1. Why need probabilistic approach? Rain probability How does that affect our behaviour? ?

2. Summary Uncertainty exists Uncertainty exists Probability helps to quantify likelihood Probability helps to quantify likelihood Probability plus consequence influence decision Probability plus consequence influence decision

3. Uncertainties in Engineering Natural Hazards Natural Hazards Material Properties Material Properties Design Models Design Models Construction Errors Construction Errors

4. Absolute Safety Not Guaranteed Engineers need to: model, analyze, update uncertainties model, analyze, update uncertainties evaluate probability of failure evaluate probability of failure

5. Question Why not leave the problem to mathematicians/statisticians?

6. Questions What is acceptable failure probability? -stadium vs shed

7. Questions Should one want to be conservative if a perfectly safe system is possible? -overbooking in airlines -parking permits

8. Questions Should one minimize risk if money is not a problem? -system consideration – e.g.dam

9. Trade-off Decision Analysis Risk vs. consequence Risk vs. consequence System risk System risk