A. Mortezaei - Ph.D. Candidate, Faculty of Civil Engineering, Semnan University, Semnan, Iran
A. Kheyroddin - Associate Professor, Faculty of Civil Engineering, Semnan University, Semnan, Iran
Ghodrati Amiri - Professor, Center of Excellence for Fundamental Studies in Structural Engineering, College of Civil Engineering, Iran University of Science and Technology, Iran

Historical buildings are an integral part of the built heritage to be preserved, and their safety is a primary requirement in seismic areas. Collapse of ancient masonry buildings due to seismic actions occur mostly due to failure of the perimeter walls. This paper addresses the issue of seismic analysis and vulnerability of historical masonary building of Imam Khomeini (Sultani) Mosque in Semnan. Imam Khomeini Mosque with four ntrances was built at the beginning of the 19th century, under Fath Ali Shah Qajar, it is a charming example of the fragile grace so characteristic of Qajar style. The mosque consists of a spacious court, several prayer halls, a tile-decorated porch and lecture hall, four ivans, a marble manbar (pulpit), and numerous inscriptions in beautiful calligraphic styles. The finite element method was adopted for analyses, introducing nonlinear ehavior of the materials. A quasi-static approach (the seismic coefficient method) for the evaluation of the seismic loads has been used (as indeed is common in many analyses of the seismic behavior of masonry structures). The comparison of demand vs. capacity confirms the susceptibility of this type of building to extensive damage and possibly to collapse, as frequently observed. The paper advocates that significant information can be obtained from advanced numerical analysis, namely with respect to the understanding of existing damage and to the minimum and adequate design of strengthening. A clear understanding of the structural behavior and reliable strengthening, based on sophisticated tools of structural nalysis, can therefore reduce the extent of the remedial measures in the restoration of ancient structures.

Nonlinear analysis; Seismic vulnerability; Historical masonry building; Imam Khomeini Mosque; Semnan.