Critical aspects in designing earthquake-resistant dual systems

A simple scheme of dual system is designed for different seismicity levels according to Italian and European standard codes. Some critical aspects on the application of the capacity design rules are evidenced. Nonlinear analyses are carried out for evaluating the actual lateral behavior, showing that the actual structural performance can significantly differ from that assumed at design level. The constructive detailing prescriptions appear to be not calibrated on the design performances and local ductility demand expected in dual systems. This can lead to over-strengthening the structure, without reference to the design assumptions, the actual site hazard, the standard safety levels.