Understanding crack patterns in masonry chimneys

A 66 m-tall masonry chimney, dating back to the end of the XIX century, is analyzed. The chimney is no longer in service, and is part of a company town located in northern Italy, which is included in the UNESCO World Heritage List. The chimney has a double wall up to a certain height, and is single-walled in the remaining part. In the lower part, the two walls are connected by vertical ribs and horizontal diaphragms. The chimney exhibits several faults (cracks, tilt), which were accurately detected by means of a direct survey. Aim of this research is the identification of the possible origin of the cracks, which can be helpful in the definition of future repair interventions. A detailed finite element model of the chimney is developed. Both wind actions and thermal changes induced by combustion fumes are taken into account. After excluding that wind can have originated cracks, attention is focused on thermal strains. The presence of most cracks can be actually motivated by thermal effects, provided that the anisotropic strength of brickwork is taken into account. Accordingly, most cracks are likely to have formed when the chimney was operational. Appropriate repairs can ensure that the disused chimney will remain safe, as the development of new, significant cracks can be excluded. The conclusion of this research can be extended to other coeval chimneys of similar geometry.