Asia-Pacific Conference on FRP in Structures (APFIS 2007) S.T. Smith (ed) © 2007 International Institute for FRP in Construction SEISMIC REHABILITATION OF HISTORICAL MASONRY VAULTS USING FRPS - A CASE STUDY S.S. Mahini 1 , H. R. Ronagh 2 , A. Eslami 3 1 Department of Civil Engineering, Yazd University, Yazd, Iran. Email: s.mahini@yazduni.ac.ir 2 Division of Civil Engineering, School of Engineering, The University of Queensland, Brisbane, Australia. 3 Department of Civil Engineering, Yazd University, Yazd, Iran. ABSTRACT Collapse of non-engineered historical buildings in seismically active regions of Iran has been reported widely. Masonry dome and vault, which were built by adobe or bricks with clay, lime/clay or chalk/clay mortar have often been used in these buildings to cover the roof. Conservation of historical heritage may become necessary in order to improve their seismic resistance. In this paper, potential failure of a heritage brick vault located in Yazd city, Iran built in 1935 is investigated under lateral loads. In this building, the piers were built by adobe masonry whereas the roof vault was made up of clay bricks with chalk/clay mortar. A nonlinear finite element model is used in the investigation in which the masonry is modelled as an anisotropic continuum using smeared material models. The material properties of continuum masonry are determined by testing. Finally, the brick vault is strengthened using CFRP sheets at extrados with different architecture and the failure mechanisms of the structure before and after strengthening are compared. Results show that when the vault is strengthened at extrados, the failure mechanism would improve to provide higher ultimate load capacities. KEYWORDS Historical buildings, brick masonry vault, carbon fibre reinforced plastic sheets. INTRODUCTION Masonry is a heterogeneous material composed of units connected by dry or mortar joints. As units, stones, adobes and bricks have been used which, can be joined together using mortar. The mechanical behaviour of the different types of masonry exhibits a very low tensile strength. This property is so important that it has determined the structural form of historical constructions. The curved structures, i.e. arches and vaults, represented a significant structural capacity, which were used in the past in spanning wide openings, with adobe or brick masonry. Indeed, in curved elements, it is usual to find only compressive stresses in a given section and consequently no tensile resistant materials are required. However, joints can be critical regions in brick masonry vaults against the severe seismic attack so the contribution of strengthening materials and repair techniques may be required to re-established their performances and to prevent the brittle collapse of the masonry in possible future hazardous conditions. Since the mechanisms related to failure of brick vaults under seismic action are not yet well known, attention should be given to this matter in order to perform repair/retrofitting schemes. Several researchers reported the weak performance of masonry vault. For example, recently, Maheri (2005) and Mahdi (2004) noted the poor seismic performance of traditional domes and vault roofs after 2003 earthquake, Bam, Iran. Retrofitting techniques have been examined in order to improve this weakness. Giordano et al (2001) performed a numerical investigation in order to assess of the seismic capacity of triumphal arches. Giordano et al (2001), identified a global mechanism type has been a priori selected for the element, and the critical zones in the arch which are the left side of both pier bases, intrados on the left haunch, and extrados on the right haunch. Further, Ascione et al.’s (2005) presented some applications of an adaptive discontinuous finite element model in order to evaluate the ultimate load and the collapse mechanism of two-dimensional FRP/reinforced masonry structures. They showed that the loading carrying capacity of the structure increased by FRP/strengthening technique. In this paper, first the performance and the collapse mechanisms of a case study brick vault belongs to a historical building located in Yazd city, Iran subjected to lateral loads is evaluated using nonlinear finite element modelling. Then, the influence of FRP sheets on the seismic performance of the case study vault is investigated. GEOMETRY OF THE CASE STUDY BRICK MASONRY VAULT The brick masonry vault examined in this chapter belongs to the Egbal historical complex. This complex building was built for a textile factory called Egbal between 1932 and 1935. In the recent years, several restorations were made by the Yazd Science and Technology Park, including recovering and partitioning of the