Behaviour of RC buildings with large lightly reinforced walls along the perimeter

摘要

Reinforced Concrete (RC) walls are defined as large lightly reinforced walls if they are not provided of high reinforcement percentage or if they are lack of reinforcement details usually required to improve the ductility of the structure. This type of walls gained relevance in 1950s-1970s constructions because of their good performances under seismic actions. Real earthquakes have, indeed, demonstrated that buildings constructed with large lightly reinforced walls, characterised by adequate area respect to the floor extension, could suffer lower damages in comparison with traditional RC framed buildings. Moreover, a widespread use of such a construction typology is outstanding thanks to the diffusion on the market of new types of integrated formworks, including insulating materials such as polystyrene, that are being used for casting concrete and are aimed to obtain a higher energetic efficiency and build structures made of continuous lightly reinforced walls. Nevertheless, there is a lack of both experimental information and specific design indications in technical codes on this type of construction. This paper firstly reviews the European code requirements for large lightly reinforced walls. Then, some experimental tests on RC walls in the existing literature are studied in detail also by means of a nonlinear Finite Element (FE) model. Finally, the performances of a whole RC building designed with both large lightly reinforced walls along the perimeter and internal frames have been also exploited by linear dynamic and static nonlinear analysis. The analysis are mainly aimed to highlight the influence of in-plane stiffness of the floor on the dynamic behaviour of the structure and to assess the contribution of both ductility and over-strength to the behaviour factor, i.e. to the seismic performance of such type of buildings, considering the lack of information in the technical literature about these features.