Abstract

Recent research has shown the importance of considering the directionality effect of the horizontal components of an earthquake on the expected performance of buildings. The variation of the roof displacements, base shear or expected damages depend on the building orientation respect to the seismic actions applied. Nowadays, this type of calculation is typically computed using the nonlinear dynamic analysis and rotating the acceleration horizontal components for all non-redundant angles, which entails a high computational cost. This paper presents a simplified approach to consider the directionality effect. The method is based on the nonlinear static analysis and in the energy balance between the capacity curve and the response spectrum to determinate the performance point. To show the advantages of this new approach, the methodology was apply to a 4-story steel frame building 3D model with seismic action from Mexico City. This case of study shows that the new method is easy to implement, demands less calculation time and provides results compatible with those obtained through the non-linear dynamic analysis. In addition, the results shows the need to apply the directionality effect in the 3D seismic analysis. A high variability in the seismic performance is observed with the building orientation. Finally, it is important to mention that this effect is not considered in the seismic codes requirements, reason why, this approach would allow its consideration.

Abstract

Most of buildings and structures are usually projected according to two main axes. However, the geographical position of these buildings varies randomly. Such random distributions of the azimuthal positions of structures, in most of the cities, generally, are not accounted for when assessing their seismic risk; certainly, the direction of the seismic loads is another highly random variable. Moreover, an additional important source of uncertainty is related to the structural response, mainly due to the random character of the mechanical properties. There is a consensus that uncertainties must be considered for adequately assessing the seismic risk of structures, but these directionality effects have not been deeply explored so far. In this article, the influence of the high uncertainty involved in these input variables on the expected seismic damage is analysed. Thus, an actual earthquake, which affected the southern part of Spain, is studied. Notably, damages on a group of affected buildings, located close to the epicentre, are analysed and discussed in detail. The results show that the influence of the random azimuthal position of structures is an important source of uncertainty and that it should be taken into account when estimating the expected seismic risk in urban areas.