Various steels
are used to fabricate bridges. The upper boxes are mainly
made of SM490Y steel, lower chords are made of SM570,
diagonal members and vertical members are made of SM520,
crossing beam, lower lateral member, and lower flower
systems are made of SM400.
Lower chords carry high axial load so that high strength
Quenched and Tampered steel(SM570) was used. Because they
are also subjected to large stress range, they are classified
as fatigue critical members. Fabrication of the Large
Truss Block and Yard AssemblyTruss was erected using the
large block erection method and the member erection method.
The connection between members and large blocks were made
by high strength friction bolts except steel deck plates
which use field welding. Small and Large Scale Fatigue
Test The Q&T steel has lower fatigue strength so that
fatigue strength of welding details and the panel points
were tested.
The tested details with lower fatigue strength were no
welding gusset, butt welding, load carrying cruciform
joint, and web gusset. In the large scale fatigue strength
of the truss panel point was tested using the large truss
test specimen.
