Steel moment resisting frames with energy-dissipation rocking columns under near-fault earthquakes: Probabilistic performance-based-plastic-design for the ultimate stage

In this paper, a probabilistic performance-based-plastic-design methodology for steel moment resisting frames with energy-dissipation rocking columns (MRF-EDRCs) was developed, and the emphasis was given to the ultimate stage of the structure subjected to near-fault earthquakes. Firstly, based on the energy balance notion and an equivalent nonlinear single-degree-of-freedom (SDOF) system representing a low-to-medium steel MRF-EDRC, nonlinear spectral analyses were carried out considering various combinations of hysteretic parameters and a wide range of structural periods. More than 55 million energy modification factors quantifying the seismic demand of the system subjected to near-fault earthquake motions were obtained. Then, a probabilistic spectral model of the energy modification factor was established, which can be utilised as the basis of the design methodology. To promote engineering applications, a stepwise design framework for the steel MRF-EDRC with target drift and a prescribed probabilistic performance target was proposed. To verify the effectiveness of the proposition, a prototype structure with two target drifts was designed and modelled by finite element approach. The rationale of the modelling strategies was confirmed by previous test data. Subsequently, the seismic performance of the designed structure was evaluated by nonlinear pushover and dynamic analyses. The results showed that the designed structure conforming to the proposed method can limit the maximum inter-storey drift to a preselected threshold with a prescribed probabilistic performance target.