Search

Smart fiber reinforced concretes (FRC) are good in intelligent environmental response. With the smart FRC being used in buildings such as bridges and tunnels, the real-time online distributed monitoring of concrete state can be realized. It provides an excellent solution to reduce the emergencies caused by the accumulation of damages, resistance attenuation, etc. This paper analyzes smart FRC's self-sensing and self-healing response characteristics under different environmental response fields. Furthermore, the intelligent response mechanism of smart carbon fiber reinforced concrete (CFRC), optical fiber reinforced concrete (OFRC), glass fiber reinforced concrete (GFRC), and nanofiber reinforced concrete (NFRC) would be summarized. The response fields include the stress field, temperature field, electromagnetic field, chemical field, and humidity field, among which the field response mechanism of smart NFRC is classified and summarized. Finally, the advantages and disadvantages, the intelligent response parameters, and the applications of smart FRC under different environmental fields are compared. [ABSTRACT FROM AUTHOR]

This paper introduces a novel steel–concrete composite column referred to as the core-steel tube with T-shaped steel reinforced concrete (CSTRC) column, which is composed of a core steel tube with T-shaped steel embedded in a reinforced concrete column. To investigate the mechanical performance of the CSTRC column under eccentric compressive load, the load–deformation response, stress, and strain distribution of CSTRC columns under eccentric load are analyzed by finite element software. Furthermore, the effects of slenderness ratio, concrete and steel strength on the eccentric compression performance of CSTRC columns are also discussed. Finally, a set of formulas for predicting the ultimate strength of the CSTRC columns is proposed. The study results reveal that: (1) The established finite element model accurately predicts bearing capacity and strain development. (2) When the eccentricity is 0.2, the specimen exhibits characteristics indicative of small eccentricity failure. Conversely, when the eccentricity is 0.8, the specimen demonstrates traits associated with large eccentricity failure. Furthermore, as the eccentricity increases, there is a notable decrease in the bearing capacity of the specimen. (3) The slenderness ratio affects the failure mode of the CSTRC columns, with consideration for second-order effects necessary when the ratio exceeds 22. (4) Increasing the concrete strength, steel strength, and steel ratio significantly enhances the ultimate load values of the CSTRC columns. (5) A comparison between calculated and simulated values demonstrates good agreement, validating the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

This research focuses on a comprehensive comparative analysis of shear strength prediction in slab–column connections, integrating machine learning, design codes, and finite element analysis (FEA). The existing empirical models lack the influencing parameters that decrease their prediction accuracy. In this paper, current design codes of American Concrete Institute 318-19 (ACI 318-19) and Eurocode 2 (EC2), as well as innovative approaches like the compressive force path method and machine learning models are employed to predict the punching shear strength using a comprehensive database of 610 samples. The database consists of seven key parameters including slab depth (ds), column dimension (cs), shear span ratio (av/d), yield strength of longitudinal steel (fy), longitudinal reinforcement ratio (ρl), ultimate load-carrying capacity (Vu), and concrete compressive strength (fc). Compared with the design codes and other machine learning models, the particle swarm optimization-based feedforward neural network (PSOFNN) performed the best predictions. PSOFNN predicted the punching shear of flat slab with maximum accuracy with R2 value of 99.37% and least MSE and MAE values of 0.0275% and 1.214%, respectively. The findings of the study are validated through FEA of slabs to confirm experimental results and machine learning predictions that showed excellent agreement with PSOFNN predictions. The research also provides insight into the application of metaheuristic models along with ANN, revealing that not all metaheuristic models can outperform ANN as usually perceived. The study also highlights superior predictive capabilities of EC2 over ACI 318-19 for punching shear values. [ABSTRACT FROM AUTHOR]

This paper investigates the effectiveness of machine learning (ML) models available in MATLAB Regression Learner app and MATLAB App Designer, both low-code applications, for accurately predicting punching shear strength (PSS) in reinforced concrete (RC) slabs. A database of 379 RC slab samples without transverse reinforcement was compiled from renowned publications. RandomSearch and Bayesian optimisation were employed for tuning hyperparameters. The performance of these models was compared with six empirical models, which included three current design codes, three equations from other researchers, and 227 finite-element simulations conducted by the authors. The ML models and finite-element method (FEM) demonstrated superior performance compared with the literature and practical codes. Furthermore, the results emphasised the exceptional performance of the Gaussian process regression (GPR) with optimised hyperparameters, exhibiting the best performance in validation, training, and testing datasets with R2 values of 0.95, 0.99, and 0.98, respectively. A user-friendly standalone application was developed, providing real-time predictions of the PSS using the two best-developed ML models, GPR and support vector machine (SVM), as well as six empirical models from the literature. This tool offers users flexibility in choosing the most appropriate model for their specific needs, delivering reliable, and accurate results for estimating the PSS of RC slabs. [ABSTRACT FROM AUTHOR]

