Advanced design and optimization of steel portal frames

This study brings new insights into the advantages of using more sophisticated design methods for steel portal frames (e.g. geometrically and materially nonlinear analysis with imperfections or GMNIA, and the general method introduced in Eurocode 3), compared to the commonly used member checks with interaction formulae. The differences between the design alternatives are discussed, focusing on assessing lateral-torsional stability, and the potential benefits of using advanced shell model instead of widely used beam elements. In addition to the advanced design methods, the topic of shape optimization of frames was explored using realcoded genetic algorithm (GA).
The developed optimisation tools highlight the possibility of using GA in everyday design in the future. The results of the study clearly point to the advantages of using advanced modelling, e.g. GMNIA, instead of the classical member checks. While both methods are accepted by the current steel design code EN 1993, using GMNIA can result in important savings, because it eliminates some of the conservativeness brought in by the unavoidable simplifications of the other methods. The experience shows that using complex 3D models is possible with current computational capabilities.