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The beam–column joint (BCJ) is a critical region in a framed structure because during such events as earthquakes it is susceptible to earlier failure than adjacent members, leading to shear failure, and will endanger building users if not designed properly. BCJs designed using preseismic code provisions follow the non-ductile approach and might not resist postelastic rotation without enduring greater damage. Retrofitting techniques offer great opportunities for strengthening damaged BCJs. In this study, the effectiveness of a novel retrofitting scheme based on carbon fibre reinforced polymer (CFRP) confined ultrahigh-performance fibre-reinforced concrete (UHPFRC) in rehabilitating initially damaged BCJ specimens was assessed. Three retrofitting schemes using UHPFRC with and without confinement are proposed: (1) in situ casting of 25 mm thick UHPFRC jackets; (2) in situ casting of steel wire mesh-confined UHPFRC and (3) in situ casting of CFRP-confined UHPFRC. The confining action was achieved by sandwiching wire or CFRP mesh between two layers of UHPFRC. The results of this study indicate that BCJ specimens retrofitted with confined UHPFRC had improved overall seismic response, compared with specimens retrofitted only with UHPFRC. Further, the wire mesh-based retrofitting scheme proved to be more efficient than the CFRP mesh-based scheme. [ABSTRACT FROM AUTHOR]

This paper contains a summary of the experience obtained by researchers at the Instituto Universitario de Ciencia y Tecnología del Hormigón (ICITECH) at Universitat Politècnica de València (Spain), in the last 30 years of investigating reinforced concrete building structures under construction. During this period, ambitious experimental campaigns and advanced computational simulations have been carried out, and new analytical methods have been formulated to assess slab–falsework load transmissions in buildings under construction. From all these campaigns the following main conclusions can be derived. First, it is important to consider construction processes when planning building projects. Second, the use of analytical methods to evaluate construction processes need to be adapted to the current requirements of efficiency and sustainability. Third, there is a need to improve the robustness of temporary shoring or propping structures. Improving the construction sector necessarily involves the implementation of the above measures in buildings under construction and the use of new monitoring and inspection technologies for the construction processes applied. [ABSTRACT FROM AUTHOR]

An investigation was carried out to improve the seismic performance of concrete columns reinforced with high-strength steel bars and subsequently retrofitted with vertical and horizontal carbon-fibre-reinforced polymer (CFRP) strips. Seven columns were constructed and tested under constant axial and cyclic lateral loading. The results showed that attaching CFRP vertical strips in or over grooves outperformed conventional externally bonded reinforcement, as evidenced by greater energy dissipation and strength. Furthermore, the use of corner strip–battens for the horizontal CFRP strips was found to outperform conventional wrapping, as evidenced by greater ductility and energy dissipation. Confining stresses were also more uniformly distributed and strip rupture shifted from the edges to the mid-sides of the section. [ABSTRACT FROM AUTHOR]

The effects of high-strength steel (HSS) on the damage indices (DIs) of four special moment frames and three beam–column connection (BCC) specimens under cyclical loading were experimentally studied. The specimens with HSS rebars (with yield strengths of 500 MPa and 580 MPa) were designed and constructed based on the special seismic provisions of ACI 318-19. Several types of DIs (from single DIs to combined DIs based on parameters such as displacement, absorbed energy and stiffness) were calculated according to the experimental results. The results showed that the application of the higher strength steel expedited the failure process of the specimens. Moreover, the DIs indicated that the specimen fitted with HSS for both the longitudinal and transverse rebars had the greatest damage propagation speed of the frames. For the BCCs, the specimen with HSS as just the longitudinal rebars showed the greatest damage propagation speed. The results also showed that the displacement-based DIs were less accurate than the other types of DIs for studying the damage behaviour of both the frame and the BCC specimens. The combined DIs were found to be more accurate than the other DIs. [ABSTRACT FROM AUTHOR]

Rapid and accurate detection of internal defects in bridges has always been a major concern of the management and maintenance departments. In the present study, an intelligent method for the detection of structural internal defects is proposed based on infrared thermography and deep learning. Through theoretical analysis, numerical simulations and laboratory experiments, the classification, localization and quantification of internal defects of concrete structures were achieved with the infrared thermography and deep learning method. The mean average precision for classification and localization of internal defects is 96.59%, the mIoU for pixel-level segmentation is 95.19%, and the average relative error for damage quantification is 0.70%. The feasibility of the trained model is verified with new images, and the results show that the trained model can capture infrared thermal features of internal defects with different sizes and depths. This method has the advantages of low cost, high accuracy, easy operation, and large area scanning of concrete structures, which can provide a good reference for the detection of internal defects of concrete structures. [ABSTRACT FROM AUTHOR]

The increase in concrete structures' durability is a milestone to improve the sustainability of buildings and infrastructures. In order to ensure a prolonged service life, it is necessary to detect the deterioration of materials by means of monitoring systems aimed at evaluating not only the penetration of aggressive substances into concrete but also the corrosion of carbon-steel reinforcement. Therefore, proper data collection makes it possible to plan suitable restoration works which can be carried out with traditional or innovative techniques and materials. This work focuses on building heritage and it highlights the most recent findings for the conservation and restoration of reinforced concrete structures and masonry buildings. [ABSTRACT FROM AUTHOR]

