As part of a continuous research and development program, we have successfully developed a timber bridge replacement system for use in road and foot bridges. The system can either replace damaged and deteriorated timber bridge components or provide a complete overhaul of the whole structure including replacement of girders, corbels, headstocks, whalers, bracing and handrails. Some of the advantages of using Wagners Fibre Reinforced Polymer (FRP) in the rehabilitation of timber bridges include its availability and high quality, durability, sustainability and design.
Scarcity of good quality hardwood timber unfortunately brings lower grade timbers which have high variance in structural properties and do not reach the strengths required into the market. Our composite sections are pultruded by an automated process which ensures each unit has the same structural and material properties. We have a stringent quality assurance process for each batch produced ensuring every product is of the highest quality.
Using composite bridge components significantly reduces the whole-of-life cost of the structure. A study performed by engineers from Cairns City Council found that a 50-year whole-of-life cost of a hardwood superstructure was almost two times greater than an equivalent FRP superstructures. Wagners FRP are not susceptible to durability issues that traditional materials such as timber and steel suffer from (such as termite attack, borers, decay, corrosion etc.). All our products are UV-stabilised with a coat of protective UV-resistant paint which ensures long-lasting durability. Our girders have also been fatigue tested to 1.2 million cycles and exhibit no loss in strength or stiffness.
In a study performed by the University of New South Wales, it was found that FRP products are more sustainable than their timber counterparts and, across their whole life-cycle, possess a lower embodied energy. Specifically, the report concluded that when compared to hardwood timber (for use as crossarms but the same can be said for all hardwood timber) Wagners FRP materials exhibited:
“An environmental impact which is 77% less than that of a hardwood timber power pole Crossarm. This equates to a lessening on the effects towards human health, the ecosystem quality, and resource use during its life cycle”.
Wagners CFT was a finalist in the 2009 Queensland Government Sustainable Industries Awards for Innovation in Sustainable Technologies and received a High Commendation for the “Use of composite fibre materials in civil engineering infrastructure at the Engineers Australia — Engineering Excellence Awards 2010”.
Our team of in-house experienced engineers can tailor the timber bridge replacement system to suit specific needs (spans, loading conditions etc.). Fibre composite members can be designed to match any required structural timber component. For example, the current design for our timber replacement girder is based on replicating the properties of hardwood timber girders used in typical 30ft (ca. 9 m) span timber bridges. It has been the product of the “Bridging the Gap” project, an extensive research and development program carried out in conjunction with the Department of Main Roads and the University of Southern Queensland, with an aim to replace existing timber girders on a “like for like” basis. The result is an FRP girder with equivalent stiffness and greater strength at only a third of the weight, making installation and handling much safer and easier.
The requirements determined by Main Roads for an equivalent 450 mm timber bridge girder were as follows:
| Beam Property | Requirement | Tolerance | Wagners CFT Girder | Units |
| Max Width |
350 |
0 |
300 |
mm |
| Max Depth |
425 |
0 |
423 |
mm |
| Stiffness |
2960000000000.00 |
+/- 10% |
2860000000000.00 |
Nmm² |
| Mmax at failure |
660 |
0 |
780 |
kNm |
| Shear Capacity |
350 |
0 |
435 |
kN |
| Max Deflection (at failure) |
170 |
+/- 10% |
172.4 |
kg/m |
| Weight |
~140-200 |
46.18 |
kg/m |
The timber bridge replacement system is quick and easy to install causing minimal disruption to traffic. A previous project which required the removal and installation of a 2-lane bridge on a major arterial road in Brisbane took only 3 days to complete. All products are readily available and manufactured in our facility in Toowoomba. Based on an order of 20 girders, we have a lead time of 28 days (including delivery).
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