Improved consideration of dynamic loads and effects in design of exposed structures

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Current structural engineering practice continues to rely extensively on static analysis methods for design. After over 30 years of extensive use of the limit states or reliability-based design method in most structural design codes worldwide, this approach has exposed its weaknesses for assessing the mechanical security and integrity of critical structures exposed to extreme environmental loads. The performance-based design approach introduced in recent years relies heavily on past methods, essentially accepting limit-states design solutions as acceptable solutions, leaving the issues of security and integrity to the interpretation of designers. Most extreme environmental loads have potentially dynamic effects on exposed structures, and consideration of failure or progressive collapse scenarios cannot generally ignore those dynamic effects when predicting structural response. As such, true performance-based design precludes reliable and relatively accurate response prediction that is rarely feasible with simplified static methods. The goal of this research program is to assess the accuracy of some simplified static load methods described in the National Building Code of Canada and other relevant Canadian structural design standards to predict the response of exposed structures to environmental load effects such as turbulent wind, atmospheric icing, and combined wind and ice effects. The types of structures to be studied are restricted to overhead transmission line supports, telecommunication towers and masts, and various exposed non-building lattice structures and cable structures (excluding bridges). The scientific approach will combine a critical review of the available experimental results (from wind-tunnel tests or monitoring) that support current simplified load calculation methods and advanced computational mechanics techniques. In particular, fluid-structure interactions will be examined, both for bare and iced flexible structures in simulated realistic turbulent wind conditions.