SUSPENSION BRIDGES DETAILS
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Here are more details of the SBEF
erection method :
With the pulling machines from TRC, the catwalk may be prefabricated and simply
pulled over instead of being assembled in the span or on site.
The center section is being transported to the lifting position under the main
cables. In this drawing, on a barge, but the girder section will float, and may
be towed into position.
The section, some 150 m long in this case, is connected to the lifting machines
situated under the girder at the hanger pad-eyes, and lifted off the barge or
out of the sea. A hydraulic power pack, and a control system / computer in a
small cabinet is what is needed. The lifting may be performed by remote control,
or the crew may actually be on the section during lifting.
Increasing the length of the sections from 12-36 meters, witch is common, to
more than half the span, will increase the forces in the outer hangers, hence
the bending moment on the girder section. From the curve, it becomes clear that
it is advantageous to fit either short sections, or very long sections ( full
span). If not, TRC has devised a load distribution system smoothing the load
between the hangers, and at the same time taking care of the geometry of the
main span cables.
The mid section is lifted up using the pulling machines. Note the two inspection
/ welding platforms under the girder. These will be used for welding the
girders, removal of lifting machines and later for inspection and maintenance.
The two side- sections are lifted up under the control of the computer system in
order to make a smooth transition and curvature on the main span cables.
The end sections are lifted and moved sideways if needed. Note that all the
girder sections, 5 off in this case study as opposed to 25 to 70 in
traditional bridge building, is complete with lighting, railing, asphalt etc.
The final welding of the 5 sections has been done, and the asphalt patched in
the welding zones. The bridge is now ready for use.
This method also makes it possible to construct the girder in aluminum,
thus reducing the weight and in fact toe total investment cost as well as
maintenance cost.
This graph show the cost saving in the different areas.
The cash flow curves for the different designs and building methods clearly
show that there are savings both in time and money.
Advantages :
TR Consulting 