The distribution of earthquake-induced energy in a 42-storey reinforced concrete dual-system building at three ground shaking intensities was investigated. The earthquake-induced energy response of the building was obtained in terms of elastic energy (kinetic energy and strain energy) and inelastic energy (hysteretic energy and structural damping energy) components for each structural member. Hysteretic energy is an indicator of inelastic deformations (i.e. potential damage) and is considered particularly important as it leads to high irrecoverable energy demands in a building and identifies critical members that require higher energy absorption capacity. The ratio of hysteretic energy to input energy was assessed among different structural members as well as along the building height. The results showed that the hysteretic energy constituted less than 10% of the total input energy and was mostly dissipated in the frame members for low-intensity events, whereas 75% of the input energy was dissipated in the hysteretic mechanism, prominently by the beams. In terms of hysteretic energy demands, the critical floor levels were found to be the 12th and 26th floors. The findings of this research will help engineers obtain a reasonable estimate of the expected hysteretic energy demand once the input energy is known. [ABSTRACT FROM AUTHOR]

Large-volume hydraulic concrete structures, such as concrete dams, often suffer from damage due to the influence of alternating loads and material aging during the service process. The occurrence and further expansion of cracks will affect the integrity, impermeability, and durability of the dam concrete. Therefore, monitoring the changing status of cracks in hydraulic concrete structures is very important for the health service of hydraulic engineering. This study combines computer vision and artificial intelligence methods to propose an automatic damage detection and diagnosis method for hydraulic structures. Specifically, to improve the crack feature extraction effect, the Xception backbone network, which has fewer parameters than the ResNet backbone network, is adopted. With the aim of addressing the problem of premature loss of image detail information and small target information of tiny cracks in hydraulic concrete structures, an adaptive attention mechanism image semantic segmentation algorithm based on Deeplab V3+ network architecture is proposed. Crack images collected from concrete structures of different types of hydraulic structures were used to develop crack datasets. The experimental results show that the proposed method can realize high-precision crack identification, and the identification results have been obtained in the test set, achieving 90.537% Intersection over Union (IOU), 91.227% Precision, 91.301% Recall, and 91.264% F1_score. In addition, the proposed method has been verified on different types of cracks in actual hydraulic concrete structures, further illustrating the effectiveness of the method. [ABSTRACT FROM AUTHOR]

The oil and gas industry is one of the harshest environments on reinforced concrete structures. Enhancing the reliability of these industries has been identified as a critical goal to meet anticipated production targets and maintain competitiveness. The purpose of this paper is to rank and prioritize risk factors on reinforced concrete structural systems in the oil and gas industry to reduce failures and improve system reliability. The risk factors influencing reinforced concrete systems are identified based on the experts interviewed who specialized in risk analysis. In this paper, a risk assessment approach based on a hybrid fuzzy failure mode and effect analysis is developed in order to rank the factors and improve the process of reinforced concrete maintenance prioritization. The developed approach is also compared with the other two methods; namely, conventional failure mode and effect analysis (FMEA) and grey rational analysis (GRA) integrated with FMEA. The three developed approaches are designed to acquire the highest risk priority number (RPN) values; conventional RPN, GRA-FMEA RPN, and Fuzzy-FMEA RPN. These values will be utilized as the focus of improvements to reduce the possibility of some kind of failure occurring a second time and improve the deteriorated reinforced concrete structure to minimize the likelihood of failures. The results revealed that high-risk systems include the compression train, steam turbine, and combustion gas turbine generator, while the majority require maintenance of the supporting concrete foundation as soon as second-degree deterioration occurs. Furthermore, the results indicated that the Fuzzy FMEA approach was appropriate for assessing deteriorated reinforced concrete structures.. This work represents a step forward in the development of a tool that can be used to assess the risk of degraded concrete structures and improve their integrity through proper monitoring and maintenance. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to compare the current design codes' predictions for reinforced concrete (RC) T-beams with the alternative physical methods – namely, the compressive force path (CFP) method and artificial neural networks (ANNs). Therefore, two databases, for T-beams without stirrups and with stirrups, are developed using the available experimental studies. The comparative study on prediction (obtained from the American Concrete Institute and Eurocode 2, CFP and ANN models) shows that the predictions of the ANN model provide a closer fit to the experimental results; after ANN the predictions of the CFP method are close to the experimental results when compared with the counterpart physical model. Comparative studies are also conducted on the critical parameters for the behaviour of RC T-beams. Furthermore, a non-linear finite-element tool (i.e. Abaqus) is used to validate the prediction of the ANN and CFP model. The crack pattern from Abaqus exhibited the same mechanics, on which the CFP models are based. [ABSTRACT FROM AUTHOR]

In Italy, the recent regulatory and legislative developments relevant to the seismic risk mitigation of the existing building stock aim to propose tax deductions and simple but reliable approaches for the quantitative evaluation of the beneficial impacts of seismic retrofitting. Nevertheless, currently policy makers need tools and models able to assess the seismic risk and the cost/benefit of the strengthening interventions at regional/national level in order to plan future mitigation policies and be aware of the effectiveness of measures taken. To this aim, this article proposes a heuristic vulnerability model for large-scale applications. Starting from macroseismic approaches widely used in Europe, fragility and vulnerability curves for masonry and RC buildings are calibrated using a specific procedure based on the new Italian 'guidelines for the seismic risk classification of constructions' approved in January 2020, namely the so-called 'Sisma Bonus.' According to the construction material, building type and number of floors, the developed curves are defined in terms of vulnerability and height classes. The derived vulnerability model can be used in exposure models which rely on poor census data. Finally, it is compared with existing vulnerability models and the comparisons are analysed to demonstrate the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

