Many constructions are built with reinforced or prestressed concrete, and most of them are designed or expected to resist earthquake actions in addition to gravity loads. To limit the effects of ...seismic events on reinforced or prestressed concrete structures, many attempts have been made by researchers in order to (i) improve the knowledge of the response of materials (steel bars and concrete) and members by means of laboratory tests, (ii) develop numerical and capacity models, (iii) enhance procedures for the dynamic analysis and assessment of the seismic performance of structures and (iv) suggest innovative interventions for the seismic retrofit of old and damaged reinforced or prestressed concrete structures. This Special Issue is a collection of 11 important research works that cover a wide range of problems related to the previously mentioned research fields. Both researchers and practical engineers are expected to greatly benefit from this Special Issue in view of their own work and for a better comprehension of the response of r.c. members and structures.
•The papers on the strengthened RC members with FRP via the grooving method are reviewed.•The efficiency of the grooving method compared to the conventional methods is demonstrated.•The grooving ...method improves the behavior of strengthened member by postponing debonding.•The influential parameters on the performance of grooving method are discussed.
In recent decades, the externally bonded reinforcement (EBR) method has been recognized as a desirable and established choice to strengthen reinforced concrete (RC) structures with fiber-reinforced polymer (FRP) composites. The major weakness of this method is the premature debonding of FRP composites from concrete substrates. The grooving method (GM) has been introduced to prevent or postpone premature debonding. This study aims to review the previous studies on strengthening structural members by the grooving method. More specifically, it sought to examine the studies addressing the behaviors of strengthened beams, slabs, columns, and beam-column joints with FRP composites by grooving methods. The effects of groove dimensions as well as the properties of concrete and FRP materials on the performance of the grooving method were evaluated. The enhancements of flexural, shear, compressive, and seismic behaviors of strengthened RC members by grooving method were assessed and their efficiency was compared with the EBR method. The results showed the considerable efficiency of the grooving method in enhancing the performance of all structural concrete members by postponing or preventing premature debonding. Additionally, this method could considerably decrease the amount of consumed material.
Artificial neural networks (ANNs)-based objective functions such as costs and weights of reinforced concrete (RC) frames with four-by-four bays and four floors are optimized simultaneously based on ...big datasets of 330,000 designs according to ACI 318-19, whereas corresponding design parameters, which minimize objective functions, are also obtained. The Pareto frontier verified by big datasets shows reductions up to 44.983% and 33.111% in costs and weights, respectively, compared with probable designs based on averages of 688 (0.1%) best designs among 688,000 samples. Optimized designs' meeting requirements imposed by codes and architects are achieved using the ANN-based Hong-Lagrange algorithm in which complex analytical objective functions are replaced by ANN-based objective functions. ANN is formulated to provide 32 forward outputs based on 18 forward inputs to minimize or maximize objective functions, such as costs and weights as a function of 18 input parameters. When good training qualities are achieved, objective functions with equality and inequality constraints are implemented in the proposed method, which determines optimal design parameters for building with accuracies and robustness equivalent to derivation-based approaches, which are hard to obtain using metaheuristic methods. The proposed AI-based auto-designs perform optimization where design variables are produced automatically while optimizing design targets.
The reinforcing steel bars embedded in the concrete of a reinforced concrete (RC) structure in a region with high airborne chloride concentrations may corrode. To avoid overestimating the seismic ...capacity assessment, it is necessary to understand the residual shear strength of an RC frame with infilled wall and localized corrosion. This work investigates the residual shear strength of an RC frame with infilled wall and localized corrosion by designing five wall specimens with corroded reinforcing steel bars to obtain the residual shear strength of each RC frame with infilled wall with different corrosion zones. Additionally, a model based on the softened strut-and-tie model is proposed to determine the residual shear strength of an RC frame with infilled wall and localized corrosion. The experimental and calculation results are compared to verify the application of the proposed model for the shear strength of an RC frame infilled corroded RC wall.
This Special Issue reprint is dedicated to presenting open and challenging issues in earthquake engineering. It consists of 29 peer-reviewed papers that cover a broad range of subjects and ...applications related to the seismic assessment and design of structures. Based on advanced computational, analytical, numerical, and experimental approaches novel results and discussions are presented. Within this context, the first studies of this issue/reprint are focused on providing an insight into the seismic performance of structures taking into account significant engineering components that still have not been fully addressed. Subsequently, there are studies with new strategies to improve the effectiveness of the dampers on the seismic mitigation performance of structures. Concerning performance-based earthquake engineering, new approaches in the seismic fragility assessment of structures are introduced. Furthermore, new innovative types of reinforced steel for the seismic design and assessment of RC structures are analytically and experimentally evaluated. The seismic performance of retrofitted structures is also addressed, while analytical modeling tools that can effectively capture the seismic behavior of substandard RC structural elements are introduced. Some other papers provide experimental results to evaluate and/or validate the structural performance of elements, such as anchors, connectors, and nuclear components. Finally, this issue/reprint also incorporates modified methodologies and identification techniques to improve seismic analysis methods in the field of structural engineering.
