Effect of lightweight steel partitions on seismic behaviour of moment resisting frames

For several years the partition walls were considered as architectural elements and were not accounted for in the structural design, despite they could significantly influence the overall performance of the structure. The principal aims of the present work is to investigate the influence of lightweight (LWS) steel partitions on the seismic performance of perimeter steel moment resisting frames (MRFs) and monitor the development of the damage within them. The behaviour of the partition walls was modelled through a non-linear spring properly calibrated on a set of five experimental tests. Static and dynamic non-linear analyses were conducted on a total of 24 MRFs, varying the design acceleration (i.e., 0.25 g and 0.35 g) and the beam span (i.e, 6 m and 8 m). Moreover, for each geometry, three sets of MRFs were alternatively designed according to the rules provided by: the current version of the EN1998-1, the North American codes, and the last draft of the next Eurocode 8. The results show that the presence of partition walls implies an increase in structural lateral stiffness and maximum resistance. The influence of the partition walls is a function of both the initial stiffness of the investigated MRF, thus more deformable is the system, larger will be the influence of the partition walls, and the rotational demand; indeed, increasing the lateral displacement will imply a gradual damage within the partition walls that for high value of interstorey drift will not provide significant contribution to the structural behaviour.