International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This paper investigates the link between earthquake damage and material strength deficiencies in four unreinforced masonry (URM) dwellings in Kruja, Albania, which all reached Damage State 4 (DS-4) during the Mw 6.4 earthquake of 26 November 2019. Post-earthquake field inspections showed similar failure patterns in all buildings, including diagonal shear cracking, corner separation and local out-of-plane instability, pointing to limited shear capacity and weak masonry bonding.
To clarify the causes of this behaviour, laboratory tests were carried out on brick units, mortar samples and masonry prisms taken from the damaged buildings. The test results indicate that both mortar and masonry compressive strengths are significantly lower than the values commonly assumed in Eurocode 6 for structural assessment. This strength deficit explains the brittle response and the rapid stiffness degradation observed during the earthquake.
The combined use of field observations and laboratory data confirms the key role of construction quality in the seismic vulnerability of older URM dwellings and underlines the importance of material-based assessment approaches for similar residential buildings.