Document Type : Geotechnical Earthquake Engineering
International Institute of Earthquake Engineering and Seismology
One of the most important challenges in analysis of non-ordinary structures is the critical angle of incidence of earthquake ground motions. To accommodate these directional effects, several procedures and combination rules have been proposed. The major limitations of these methods are that they are restricted to elastic analyses, rarely considered near-fault earthquakes and are almost related to the building structures or bridges. The main objective of this work is to assess the influence of incident angle of ground motions on several engineering demand parameters (EDPs) of an embankment dam under Sarpol-e Zahab earthquake. To achieve this goal, after selecting proper ground motions, the as-recorded horizontal components (two orthogonal) were rotated to: fault-normal/parallel direction, principal direction, direction related to GMrotIpp (NGA relationships) and maximum direction of response history analysis of two degree of freedom system (MSD). In the next step, a typical embankment dam in the earthquakeaffected areas was modeled using the shear beam method. The model was excited by as-recorded motions with various directions in the range of 0-360 degrees with a step of 10 degrees and all four above-mentioned reference axes directions. Numerous equivalent linear analyses were carried out to obtain the critical angles of excitation that leads to maximum responses. The analyses results showed that the critical orientations of ground motions depend on: input motions, structure characteristics and EDPs.