1. Field of the Invention
The invention relates to an apparatus for temporarily increasing the load-bearing capacity of bridge girders, of the kind used in bridge cranes or polar bridge cranes.
When heavy components are lifted, an installed load-bearing capacity of existing bridge girders is often less than a capacity which is actually required. Such a situation arises, for instance, in unusual conversion or repair provisions in a power house of a power plant or other industrial plants, for instance when generators or steam generators in nuclear power plants are being replaced. Until now, in order to lift heavy machine parts or when placing other unplanned stresses on bridge girders, relief devices such as central support masts that are each constructed for a particular application which is involved have been put in place, or else separate hoisting tools have been installed at high cost.
2.Summary of the Invention
It is accordingly an object of the invention to provide an apparatus for temporarily increasing the load-bearing capacity of bridge girders, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which is universally usable and which is easily mounted.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for temporarily increasing a load-bearing capacity of a bridge girder, comprising portable supports having deflection pulleys; a relief cable associated with the pulleys; the supports, the pulleys and the cable temporarily mounted above bracing points of a bridge girder on both sides of a support point; and a load-bearing element carried by the relief cable for relieving the bridge girder at the support point.
Therefore, the object of temporarily increasing the load-bearing capacity of crane bridges is attained according to the invention by using a portable cable structure to reinforce the bridge girder.
In accordance with another feature of the invention, the relief cable has two ends and tensioning devices securing the two ends to the bracing points or to the bridge girder.
The supports are mounted on both ends of the bridge girder, above the bracing points and protrude upward beyond the bridge girder. The deflection pulleys that serve to receive the relief cable are associated with upper ends of the supports.
The supports are connected to one another by the relief cable, which passes over the two deflection pulleys. The relief cable is connected to the bridge girder at least at one point between the two supports, preferably in the middle of the girder. This is carried out, for instance, through the use of a load-bearing element having a lower end, for instance, which reaches under the bridge girder whose capacity is to be increased and supports it from below at this point. Thus an upwardly-directed vertical force, which engages the bridge girder at the support point, is generated from the height of the associated supports and the cable tension of the relief cable, which is tightened with the aid of the tensioning devices, such as hydraulic cylinders, or screw elements. The forces occurring as the relief cable is tightened can be favorably introduced advantageously and statically at end surfaces of the bridge girder through the use of an abutment that engages the bridge girder from below.
The load-bearing element associated with the relief cable acts like a center support that supports the bridge girder from below with a vertical force.
In accordance with a concomitant feature of the invention, the bridge girder is disposed in a power house of a power plant or in a reactor building of a nuclear power plant.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an apparatus for temporarily increasing the load-bearing capacity of bridge girders, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.