Abstract
Bridges are known to be crucial structures, which assist in the overall transportation infrastructure systems. They continue to serve for a long period of time and thus, they are usually subjected to multiple loadings in addition to several risks in their service life. Therefore, they require a great deal of maintenance in order to preserve their functionality. Risk management of bridges is particularly important for understanding the likelihood of extreme events and service distribution along with the consequences of service disruption. Thus, this thesis is concerned with developing and providing a detailed reliability risk-based methodology for the decision making of highway bridges made of concrete and steel. This research was aimed on delivering a successful tool which can provide a safety risk analysis for bridge structures. A review of the relevant literature was first carried out which assisted in providing a detailed background on bridges. This included discussing studies exploring bridge accidents in order to understand the reasons behind such accidents. Next, the aim of this study was successfully achieved by basing the proposed tool on a numerical model, which is relevant to the maintenance of bridge structures. The goals of this research were satisfied by reviewing, analysing and utilising the Fuzzy Reasoning Approach (FRA), Fuzzy Analytical Hierarchy Process (FAHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) techniques. A new safety risk model applicable for bridges was then proposed. Three input parameters, Consequence Severity (CS), Failure Frequency (FF) and Weight Factor (WF) were introduced and then used for assessing the risks from components levels all the way to system level. Moreover, the Consequence Severity Criteria (CSC) parameter is introduced as the multi-consequences parameter, which takes into consideration eight factors that are considered significant for the risk analysis of bridges. The eight factors, which are, functionality, safety, value for money, environment, traffic delay, time, reputational damage and socio-economic consequences are discussed in detail. Three case studies were used for validating and verifying the reliability of the proposed risk assessment and safety management model. Overall, for the first time, this work has carried out research as well as propose a safety model for risk assessment of highway bridges. In the case of no available information or risk data, it is possible to use subjective estimations with the proposed risk model. This is because the model permits the use of imprecise as well as vague descriptors for directly capturing experts' judgements. While there are certain complexities associated with the application of FAHP, the proposed risk assessment model uses an enhanced version of FAHP, which needs only a few expert judgements. The developed model is based specifically on highway bridges. Hence, the benefits of the model can be summarised in its ability to combine engineering judgements as well as expert knowledge with various risk information for the assessment of highway bridges in a reliable approach.