Design and Structural Dynamic Characteristics of an Irregular Staircase Under Earthquake Loading John Magdy 1(&) , Zeyad Khalil 1 , Mohamed Ashraf 1 , and Mohamed Darwish 1,2 1 The German University in Cairo, Cairo, Egypt {john.mousa,zeyad.khalil,mohamed.ashrafismail} @student.guc.edu.eg, mdarwish@aucegypt.edu 2 The American University in Cairo, Cairo, Egypt Abstract. Reinforced concrete staircases are structurally designed as can- tilevered, slab type or beam-slab type. Within this study an irregular cantilevered staircase is studied and its structural dynamic characteristics are explored. An eigen-value modal analysis is performed to determine the mode shapes, their corresponding modal participation factors and natural periods of vibration. The highest modes of interest are identified. Following on that, a scaled record of a previous historical earthquake was applied within a direct integration time-history analysis in order to assess the performance of that irregular stair case under earthquake loading. That load was applied within two perpendicular load cases representing the different possible directions of earthquake vibrations in which the effect of the structure irregularity was assessed per direction. The structure was found to have large drifts creating a need to change the structural system. Keywords: Structural dynamics Á Earthquake engineering Á Irregular staircase Á Modal analysis Á Dynamic analysis Á Hurghada 1 Introduction The coastal city of Hurghada at the entrance of the southern Suez Gulf of the Red Sea was founded in the early 20 th century, and until a few years ago it was a small fishing village. But since the 1980s, it has been continually enlarged by Egyptian and foreign investors to become the leading coastal resort on the Red Sea. Throughout the most recent decade, the population in Hurghada city expanded quickly as a consequence of expanding of financial action identified with tourism. Most of the structures there were not initially designed to resist earthquakes; thusly, generally little occasions later on can be source of socio-economic disasters. The Egyptian Red Sea city constitutes a major tourism destination, especially for diving, and the coral reefs (Hilmi et al. 2012). Situated at 27.23°N and 33.82°E, Hurghada is known to be in the range of high seismic zone in Egypt (Housing and Building National Research Center 2008). The high rate of seismic movement there is mostly related to the modification in movement © Springer International Publishing AG 2018 H. Rodrigues et al. (eds.), Facing the Challenges in Structural Engineering, Sustainable Civil Infrastructures, DOI 10.1007/978-3-319-61914-9_7