Summary: Chloride ions are a potential cause of rebar corrosion in a reinforced concrete (RC) structure. Corrosion causes the rebar to expand, thereby stressing the concrete and causing the structure to deteriorate in time. An embedded chloride ion sensory system would enable real‐time detection of chloride ions in the pore solution which enables timely corrective action to be taken to save the structure. Ideally, such a sensory system would be a miniature, low‐cost and durable integrated circuit (IC)‐sized device. This would enable widespread deployment of such a system inside many of the RC structures being built around the world. This literature review paper endeavours to look at currently existing technology in a bid to identify technology areas which can be developed through future research to design an operational IC‐sized chloride ion detection system. Such a review is highly innovative as such sensors have not yet been miniaturised to the microscale IC level. The paper also uses a specifically developed parametric score system through which the best technology for miniaturisation could be identified. After comparing the various technologies which can be used to build the miniaturised chloride ion detection, the area which was found to be most promising was one based on potential measurement using galvanic voltage measurement. [ABSTRACT FROM AUTHOR]

The motive of building sustainable structures and strengthening the structural members is important to overcome the problems associated with poor initial design and/or construction, accidental events, and degradation related to the environment. This paper aims to assess the flexural behavior of a prestressed basaltic fiber-reinforced polymer- (FRP-) strengthened reinforced concrete (RC) beam under static load through the finite-element method using ABAQUS CAE that is validated with experimental results from relevant literature. To achieve the desired objective, 18 models were prepared based on prestressing level, thickness of basalt FRP (BFRP), width of BFRP, length of BFRP, bond between concrete and BFRP, and type of FRP as study parameters. The results indicate that the use of prestressed BFRP is efficient in strengthening the flexural strength of the RC beam. Compared to nonstrengthened specimens, the flexural capacity of the specimens strengthened with BFRP at prestressing levels of 0%, 15%, 35%, and 45% show enhancement of 6.09%, 9.17%, 13.89%, and 17.57%, respectively. While increasing the width, length, and thickness of the prestressed BFRP section, increased yielding and ultimate load capacity of the specimen have been obtained; however, the ductility has been reduced up to 13.87% with increasing the BFRP thickness. The result also shows that the specimen strengthened with prestressed BFRP has better ductility than the prestressed carbon FRP (CFRP)-strengthened specimen; however, the model strengthened with prestressed CFRP has shown higher load-carrying capacity. It is also noticed that a cohesive bond better suited the experimental specimen than the fixed interference of the concrete surface, and relative to the cohesive bond, the fixed interference has shown a 17.4% higher ultimate load carrying capacity. [ABSTRACT FROM AUTHOR]

The booming growth of computational abilities in the 21st century has led to its assimilation and benefit in all horizons of engineering. For civil engineers, these advancements have led to groundbreaking technologies such as BIM, automation, and optimization. Unfortunately, even in an era of dwindling resources and dire need for sustainability, optimization has failed to attract implementation in practice. Despite an exponential growth as an area of research interest, the optimization of engineering structures such as reinforced concrete (RC) is still a complex task that requires multidisciplinary knowledge, hindering its practicability. Although past review papers have delved into this topic, they have only been able to cover the breadth of information available by covering broader aspects of optimization of structures. This study on the other hand aims to cover this topic in depth to uncover problem specific trends and issues, by focusing only on optimization of RC cantilever retaining walls. Although there is an abundance of research studies on this topic, there is an absence of any critical review to tie them up, and concurrently with its broader scope, it suffers the same lack of applicability in the field. The in-depth review presents a summarization of all the online publications including research articles, conference papers, and theses to the best of authors' knowledge on the topic of RC cantilever retaining wall optimization. Geographical trends, regional developments, and prominent journals have been identified. The design codes, problem formulation, objectives, constraints, variables, and their optimization techniques are tabulated for ease of understanding. Unique areas of development investigated by the different researchers have been highlighted. Lastly, comprehensive recommendations for future works have been detailed with a focus on improving its applicability and assimilation into the construction industry. [ABSTRACT FROM AUTHOR]

