Boggo Road Pedestrian Bridge: Cross River Rail - Parametric Design

Cross River Rail is a 10.2km rail line between Dutton Park and Bowen Hills, which includes 5.9km twin tunnels under the Brisbane River and Brisbane CBD. As part of the package RBG provided BIM management for the Boggo Road Cable Stayed Pedestrian Bridge. The Pedestrian Bridge includes the following defining features:

• Cable stayed bridge crossing the Queensland Rail corridor
• Length of approx. 110 metres with a total deck width of 7 metres
• Consisting of two spans (a western span of 36 metres and an eastern span of 74 metres)

Parametric Design

The use of parametric design in structural modelling is becoming an essential aspect of staying ahead in complex projects and meeting clients’ requirements. Recognising this opportunity, RBG developed a script to construct a digital parametric model for the east and west ends of the bridge. This was done to help facilitate any changes in geometry that might take place during the design stage.

To tackle the challenge of managing potential changes in geometry during the design process, the technician and engineering teams devised a solution. They decided to build a parametric design script that would be flexible enough to accommodate any modifications to the bridge’s position, design surface, and structural design requirements.

The teams worked closely together to identify all the possible parameters that could drive changes to the bridge. They then compiled a comprehensive list of input requirements necessary to construct the bridge. With these inputs in hand, they created the bridge script, which would serve as the foundation for the parametric design.

The script was designed to hold all the design parameters and input specifications and was constructed in a hierarchical manner. Starting with the civil engineering surface level, the parameters were built from the top down, incorporating all the design details all the way down to the piles. In this way, the script was able to support the bridge’s entire design, with its parameters adjusting automatically in response to any changes that might occur.

In the parametric design of the bridge, each structural component was related to every other component in the design. If the design surface changed its position, all the structural elements beneath would adjust accordingly to conform to the new design surface. Another illustration of the parametric nature of the script was the ability to modify the head stock type. If the Structural Engineer made this change, the supporting column would automatically adjust to align with the new specification.

As the project progressed, more geometry such as splice connection plates and diaphragm stiffener plates were incorporated into the parametric design script. There were established guidelines, in the form of parameters, for the type of stiffeners, spacing, and thickness. By building these rules into the script, quick changes could be made to the model, and this in turn facilitated efficient documentation.

The next elements that were integrated into the parametric design script were the numerous guardrail posts. Manually modelling each post to the proper height and aligned with the road centreline would have taken many hours of modelling within Revit. The architectural location was linked to the engineering design specifications for the post structural member type, baseplate, grout, and any additional stiffeners that needed to be added to the girder. Upon completion of this process, RBG was ready to document the geometry in Revit. To accomplish this, RBG utilised the Rhino.Inside.Revit plugin, which enables geometry from Rhino to be brought into Revit. All geometry from Rhino was incorporated into Revit using three different methods for the Cross River Rail project:

Not only was RBG able to automate changes using parametric design, but RBG was also able to push all parameter data required for the project geometry elements. Rhino.Inside.Revit gives you an advantage to read and write parameters to Revit families. Therefore, RBG could push data from the Excel Data source to the Revit Model parameters. Parametric Design was successfully delivered on the Pedestrian Bridge and has potential for application on future RBG projects. RBG was able to automate modelling tasks, and adjust models quickly to revised referenced documents and changes made by RBG Structural Engineers. The use of RhinoInsideRevit also helped RBG streamline documentation and data behind its Revit models to production drawings. RBG looks forward to using this and other parametric processes and tools more in the future.

A heartfelt thank you to all those who were involved in the Boggo Road Pedestrian Bridge for the Cross River Rail project.