The Barcelona model is one of the most widespread models used in the nonlinear finite element method for simulating the real behavior of concrete. The strong robustness of this model can be attributed to two main reasons, the first one being its ability to account for the elastic stiffness degradation induced by plastic straining and the second one the aptness of considering the stiffness recovery effects under cyclic loading. This model was examined in the paper by comparing the generated stress-strain diagrams with several analytical solutions from the literature. The comparing process in the compression and tension cases with the closed-form solutions of Desayi, Krätzig, Lubliner and Thorenfeldt proved that the Barcelona model provided identical outcomes with Lubliner's formula, which was used as the hardening function in the finite element implementation of this model. What is more, this model provided the same curves in case of the others in the ascending branches, and for the descending branch, this study proved that the outcomes of the Barcelona model are completely different from the ones of Desayi in the compression case and slightly similar to Thorenfeldt's curves in the tension case. [ABSTRACT FROM AUTHOR]

Major cities worldwide are densely built with concrete structures. Moreover, urban infrastructures partly cause, and are in return adversely impacted by, the urban heat island (UHI) effect that elevates localized temperature, further to the rise caused by the climate change-induced (CCI) impact of CO2 emissions. While the influence of temperature on carbonation is generally well established based on experimental research, there are hardly any analytical engineering methods specifically for evaluating temperature effect on natural carbonation. In the present study, an equation referred to as the temperature correction factor (TCF) submodel, capable of accounting for temperature effect on natural carbonation, was nested into the natural carbonation prediction (NCP) model, then used to conduct the evaluation. Major cities worldwide are densely built with concrete structures. Moreover, urban infrastructures partly cause, and are in return adversely impacted by, the urban heat island (UHI) effect that elevates localized temperature, further to the rise caused by the climate change-induced (CCI) impact of CO2 emissions. While the influence of temperature on carbonation is generally well established based on experimental research, there are hardly any analytical engineering methods specifically for evaluating temperature effect on natural carbonation. In the present study, an equation referred to as the temperature correction factor (TCF) submodel, capable of accounting for temperature effect on natural carbonation, was nested into the natural carbonation prediction (NCP) model, then used to conduct the evaluation. [ABSTRACT FROM AUTHOR]

Reliable measurement of deformations and crack assessment of concrete structural elements under loading is essential for evaluating the performance and durability of these elements. Traditionally, structural elements are monitored under loading with strain gauges, deflectometer, and data acquisition systems. Limited studies have investigated the potential of close-range photogrammetry and three-dimensional (3D) modeling in analyzing deformations, internal stresses/strains, and crack propagation. This research proposes an innovative four-phase testing method to develop 3D models of the concrete beam with close-range photogrammetry and image processing techniques. The proposed method entails the capabilities of analyzing deformations, internal stresses/strains, and monitoring crack propagation. The main phases of the proposed method are as follows: 1) preparing the test setups, beam preparation, photogrammetry preparation, and surveying preparation; 2) testing the beam under loading while recording deformation data, collecting high-resolution images, and conducting ground-controlled surveying from nine points around the beam; 3) performing photogrammetric processing of the images to generate a textured 3D model of the beam; and 4) comparing the results from both the 3D model and the direct measurements. For triangulation accuracy, the overall RMSE of the generated model is 4.974 mm. While for product accuracy, the RMSE is 9.303 mm. Moreover, the RMSE for deformations is 0.115 mm, indicating acceptable accuracy of measurements through the model. In addition, a photogrammetric-based deformation model can be generated for the beam surface, and cracks area, length, and width are efficiently extracted and monitored.

The utilization of externally bonded carbon fiber-reinforced polymers (CFRPs) and glass fiber-reinforced polymers (GFRPs) for reinforcing and retrofitting components has garnered considerable interest recently, as such composites provide beneficial properties, including a high modulus of elasticity, high strength, and low weight. This work conducts a finite element analysis, verified through laboratory experiments on 14 reinforced concrete (RC) beams. The primary focus is the final load of these components, considering varying CFRP orientations relative to the loading direction. In this research, the performances of control beams and RC beams are compared to assess the effectiveness and efficiency of different strengthening methods. The results demonstrated that bonding CFRP sheets with V-shaped end anchorages on the tension side was highly effective in improving the flexural capacity of RC beams in the weaker concrete strength group. This strengthening method resulted in a substantial increase in strength (of around 29.8%) in the higher concrete strength group. In addition, utilizing V-shaped end anchorages to bond CFRP sheets on the tension side proved to be a highly efficient technique for improving flexural strength. Conversely, bonding inclined CFRP strips to the sides of RC beams was highly effective at enhancing the shear capacity of the beams. These outcomes convincingly demonstrate the effectiveness of FRP for the reinforcement of structural components. The specimens strengthened with inclined strips exhibited enhanced shear and deformation capacity compared to those strengthened with vertical strips.

Modern infrastructure heavily relies on robust concrete structures, underscoring the critical need for effective monitoring to ensure their safety and durability. This paper addresses this imperative issue by introducing an innovative automated and wireless system for continuous structural monitoring. By employing embedded electrical resistivity sensors coupled with a wireless-based data transmission mechanism, real-time data collection becomes feasible. We provide a general description of the system’s architecture and its application in a pilot study covering the effects of the devices on concrete properties and data transmission. The dielectric properties of concrete specimens were investigated under natural and accelerated curing/degradation and the results were used in the final design of the antenna device. Furthermore, a pilot test comprising four reinforced concrete columns was used to investigate the range of data transmission from inside to outside of the concrete, the effects of the hardware device on the compressive strength and concrete distribution in the columns, and the data transmission quality in real time under realistic exposure conditions.

