Seismic Behavior of Medium and High Strength Concrete Buildings

Current concrete technology has made higher concrete grades more affordable to mid and high-rise buildings; hence its use has been increasing in the late years as it allows for smaller cross-sections, reduction of the structure’s weight, improve durability, among other benefits. However, it is known that brittleness of plain concrete increases with the strength; therefore, some national codes have limited the concrete’s strength in high seismic zones. In this paper, the seismic behavior of a 10 storey dual frame-wall building, designed with concrete grades C30, C60 and C90 is studied in order to assess the advantages and disadvantages of this material and investigate the effects of high concrete strength on the seismic behavior of buildings. In total, three models were studied. Furthermore, a comparison between Force-Based-Design (FBD) and Displacement-Based-Design (DBD) methodologies is made. DBD showed advantages in determining the adequate design ductility and the distribution of forces between frame and wall. The structures are designed according to Eurocode 8 for seismic design high ductility structures. To assess the seismic performance of the building, pushover analyses were made according to the Eurocode 8 (N2 method) in order to determine the performance point. It is observed that adequate design could accommodate concrete’s reduction of ductility. Needed confinement levels can objectively be defined for different concrete strength. Some benefits of the overall increase of strength are highlighted in the paper. The C90 building showed adequate response, although changes on the failure mode were observed.