This year GRPC produced its first vacuum infused box beam bridge and installed it in Nagano-ryokuchi in Fukuoka, Japan.
This year GRPC produced its first vacuum infused box beam bridge and installed it in Nagano-ryokuchi in Fukuoka, Japan.

For decades GRP Constructions Inc (CRPC) has designed and built hardwood bridges (mostly pedestrian) for the Japanese market. The company has also produced several composite bridges based on pultruded elements.

Looking for alternative designs and production processes which do not have the geometrical and structural limitations associated with pultrusion, GRPC connected with Infra Composites BV.

Infra Composites designs and builds full composite bridges using the vacuum infusion process and a structural box beam concept. In this design glass fibre reinforced polyester parts (two sides, one or more girders, deck and bottom shells and bulkheads) are infused and assembled using an adhesive. The concept has proven to be efficient and flexible in terms of easy change of geometries and change between pedestrian and vehicle loads.

Knowledge transfer

2 years ago a cooperation was created in which Infra Composites transferred knowledge about this bridge design and its production to GRPC's Japanese engineers.

Last year a full-scale segment of a vacuum infused bridge was produced in Infra Composites' production facility during a 2-week session in which GRPC workers were trained. Various smaller test articles were also produced, including bridge deck samples and parapet attachment sections.

A few weeks later a complete bridge was produced in GRPC's new dedicated production facility in Japan under the supervision of an Infra Composites project manager. This bridge was used for mechanical testing and for promotional activities, while the employees were further trained.

This year GRPC sold and produced its first vacuum infused box beam bridge and installed it in Nagano-ryokuchi in Fukuoka, Japan. More are expected to follow shortly.

Designing for Japan

The box beam design for the Japanese market could be kept identical to the original design, with two exceptions due to local challenges.

Firstly, the occurrence of an aggressive type of fungus in certain districts in Japan prohibited the use of balsa wood as a core in the sandwich deck. Fibre reinforced polyurethane cores were used instead. For higher loaded traffic bridges, a multiweb type of bridge deck design will be employed.

Secondly, the bridge supports also need to keep the bridge in place in typhoon season while still allowing for thermal expansion.