗ Stress relieving is often required.
† Stress concentrations may be large for butt welded connections subject to tension.