Concrete is the most commonly used construction material in infrastructural projects, but it may suffer from damages because of the heavy loads, fatigue, and harsh service environments. Therefore, it is crucial to detect damage for evaluating the structural conditions and providing guidance for daily maintenance and timely alarm. This paper presents a novel method for damage assessment that offers an easy-carried detection process with a large monitoring range. The proposed method involves exciting stress waves using a force-hammer and receiving them with piezoceramics pasted on the structure. The structural conditions are then evaluated using the Pearson correlation coefficient (PCC) of stress waves received from different stages. To verify the feasibility of the proposed method, a numerical model is innovatively established to study the stress wave propagation in a reinforced concrete (RC) beam with actual damage induced by the external load based on the concrete damaged plasticity (CDP) model. The experimental study is then conducted to demonstrate the effectiveness of the method and the accuracy of the numerical simulation. The numerical and experimental results show a good correlation, illustrating that the proposed method can not only effectively distinguish whether damage occurs but also determine the structural condition from the elastic phase to failure. The proposed monitoring method in this study has great potential for fast damage assessment of RC structures for both lab research and practical applications. [ABSTRACT FROM AUTHOR]

Corrosion in steel leads to the deterioration of reinforced concrete structures due to chemical reactions between steel and its surrounding atmosphere. In this paper, a novel anticorrosive powder was derived from the waste Printed Circuit Board (PCB) and manually coated on the steel rebar of the reinforced concrete specimen. The corrosion-resistant efficiency of the developed nano PCB-coating on the steel bars was studied by polarization, electrochemical impedance spectroscopy, and accelerated corrosion technique. Also, the applicability of the nano PCB-coated rebar as reinforcement in the concrete environment was investigated. From the results, it was observed that the nano PCB-coated specimens exhibited 3.5 times reduced rate of corrosion and lost only 46.15% strength and 52.5% diameter under the accelerated rate of 6 V after 48 hours. The presence of nano PCB powder improved the corrosion-resistant behaviour of the steel rebar by 1.65 times of the noncoated specimen. Also, the nano PCB-coating reduced the loss in residual yield strength of the corroded steel rebar by 32% lesser than the noncoated specimens and exhibited similar corrosion-resistant properties as that of the existing zinc coating. In addition to the corrosion resistance, the nano PCB-coated steel rebar exhibited almost similar adhesion with concrete as that of the commercial zinc coating which is 7% lower than uncoated steel rebars. It was inferred from this research work that the proposed anticorrosive coating prepared from the waste nano PCB powder showed better corrosion-resistant behaviour and reduced the overall cost of coating by 42%, which ensures economy and serviceability. [ABSTRACT FROM AUTHOR]

As the composite pile, the precast concrete piles reinforced with cement-treated soil (PCCS) is formed by driving the precast cement (PC) pile into the deep mixing (DM) column, which has been successfully and widely utilized to support buildings and embankments over soft soil. To increase the pile spacing and give full play to the economic merits of the PCCS, a reinforcement scheme, which involves the combined use of rigid piles and flexible columns, employing penetrated PCCSs and floating DM columns is proposed and utilized for soft soil ground treatment. However, there is a lack of feasible method for consolidation behaviors of this combined composite foundation (CCF) reinforced with penetrated PCCSs and floating DM columns under flexible loads. This paper developed an analytical solution to predict the average consolidation degree of this CCF based on a cylinder consolidation model and double-layer ground consolidation theory. The excess pore pressure and average consolidation degree were calculated by considering the composite pile penetration into the cushion. The analytical method agrees well with results obtained by numerical analysis. Additionally, a parametric study was conducted systematically to analyze the effect of key influence factors on the average consolidation degree of this CCF. The results indicate that the consolidation rate of this CCF can be much faster than that of the natural ground. The consolidation rate strongly depends on the compressive modulus and area replacement ratio of PCCSs. The increasing inner core-outer core modulus ratio and the inner core-subsoil modulus ratio increase the consolidation rate of this CCF. In addition, the consolidation rate increases with the gravel cushion-subsoil modulus ratio, while it decreases with the loading period. [ABSTRACT FROM AUTHOR]

Dry-type joints are an advanced type of sustainable beam-column connection mode used in the prefabricated concrete frame structural system. This paper proposed an improvement scheme for high-strength bolt dry-type joints and designed a new type of common bolt dry-type joints. A pseudo test involving low-cycle repeated loading is conducted to assess the seismic resistance properties of new joints including damage mode, hysteretic curve, skeleton curve, and ductility factor. Numerical simulation is applied to validate the rationality of experimental results. It is found that when the bending capacity of the end block of the beam is consistent with that of the bolt, the deformation of the bolt will no longer increase greatly after a period of large deformation; at this period, the bolt does not fully enter the plastic stage, but at this time, the end block of the beam begins to appear large cracks and enter the plastic deformation and has good energy dissipation performance. [ABSTRACT FROM AUTHOR]

