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.
The current paper provides a comprehensive review of experimental studies on corrosion damaged reinforced concrete (RC) components, and the ability of current state-of-the-art numerical models to predict the residual capacity of these corroded RC components. The experimental studies on corroded RC components are classified into five different categories including: (i) beams in flexure, (ii) beams in shear, (iii) columns under pure axial compression, (iv) circular columns in flexure, and (v) rectangular columns in flexure. For each group, a summary of all the previous research are provided. Through the regression analyses, the experimental results of each abovementioned groups are used to examine the adverse effect of corrosion on ductility and, flexural, shear, and axial capacity loss of the corroded RC components. Finally, the observed results of the previous experimental studies are compared with the predicted values using the state-of-the-art numerical models currently available in the literature. The summarised experimental results show that corrosion has much more adverse impact on ductility of the RC columns than strength. However, the effect of corrosion on ductility and strength reduction of RC beams is the same. Moreover, results of cross-sectional moment-curvature analyses using the state-of-the-art corrosion damage models show a good correlation between the predicted residual flexural capacity and observed experimental results. Finally, the existing shortcomings in the literature and open issues to be addressed in the future research are discussed, and some recommendations are provided.
Different kinds of bracing systems are used as the basic methods for providing lateral stiffness and strength in building frames. In recent years, tension-only bracing systems have been suggested by researchers. Steel cable has been recognized as a flexible member which can tolerate tensional forces only. Using the tension-only members as bracing for structures has triggered the concept of applying cables as the lateral braces of structures. Despite the high stiffness and tensional strength of steel cables, they cannot be considered as proper devices in cross bracing due to their low ductility. One of the modern bracing systems is using cables along with a cylinder through which a pair of cables passes from their crossing point. Such bracing systems can be used in strengthening of moment-resisting frames. This research presents the equations that are related to the behavior of cable steel cylinder bracing. Also, the effects of cylinder dimensions and prestressing of cables on the behavior of the mentioned bracing were assessed. In such bracing with steel cylinder, both cables are under tension; therefore, the loosening of cables and their ability to cause impulses will be removed. Moreover, the cables reach their final strengths at higher frame lateral displacements. It is recommended to select the dimensions of the cylinder in such a way that the cables also reach their yielding limit in the damage limit displacement of the frame.
A nonlinear finite element (FE) framework for time-dependent capacity assessment of corroded rectangular RC columns is developed. The proposed nonlinear FE model includes the impact of corrosion on inelastic buckling and low-cycle fatigue degradation of longitudinal reinforcement. The proposed nonlinear FE model is validated against a set of experimental data and then extended to evaluate the impact of corrosion on damage limit states to be used in seismic performance and evaluation of corroded structures. This is done through a parametric study on hypothetical RC columns, varied in axial force ratios, mass loss ratios, cover crack widths, and confinement levels. Moreover, the application of the proposed model in seismic collapse capacity assessment of corroded structures is shown through nonlinear dynamic analyses of prototype columns. Results show that, depending on the axial force ratio, corrosion changes the failure mechanism of the columns. The results of this study suggest for seismic fragility analysis of corroded structures the damage limit states should be considered as timevariant parameters. µ loss ductility loss = (ductility factor of uncorroded column-ductility factor of corroded column) / ductility factor of uncorroded column
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