3D FE pushover and non-linear dynamic analyses of a masonry chimney before and after shortening

A masonry chimney 50 meters high, severely damaged by the May 2012 Emilia-Romagna (Italy) seismic sequence is numerically analyzed by means of non linear static and dynamic FE techniques. The state of damage on the upper part of the structure led to take the decision to shorten the chimney for security reasons, with a reduction of the height up to 37 meters. A modal pushover analysis (MPA) where force distributions based on the principal vibration modes is used to analyze the structure, finding for the 50 meters case crack patterns consistent with the observed ones. In addition, it is shown how, before and after shortening, the behavior factor to be used in modal response spectrum analyses, estimated directly from the MPA results, is slightly higher than unity, indicating a very low dissipative capacity. To validate static approach results, non-linear dynamic analyses are carried out using natural accelerograms and for the masonry material a damage-plasticity model. The residual deformations obtained and the crack patterns found exhibit convincing similarities with the real behaviour and address how the shortening may be beneficial to improve stability.