Influence of ground motion characteristics on drift demands in steel moment frames designed to Eurocode 8

• The influence of ground motion frequency content on drift demands in frames designed to EC8 is examined.
• Incremental nonlinear dynamic analyses are carried out using a large suite of frames and ground motion records.
• Key parameters are shown to include the period ratio, behaviour factor, storey stiffness ratio and first mode participation.
• Prediction models for global and storey drifts are proposed and compared with current design expressions.

This paper investigates the influence of the frequency content of ground motion, as well as the structural characteristics and level of inelasticity, on the global and inter-storey drift demands in frames designed to comply with Eurocode 8 provisions. To represent a wide range of structural characteristics, a suite of 39 steel moment frames is considered by varying the number of storeys, intensity of loading, performance requirements and compliance criteria. Extensive incremental dynamic analyses are carried out on the study frames using 72 far-field ground motion records, which are scaled to simulate four levels of behaviour factor. It is shown that the salient parameters that influence the global drift are the ratio of fundamental period to mean period and the behaviour factor. In addition to these, the relative storey stiffness ratio and the first-mode participation factor have a direct, though less influential, effect on the maximum inter-storey drifts. Based on the parametric assessments, regression models are proposed for predicting the global and storey drifts. Finally, the implications of the findings on the rules incorporated in European and United States design codes are highlighted and discussed.