MODELLING OF PLASTIC HINGES IN EXTERNALLY CONFINED REINFORCED CONCRETE COLUMNS

摘要: The external confinement of reinforced concrete columns by collars made from steel hollow structural sections (HSS) has proved to be a successful rehabilitation scheme for seismically deficient existing reinforced concrete frame buildings, as has been demonstrated through extensive experimental study conducted at the University of Alberta. The experimental programme consisted of two phases: in phase one, the behaviour of externally confined columns under concentric monotonic loading was studied and in phase two, the behaviour of externally confined columns under simulated seismic loading was studied. The first step in the modelling of plastic hinges is the development of a model to predict the material curves of externally confined concrete. In this paper, a confinement model is proposed that takes into account both the flexural and axial stiffnesses of the collars to predict the behaviour of externally confined columns under concentric monotonic axial loading. The model predictions show very good agreement with the experimental results of the columns tested in phase one. In addition, using the proposed model the confined concrete material curves for the columns tested in phase two were obtained which, in turn, were used to predict their moment–curvature and moment–lateral drift envelope curves. The predicted envelope curves show very good agreement with the experimentally obtained curves at low and moderate values of lateral drift. Currently, the predictions overestimate the capacity at high levels of lateral drift due to the lack of a failure criterion in the stress vs. strain model. The post-peak portion of the model is still under …