The Four North West Rail Bridges were originally constructed as early as 1885, and have gradually been deteriorating due to the exposure of wind and the saline environment. The bridges are all in exposed locations along the North West Coast of Tasmania, close to the Bass Strait. The original constructions were timber ballast deck. An analysis of options lead to recommending the complete replacement of the existing structures.
Forth River Rail Bridge
The works included the design and construction of a new 135 metre, 4 span reinforced concrete bridge with new concrete sleepers and a full length walkway together with 490 metres of new rail approaches with improved curvature.
The benefits of the new bridge is increased load capacity to 300LA, improved rail alignment, a 100 year maintenance-free structure and the potential to re-purpose the heritage listed original rail bridge.
Due to a serious incident piling occurring (non VEC related) within the construction industry, VEC took the proactive steps to design a piling support mechanism that would prevent such an occurrence happening again. Workplace Standards inspected our innovation and were impressed with VEC’s solution. This innovation was nominated for an award at the Worksafe Tasmania Awards.
Due to incorporating all lessons learnt from the Blythe, Don and Leven River Rail Bridge projects, this project was completed on budget and three months ahead of schedule.
Leven River Rail Bridge
The project comprises of the design and construction of a 160 metre long railway bridge. This construction required the use of a false-work bridge to build the bridge over water. The false-work consisted of steel beams spanning between timber pile bents, a timber deck and running boards. This system was designed to accept a 70t pile driving rig, a 30t pile driving excavator and a 160t crane.
The VEC Planning System was utilised for project planning and delivery to ensure a safe, deliberate and successful execution. Extensive project specific planning activities were held.
VEC utilised the propriety false-work system, as improved from the Blythe River Rail Bridge project. The redundant bridge beams were used from the Blythe River Rail Bridge Project to act as supports for de-launching the Leven River Rail Bridge Superstructure. Underwater explosives were utilised for the removal of piers in a deep section of the river.
Blythe River Rail Bridge
VEC’s modular false-work system allowed for an expedited construction with flexibilities in design accounting for site conditions. Steel work from the false-work system could potentially be used for all rail bridge projects with minor modifications.
Precast ballast retainers allowed the ballast retainers to become part of the deck form-work for pouring of the deck. This reduced the overall construction period.
VEC’s demolition methodology allowed the safest most efficient demolition of the redundant structure. The superstructure was strengthened and jacked up, heavy duty rollers were welded onto the redundant abutments and piers and the entire superstructure was progressively de-launched directly into a loading bay where the beams were carted away for lead paint decontamination.
Don River Rail Bridge
With only a 84 hour rail closure, the Don River Rail Bridge was the most challenging of the four projects. After months of extensive planning and preparation, the VEC crew completed the works over the Christmas period and were able to open the track 6.5 hours ahead of schedule. Critical planning and hourly programming checks ensured the team were completing works as per schedule.
There were four original mass concrete piers with a more recent reinforced concrete footing extension protecting the base of the pier. The abutments were also mass concrete of similar construction.
Upon re-examination of the final concept design, VEC’s Design Engineer advised that the specified strengthening work would only guarantee a maximum live load rating of 250LA. Once this constraint had been formally communicated to the client, VEC worked with the Design Engineer to develop a proposal to replace the old riveted wrought iron beams with new welded beams and a new precast concrete deck, thus replacing the entire superstructure in order to achieve the target load rating of 300LA and a 60 year design life.
This proposal also mitigated the requirement to remove the old lead paint onsite, therefore removing any potential environmental issues related to the paint removal.
When the final design was approved for construction, VEC was able to start fabricating the precast elements in our precast yard and procuring and modifying the steel beams to achieve the approved design.