@article {bnh-8016, title = {Enhancing resilience of critical road structures: bridges, culvers and floodways under natural hazards {\textendash} final project report}, number = {671}, year = {2021}, month = {05/2021}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

Bridges, culverts and floodways are lifeline road structures and part of road networks, which have a significant role in ensuring resilience of a community before, during and after a natural disaster. Historical data demonstrates that the failure of road structures can have catastrophic consequences on a community affected by disaster due to the impact on evacuation and post disaster recovery.\  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. In the first stage of the project, major failure scenarios and the consequences of failure were identified as a precursor for a focused research program on vulnerability modelling and prioritization of road structures under natural hazards. The research conducted included assessment of vulnerability of road bridges under flood, bush fire and earthquakes and floodways and culverts under flood. Further, three approaches were used to identify the consequences of failure of road structures under natural hazards: economic impact on the closure of structures on the community, prioritization of structures using analytical techniques and post disaster social, economic and environmental impacts of failure of road structures.

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.

Three different tools are developed for determining the impact of failure of road structures considering economic as well as social, environmental and economic impacts.

A major utilisation outcome of the project is a resilient floodway design guide, published in collaboration with the Institution of Public Works Engineers Australia (Qld) (IPWEAQ). A utilisation project is currently in progress jointly funded by the IPWEAQ and BNH CRC. The guide has been reviewed by the IPWEAQ and is currently being revised by the researchers to enable uptake by local council Engineers. An asset management and vulnerability modeling tool for bridges has been developed for the DoT Victoria (formerly known as VicRoads) where the bridges prone to significant damage are highlighted in a GIS map of the road network.

There are two different models developed to evaluate the consequences of the failure of road structures: first considering economic impact of detour required and a second model capturing post disaster social environmental and economic impact of failure of road structures. The first tool has been incorporated into the vulnerability modeling GIS platform developed for \ the DoT, Victoria.

In addition to the above deliverables in the BNH CRC project, two subsidiary projects were undertaken to understand the effect of cyclonic events on bridge structures and also resilience of timber bridges under natural disasters.

The research team is working with the end users to socialize the vulnerability modeling and decision-making tools developed to enable optimized decision making to enhance resilience of road structures under natural hazards. This is currently being continued with direct funding from the DoT, Victoria.

}, keywords = {Bridge, critical, culvert, enhancing, Floodway, Natural hazards, resilience, road, structure}, issn = {671}, author = {Sujeeva Setunge and Priyan Mendis and Karu Karunasena and Kevin Zhang and Dilanthi Amaratunga and Weena Lokuge and Nilupa Herath and Long Shi and Hessam Mohseni and Huu Tran and Kanishka Atapattu} } @article {bnh-6040, title = {Predicting the probability of failure of timber bridges using fault tree analysis}, journal = {Structure and Infrastructure Engineering}, volume = {15}, year = {2019}, month = {02/2019}, pages = {783-797}, abstract = {

The resilience of a community in an extreme event depends mainly on the robustness of the critical infrastructures. Road bridges are a critical link of the road network, which plays a focal role in Australia{\textquoteright}s economy, prosperity, social well-being and quality of life. Timber bridges are a weaker link of the Australian road network and they often provide critical access to the rural communities. This research uses a number of bridge inspection reports to develop a method to predict the probability of failure of a timber bridge. The inspected condition states of the elements in the timber bridge are used to develop a Markov chain based model and Gamma process model to predict the deterioration of each element. The probability of condition state movement for each element thus calculated were used in fault tree analysis to estimate likelihood of failure of a bridge in a given time period. Although the developed method is based on limited data and it has several limitations, model can be further refined with the availability of more inspection reports. The method developed is demonstrated using an inspection report for a timber bridge, which was not used in the development of the models.

}, keywords = {bridge failure, fault tree analysis, inspection, Markov process, rehabilitation, Timber structures}, doi = {https://doi.org/10.1080/15732479.2019.1569069}, url = {https://www.tandfonline.com/doi/abs/10.1080/15732479.2019.1569069}, author = {Weena Lokuge and Matthew Wilson and Huu Tran and Sujeeva Setunge} } @article {bnh-5191, title = {Predicting the failure of timber bridges by using current inspection reports}, journal = {Engineering for Public Works}, volume = {7}, year = {2017}, month = {11/2017}, pages = {85-89}, chapter = {85}, abstract = {

There is a large timber bridge stock in service within Australia and currently over 300 timber bridges on Queensland state controlled roads. Majority of these timber bridges are in the latter half of their service life and require constant maintenance as the timber components deteriorate over time. Detailed level 2 inspections are performed as part of the bridge management systems used by road authorities. This paper discusses a simple method to use an inspection report to predict the chance of the failure of the bridge in a given number of years. Although the Markov process adopted in this research was based on inspection reports for several timber bridges for three time periods, it can further be refined using a data base of inspections for many time periods and environmental conditions. The proposed method is demonstrated using an inspection report for a hypothetical timber bridge.

}, url = {https://issuu.com/ipweaqld/docs/epw_september_2017}, author = {Weena Lokuge and Matthew Wilson and Huu Tran and Sujeeva Setunge} }