Development of connections for fibre reinforced bridge elements and an analysis of sustainability

Doktorsavhandling, 2015

The deterioration of existing bridge structures due to a number of causes has led researchers to pursue new construction materials with high performance, such as fibre reinforced polymer (FRP) composite materials. The inherent properties of FRP materials are their light weight, high strength and high resistance to aggressive environments. Thanks to their light weight and the potential for prefabrication, the use of FRP bridge elements brings the benefits of industrial bridge construction and swift on-site assembly, resulting in the minimisation of traffic disruption. The application of FRP members in bridges started in the early 1990s and there remains a need for research in various technical areas. To map out these areas and specify the current level of knowledge, a literature review focusing on FRP bridge decks was carried out. This resulted in the identification of a number of research needs and two of them were pursued for research in this thesis. The first was to determine the potential of bridges with FRP bridge decks with respect to sustainability. Life-cycle cost analyses and life-cycle assessments in terms of carbon emissions were carried out on an existing steel-concrete bridge with a deck that had deteriorated where two scenarios were compared: the total replacement of the bridge with a new steel-concrete bridge and the replacement of the concrete deck with an FRP deck. The analyses revealed that the latter scenario contributes to potential cost savings and a reduced environmental impact in terms of carbon emissions over the life cycle of the bridge. The second identified research need was the development of integral connections and joints which enable rapid on-site assembly. Firstly, an innovative panel-level connection was developed by following an approach in which the bridge owner, designer, manufacturer and contractor were all involved. Numerical and experimental work was carried out to investigate the overall structural behaviour of the developed connection. The results showed that the proposed connection has good potential to be used for FRP decks, but more experimental tests encompassing specimens with a higher level of precision are required. In addition, a detailed study of bolted joints with the aim of obtaining non-slip joints, when clearance is present, in the service state of bridges was carried out. The utilisation of steel inserts and pretensioned bolts was investigated numerically and experimentally. The results indicated that it is possible to benefit from the bolt tension and rely on the load being transferred by friction if steel inserts are used. Bolt-tension-relaxation issues are reduced by using inserts and joint efficiency can be increased.