Performance criteria expressed by means of relative displacements for a retrofitted masonry school building

Abstract

In order to study how retrofitting techniques applied to URM structures influence the failure modes and the displacement capacity of the buildings, a school building from Bucharest was modelled using 3DMacro software. The mixed structural system required a particular approach for the calculation model, in a software able to capture the interaction between the reinforced concrete elements (columns and tie beams) and the URM masonry panels.Damage pattern evolution was analyzed for the three models capturing the gradual seismic improvements done in the past century, transforming the unreinforced masonry structure into a confined masonry one, with few RC elements, and eventually into a fully jacketed structure with densely spaced RC columns. The results obtained from the nonlinear static analyses were validated by means of global and local displacement limits associated with specific damage criteria.The damage suffered after 1977 Vrancea earthquake and the current performance requirements in terms of seismic safety led to structural changes aimed at improving the behavior of masonry structures by means of interventions that marked the transition from an unreinforced masonry structural system to a retrofitted masonry structural system. The comparative analyses carried out between the behavior of the initial and the strengthened structure of the school intend to highlight the benefits of the retrofitting interventions performed, but also the situations in which the applied strengthening measures might prove to be excessive. Considering the case study is representative for the existing building stock in the education sector in Romania which needed subsequent seismic retrofitting in order to reach the required seismic safety, the results highlight the improved behavior after these interventions. The present works represent a topic of interest at national level, since it targets a large part of the existing building stock subjected to losses in case of an earthquake. Moreover, the past retrofitting interventions assessed in this paper represent a typical intervention done for similar structures, and therefore, the results obtained are representative for the Romanian building stock.