Application of Sequentially Linear Analysis to the seismic assessment of slender masonry towers.

Brittle failure behavior is an intrinsic characteristic of slender masonry towers that behave as cantilever beams. The application of the classical nonlinear finite element analysis (NLFEA) methods for the seismic assessment of such structures often involves difficulties in the definition of post-peak behavior, which can be characterized by a sudden decay. In order to investigate the post-peak behavior of such structures the sequentially linear analysis (SLA) method has been used as possible alternative tool to the usual nonlinear static analysis methods. Both NLFEA and SLA have been applied to a historical Italian masonry tower. A 2D plane stress and a 3D solid finite element model of the tower have been set up. The nonlinear behavior of the masonry material, both in tension and compression, has been taken into account. The different modeling approaches and the different analysis methods allowed for the comparison of the results. NLFEA showed a very brittle collapse, with convergence problems after the attainment of the peak load. The application of SLA confirmed the results of NLFEA in terms of base shear-top displacement curves and in terms of damage patterns at the peak load. In addition SLA allowed for the investigation of the post-peak behavior and confirmed the very brittle nature of collapse of the tower, since equilibrium has no longer been found after the peak. In conclusion, the application of SLA to the case study demonstrated the potential of the SLA method as alternative and very robust tool for seismic assessment of masonry towers.