Fragility functions for unreinforced masonry walls made from hollow clay units

A relatively large database of masonry specimens tested in laboratories across Europe was established and used for the estimation of fragility functions for unreinforced masonry walls built from hollow clay units, which are the most common type of masonry units for the construction of new buildings in Europe. The proposed fragility functions can be used to predict minor, moderate, and near collapse damage states for structural walls with expected predominantly shear or flexural behaviour. The results indicate that in addition to failure mode, the h/l ratio, the normalized compressive load, and the boundary conditions have a significant impact on fragility functions. However, due to small sample size, it was not possible to explicitly incorporate their effect in fragility functions. It is shown that the near collapse damage state of the investigated type of masonry wall is most likely attained at drifts of 0.4% or 0.7%, respectively, in the case of shear or flexural behaviour. Useful additional information is provided by the total dispersions of the structural component drifts corresponding to a designated damage state, these dispersions being large regardless of the damage state. In the case of the near collapse damage state, it was estimated that they amounted to 0.57 and 0.47, respectively, depending upon whether the structural components behaved in a predominantly shear or a predominantly flexural manner. It is also shown how the proposed fragility functions can be used to predict the probability of occurrence of a certain damage state, which can be used for loss estimation of masonry buildings.