IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 17, Issue 3 Ser. III (May - June 2020), PP 21-30 www.iosrjournals.org DOI: 10.9790/1684-1703032130 www.iosrjournals.org 21 | Page Numerical Study of the Seismic Behavior of a Historic Stone MasonryTower Amr M. Abdel-Halim 1 , Mohamed N. Fayed 2 , Gehan A. Hamdy 3 , Mohamed A. Abdel-Wahab 4 1, 2, 4 Faculty of Engineering, Ain-Shams University, Egypt 3 Faculty of Engineering at Shoubra, Benha University, Egypt Abstract: Background:Unreinforced masonry towers are especially vulnerable to damage during earthquakes.A historic stone masonry minaret in Cairo (1468 A.D.) showed signs of damage and obvious inclination after occurrence of strong earthquakes in 1992 and 2015. Investigating the dynamic behavior of this historical tower is of primary importance to assure its structural safety and seismic vulnerability and enable conservation of thisheritagemonument. Materials and Methods: Numerical modeling and seismic analysis are performed for the minaret in its current condition using finite element commercial software in order to investigate its seismic behavior and to assess its structural efficiency. Several numerical models are made for the minaret to study the influence of openings and of the spiral stairs to the dynamic behavior. Results: The obtained numerical results regarding stresses and deformations are analyzed and correlatedto the observed damages and inclination. The results indicate overall stability of the structure in its current condition while high stresses occur at several locations. Conclusion:The numerical results demonstrated the need for retrofit actions for the minaret in order to improveits seismic behavior. Key Word: Masonry; Tower; Historic;Finite Elements; Dynamic Analysis; Seismic; Assessment. --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 04-06-2020 Date of Acceptance: 20-06-2020 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction Unreinforced masonry towersare highly vulnerable to damage due to dynamic action occurring during earthquake ground motions. This is attributed tothe anisotropy, heterogeneity and poor tensile strength of masonry and other factorssuch as the distribution of masses and inertia forces along the structure 1, 2 . Additionally, many of the historic towers suffer from long harsh environmental exposure and different levels of deterioration and damage, whichplaces these structuresat significant risk inearthquakes events. A destructive earthquake struck Egypt in October 1992 (Mw 5.9) and caused damage or collapse of many of the monumental minarets; the most severely damaged minarets were the stone minarets constructed from 1250 to 1520 A.D. 3 . Numerical investigation of four masonry minarets in Cairo representing different historical eras showed that stress concentrations occurred at locations of abrupt change of cross-section or variation of materials 4, 5 . The monumental stone minaret of the Mosque of Fatma El-Shaqra(1468 A.D.) is located in a very crowded residential and commercial district in the center of Cairo, Egypt. Following the destructive 1992 earthquake, several stone walls of the mosque were cracked and damaged. The slender minaret showed observed inclination which increased after another strong earthquake in 2015;the deviation at the top reached 300 mm from the central position.In-situ survey showed degradation of material due to weathering conditions and physical attack and cracks at almost several locations of the minaret body, especially in the lower part, as well as wide cracks and displacements of stones near the door opening. The threat to its structural safety imposed closure of the mosque and scaffolding the minaret,as shown in Figure 1, to avoid failure or collapse in case of another earthquake event. Numerical modeling and analysis of historic masonry structures is a difficult task because the mechanical behavior of masonry exhibits non-homogeneity, low shear and tensile strength and brittleness of mortar joints 6 . Different modeling strategies and analysis methods can be adopted to represent masonry behavior with different levels of accuracy 7 . Finite element (FE) method have been used to represent masonrystructures usingeither planar elements (plates or shells) or three-dimensional (3D) elementssuch as brick or solid elements; FE macro-models were reported to provide accurate simulation of the response of masonry structures 8, 9 .Zaki et al. 10 studied the dynamic behavior of two 20 m high historical stone minarets in Cairo using 3D FE modeling and linear elastic analysis using SAP2000 program; the dynamic characteristics obtained from ambient vibration