@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-6643, title = {Floodway inspection and maintenance framework}, number = {540}, year = {2018}, month = {04/2018}, institution = {Bushfire \& Natural Hazards CRC}, address = {Melbourne}, abstract = {

Bridges, culverts, and floodways are vital road infrastructures for the operation of a road network. Their application may vary based on geographic and demographic features of the territory. Floodways are common in rural road networks as they provide economic and environmental friendly solutions over bridges and culverts. Floodways play a significant role in the economy of a country by connecting regional communities, farmlands and agricultural areas to city centers. For example, 48\% of total agricultural production in Australia in 2006 had been produced from regional council areas, those covering only about 6.9\% of Australia{\textquoteright}s population, 11\% of total Australian land mass and 24\% of roads in length [1]. Floodways are common in most of these rural road networks and, hence, play a vital role to distribute agricultural and farming products to highly populated city centers. Therefore, healthy operational levels of floodways are of paramount importance to maintain the continuous supply of essential commodities and the economic balance of Australia.

Floodways are different from bridges and culverts in the design and operational aspects. By definition, floodways are sections of roads which have been designed to be overtopped by floodwater during relatively low average recurrence interval (ARI) floods and are expected to return to fully serviceable level after the flood water recedes [2]. Although, floodways are designed to withstand at low flood levels, extreme natural disasters can damage these vital road infrastructures as evident from the 2011 and 2013 Queensland flood events. 58\% of floodway structures in the Lockyer Valley Regional Council (LVRC) area in Queensland, Australia, were damaged during the 2013 Queensland flood event leading to operational failures in rural road networks. Floodway damage leads to isolating regional communities and hindering the supply of agricultural products to other regions. In a post-disaster period, the long-term impacts on the community and the economy of the country depend on the speed of reestablishing the fully operational level of those floodways.

}, keywords = {Flood, Floodway, framework, maintenance}, issn = {540}, author = {Sujeeva Setunge and Chun Qing Li and Darryn McEvoy and Kevin Zhang and Priyan Mendis and Tuan Ngo and Nilupa Herath and Karu Karunasena and Weena Lokuge and Dilanthi Amaratunga} } @article {bnh-1950, title = {Vulnerability of Floodways under Extreme Flood Events}, journal = {Natural Hazards Review}, volume = {17}, year = {2015}, month = {13/07/2015}, abstract = {

Floodways are commonly used in rural road networks due to the economic and environmental benefits offered as a low-cost and practical road crossing in flood-prone areas. They are designed with provision for submergence so that water flows over with minimum impediment to flow, at a probability given design flood. The floodway design process is traditionally governed by hydraulic aspects rather than structural aspects. Hydrological condition, availability of material, and familiarity of construction techniques are significant when selecting the floodway type. Nevertheless, extreme conditions can cause significant damage to floodways, as was evident from the 2011 and 2013 Queensland flood events, during which 58\% of floodways in the Lockyer Valley Regional Council (LVRC) area in Queensland, Australia, which is the case study area of this paper, were damaged, causing huge economic lost at council and national level. This created a new track in research and development activities to assess vulnerability and to find methods for improving the resilience of floodways during extreme flood events. In line with this, the present study evaluates local design guidelines and damaged floodways to assess failure modes and severity of damage using a damage index (DI) method.

}, keywords = {Damage index, Damage severity, Design guidelines, Flood, Floodway, Vulnerability}, issn = {1527-6996}, doi = {10.1061/(ASCE)NH.1527-6996.0000194}, url = {http://ascelibrary.org/doi/abs/10.1061/(ASCE)NH.1527-6996.0000194}, author = {Buddhi Wahalathantri and Weena Lokuge and Karu Karunasena and Sujeeva Setunge} }