Seismic analysis of strength degraded structures

Structures such as unreinforced masonrywalls, soft-storey buildings, gravity structures and nonstructural components which include free-standing objects are well known to be non-ductile and yet commonly found in regions of low-moderate seismicity. Potential significant degradation in strength in these structural systems in projected earthquake scenarios has been a cause for concern. Shaking table experiments undertaken earlier by the authors revealed very interesting phenomena with the behaviour of ("non-ductile") free-standing objects in an earthquake. Importantly, the displacement time histories predicted by non-linear time history analysis are shown to be consistent with recordings from shaking table experiments. Push-over field tests on a soft-storey building in Melbourne demonstrated force-displacement behaviour that is characterized by predominant P-Δ effects (as is observed with free-standing objects). The force-displacement relationship obtained from field-tests has been used for analytical simulations of seismic response. This paper presents results of parametric studies based on non- linear THA of such structures.