There is a famous saying: 'How do you eat an elephant? One bite at a time!'. Or, in other words: cut the elephant into pieces. That means, dividing something big, which is difficult to handle, into smaller parts, which are more manageable. A similar method can be used when approaching a difficult or complicated project. On the Randselva Bridge, because of its size, early in the project it was decided to divide the models into 8 substructure parts for every single axis and 3 superstructure parts.

What is most important, is to divide the structure into practical construction parts, according to the production method of the contractor. This is why, for instance, the substructure had 8 independent models. For each axis from 1-8, the model comprised piles, foundation, and column. In that way, the working team from the contractor could open just the relevant model that they needed for the production.

Figure: One of the parts of the substructure, a model of axis 2 with piles, foundation, and column

In the tender phase of the project, because of the time schedule, the contractor decided to start building the superstructure in three places: on axis 2 (free cantilever method), on axis 3 (also free cantilever method), and on axis 8 (moveable scaffolding system, or MSS). For that, three sets of equipment were employed. As a result, the designer divided the superstructure into 3 parts:

• From axis 1 to axis 2,5 - Free cantilever method
• From axis 2,5 to axis 4 - Free cantilever method
• From axis 4 to axis 8 - Moveable scaffolding system

Another advantage of dividing the project into parts are smaller models (with less file size), which could be opened and managed more quickly. However, there is also a challenge connected with these divisions: the design team needs to remember the interface between the models. For example, the starting reinforcing bars that are in the superstructure, need to be modeled in the columns, since they will be executed in the first place. The designers should make quality control by merging the models together and checking if the interfaces between the parts are taken care of.

Pictures: Different construction methods of the superstructure, with 3 independent sets of equipment