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A new phenomenological hysteretic model for reinforcing bars with and without corrosion damage is presented. The model simulates buckling of reinforcement, deterioration in postbuckling compressive strength due to strain history and the impact of low-cycle fatigue on tension response. The model, for uncorroded reinforcing bars, is calibrated using data from numerical simulations and corrosion damage parameters are calibrated using experimental data. The model is evaluated using a comprehensive experimental data set, and the results show that the model is in a good agreement with the data.

An advanced modelling technique is developed to model the nonlinear cyclic response of circular RC columns using fibre-based section discretisation method. A comparison between different reinforcing steel models is made. Through a comprehensive parametric study the influence of inelastic buckling of vertical reinforcement on the cyclic response of circular RC columns is investigated. The results have been compared and validated against a set of experimental datasets. The proposed calibrated model accounts for the influence of inelastic buckling of vertical reinforcement and interaction of stiffness of horizontal ties reinforcement with vertical reinforcement. The model also accounts for the fracture of vertical bars due to low-cycle high-amplitude fatigue degradation. Therefore, this model is able to predict the nonlinear cyclic response of circular RC columns up to complete collapse. The results show that the existing uniaxial material models of reinforcing bars that are calibrated using stressstrain behaviour of isolated bars cannot represent the behaviour of reinforcing bars inside RC columns. Moreover, it is found that the buckling length of vertical reinforcement has a significant influence on the pinching response of RC columns and also reduces the low-cycle fatigue life of buckled reinforcement.

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A probabilistic framework for seismic vulnerability analysis of corroded Reinforced Concrete (RC) frame structures is developed. An advanced nonlinear finite element modelling technique is used to accurately simulate the nonlinear behaviour of prototype corroded RC frames over their service life. Different sources of uncertainties including modelling uncertainties, geometrical uncertainties and spatial variability of pitting corrosion are considered through Monte Carlo simulation and using Latin Hypercube Sampling (LHS) technique. A set of new seismic damage limit states (SDLS) are defined accounting for multiple failure modes of the corrosion damaged frames by means of pushover analyses. The influence of corrosion on nonlinear dynamic behaviour of corroded RC frames is investigated through Incremental Dynamic Analysis (IDA) of proposed frame structures under 44 far-field ground motions. The impact of considering corrosion damaged SDLS, spatial variability of pitting corrosion, and record-to-record variability on seismic vulnerability of RC frames are explored and discussed in detail. It is concluded that disregarding the influence of corrosion on SDLS significantly underestimates the probability of failure of corroded RC frames. The analyses results show that spatial variability of pitting corrosion does not have a significant impact on global nonlinear behaviour and seismic vulnerability/reliability of corroded RC frames.

h i g h l i g h t s Influence of buckling low-cycle fatigue life. Influence of bar diameter and surface condition on fatigue life. Low-cycle fatigue life model accounting for the inelastic buckling. New material model accounting for the combined effect of inelastic buckling and low-cycle fatigue degradation. a b s t r a c t The effect of inelastic buckling on low-cycle high amplitude fatigue life of reinforcing bars is investigated experimentally. Ninety low-cycle fatigue tests on reinforcing bars varied in amplitudes and buckling lengths are conducted. Using scanning electron microscope the fractography of fractured surfaces are studied. The results show that the inelastic buckling, bar diameter and surface condition are the main parameters affecting the low-cycle fatigue life of reinforcing bars. Through nonlinear regression analyses of the experimental data a new set of empirical equations for fatigue life prediction of reinforcing bars as a function of the buckling length and yield strength are developed. Finally, these empirical models have been implemented into a new phenomenological hysteretic material model for reinforcing bars. The new material model is able to simulate the nonlinear stress-strain behaviour of reinforcing bars with the effect of inelastic buckling and low-cycle fatigue degradation. The results of simulation using the analytical model show a good agreement with the observed experimental results.