A new model-free output-only signal processing-based damage detection procedure was carried out in this paper. First of all, a finite element model as the representative of reinforced concrete (RC) frames was constructed and subjected to a specific loading protocol in OpenSees. The protocol consisted of 9 consequent different near-fault fling-step pulse-type earthquake records with low-amplitude white noises among them to simulate the collapse procedure. The analysis process was complemented in three levels: (a) the Fourier transform was utilized to extract the vibration frequency, (b) the time instants of damage occurrence were detected by using the discrete wavelet transform, and (c) accurate damage detection was made by using the extracted pulse components of the records as loading protocol for earthquake simulation and the discrete wavelet transform. The results revealed that the proposed combinatorial method could efficiently diagnose the damage in the RC frames. Also, applying a pulse component instead of an original record increases the accuracy of damage detection by 70%. [ABSTRACT FROM AUTHOR]

Transverse reinforcement of reinforced concrete (RC) columns contributes greatly to the ductility deformation capacity of RC structures. The existing models to predict the amount of transverse reinforcement required are all empirical models with low accuracy and large dispersion and have not considered the real ductility demand of individual components. This paper proposes a ductility design method of RC structure based on component drift ratio demand obtained from nonlinear structural dynamic analysis. To establish the best transverse reinforcement ratio prediction model for RC columns, based on an experimental database consisting of 498 columns, 12 machine learning (ML) models are trained. To solve the over-fitting problem caused by the current situation of "few samples and big errors" of the experimental database, feature engineering aiming at dimension reduction is systematically carried out through an iterative process. Through comprehensive performance evaluation on the testing set, an XGBoost model is selected. To interpret the "black box" ML model, the SHAP method and partial dependence plots are used to analyse the correlation between the input parameters and the transverse reinforcement ratio. The interpretation results are consistent with mechanical laws and engineering experience, which prove the reliability of the selected ML model. Compared with two existing empirical models, the proposed XGBoost model shows higher accuracy and smaller deviation. After safety probability analysis, the trained XGBoost model is transformed into C code and integrated into seismic design software for productive practice. An open-source data-driven model to predict the transverse reinforcement ratio required for RC columns is provided worldwide, with the flexibility to account for additional experimental results. [ABSTRACT FROM AUTHOR]

The influence of masonry infill walls on the progressive collapse performance of reinforced concrete (RC) frame structures was investigated in this paper, using a nonlinear dynamic analysis approach. Based on ANSYS/LS-DYNA finite element software, two finite element models of RC frame structures with and without masonry infilled walls were established. Then, the collapse modes of the two RC frame structure models were analyzed for different scaled distance blast loads, different locations of column damage, and different span numbers. The results show that with the increase of explosive amount, the collapse degree of the structure is more serious in the same time. Under the condition of destroying the outermost central column, the degree of progressive collapse of the RC frame model with infilled walls in the same time is lower than that of the RC frame model without infilled walls. The RC frame model with infilled walls is more resistant to collapse when the outermost side columns are damaged. With the increase of span number, the structure is more likely to be damaged and collapsed. [ABSTRACT FROM AUTHOR]

Summary: This paper provides a novel and effective self‐adaptive real‐time clustering (SARTC) strategy for clustering real‐world large datasets real time, and a novel feature selection method (LS‐MI) was proposed to enhance the clustering efficiency. The effectiveness of the novel methods was validated by theoretical analysis and experimental verification on three benchmark datasets; the result shows that the novel methods achieved the superiorities of high efficiency, high accuracy, and adaptive convergence. And the novel methods were applied to damage pattern recognition for steel tube confined reinforced concrete columns through acoustic emission (AE) signals; the result shows that the proposed LS‐MI procedure can retain AE features with strong representativity but low redundancy, while the SARTC strategy can classify the real‐time AE signals into three clusters with clear bonds. The generalized AE clustering structure was discussed, and possible relation of the clusters to the damage types were explicated; these results create a foundation for establishment of general AE interpretation rules for damage mode identification in future works. [ABSTRACT FROM AUTHOR]

