New vector-valued intensity measure for predicting the collapse capacity of steel moment resisting frames with viscous dampers

Viscous Dampers (VDs), as a passive energy dissipation system, are increasingly applied for the seismic design and retrofit of structures. In general, probabilistic seismic assessment of structures with VDs is performed by traditional scalar Intensity Measures (IMs) such as pseudo-spectral acceleration at the first mode period of the structure, Sa(T-1). In this paper, the seismic collapse of steel Special Moment Resisting Frames (SMRFs) with VDs is assessed by 18 vector-valued IMs. The first component of the vector-valued IMs is Sa(T-1) and their second components are un-scalable. Incremental Dynamic Analyses (IDAs) are performed to compute the seismic collapse capacity, Sa(col), values of steel SMRFs with VDs. Then, the efficiency and sufficiency of the IMs for the prediction of the collapse capacity of the structures are studied, and (Sa(T-1), SaRatio(M-D)) is proposed as an advanced vector-valued IM that includes the spectral shape and Ground Motion (GM) duration effects. The results indicate that (Sa(T-1), SaRatio(M-D)) possesses high efficiency and sufficiency, and can reliably predict the collapse capacity of steel SMRFs with VDs.