The metal superstructure of small lengths, as a rule, replaced with the assistance of jib, gateway, and console consolability taps under the guise of “Windows” in movement of trains. This cantilever crane GEPK-130-17,5, you can replace the spans with low ride length up to 45 m. the Length of the “window” is 6 to 8 h. the Minimum duration of the “window” reach in cases, when the new span is in advance delivered to the bridge and installed in a position convenient for taking cock.
Replacement steel spans up to 25 m specially designed cantilever-beam crane is composed of beam, carriage and lifting winches. Move the crane locomotive. When replacing the spans of the cantilever beam of the crane work performed in the following sequence (Fig. 134). On the next to bridge separate paragraph or directly from the bridge cross the moving sum under the new crane superstructure. To install the superstructure a crane having a bridge removed and replaced superstructure (I position). Then the crane is moved to position II, install a new superstructure and after the restoration the way the crane is removed the superstructure was gone, and the closest split points, or unload the superstructure of blizkost axle path, and from there move on platforms prepared in advance. Released the crane in the same sequence used for the second replacement of the superstructure, etc.
When replacing spans of cantilever cranes should be borne in mind that the jib crane due to insufficient boom cannot zastroitj the center of gravity of the superstructure with a length of 45 m. To avoid the distortion of the superstructure when the lift should be on the short end to tuck the weights. The value of the cargo is determined by actual weight of the superstructure and the eccentricity of lifting points.
Spans longer than 45 m replace transverse relocation, or using floating equipment. The methods of conducting the work specified, as well as used equipment studied in the course “Organization and planning of construction of bridges”. However, the requirement of minimum restriction of traffic during the reconstruction of the bridges makes the features in these methods the replacement superstructures.
So, when replacing the spans of the transverse displacement of each span from the upper and lower sides erect scaffold for the Assembly of the new and dismantling the old spans, as well as arrangements for their relocation. When replacing the same superstructures with the aid of floating equipment self-arrange piers to build new and dismantling the old spans, and also use two sets of floating equipment — one for removal and one for installation of superstructures.
The method of replacing the spans chosen on the basis of feasibility analysis with consideration of the legislative period of the reconstruction of the bridge, and when replacing the spans in the navigable bays, also, and shipping requirements.
Replacement of superstructures transverse displacement can be carried out in any season and in almost any local conditions. At the same time, the replacement of the spans with the use of watercraft is limited in time, and in many cases impossible due to the insufficient depth of the river. When the techno-economic assessment of ways to replace the spans to a first approximation we can assume that the replacement of using floating equipment cheaper replacement, relocation, transverse, with four spans or more.