Ensuring the safety and stability of buildings during earthquakes is of utmost importance. This can be achieved by assessing the seismic performance of reinforced concrete structures with consideration of design details. This study focused on the seismic behavior of reinforced concrete buildings by comparing the effects of two different types of stirrups, namely those with a 135° angled end-hook shape and straight hooks, with variation of concrete strength. Pushover analysis of a sample building was performed to determine the effect of hook shape on stirrup reinforcement with a constant volumetric ratio for various concrete strength classes. The results of the analysis indicated significant differences in concrete strength and seismic behavior between the two stirrup configurations. The hooked stirrups demonstrated superior energy dissipation capability and ductility, which led to better seismic performance compared to unhooked stirrups across varying levels of concrete strength. To extend the investigation, the study compared the Mander et al., Kent–Scott–Park, and Kappos–Konstantinidis concrete models with different concrete classes (C50-C25-C20-C16-C10). The findings emphasized the importance of stirrup configuration in the design of earthquake-resistant structures. The study concluded that RC structural performance with the 135-degree hooked concrete members exhibited much better behavior of the 90-degree members for the various concrete strength. In this way, it has been revealed the arrangement and detailing of reinforcement in the construction beams and columns improves the governing effect on seismic structural performance.

An algebraic approach to the design of resource-efficient carbon-reinforced concrete structures is presented. Interdisciplinary research in the fields of mathematics and algebra on the one hand and civil engineering and concrete structures on the other can lead to fruitful interactions and can contribute to the development of resource-efficient and sustainable concrete structures. Textile-reinforced concrete (TRC) using non-crimp fabric carbon reinforcement enables very thin and lightweight constructions and thus requires new construction strategies and new manufacturing methods. Algebraic methods applied to topological interlocking contribute to modular, reusable, and hence resource-efficient TRC structures. A modular approach to construct new interlocking blocks by combining different Platonic and Archimedean solids is presented. In particular, the design of blocks that can be decomposed into various n-prisms is the focus of this paper. It is demonstrated that the resulting blocks are highly versatile and offer numerous possibilities for the creation of interlocking assemblies, and a rigorous proof of the interlocking property is outlined.

The Barcelona model is one of the most widespread models used in the nonlinear finite element method for simulating the real behavior of concrete. The strong robustness of this model can be attributed to two main reasons, the first one being its ability to account for the elastic stiffness degradation induced by plastic straining and the second one the aptness of considering the stiffness recovery effects under cyclic loading. This model was examined in the paper by comparing the generated stress–strain diagrams with several analytical solutions from the literature. The comparing process in the compression and tension cases with the closed-form solutions of Desayi, Krätzig, Lubliner and Thorenfeldt proved that the Barcelona model provided identical outcomes with Lubliner’s formula, which was used as the hardening function in the finite element implementation of this model. What is more, this model provided the same curves in case of the others in the ascending branches, and for the descending branch, this study proved that the outcomes of the Barcelona model are completely different from the ones of Desayi in the compression case and slightly similar to Thorenfeldt’s curves in the tension case.

An efficient yet accurate procedure was developed for the seismic assessment of reinforced concrete (RC) bridges subject to chloride-induced corrosion. The procedure involves using incremental modal pushover analysis to assess corroded bridges as an alternative and less computationally demanding approach to non-linear dynamic analysis. A multi-physics finite-element analysis is performed to evaluate the effects of chloride-induced corrosion on bridge columns. In doing so, chloride ingress in concrete is numerically simulated as a diffusion process by considering the effects of temperature, humidity, corrosion-induced cover cracking and concrete aging. The estimated chloride concentration is then employed to evaluate the corrosion current density, from which the effects of corrosion on reinforcement, cracked cover concrete, confinement and plastic hinge length can be determined for subsequent non-linear static analysis. A case study of a typical bridge structure is presented. The proposed procedure can be used to assess the seismic performance of irregular RC bridges exposed to severe corrosive environments. [ABSTRACT FROM AUTHOR]

The seismic performance of reinforced concrete (RC) bridges in the coastal environment of Bandar Abbas, Iran, was investigated. Probabilistic seismic hazard analysis results of the region, covering a radius of 150 km keeping Bandar Abbas as the centre, are first presented. To determine the dominant earthquake scenario characterised by magnitude and source-to-site distance, disaggregation of peak ground acceleration (PGA) hazards corresponding to mean return periods of 475 and 2475 years was carried out. Results of the disaggregation analysis were then used to select a ground motion set for non-linear dynamic time history analysis of a bridge. In the next step, the effects of chloride-induced corrosion of the bridge columns, including degradation of steel bars, cover concrete and core concrete properties, were considered at different time steps in the bridge's service life. Finally, seismic fragility curves of the corroded bridge at selected time steps were developed based on multiple-stripe analysis results and the maximum likelihood approach. Based on these analyses, to ensure the appropriate seismic performance of a RC bridge over its service life, it is proposed that the design PGA should be increased approximately by 37%. [ABSTRACT FROM AUTHOR]

