Data introduction. Bridge cranes

The issues surrounding the introduction of the bridge crane is varied and many articles have been published regarding the matter. In this case, the most simple case is going to be explored: a bridge crane in a warehouse consisting of a single symmetrical bay, although the process will be explored for a two bay warehouse.

For a warehouse consisting of one symmetrical bay, the introduction could be resolved in the following manner:

  1. Ungroup the frames and select a single frame; the centre frame, for example.

  2. Create an additional live loadcase where the loads of the bridge crane producing the worst case will be introduced. This situation will be, for example, the crane situated to the left and braking transversely whilst it is displaced to the right. All the loads will always be placed in the same live load loadcase where:

    P: Weight of the bridge
    G: Weight of the crane
    Q: Load to lift

    The left support will have an applied vertical load of: P/2 + G + Q
    The left support will have to resist a horizontal load to the right of: (P/2 + G + Q)/10
    The right support will have an applied load of: P/2
    The right support will have to resist a horizontal load to the right of: (P/2) / 10

    All these loads and braking load fractions have to be provided by the manufacturer of the bridge crane, although in this case, the most common values have been used.

    If you wish to contemplate another possible situation (because the frame is not symmetrical, for example) the job can be duplicated in another file, deleting the previous loads and introducing the new loads.

    As the live load of the crane is being applied at one of the ends of the bridge, the program will not provide symmetrical baseplate and footing results. The user will have to match these for both supports.

  3. The longitudinal braking of the bridge crane will be calculated in a separate file, with a longitudinal braking force of: (P/2 + G + Q) / 7.

If there are two adjacent warehouses, and symmetrical, it may be resolved in the following manner: The loads of the left bridge assigned to a live load loadcase called LL1, for example, and those of the right bridge to another live load loadcase LL2.

As an additional comment, to simply mention that the various live load loadcases are combined amongst one another, by default, (although this can be reconfigured). Therefore, a combination always exists which adds the simple live load loadcases that have been defined. This is not the case for simple wind loadcases; these are independent.

Having said this, a central frame of the warehouse is analysed in four separate files, without the rest of the structure.

  • First file: left bridge crane with crane to the left and right bridge crane with crane to the left.
  • Second file: left bridge crane with crane to the right and right bridge crane with crane to the right.
  • Third file: left bridge crane with crane to the left and right bridge crane with crane to the right.
  • Fourth file: left bridge crane with crane to the right and right bridge crane with crane to the left.

    The four load combinations are to be defined in the program so to mirror the following cases:

    • Neither bridge exists
    • Only the left bridge crane exists
    • Only the right bridge crane exists
    • Both bridge cranes exist

Of course, each file must have the corresponding wind loads applied.

The results of the worst case sections, footings, baseplates, etc. of the four files are those which must be used.

The longitudinal braking of the bridges is also resolved independently.

Regarding the runway beam. In a similar manner, the user will have to create as many independent files as there are positions to be studied along the beam. In each file, the reactions of the two wheels of the bridge crane trolley have to be applied in the same live load loadcase. 

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