This paper examines the effectiveness of pure torsional loads on hollow reinforced concrete high-strengthened beams. Engineers need to know how much twist a structural member generates when exposed to torsional loads to design it properly. This is done through an experimental investigation of the torsional behavior of reinforced concrete (RC) beams using twelve hollow rectangular beams with varying parameters, such as the spacing of the stirrups, the influence of the steel fiber fraction, and the main reinforcement amount. Four values of fiber volume fractions (0, 0.5%, 0.75%, and 1%), three spacings of transverse reinforcements (60,100, and 150 mm), and various longitudinal reinforcements (8Ф12 mm, 6Ф12 mm, and 4Ф12 mm) have been used. The tested beams had the same length (1000 mm), cross-sections, concrete mixture, and quality control. In the hollow beams, the interior dimensions were 180 mm × 180 mm, while the exterior dimensions were 300 mm × 300 mm. Torsional loads were applied to all the beams using custom-built test equipment. This study highlighted that the structural characteristics of hollow RC beams could be improved by increasing the fiber volume, lowering the stirrup spacing, and increasing the longitudinal reinforcement. Torsion moments rose by 132% when the fractional volume of fiber was increased from 0% to 1%, while they rose by 71.27% when the longitudinal reinforcement was increased from 4 to 8 bars for beams with fractional volumes of fiber of 0.5 percent and the same transverse reinforcement ratios. [ABSTRACT FROM AUTHOR]

Summary: During the Emilia‐Romagna earthquake (2012), a great number of steel racks used to store cheese wheels collapsed, causing a non‐negligible damage to the Italian economy. Therefore, for similar structures that survived and are in service, a deep investigation towards the assessment of their effective safety is required. In the seismic analysis of these frames, the mechanical constraint acting onto the racks due to the reinforced concrete sidewalls, possible nonlinearities exhibited by the base‐plate joints and the in‐plane restraint provided by wooden boards that connects adjacent columns should be carefully modelled to ensure realistic design results. In the paper, an experimental activity, based on suitable modal identification techniques, is presented to capture the dynamic behaviour of these peculiar structures. The scope is to collect data useful to calibrate numerical finite element models in order to accurately define the aforementioned unknown parameters. Furthermore, a few numerical models based on ideal restraints are herein discussed stressing out non‐negligible differences in terms of expected seismic and static response. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a methodology is developed for seismic damage identification of non‐ductile reinforced concrete moment frames using surface crack images. A comprehensive database comprising 264 surface crack patterns from quasi‐static test results of 61 non‐ductile beam‐column joint specimens at various damage levels is collected. The database covers a broad range of structural and geometric properties. Multifractal dimensions of the column and joint regions of damaged beam‐column subassembly images are obtained and used as the complexity and irregularity index of the surface crack patterns. Predictive equations are developed that estimate the peak drift ratio during an earthquake using the multifractal dimensions of surface crack patterns. Six scenarios are considered for obtaining the predictive equations. The developed empirical equations rely on the multifractal dimensions along with the structural properties of the non‐ductile beam‐column joint. The peak drift ratio estimated by the proposed methodology can finally be used as the input engineering demand parameter to the existing fragility curves in the literature to identify the probability of exceedance from damage states of non‐ductile reinforced concrete moment frames. [ABSTRACT FROM AUTHOR]

In this paper, the elastoplastic damage constitutive model of concrete is established based on the damage energy release rate to analyze the failure of concrete structures. Based on the user-defined material program VUMAT interface provided by the ABAQUS, the explicit algorithm is used to secondary develop the concrete model. The model is verified from mechanical behavior, mesh-dependence, and stress state under reciprocating loading. The results show that the model can reasonably simulate the mechanical state of concrete under compression and tension and can effectively solve the mesh-dependence problem in finite element problems. The simulation results were still consistent when the mesh size was 2.5 mm. The low cycle reciprocating simulation test of the concrete column also proves that the model has better hysteretic and bidirectional coupling performance. It is verified that the VUMAT material subroutine can meet the analysis requirements of reinforced concrete structures and can be used to simulate the dynamic response of structures with strong nonlinear stages. [ABSTRACT FROM AUTHOR]

This paper presents a joint mode for a vertical grouting sleeve and a partially distributed reinforced composite connection. The seismic performance of four hybrids precast shear walls with a shear span ratio of 1.83, an axial compression ratio of 0.20, and partially connected vertically distributed rebar was studied by pseudo-static tests. The connection ratios of the reinforced concrete with a vertical distribution were 100%, 67%, 50%, and 33% and were compared with cast-in-place shear walls. It was found that both the precast and cast-in-place specimens demonstrated bending and shear failure modes. Both ends of the mortar layer were cracked under compression, and steel connection failure occurred under the ultimate load. The load-displacement hysteresis curve was bow-shaped and relatively full; the yield load increased from 11.4 to 16.6, and the peak load increased from 4.2 to 6.8 compared with those of the cast-in-situ specimen. The strength degradation performance of the precast specimen was slightly weaker than that of the cast-in-place specimen. The ductility coefficient of the precast specimens was approximately 4, and the ultimate displacement angle was between 1/30 and 1/32, which was larger than the limit value of elastic-plastic interlayer displacement of shear wall structures required by the code. The reduction in the number of vertically distributed rebar connections led to a decrease in the bearing capacity, stiffness, ductility, and energy dissipation, but the impact was very small. [ABSTRACT FROM AUTHOR]