•An accelerated retrofit approach is developed.•The axial compressive behaviour of retrofitted columns are analyzed in detail.•A simple model was proposed with relatively conservative predictions.
...Steel reinforced concrete (RC) members suffer from severe corrosion in some scenarios. New techniques and materials are required for the timely rehabilitation of the deficient structures. To address this challenge, an accelerated retrofit approach using a basalt fibre reinforced polymer (BFRP) sheet combined with ultrahigh performance concrete (UHPC) jacket has been developed. The BFRP sheet was internally embedded within the UHPC matrix to enhance its durability under marine environmental conditions. The treatment of corroded steel stirrups in RC columns replaced with fiber reinforced polymer (FRP) composites is also considered in the retrofit approach. The axial compressive behaviour of a series of corroded RC columns retrofitted with BFRP–UHPC jacket or UHPC jacket is investigated. Specifically, 16 RC columns (six control specimens and 10 retrofitted specimens) were prepared and tested under monotonic axial compression. The test variables were the sectional geometry (i.e. circular or square cross-section), transverse steel reinforcement ratio (i.e. two different stirrup spacings), and retrofitting method (i.e. BFRP–UHPC jacket or UHPC jacket). The test results showed that the maximum increase in the peak load after retrofitting was as large as 145.9%. A simple model for retrofitted RC columns that can provide reasonably accurate but relatively conservative predictions is developed.
This study investigated the flexural strengthening effect of the Thick Hybrid Wall (THW) technique as a seismic retrofit approach for Unreinforced Masonry Wall (URM)-infilled Reinforced Concrete (RC) ...frames. THW is a strength–ductility-type seismic retrofit technique, which was developed for pilotis-type RC buildings. In this study, the flexural strength and failure mechanisms of URM-infilled RC frames retrofitted using the THW technique were investigated. Consequently, a comprehensive theoretical model was developed to measure the flexural strength, and a previously proposed equation was modified. Additionally, an equation was developed to determine the minimum additional-wall length, and another equation was developed to determine the demand length of the additional wall to obtain the demand flexural strength. These equations enhance the cost-efficiency and reduce the irregularities risks. The interaction between the URM infill and surrounding RC columns was modeled, and a cyclic loading test was performed under the influence of a constant axial force on the four specimens. The results indicate that THW technique changes the failure mechanism of URM-infilled RC frames from shear to flexure and that the retrofitted URM acts as part of the lateral resisting system owing to the active lateral confinement pressure. The accuracy of the analytical models was confirmed via experimental results, and the developed models facilitate the practical implementation of the THW technique on intended frames.
•Flexural strength and failure mode of retrofitted URM-infilled RC frames were investigated.•A comprehensive flexural-strength calculation model was developed.•Equations for minimum and demand additional wall lengths were developed.•The interaction between the URM infill and the surrounding RC columns was defined.•The accuracy of the proposed analytical model was examined using the test results.
This article presents cyclic voltammetry, Tafel polarization, and ac. impedance spectroscopy examinations of resorcinol (RC) ion reactivity on Pt(511) single-crystal plane and the effect of ...surface-electrosorbed RC ions on the kinetics of UPD H (underpotentially deposited hydrogen) and HER (hydrogen evolution reaction) processes in 0.1 M NaOH solution. Obtained data delivered a proof for the RC ion surface adsorption and its later electroreduction over the potential range characteristic for the UPD H. A favourable role of platinum-adsorbed resorcinol anions on the kinetics of the UPD H and HER processes is also discussed. The above was explained via the recorded capacitance and charge-transfer resistance parameters (the presence of resorcinol at 1.5 × 10−3 M in 0.1 M NaOH caused significant reduction in the resistance parameter values by 3.9 and 2.6 times, correspondingly, for the UPD of H at 50 mV and the HER process, examined at −50 mV vs. RHE) along with the charge transients, produced by injecting small amounts of RC-based 0.1 M NaOH solution to initially RC-free base electrolyte on the Pt(511) electrode plane (a large cathodic charge-transient density of −90 µC cm−2 was recorded at the electrode potential of 50 mV).
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