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Abstract. The latest earthquake disasters have highlighted, once again, poor functioning of the existing masonry structures, and the need to intervene all these structures which have been designed with old regulatory criteria, inadequate or those that have been built before the emergence of design codes. The significant progress made in new criteria of earthquake resistant design, should be extended to all the existing structures, it is therefore essential to identify the degree of seismic performance. Unreinforced masonry (URM) buildings represent a significant portion of the residential structures in Algeria, accounting for more than 60% of existing buildings. In addition to significant population, the brittle nature of URM buildings further supports a thorough consideration of seismic response given the susceptibility to severe failure modes. Currently, there is a pressing need for analytically based fragility curves for URM buildings. In order to improve the estimation of damage state probabilities through the development of simulation-based masonry fragilities, an extensive literature survey is conducted on pushover analysis of URM structures. Structural response is evaluated using an advanced capacity spectrum method. Capacity, demand, and response are thus derived analytically and response data is used to generate an improved and uniform set of fragility curves for use in risk assessment. Seismic fragility curves are expressed in multiple forms for wide range of use in loss-assessment applications. Results are discussed and compared with other relationships developed in the literature.

This paper presents a method for developing fragility curves for assessing the seismic performance of existing reinforced concrete structures in Algeria. A two-storey 1980s reinforced concrete building in the northern city of Constantine was studied using the proposed method as part of a vulnerability assessment and strengthening proposal. Fragility curves for the existing and strengthened structure were derived and log-normal cumulative distribution function parameters were obtained for the four defined damage states by considering maximum inter-storey drift ratio. Incremental dynamic analysis was then used to assess spectral acceleration by conducting 300 non-linear time-history analyses based on 15 ground motions. The records were then selected and scaled to fit with Algerian design response spectra, and fragility curves were subsequently developed. The method can be used for any type of reinforced concrete structure in Algeria, including bridges.

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