Based on the TBM tunnel of Red Line of Tel Aviv in Israel, this paper carried out laboratory tests of shield cutting concrete and reinforced concrete piles and investigated cutting performance of cutter, failure model of rebars, length of damaged rebars, and cutter vibration. The results indicate that under the condition of low tunneling speed and rotating speed, vibration of the cutterhead is small, and vibration of the center cutterhead is more obvious in the radial direction of the cutterhead. Cross sections of broken rebars mainly consist of shear section, tensile-shear section, tensile-compressive section, and bending section. Considering the tunnel status, it is recommended to adopt excavation speed of 3∼5 mm/min, and rotating speed of 1.0∼1.3 r/min. While cutting RC piles, the principle of "low excavation speed, high rotating speed, and less disturbance" is recommended. Cutting with disc cutters is efficient and the torque of which is stable but the length of the rebars got from cutting varies a lot. It is recommended that majorities of the cutters shall be disc cutters and supplemented with drag bits and tear cutters. [ABSTRACT FROM AUTHOR]

Concrete is the most widely used building material in the world, and it plays a very important role in building modern infrastructures that stand the test of time. X. Peng et al. [[25]] studied the size effects on compressive and tensile strengths of recycled aggregate concrete. According to experimental results, both compressive and tensile strengths of recycled concrete have obvious size effects as the strength value decreases gradually with increased specimen size. A. M. Song et al. [[36]] investigated the static and fatigue properties of steel concrete composite beams under the hogging moment via experimental tests and analytical models and the structural deformation were also discussed. [Extracted from the article]

For water purification plants and sewage treatment plants, there is no reference optimal steel content for the wall of reinforced concrete water pool. Focusing on the reinforced concrete water pool, this paper explores the optimal wall thickness and optimal reinforcement area at different bending moments and identifies the optimal steel content. To solve the problem, the authors established the discrete distribution function for the engineering cost per unit length of pool wall and steel content. The theoretical model was verified by numerous data through Excel numerical simulation. The research results provide a reference optimal steel content for designers and help to save the engineering cost of pool wall. [ABSTRACT FROM AUTHOR]

The river sand is a primary parameter in the concrete structure. This work replaces accessible locally accessible substitution materials like red soil and manufactured sand (M-Sand). In this paper, the mechanical properties and durability of concrete containing red soil and M-Sand have been studied. In this investigation, M30 grade concrete was used, and tests were conducted for two sets of combinations; i.e., red soil as a partial replacement for river sand seems to be 20%, 30%, 40%, 50%, and 60%, and red soil as a partial replacement for manufactured sand (M-Sand) seems to be 60%, 50%, 40%, 30%, and 20%. The compressive strength (7 days, 28 days, 90 days), split tensile strength (28 days), and flexural strength (28 days) have been determined. The combination S4-50% river sand + 50 % red soil and S9-70% M- Sand + 30 % red soil gives more compressive strength than other combinations. Similarly, the combination S3-60% river sand + 40 % red soil and S6-40% M- Sand + 60 % red soil gives more flexural and split tensile strength than other combinations. The scanning electron microscope (SEM) analysis, EDAX analysis, and durability tests like alkalinity, sulfate attack, and chloride attack have also been studied. [ABSTRACT FROM AUTHOR]

