Influence of the constructive features of RC existing buildings in their ductility and seismic performance

This paper aims to analyse the ductility of existing buildings to evaluate its influence in their seismic performance. This has been achieved through the retrospective analysis of an existing building in accordance with current seismic codes. This study has revealed the lack of guidance in the NCSE02 and the EC8 regarding the assessment of the ductility of existing buildings. This manuscript proposes a methodology to assess the ductility of Spanish existing buildings. For this purpose, this paper has implemented the American code procedure combined with the EC8 and the Spanish seismic code (NCSE02) requirements. A two-storey RC frame school located in the Spanish region of Huelva has been selected as a case study. Different versions of this school have been compared: as built, designed according to current best practice, EC8 provisions and NCSE02 provisions. To do so, different constructive features have been varied according to each of the ductility class requirements: geometrical properties and the reinforcement ratio of the structural elements. Nonlinear static analyses have been carried out to obtain the displacement ductility factor (mu) and the behaviour factor (q) of each model. Construction costs and the expected damage index have been determined and compared. Results have shown that the best performance, regarding the ductility and the costs, has been obtained with the models designed with deep beams. Conversely, models with wide beams, and where only the reinforcement ratios have been varied, have merely shown a slight enhancement of the resistant and ductile capacity. It has been concluded that the ductility affects the shear capacity, the seismic performance and the expected damage of RC buildings.