The paper is focused on assessment of existing prestressed concrete bridge by simplified methods for estimation of coefficient of variation. The bridge was selected in the framework of the European Project INTERREG AUSTRIA-CZECH REPUBLIC "ATCZ190 SAFEBRIDGE" focused on advanced numerical analysis of existing bridges represented by non-linear finite element model. The key ingredient in semi-probabilistic design and assessment of structures is an estimation of coefficient of variation (ECoV). Recently, correlation interval approach together with novel Eigen ECoV were proposed by authors of this paper and theoretically proved to be an efficient and accurate alternative to existing methods. This contribution is focused on practical application of Eigen ECoV on real example solved by NLFEM and its comparison with other existing simplified methods. [ABSTRACT FROM AUTHOR]

The paper is focused on probabilistic assessment and sensitivity analysis of existing prestressed concrete bridge using surrogate model in form of Polynomial Chaos Expansion (PCE). The bridge was selected in the framework of the European Project INTERREG AUSTRIA-CZECH REPUBLIC "TCZ190 SAFEBRIDGE" focused on advanced numerical analysis of existing bridges represented by non-linear finite element model. In this study, surrogate model in form of PCE was created, which represents very efficient type of surrogate model. One of significant advantages of PCE is powerful post-processing including sensitivity and moment analysis of the response, which is important part of probabilistic analysis. The obtained numerical results of advanced stochastic analysis consisting of uncertainty quantification and sensitivity analysis of the existing bridge structure are presented in the paper. [ABSTRACT FROM AUTHOR]

Generally, in reinforced concrete (RC) core wall buildings, the formation of one plastic hinge at the base is preferred; this is called the single plastic hinge (SPH) approach. During a severe earthquake, this approach results in significant moment demand in the upper regions of the wall due to the effect of higher modes of vibration. This study considered RC core walls of 30-, 40- and 50-storey buildings, designed using a response spectrum analysis. The SPH, dual plastic hinge (DPH), triple plastic hinge (TPH) and extended plastic hinge (EPH) approaches were examined using fibre element models and non-linear time history analysis. The DPH and TPH approaches respectively contain one and two plastic hinges at the upper levels of the wall in addition to the base plastic hinge. The effect of the locations of the upper plastic hinges on the seismic response of the core wall was investigated. The results showed that there is not a distinct level for the upper plastic hinge location to minimise the envelope of different demand quantities simultaneously. The curvature demand of the middle plastic hinge in the TPH case was higher than the base curvature demands. Reducing the resistant moment at the wall base by reducing the reinforcement ratio can help to balance curvature demands along the height of the TPH model. [ABSTRACT FROM AUTHOR]

Breakwater structures made of concrete are used widely around the world, and the bacteria living on these surfaces can cause the concrete to deteriorate. In this study, we collected bacterial biofilms from concrete breakwater structures located along the coast of an island, a mainland coast, and a freshwater riverbank as well as planktonic water samples from each site, and we analysed their bacterial community structures using Illumina sequencing. At the phylum level, Proteobacteria and Actinobacteria dominated planktonic samples, whereas Cyanobacteria, Proteobacteria and Bacteroidetes dominated the biofilm samples. High Cyanobacteria abundance was found in all biofilm samples. Bacterial communities significantly varied between planktonic and biofilm samples and between biofilm samples from seawater and freshwater. Only a small number of bacterial operational taxonomic units were shared by planktonic and biofilm samples from each sampling site. The permanganate index in ambient water had a more significant impact on biofilm bacterial communities than on planktonic samples. Additionally, ammonia nitrogen and total nitrogen contents were positively correlated and salinity was negatively correlated with bacterial beta diversity in biofilm samples. [ABSTRACT FROM AUTHOR]

This article describes the publicly available dataset of multiple shaking table tests on a restrained rocking and sliding bridge system exhibiting negative lateral stiffness. Given the scarcity of experimental campaigns on such systems, this dataset is valuable for the development and validation of analytical and numerical models, with 184 tests. This large body of data allows the models to be validated in a statistical sense. This work describes in detail the specimen and its construction, as well as all instrumentation used during the tests. It presents the organization of the shared data, and concludes with some examples of how the available data can be postprocessed for assessing the behavior of the system. [ABSTRACT FROM AUTHOR]

In the seismic design and evaluation of bridges, a method is required for determining the shear strength of reinforced concrete columns to avoid brittle shear failures. In addition, detailed design and evaluation often require predictions of the complete hysteretic response of bridge columns to accurately model the nonlinear dynamic response of the bridge. Predictions of the shear strength of columns using the provisions of the AASHTO Specifications are compared with the reversed-cyclic loading test results of shear-critical columns. It is found that the Simplified Procedure results in very conservative predictions of the seismic shear strength. The General Procedure provides conservative and more accurate predictions of the seismic shear strength. It is suggested that the AASHTO reduction factor on the concrete contribution resisting shear for low compressive axial load levels be removed. Nonlinear finite element analysis predictions are made for a selection of rectangular and circular columns tested in reversed-cyclic loading and are compared with the experimental results. The ability of nonlinear finite element analysis to predict the reversed-cyclic loading responses of columns with a wide range of variables and having different failure modes is demonstrated. [ABSTRACT FROM AUTHOR]

