Highfields Cycleway Bridge Design

The Highfields Cycleway Bridge project involved a high level bridge structure located at the intersection of Obrien Rd and Barracks Rd, that meanders through a heavily treed landscape across Klein Creek. The creek is subjected to flooding and extends between two steep batters. The design scope involved engineering design, specifications and documentation for handover to the client, Toowoomba Regional Council. The Harrison Infrastructure Group (HIG) as project managers were required to liaise with client to achieve funding and approval and meet all compliance regulations surrounding the bridge. HIG engaged the services of TEG to undertake the preliminary and detailed structural design of the cycleway and prepare engineering drawings as part of a joint project with Toowoomba Regional Council and Transport Main Roads Queensland (TMR).

The role required the following:  

• Review of geotechnical reports and Hydraulic Studies.
• Calculating design loads for the superstructure including pedestrian, hydraulic, wind and earthquake loading as per Australian standards.
• Modelling of the bridge superstructure using Spacegass, RAPT and other software.
• Detailed design of bridge superstructure components including headstock, blade wall piers, abutments, pile caps and screw piles.

TEG provided a complete work package that included:

• Preliminary & Detailed Design, Documentation Specifications involving selection and co-ordination with stakeholders.
• Liase with FRP Composite bridge supplier for a Callander Hamilton Style Superstructure.
• Safety in Design Risk Assessment.
• Safe Work methods construction methodology.
• Certification of the works to current Australian Standards.

TEG undertook all design and documentation for the construction of the cycleway super and substructures. Including the concept design and development of construction methodology and budget estimate of the project. The final product being a project package ready for construction.

TEG faced a number of challenges not normally associated with bridge design.

• Steep embankments in heavily treed area with restrictions to clearing and disturbance of natural topography.
• The needs to design for a stepped bridge alignment in 3 sections.
• Construction methodology for limited site laydown area and installation.
• High superstructure level, with hydraulic loading.

TEG resolved all issues as follows:

• Adoption of Callander Hamilton FRP bridge superstructure that could be manufactured off site and craned into place over 3 spans, within the tree line clearing.
• Use of screw piles and pile cap to reduce earthworks footprint and ensure that adequate capacity achieved based on Geotech report
• Design & Development of what we have called a Headstock biscuit which enables the change in span alignment across the headstock to follow the zigzag bridge alignment required.
• Adoption of precast Headstocks and blade Walls that will be post tensioned to lock the superstructure in place in preparation for the superstructure.