Crack patterns in double-wall industrial masonry chimneys: Possible causes and numerical modelling

The origin of crack patterns in industrial masonry chimneys is investigated. This information is of utmost importance in defining any preservation project, and designing suitable repair interventions. Attention is focused on a 66 m-tall chimney built at the end of the XIX century, which is representative of numerous coeval chimneys of similar geometry. The base and the shaft of the chimney are double-walled: vertical ribs and horizontal diaphragms partially connect the walls of the shaft; the crown is single-walled. Vertical cracks can be observed in the lower part, horizontal cracks in the upper part, and zig-zag cracks in the central part. The structural behaviour of the chimney was investigated by means of finite elements, under gravity loads and thermal variations. Most of the cracks can be explained by thermal effects, if the anisotropic strength of masonry is duly accounted for. Therefore, new cracking phenomena can be excluded, and suitable repair interventions may allow an adequate level of safety to be attained.