This study aims to numerically investigate the behaviour of corroded circular reinforced concrete (RC) columns strengthened by carbon-fabric-reinforced cementitious matrix (C-FRCM) composites. Three-dimensional finite element (FE) models of the corroded circular RC columns with and without strengthening were set up and validated against previous experimental results. Based on the validated FE models, the parametric studies were carried out to investigate the effects of axial compression ratio, degree of corrosion and layer of carbon fabrics on the behaviour of corroded RC columns under cyclic loading. It shows that the lateral load resistance increased when the axial compression ratio ranged from 0.3 to 0.4, but decreased when the axial compression ratio ranged from 0.4 to 0.6; also the ductility of the corroded RC columns reduced with increasing axial compression ratio. The ultimate capacity of corroded RC columns decreased gradually with the increasing degree of corrosion. Based on the results of parametric studies, equations were developed to estimate the ultimate capacity and displacement of the corroded RC columns repaired by the C-FRCM. The proposed equations can well estimate the ultimate lateral load resisting capacity and ultimate displacement of the corroded circular RC columns strengthened by C-FRCM. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to investigate the effects of stirrup corrosion, concrete strength and casting position on the behaviour of the bond between steel bars and concrete. Accelerated corrosion was applied to corrode the stirrups in concrete specimens under laboratory conditions. In total, 180 specimens were cast and tested in this experiment. The specimens had three nominal concrete strengths of C20, C40 and C50 with two deformed steel bars of 18 mm in diameter set in a 200 × 200 mm diagonal concrete prism with two stirrups of 8 mm in diameter to provide confinement. The steel bars were cast with different pouring positions, namely the upper and lower ends. Five corrosion levels were investigated, namely 0, 5, 10, 15 and 20%; 12 specimens were investigated for each corrosion level. A pull-out test was carried out to obtain the bond–slip curves. The test results indicate that the porosity of concrete has a great effect on bond degradation with the increase of the steel corrosion level. [ABSTRACT FROM AUTHOR]

Fire and extreme heat environmental changes can have an impact on concrete performance, and as climate change increases, new concrete structures are being developed. Nano-silica and nano-calcium carbonate have shown excellent performances in modifying concrete due to their large specific surface areas. This review describes the changes in concrete modified with nano-silica (NS) and nano-calcium carbonate (NC), which accelerate the hydration reaction with the cementitious materials to produce more C-S-H, resulting in a denser microstructure and improved mechanical properties and durability of the concrete. The mechanical property decay and visualization of deformation of mixed NS and NC concrete were tested by exposure to high temperatures to investigate the practical application of mixed composite nanomaterials (NC+NS) to concrete. The nano-modified concrete had better overall properties and was heated at 200 °C, 400 °C, 600 °C and 800 °C to relatively improve the mechanical properties of the nano concrete structures. The review concluded that high temperatures of 800 °C to 1000 °C severely damaged the structure of the concrete, reducing the mechanical properties by around 60%, and the dense nano concrete structures were more susceptible to cracking and damage. The high temperature resistance of NS and NC-modified nano concrete was relatively higher than that of normal concrete, with NC concrete being more resistant to damage at high temperatures than the NS samples. [ABSTRACT FROM AUTHOR]

The effects of graphene oxide (GO) on the microstructure and resistance to chloride ion (Cl−) penetration of matrix containing 0-0.05% GO were investigated through isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, mercury intrusion porosimetry and the rapid chloride penetration test method. A proper dosage of GO promoted the hydration process of cement, increased the calcium hydroxide (Ca(OH)2) content, refined the size of calcium hydroxide, promoted the formation of high-density calcium silicate hydrate and improved the pore size distribution of cement matrix. Compared to the group without GO, the porosity of concrete containing 0.03% GO decreased by 8.56%, the largest pore diameter decreased by 29.05% and pores larger than 50 nm were reduced by 36.93%. In addition, the incorporation of GO improved the resistance to chloride ion penetration of concrete. The charge passed through the concrete first decreased and then increased with the increasing GO dosage. When the dosage of GO was 0.03%, the charge passed through the concrete was 27.71% lower than that of the control group. There was a significant correlation between the permeability of chloride ions and pore structure, especially the proportion of pores larger than 50 nm of concrete. [ABSTRACT FROM AUTHOR]

This study seeks to analyze how the degree of carbonation and the application of waterproofing and anticorrosive materials affect carbonation in water reservoirs among the water treatment facilities managed by the Seoul Metropolitan Government. To guarantee similarity of the experimental group, 42 highly similar water reservoirs were selected from among the water supply reservoirs currently in operation in Seoul. On-site carbonation assessments were performed in order to derive the carbonation rate coefficients. In the water reservoirs with applied waterproofing and anticorrosive materials immediately after public service, the upper and lower limits were D = 1.13 t and D = 0.29 t , respectively, whereas those of the water reservoir applied with waterproofing and anticorrosive materials after 15 years of service life were D = 1.89 t and D = 0.94 t , respectively. The comparative analysis showed that the rate of reduction in the carbonation rate was about 10.4% to 16.8% in the water reservoirs applied with waterproofing and anticorrosive methods after 15 years of service life. However, reduction in the carbonation rate was about 46.4% to 74.3% in the water reservoirs applied with waterproofing and anticorrosive methods at the initial stage of service life. It was confirmed that the early application of waterproofing and anticorrosive materials is effective in suppressing carbonation of concrete water reservoir structures. [ABSTRACT FROM AUTHOR]

