COMPARISON OF DUCTILITY CLASS REQUIREMENTS FOR SEISMIC DESIGN OF REINFORCED CONCRETE WALLS IN A TALL BUILDING

Abstract

The seismic design of reinforced concrete walls is greatly influenced by the selected ductility class. The ductility class directly determines the reduction of seismic loading by reducing the response spectrum using an appropriate behaviour factor. A higher ductility class can only be achieved by following more stringent design rules related to the type, amount, and detailing of reinforcement. In this paper, an overview of the differences in the design criteria required to achieve a medium (DCM) and high (DCH) ductility class is presented. The difference in behaviour factor between these two ductility classes is 50%. Three buildings of different heights (40 m, 50 m, and 60 m) in which reinforced concrete walls are arranged around a central core are analysed. The dimensions of the core and the thickness of the walls were chosen primarily to achieve the required stiffness of the building and to meet the conditions for total and inter-story displacements. Seismic loads for ductility classes DCM and DCH were calculated for all buildings, and a seismic response spectrum analysis was performed. Finally, a seismic design of selected walls was performed for each ductility class according to EN 1998-1-1. The results show a difference in the required amount of reinforcement, and its placement, depending on the reinforcement type (B500B or B500C). The main difference in design was found to be the resistance to sliding shear failure, which requires additional angled reinforcement for DCH ductility class. Examples of reinforcement detailing are shown graphically for each ductility class. A conclusion is drawn regarding the advantages of choosing the highest ductility class, taking into account the cost of reinforcement.