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CHAPTER THREE
FABRICATOR PRACTICES AND VIEWS
This chapter discusses fabricator practices and views related to a minimum of three girders. Two assemble pier diaphragms
steel bridge erection, as reported in the questionnaires and and two others assemble with crossframes--one only if they
follow-up telephone interviews that were part of this synthesis. attach to the web and flange. One also may drill crossframe
connections from the solid in assembly.
GIRDER ASSEMBLY PRACTICES
Curved Box-Girder Assembly
Girder assembly refers to the shop practice of assembling
girders to drill or ream the field splices and in some instances All respondents that fabricate boxes do bearing-to-bearing
test-fit the crossframes. Questions pertain to whether the gird- and/or a minimum of three-girder assembly. Five assemble
ers are assembled with the webs vertical or horizontal, the curved box girders with crossframes. Two others assemble
number of girders that are in an assembly, and whether the them with crossframes if the geometry is complex and one
crossframes are assembled with the girders. assembles them with crossframes if the radius is less than
500 ft. Two others assemble them with pier diaphragms only.
One also drills the crossframes in assembly.
Straight I-Girder Assembly
Most of the fabricators, that is, 13 of 15, assemble the gird-
ers with their webs in the horizontal position without cross- FIELD CONNECTION PRACTICES
frames. The other two assemble them with the webs vertical,
The fabricators' opinions on proper field connection prac-
generally without crossframes. Several fabricators test-fit sev-
tices of erectors are briefly summarized in this section.
eral crossframes if there is a large skew or complex geome-
try. Six fabricators assemble bearing to bearing (several with
a minimum of three girders). Nine assemble a minimum of
Drift Pins
three girders. One fabricator pointed out that the issue of the
minimum number of girders in an assembly depends primar-
The proper use of drift pins during erection was the most com-
ily on span lengths, individual girder lengths, and the radius
mon issue reported by the fabricators, who noted the following:
for curved structures.
· Erectors do not use enough pins.
· Some erectors take the position that if they can install a
Curved I-Girder Assembly
bolt, they do not need to use pins.
Ten of the fabricators assemble curved I-girders with their · Erectors need to use full-size pins.
webs in the horizontal position. The remaining five assemble
them mostly with their webs vertical, the exceptions being
when the radii are short. (The responses included limits of Crossframes
less than 1,000 ft, 600 ft, and 500 ft, depending on the fabri-
cator.) Eight fabricators assemble bearing to bearing, and the Sufficient crossframes need to be installed to stabilize the
balance use a minimum of three members. Of those that structure. Other comments provided by the fabricators rel-
assemble the girders with the webs vertical, a large number ative to crossframes include that progressive assembly of
will assemble some, many, or all crossframes for test-fit, crossframes and bolted crossframes for skewed bridges are
depending on the complexity of the structure. difficult to do.
Straight Box-Girder Assembly Bolt Tightening
Of the 15 fabricator respondents, 13 fabricate box girders. Bolts should not be tightened until a horizontal and vertical
Nine of these fabricators assemble bearing to bearing and/or alignment of the members has been made and accepted.
