Design your Bridge

Overview

This is a configurator tool that create a parametric arch bridge based on a basic Arch bridge form as shown in the figure. The user will be able to change the form of the bridge based on user-defined inputs and create a Revit model for their own future works.

User-defined Inputs

Bridge Width

Bridge Span

Arch Height

Number of Arches

Number of Cables(hangers)

Structural Members Section Properties:

Bridge Cable Type

Bridge Arch Type

Live Load on Bridge

Outputs

Weight of the Cables

Weight of the Arches

Weight of the Deck

Weight of the Bridge

Estimated total cost of materials

Revit Model

Robot Structural Model

Dynamo Scripts

Figure 1

The inputs for Dynamo scripts as well as inputs shown in the Dynamo Player interface are shown in figure2 and Figure 3. All the dynamo input can be user-defined except for the type of deck and level of the structure. The default value of the bridge is 12-inch concrete and the level is set to be level 1. Moreover, users can modify the live load on the bridge if they want to conduct a simple structural analysis with the bridge.

Note: The bridge height should be smaller than the radius of the arch (half of the span/number of the arch) to avoid overlapping.

Figure 2

Figure 2

Users are allowed to determine the geometry of the bridge and the materials of each element. The scripts used to generate the bridge are shown in figure 4.

Figure 4

Based on the bridge span and width, a simple rectangular will be generated as the base form of the bridge deck. Then, the transverse sides of the bridge will be divided into several segments as defined by the number of arches. With the bridge height as the center point, the arches are generated through the dynamo function - an arc from three points. Then, the transverse sides and the arch are divided again based on a number of cables. The points generated on the arch and deck are treated as the start and end points of the cable.

Figure 5

After the Dynamo form is completed, the Revit model is generated with the Dynamo function - StructuralFraming. Then, with the inherent volume property of Revit elements, the weight of the element is calculated based on assumed density. For steel, the density is 400lb/cft and for concrete is 150lb/cft. Similarly, the cost of the material is calculated based on assumption that steel costs 0.42 per pound and concrete costs 4.43 per cubic foot.

To conduct structural analysis, the cable and arch of the bridge are converted to analytical bars and the bridge is converted to an analytical panel. Since the arc curves in Dynamo cannot be converted to curves in Robot directly. The arches are discretized into 20 short straight lines to simulate the curvy form. The 4 corners of the deck and 4 endpoints of arches are set as the supports in Robot and live load is applied to the bridge deck as surface load. Then, with the analysis package in Dynamo, results including max stress, max moment, and max displacement can be displayed on the dynamo. However, since the results shown in Dynamo is just a list and may be hard to follow, several Dynamo scripts are created to visualize the stress distribution. Therefore, the users are encouraged to use the Robot software interface to explore more structural analysis results.