The corrosion of steel reinforcement in reinforced concrete is a serious problem affecting the durability of concrete structures. And the steel corrosion caused by chloride ion erosion is the most serious damage to reinforced concrete structures, which affects the safety and service life of the structure. In order to prevent steel corrosion caused by chloride, it is necessary to pay more attention to chloride ion penetration damage. At present, the most commonly used method is to use additives in concrete structures, so as to improve the durability of concrete by reducing its permeability coefficient. Cement-based permeable crystalline admixtures can effectively improve the impermeability and mechanical properties of concrete by complex crystallization reactions between reactive chemicals and cement gels. In the paper, the Penetron admix 803 was selected as a typical CPCA in the experimental study, and the rapid chloride migration (RCM) experiments and mechanics experiments were carried out for four concrete structures with different dosages of Penetron admix 803 (PA8). Compared with plain concrete, the concrete structure containing PA8 makes it difficult for water and other liquids to enter by filling micropores and shrinkage cracks by scanning electron microscope test, so its impermeability is greatly improved. And concrete structure containing permeable crystalline admixture can reduce chloride ion permeability effectively. The experimental results showed that with the increase of PA8 content, the diffusion coefficient of the concrete structure decreased rapidly from 45.8 × 10−12 m2/s to 17.7 × 10−12 m2/s, while the service life of concrete structures increased continuously. And the mechanism of the chemical reaction between PA8 and the internal components of concrete structure was revealed, which was mainly due to the catalytic reaction between the reactive chemicals of PA8 and the cement hydrates of concrete structure forming insoluble crystals filled with concrete micropores. Experimental and theoretical results indicate that the permeable crystalline admixture can greatly improve the chloride-related durability and mechanical properties of the concrete structure. [ABSTRACT FROM AUTHOR]

This paper presents the findings of investigation, which was instigated to assess the effects of fibre aspect-ratio on the fresh and mechanical properties of SCC. The investigational parameters were aspect-ratio of the fibre and fibre addition rate. Two different aspect-ratios (64 and 73) of steel fibre were used and the fibre addition rate was between 0.2% and 1.0% with the increment of 0.2% and the fibres were added to the SCC in volume fraction. A series of tests were performed to determine the impact of fibre aspect-ratio and fibre inclusion rate on the engineering/mechanical properties of SCC. The presence of steel fibre in the SCC lessened the workability; furthermore, the upsurge in the inclusion rate of steel fibre abridged the workability further. The inclusion of fibre boosted the compressive strength of the SCC moderately, and conversely, an overwhelming increase in flexural and tensile strength was observed. The rise in the fibre aspect-ratio caused a 2.53% augmentation in the compressive strength of the SCC. Nevertheless, more than 11% improvement in tensile strength was observed, because of the bridging/anchorage established by the fibre. From the obtained results, it can be inferred that the impact of fibre aspect-ratio on the compressive strength of the SCC is not substantial; however, the tensile strength properties of the SCC can be enhanced moderately by increasing the fibre aspect-ratio. [ABSTRACT FROM AUTHOR]

Many reinforced concrete frame buildings were developed and constructed in Coimbatore zone III before 2002. In 2002, the seismic code IS 1893 was updated. As a result, structures constructed earlier in 2002 do not meet the codal criterion. The majority of structures through infilled walls were nondesigned with infills in consideration. This paper goals to appraise seismic exposure of an advanced reinforced present concrete building with infilled and without infilled frames. A pushover analysis was used to conduct this analysis. According to ATC40, the analysis shows the comportment levels of several building components for various stated concert objectives. [ABSTRACT FROM AUTHOR]

Summary: The unscented Kalman filter (UKF) can be used to identify model parameters of structural systems from the measurement data. However, the standard UKF may provide unreliable and nonphysical estimates, since no parameter constraints are incorporated in the identification process. This paper discusses and compares several constrained UKF (CUKF) methods for parameter identification of structural systems. The effectiveness and robustness of the methods are evaluated through numerical simulation on a Bouc–Wen hysteretic system. The results demonstrate that with properly handling of the constraints, the identification accuracy can be improved. The proposed CUKF method is further validated using experimental data collected from a full‐scale reinforced concrete structure. Based on the identified model parameters, the updated models can achieve more accurate simulation responses than the initial model. [ABSTRACT FROM AUTHOR]

Most of the prediction models for the shear capacity of FRP bar reinforced concrete beams without web reinforcement in current codes are reported to be conservative and do not consider the effect of span-to-depth ratio. Grey relational analysis (GRA) method was used in this paper to investigate the relevance of span-to-depth ratio with the shear capacity, and the results shown that the span-to-depth ratio greatly affects the shear capacity of FRP bar reinforced concrete beams without web reinforcement. A prediction model which considers the effect of span-to-depth ratio was proposed for the shear capacity of FRP bar reinforced concrete beams without web reinforcement by regression analysis, which is more accurate and reasonable in comparison with the current models. [ABSTRACT FROM AUTHOR]

