Holistic approach in engineering design - controlling risks from accidental hazards in bridge design

Sammanfattning: Engineering design, in concise terms, is what engineers do using what they know. It is the underlying decision making activity that determines what is to be built and how it should be built. An ever present requirement in engineering design is that the structure should be safe. While historical approaches to safety in design relied on experience and engineering judgment, modern approaches have rationalized uncertainty in an effort to treat risks in a more consistent and objective way. Concurrent to these advancements, design codes have been developed which include safety formats that are calibrated using these rationalized approaches. This thesis investigates the limitations of the design codes in controlling risks in engineering design and proposes that a complementary approach – involving case-specific risk assessments – is necessary for addressing the risks that are not properly treated by the design codes. The main advantage of such an approach is that:
• it broadens the scope of assessment to consider structural systems and possibly non-structural constituents;
• it is also applicable during the conceptual design phase for the bridge structure; and
• it is complementary to current codified approaches
While similar approaches are common in large scale construction projects they are rarely applied in the design of more conventional bridge structures. However, in this thesis it is argued that the application of such approaches is also useful in more common bridge projects to better control risks inadequately treated by design based on code compliance. A framework for a holistic risk-informed approach is provided which focuses on the conceptual design of bridge structures and on the control of risks from accidental hazards. Case studies are conducted to highlight the usefulness of the approach and to help develop crucial aspects of the approach while providing useful background information for its possible implementation in future projects. Specific attention is also paid to the modeling of risks from heavy goods vehicle (HGV) impacts to bridge substructures – a design situation which was found to be inadequate treated using current codified approaches.