Collapse and upgrading mechanisms associated to the structural materials of a deteriorated masonry tower. Nonlinear assessment under different damage and loading levels

• Material parameters, directly related to the dynamic behaviour of a square tower, are provided.
• Degrading mechanism/structural damage origin are analysed in the nonlinear range.
• Effect of traditional restoration materials on the structural improvement
• Results optimize repair works making the most of traditional materials.

This research focuses on a specific issue: the role of both structural and retrofitting traditional materials (mortar and bricks) on the collapse and structural upgrading mechanisms of a damaged square masonry structure under static and dynamic loading. The potential/limitation of traditional structural materials as retrofitting elements is analysed, as well as their implication in failure/improvement progression. The sensitivity of the structural response to different damage states is investigated using finite element models. A constitutive model is arranged on the basis of prior theories, in order to take into account the singularities of the dynamic response of deteriorated masonry structures, including interlocking, and cracking/crushing. Static, modal and transient analyses are computed in the nonlinear range. The degrading mechanisms and the damage origin are analysed and singled out, as well as the effect of the restoration materials on the safety response improvement. As a main result, it was found the possible origin of a foundation settlement and weak points which are prone to suffer damage were identified. The poor quality of the structural materials increases the fundamental period more than the inclusion of the complete crack pattern The transient simulations carried out showed that when traditional repair materials are applied, 60% increase for shear and 24% decrease for displacement are achieved, and the fundamental period is significantly decreased. Results allow optimizing future repair works, making the most of traditional materials.