@mastersthesis {bnh-6161, title = {Fragility and resilience of bridges subjected to extreme wave-induced forces}, volume = {Doctor of Philosophy}, year = {2019}, month = {08/2019}, school = {RMIT University}, type = {Doctorate}, address = {Melbourne}, abstract = {

Bridges are susceptible to severe damage due to wave-induced forces during extreme events such as floods, hurricanes, storm surges and tsunamis. As a direct impact of climate change, the frequency and intensity of these events are also expected to increase in the future. The damages to bridges lead to substantial community impact during emergency and post-disaster recovery activities. Hence, viable restoration strategies are needed to enhance the resilience of bridges under extreme wave hazards. The research on the quantification of vulnerability and resilience of bridges under extreme wave forces is limited. In particular, vulnerability and resilience assessment tools for bridges under different hazard intensity levels are required to quantify the resilience. This research addresses these research needs by providing a comprehensive vulnerability assessment framework for bridges subjected to extreme hydrodynamic forces.

A comprehensive literature review is first conducted on the four resilience assessment elements, namely external wave force characterization, structural response, vulnerability assessment and resilience quantification to identify the existing gaps in knowledge, particularly in vulnerability and assessment methods.
Unified resilience indices, based on the {\textquotedblleft}resilience triangle{\textquotedblright} concept, are proposed to take into account the effect of the consideration of resources (cost) and environmental impact and their relative importance to the decision makers in the resilience quantification. Such indices are important for stakeholders as they provide a linkage between the social (time), economic and environmental impacts in the assessment of restoration strategies.

An integrated vulnerability assessment framework for bridges with strong connectivity between super- and sub-structure is proposed. The framework includes both static and time-history analyses to examine the performance of bridges subjected to significant hydrodynamic forces. The uncertainties in force and structural parameters are taken into account and the probability of damage is estimated using six damage states that define the pre- and post-peak response of bridge. The pier drift is taken as the engineering demand parameter. The use of two-parameter intensity measures that can provide an accurate estimation of the response of bridge such as momentum flux (hu2) and moment of momentum flux (h2u2/2) is investigated.

To demonstrate the proposed framework, a numerical model is developed for a case study bridge located in a flood-prone region in Queensland, Australia. The accuracy of the piers model is validated using published works on small-scale pier specimens that have limited ductility. The effect of strengthening of bridge piers using fibre reinforced polymer (FRP) jackets is examined.

The overall fragility functions for all intensity measures (velocity, inundation depth, momentum flux and moment of momentum flux) are obtained for both initial and strengthened bridge. The reduction in scatter of fragility data is examined for the two-parameter intensity measures for all damage states. The viability of the use of FRP jackets for enhancing the resilience of bridges under extreme wave forces is also evaluated. The application of unified resilience indices based on the damage probability data obtained from fragility analysis is discussed for different intensities of the hazard.

The main contribution provided by this research is the comprehensive vulnerability and resilience assessment methods for bridges under extreme wave hazards. Such methodologies can assist in the evaluation of the different pre-disaster strengthening and recovery schemes for bridges. Decision makers (e.g., road authorities) can use the outcome of this research to assess the different retrofitting options for bridges taking into consideration the time, cost and energy consumption associated with each option.

}, keywords = {bridges, Emergency management, engineering, Fragility, Natural disasters, resilience}, author = {Ismail Qeshta} } @article {bnh-6054, title = {Fragility and climate impact assessment of contemporary housing roof sheeting failure due to extreme wind}, journal = {Engineering Structures}, volume = {117}, year = {2018}, month = {09/2018}, pages = {464-475}, abstract = {

The paper describes a risk analysis of the economic impact of damage to metal roofing of a typical contemporary (new) Australian house subject to extreme wind loading. The failure modes considered are roof cladding and batten-to-truss connection failures, with the effect of defective construction also considered. Monte-Carlo simulation and structural reliability methods are used to stochastically model spatially varying pressure coefficients, roof component failure, and load re-distribution across the roof. This spatial reliability analysis enables fragility curves to be developed that relate likelihood and extent of roof cover loss to gust wind speed. The annual economic risk is up to 0.3\% of house replacement value. A typical house with construction defects increases economic risk more than sixfold when compared to the defect-free house. There is a 10\% chance that a changing climate will increase expected losses for houses in Brisbane and Melbourne by 6{\textendash}18\% over the next 50 years.

}, keywords = {Climate change, Damage, Fragility, Housing, Reliability, Wind load}, doi = {https://doi.org/10.1016/j.engstruct.2018.05.125}, url = {https://www.sciencedirect.com/science/article/pii/S0141029618302499}, author = {Mark Stewart and John Ginger and David Henderson and Paraic Ryan} }