Behaviour of fibre composite piles for timber pile rehabilitation

Behaviour of fibre composite piles for timber pile rehabilitation

Fibre composites have inherent material properties that are better than other existing materials such as steel, timber, or concrete in numerous environments. In the marine and ground-zone environments in particular, fibre composite materials can be selected for their corrosion, rot, and pest resistance, as well as high strength-to-weight ratio. The advantages of fibre composites over traditional construction materials, is their high strength, light weight, less corrosive, durable, and most importantly, no decay / deterioration by natural organisms, which is the dominant problem for timber piles used in water front structures.

This research project, focused on the development of a system for decayed timber piles replacement, for piers, jetties, bridges and boardwalks, using fibre composite technology to enable rehabilitation of the structures, as well as new construction, by using Glass Fibre Reinforced Polymer (GFRP) tubular pile and connector.

Three objectives were considered to examine the structural behaviour of GFRP tubular piles and connector used for novel timber pile rehabilitation technique. As the first objective, the effects of various loading scenarios on the capacity of the GFRP hollow tubular piles were investigated.

Then as a second objective, numerical simulations were performed using the finite element analysis approach to verify experiments, and study the behaviour of the overall pile rehabilitation system. Based on the results of these numerical simulations, further research areas were highlighted for filler material development, which was used to fill the space between the GFRP connector and the existing timber pile. Due to durability, pumpability, workability and compressive strength requirements, polyester resin based filler development was chosen.

As the third objective, appropriate polyester based filler materials were developed for the GFRP tubular connector, to transfer the vertical load from the super structure, to the original timber stump, by the connector. A research program has been initiated to improve the fundamental understanding of this rehabilitation concept. A new polyester based filler material has been considered to provide the working knowledge required for its broad utilisation.

Fibre composites have not been used in this specific manner previously. While there have been fibre composite wraps developed, these are not the replacement systems, and have inherent weaknesses in their application, being more difficult to install, and needing to be highly tailored to specific instances. The concept developed, tested and verified in this study is viable for general timber pile rehabilitations in piers / jetties with reasonable factor of safety and will be possible to extended rural two lane timber bridges. The results of this research, reveals a system, designed from an engineering perspective, relatively simple to install. Further, it is favourably disposed to mass production processes, to gain efficiencies of scale. Finally, this targeted research project, uncovers a timber pile rehabilitation system, capable of accepting the full working loads, while also ensuring a life span of some 50-100 years, with minimal maintenance.