Seismic performance of heritage clay brick and lime mortar masonry structures
This paper summarises recent investigations undertaken into the structural and material response of ambient-dry and wet clay-brick and lime-mortar masonry elements, with focus on those used in heritage structures in Historic Cairo. In addition to cyclic tests on large-scale masonry walls subjected to lateral displacement and compressive gravity loads, the investigations included extensive complementary tests on small scale masonry panels and material specimens. The main results and observations, coupled with complementary numerical simulations, enable a detailed assessment of the material shear-compression strength envelopes, and permit a direct comparison with the strength characteristics of structural walls, as well as their ductility and failure modes. It is shown that moisture has a notable effect on the main material properties, including the shear and compression strengths, brick-mortar interaction parameters, and the elastic and shear moduli. The extent of the moisture effects is a function of the governing behaviour and material characteristics as well as the interaction between shear and precompression stresses and can lead to a loss of more than a third of the stiffness and strength in addition to a notable reduction in ductility. Overall, provided that the key moisture-dependent material properties are appropriately evaluated, it is shown that analytical assessment methods can be reliably adapted for predicting the response, in terms of the lateral stiffness, strength and overall load-deformation behaviour, for both dry and wet masonry elements. The paper concludes with recommendations for the evaluation of the main characteristics of such heritage structures and for selecting effective strengthening and upgrading techniques in deficient cases.