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The main objective of the project is to understand the vulnerability of critical road structures: bridges, culverts and floodways under natural hazards of flood, bush fire and earthquakes. Once the level of vulnerability is established, the evaluation of importance of the structures for prioritization for hardening is important for decision making by road authorities. The project funded by the BNH CRC addressed the above gap in knowledge through a comprehensive research program undertaken in collaboration with three research partners and six end user partners.

Major findings of the research include identification of the levels of hazard exposure which could lead to failure of structures and the other parameters affecting failure. Further, methods of modeling road structures under different loading regimes has been developed with case studies of typical structures. New design approaches for building back better have been proposed for floodway structures based on parametric analysis of typical types of floodways.

Major findings of the analysis of bridges under flood loading include (a) the current design process in the design standards for log and object impact are unconservative and rigorous analysis is recommended (b) when the flood velocity is over 4 m/s and the flood level reaches the soffit of the bridge deck, the failure probability of the bridge decks are very high. (c) particle size near the bridge pier foundations have a significant impact on the scour of bridge piers and placement of irregular shaped crushed rock at river-bed level can reduce the scour failure. Research conducted on impact of bush fires on composite structures indicated that the shear failure of the web of the girders is the major failure mode. Under earthquake loading, a major finding is that in the areas where peak ground acceleration is over 0.08g, girder bridges could have a high failure probability and a risk mitigation strategy is essential.