Bridges are essential components of transportation systems and their unacceptable performance following a disaster may lead to disruption to relief operations. Many existing bridges all around the world were designed based on early editions of seismic codes and the performance of some old bridges following seismic events has revealed that they are seismically vulnerable. This paper provides a comparison of the seismic performance of reinforced concrete (RC) bridges designed according to recent code editions and according to earlier provisions. To this end, a probabilistic seismic safety assessment of RC bridges was conducted. Non-linear response history analyses were performed for each set of bridge samples subjected to earthquake ground motions with different severities employing three-dimensional models. The effect of the earthquake focal mechanism on the seismic vulnerability of the bridges was investigated. Moreover, fragility curves were developed for RC bridges designed according to the latest edition of the American Association of State Highway and Transportation Officials (Aashto) specifications (so-called new bridges) and those designed based on pre-1980 specifications (so-called old bridges). The fragility curves are presented in terms of the geometrical specifications of the bridges and the focal mechanism associated with input motions for both new and old bridges. [ABSTRACT FROM AUTHOR]

The presented study investigates the efficiency of repairing damaged reinforced concrete beams by a novel technique, which is the injection of epoxy resin to the cracks. The two main test parameters were the amount of flexural reinforcement (low, medium, and high) and the level of seismic damage before repair (light, moderate, and heavy). Nine cantilever beams were tested under reversed cyclic transverse loading in the undamaged (original) and repaired (after damaging) states. The test results were examined and discussed in terms of the initial flexural rigidity and ultimate load capacity. The technique was shown to be the most effective in damaged beams with mid-sized cracks. The minor cracks particularly in lightly-reinforced beams were not suitable for proper injection of resin, while the major cracks resulted in the epoxy to govern the flexural behavior of the beam after repair. The experimental load capacities were shown to be in close agreement with the analytical flexural capacities of the respective beams. The sizes of the cracks before repair and the longitudinal reinforcement did not affect the repaired beam to reach the load capacity of the original counterpart but affected the extent of deformations before reaching this load level. [ABSTRACT FROM AUTHOR]

The concrete industry accounts for a significant amount of CO2 emissions worldwide. One approach to counter this issue includes material reduction of structural components via the use of non-metallic reinforcement, such as carbon, glass and basalt fibre reinforced polymers. On the one hand, non-metallic reinforcement. However, as its environmental impact has not been sufficiently investigated yet, a Life Cycle Assessment of the production phase is presented within this paper. In a first step, the environmental impact of the sole various reinforcement components and types is compared to each other per mass, per tensile or rather yield strength as well as density unit, at which an environmental disadvantage of especially carbon-fibre reinforced polymers is apparent in most cases. In a further step, a focus is put on applying the environmental data of carbon-fibre reinforced polymers to a pedestrian bridge, which is finally compared to a conventionally reinforced concrete bridge and a steel bridge with similar boundary conditions. The latter results indicate that an adequate application of carbon-fibre reinforcement in structural components has the potential to lead to designs of less environmental impact in comparison to conventionally reinforced pendants.

Carbonation of concretes is a natural physico-chemical process that can be described as a reaction between the carbon dioxide contained in the air and the cement matrix. Carbonation concerns all concretes types in contact with the ambient air but also concretes in ground, from production stage to use and end-of-life stages. The amount of carbon dioxide bound varies according to the type of binder, the compacity of concrete and the environmental conditions during the use and the end-of-life stages. To consider the re-carbonation of concrete, works have been carried out within the framework of the European standardization group CEN/TC229/WG5 and in CEN/TC104. A methodology to consider the re-carbonation of concrete structures has been proposed in the NF EN 16757 standard on environmental product declarations for concrete and concrete elements. In addition, FD CEN/TR 17310 provides detailed recommendations regarding carbonation and absorption of carbon dioxide in concrete and give some precisions for application of NF EN 16757. This is an important topic towards a sustainable development in the current context of circular economy and CO2 uptake related to the French energy labelling (E+C-). In this paper, numerical and analytical carbonation models are used to estimate the CO2 binding ability of concrete structures. The obtained results are compared to the methodology proposed in Appendix BB of NF EN 16757 standard. They confirm that the methodology described in the NF EN 16757 standard leads to estimated degree of carbonation of the same order of magnitude. The advantage of using more advanced models lies in a better consideration of environmental parameters, the possibility to simulate the behaviour of crushed concrete, its reuse in new concrete as recycled aggregate and the possibility to simulate the carbonation of concretes in ground. This is an immediate perspective in the ongoing work in the French national project FastCarb on accelerated carbonation of recycled concrete aggregates.

The noninvasive technique of ultrasonic pulse rate (UPV) is increasingly used in the evaluation of the quality of concrete, providing information about the integrity of structures and preventing possible disasters. Therefore, for its direct application, it is necessary to have a prior correlation between the noninvasive UPV technique and the invasive uniaxial compression resistance (UCS) assay. While correlations have been determined by various authors, each has been given specific conditions and guidelines by the authors because there is no standardized way to perform the correlations. Rather, there are only experimental tests that have generated experimental correlations—both linear and logarithmic—with different graphic shapes. Therefore, this research aims, first, to validate the aforementioned relationship, which allows the compressure resistance of concrete (f'c) to be determined for a given design of concrete mixtures following the American Concrete Institute (ACI. 211.1.). Second, it aims to determine the most accurate trend and the possibly correct form of the correlation plot between the UPV and UCS. In the first instance, 15 plain concrete specimens were designed with an f’c of 28 MPa, whose dosage was carried out following the method of ACI. 211.1. Then, UPV and UCS tests were performed according to regulations in the first 28 days of curing the specimens. Finally, a logarithmic correlation was obtained between the UPV values and the values of the invasive tests for the UCS of concrete. A graphical analysis with some existing correlations of other investigations was then performed, and a similarity in the logarithmic tendency, with a coefficient of determination greater than that of the linear trend, was observed.

