Design Challenge:
The design challenge is to create a parametric model of a cable-stayed bridge, ensuring that the number of cables and the spacing between the crossbeams are perfectly aligned with the length of the bridge.
Parameters:
The user can adjust the following parameters:
| Input Parameter | Unit |
Range |
| Ratio Outer Field Inner Field | double | 0.3…0.5 |
| Length of the bridge | double | - |
| Pylon Ratio H/L | double | 1/5…1/4 |
| Pylon height under superstructure | double | - |
| Number of Carlanes | integer | 0…3 |
| Pedestrian lane? | boolean | - |
| Bicycle lane? | boolean | - |
| SuspensionCablesMainField | integer | - |
High Performance Criteria:
The model can independently determine a sensible spacing of the crossbeams in the main and side spans.
Additionally, the program can provide feedback on whether the number of cables in the main span has been chosen appropriately.
The model also incorporates the High-Performance Criteria, which ensures that, based on the selected number of traffic lanes, bicycle and pedestrian paths, and the calculated spacing between the crossbeams, it independently computes a structurally sound height for the crossbeams.
As an additional output, it also provides the traffic loads per running meter.
3 Design alternatives
Combined Pedestrian and Street Bridge
The first option is a 700 metre long bridge with 2 lanes, cycle paths and footpaths. The ratio of the outer spans is 0.4. A number of cables between 26 and 38 is recommended for this alternative. Due to the parameterisation, however, 27 cables would create too great a distance in the outer fields, so 28 cables were selected here. The height of the cross members is 3 metres.
Pedestrian / Bike Bridge
The second good alternative is a possible but unusual design. For aesthetic reasons, footpath and cycle path bridges are also regularly constructed using a cable-stayed design. In this case, the recommendations for the length of the bridge no longer apply, as it is not primarily a question of cost-effectiveness but above all of the appearance of the bridge.
For the reasons mentioned above, a 250 m long pedestrian and cycle bridge was modelled here using a cable-stayed design. The programme suggests arranging between 10 and 13 stay cables in the main span. Here, 11 cables were arranged.
Motorway Bridge
The third alternative is a 1 km long motorway bridge with three lanes, without footpath and cycle path. The optimum number of cables is between 34 and 50; 48 cables were selected. Here too, the required crossbeam height is calculated at 3 metres.
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