Influence of Initial Geometric Imperfections on the Structural Behaviour of Unreinforced Masonry Heritage Buildings

The structural behaviour of heritage buildings is influenced by the presence of initial geometric imperfections, which may significantly amplify second-order effects.Nevertheless, many numerical analyses of historic structures neglect these imperfections and adopt idealised geometries that do not accurately reproduce the actual condition of the buildings.

This study evaluates the influence of initial geometric imperfections on unreinforced masonry heritage structures. The north-western sector of the Mosque–Cathedral of Cordoba was selected as the case study. This sector dates from the 8th century, covers approximately 2,700 m² and comprises ten longitudinal arcades supported by columns. The modal response of two finite-element numerical models developed within the OpenSees framework was compared. The first model reproduces an idealised geometry, whereas the second incorporates the actual out-of-plumbness of the columns, obtained from in situ measurements. The response parameters investigated are the natural frequencies and the corresponding global mode shapes. It is expected that the model including initial geometric imperfections will exhibit lower natural frequencies, due to the associated reduction in lateral stiffness.

This work extends previous research conducted by the authors on a single arcade of the Mosque–Cathedral, which revealed that initial geometric imperfections reduced its ultimate load-bearing capacity by approximately 30%. The results of the present study are intended to emphasise the importance of including initial imperfections when assessing the structural vulnerability of the built heritage.