Concrete building structures are prone to cracking as they are subjected to environmental temperatures, freeze-thaw cycles, and other operational environmental factors. Failure to detect cracks in the key building structure at the early stage can result in serious accidents and associated economic losses. A new method using the SE-U-Net model based on a conditional generative adversarial network (CGAN) has been developed to identify small cracks in concrete structures in this paper. This proposed method was a pixel-level U-Net model based on a generative network, that was integrated the original convolutional layer with an attention mechanism, and an SE module in the jump connection section was added to improve the identifiability of the model. The discriminative network compared the generated images with real images using the PatchGAN model. Through the adversarial training of generator and discriminator, the performance of generator in crack image segmentation task is improved, and the trained generation network is used to segment cracks. In damage assessments, the crack skeleton was represented by the individual pixel width and recognized using the binary morphological crack skeleton method, in which the final length, area, and average width of the crack could be determined through the geometric correction index. The results showed that compared with other methods, the proposed method could better identify subtle pixel-level cracks, and the identification accuracy is 98.48%. These methods are of great significance for the identification of cracks and the damage assessment of concrete structures in practice. [ABSTRACT FROM AUTHOR]

Due to many uncertainties arising from the seismic process, the current mechanism model-driven forward prediction methods or data-driven smart inversion methods are difficult to achieve reliable damage prediction of one specific structure under the sudden earthquake. To overcome this difficulty, a mechanism-driven and data-driven fusion method is developed to predict seismic damage evolution of concrete structures. In this method, the developed cooperative multi-particle swarm optimization (CMPSO) algorithm is utilized to optimize the seismic damage by combining with finite element computation, which can reduce the optimization variables for searching optimal solution easily. Additionally, a prior knowledge-based mutation procedure is utilized to consider the physical mechanism that damage index is proportional to the stress level during optimization process, which can support the physical guidance for searching optimal solution randomly during the optimization process. Based on the two advantages, a representative numerical case of a concrete frame structure under seismic loading is utilized to support the effectiveness of the method. A comparison of prediction results with experimental results verifies the ability of the developed mechanism-driven and data-driven fusion method, which can be capable of seismic damage prediction of concrete structures. [Display omitted] • A mechanism-driven and data-driven fusion prediction method is developed. • Seismic damage evolution can be predicted based on the structural response. • The method have the advantages of mechanism-driven and data-driven methods. • A case of a concrete frame structure under cyclic loading supports the method. [ABSTRACT FROM AUTHOR]

• An improved AE crack localization method is proposed. • Empirical mode decomposition is first-ever integrated with a source localization model. • The proposed method is free of the use of bulk AE parameters. • The proposed method is verified using a suite of experimental studies with different damage types. Acoustic Emission (AE) monitoring is considered one of the popular non-destructive testing (NDT) methodologies that have been used to predict and identify the location of damage in critical civil infrastructure. In this paper, an improved AE crack localization method is proposed by integrating the empirical mode decomposition (EMD)-based signal decomposition method with a source localization model. Unlike the conventional AE method, the proposed method is free of the use of bulk AE parameters such as counts, rise time, signal strength, and energy. First, EMD is used to minimize the presence of noise in the recorded AE waveforms and extract the key AE components. Then, key AE events are located using the source localization model to localize the crack in concrete structures. The performance of the proposed method is validated experimentally on small and large-scale concrete beams, where the damage is induced using progressive static load testing. In particular, the large-scale beams are designed for flexural and shear mode failure to evaluate the performance of the proposed method under various types of damage. Finally, the results of the proposed method are compared with the traditional method that uses raw AE waveforms and the method that uses bandpass-filtered AE waveforms. The results show higher crack location accuracy of the proposed method than the other methods, which makes it a suitable approach as a crack localization technology. [ABSTRACT FROM AUTHOR]

• Field tests revealed the failure mechanism of concrete structures subjected to embedded explosion of cylindrical shelled explosive. • Both 3D and 2D numerical models were established and verified. • The effect of length-to-diameter ratio, embedded depth, shell thickness, and shell head length on the CCT for a buried explosion was revealed. This paper broadens previous research concerning spalling damage in concrete structures under buried explosions, by additionally examining the effects of shell thickness and shell head length of the warhead experimentally and numerically. In the experiment, concrete targets were subjected to the embedded explosion of cylindrical shelled explosives with different charge masses, shell thicknesses, and shell head lengths. The results reveal that thicker charge shells and longer shell heads decrease the surface area and the depth of spalling damage on the rear surface of concrete structures. In addition, to investigate the damage mechanism and predict the critical collapse thickness (CCT), two- and three-dimensional finite-element models were developed and correlated well with the experimental results. Parametric analyses are also applied to examine how the embedded depth, length-to-diameter ratio, shell thickness, and shell head length affect the CCT for a buried explosion. Finally, an empirical formula is proposed to estimate the CCT based on these factors. [ABSTRACT FROM AUTHOR]

This paper presents the novel concept of titanium alloy reinforced ultra-high performance concrete (TARUHPC) that can be utilized in bridges. This research highlights the advantages associated with titanium alloy bars (TiABs) and ultra-high performance concrete (UHPC). To validate the concept, pullout tests were implemented to assess the pullout behavior of TiABs with concrete and UHPC. Twelve beam samples (normal concrete and UHPC) were prepared using #6 (ø 0.75 inch) TiABs with different embedment lengths. TARUHPC specimens performed exceedingly better, with an average ultimate force of about 29 kips and a resulting shear stress of 1.82 ksi.