The significance of considering multiple angles of seismic incidence for estimating engineering demand parameters

Abstract

The accurate determination of demand during the seismic analysis of buildings requires that all factors having a significant contribution must be accounted for. The present study examines the effect of the angle of seismic incidence of earthquake ground motions on the inelastic demand of reinforced concrete buildings and defines its significance for different engineering applications, including both deterministic and probabilistic analyses. Three commonly used engineering demand parameters are examined by analysing three statistics obtained from their empirical distributions at several intensity levels. The results show that the influence of the angle of seismic incidence is different for the three statistics, and that this effect depends also on the engineering demand parameter under consideration. Central tendencies of the demand appear to be less affected by the angle of seismic incidence when compared to its variability, thus showing the potentially larger influence of the angle of seismic incidence for probabilistic analyses rather than for standard-based (i.e. deterministic) applications. Finally, recommendations on the minimum number of angles of seismic incidence that should be considered are given as a function of the number of ground motions used in the analysis.