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Uncertainties associated with structural design and assessment stem from variability in material properties, geometry, simplifications in load models, diverse structural behaviour models, etc.  With increasing requirements for risk evaluation for infrastructure ever more sophisticated methods are needed to deal with relevant uncertainties and likelihood of critical events.  Practical formulation for design and assessment of built infrastructure will be identified both for ultimate and serviceability limit states. Using an example of steel portal frame specific techniques used for uncertainty modelling for built infrastructure will be reviewed and future trends identified. Modelling for twin problem of ageing infrastructure and changing environmental conditions (climate change in particular) will be addressed.