The need for assessing and retrofitting structures increased with time as terrorism-induced explosion trends rose with time. This paper presents a numerical investigation on performance assessment of a two-story, one-bay seismic resistant reinforced concrete framed building under close-in blast loading. ANSYS AUTODYN, an explicit nonlinear finite element software program, was used for 3D model development and analysis. The experimental results reported in the literature were used to validate proposed FE models. Furthermore, parametric studies on close-in explosive story-to-story locations and charge masses were performed on both conventional and seismically detailed RC framed structures. FEA results showed that a decrease in scaled distance raised effective plastic strain and damage index values. Furthermore, simultaneous use of close-spaced transverse steel reinforcement spacing in mid-height and ends of reinforced concrete columns is found to be effective in reducing both effective plastic strains and damage index values. [ABSTRACT FROM AUTHOR]

At present, concrete frame structures are widely used, and the frame beam-column joints are the key parts of the whole frame in seismic resistance. In previous studies, recycled steel fiber-reinforced concrete is a new type of environment-friendly reinforcement material, which can also be widely used in the construction industry. Therefore, in this paper, MTS electrohydraulic servo loading systems were used to carry out low-cycle reciprocating cyclic loading tests to study the seismic performance of five 1/2 scale cruciform concrete frame beam-column joint specimens with plain concrete, normal steel fiber-reinforced concrete, and three recycled steel fiber-reinforced concrete with different fiber contents in the joint core area. The results show that the addition of normal steel fibers can improve the bearing capacity, ductility, energy dissipation capacity, and shear strength of concrete frame joint specimens and delay the stiffness degradation of joint specimens, recycled steel fibers can improve the seismic performance of the cruciform concrete frame joints better than normal steel fibers, and the seismic performance increases gradually with the increases of volume ratio of recycled steel fibers. Moreover, with the recycled steel fiber content from 0.5% to 1.0% and then to 1.5%, the increased amplitude of the seismic performance of joint specimens increases. Considering the reinforcing effect of recycled steel fibers on concrete matrix and based on the design formula of shear capacity of reinforced concrete joints, the design formulas of shear capacity of recycled steel fiber-reinforced concrete beam-column joints were established by using the statistical analysis method and the baroclinic rod-truss model, and the calculation results were in good agreement with the test results. This study can provide references for seismic performance research of steel fiber-reinforced beam-column joints and the recycling of steel wire from waste tires. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) beams strengthened with fiber reinforced polymers (FRPs) are structurally complex and prone to plate-end (PE) debonding. In this study, considering the extremely complicated nonlinear relationship between the PE debonding and the parameters, machine learning algorithms, namely, linear regression, ridge regression, decision tree, random forest, and neural network improved by sparrow search algorithm, are established to predict the PE debonding of RC beams strengthened with FRP. The results of reliability evaluation and parameter analysis reveal that ACI, CNR, fib-1, fib-2, and TR55-2 are a little conservative; AS and TR55-1 have the problem of overestimating the shear force; the accuracy and robustness of the SSA-BP model developed in this paper are good; the stirrup reinforcement has the greatest effect on PE debonding; and each parameter shows a complex nonlinear relationship with the shear force when PE debonding occurs. [ABSTRACT FROM AUTHOR]

This paper studied numerically the behavior of carbon fiber reinforced polymer (CFRP) confined bundle reinforced concrete (BRC) columns subjected to repeated impact load. To verify the numerical models with previous experimental tests, Abaqus/Explicit based nonlinear finite element (FE) model was developed. Based on the proposed FE analysis, a parametric study was conducted to investigate the effects of different factors such as CFRP confinement, eccentric axial load, bundle reinforcement arrangement, and column height on repeated impact capacity of RC column. While modeling the structural element, concrete damage plasticity (CDP) model is adopted to account for the plastic and strain rate-dependent behaviors of concrete material under impact load. From the nonlinear FE analysis result, it was found that CFRP confinement improved the impact capacity of bundle reinforced concrete column. As column height increased, the column impact resistance was found to decrease. Moreover, when the CFRP strengthened BRC column specimens were repeatedly impacted, the continuous matrix material was severely damaged, while the fiber showed only minor and gradual compressive failures. [ABSTRACT FROM AUTHOR]

The use of externally bonded fiber-reinforced polymer (EB-FRP) composites for shear strengthening of reinforced concrete (RC) beams presents many challenges given the complex phenomena that come into play. Premature bond failure, the behavior of the interface layer between FRP composites and the concrete substrate, the complex and brittle nature of shear cracks, and the adverse interaction between internal steel stirrups and EB-FRP are some of these phenomena. Compared to experimental investigations, the finite element (FE) technique provides an accurate, cost-effective, and less time-consuming tool, enabling practicing engineers to perform efficient, accurate nonlinear and dynamic analysis as well as parametric studies on RC beams strengthened with EB-FRP. Since 1996, many numerical studies have been carried out on the response of RC beams strengthened using FRP. However, only a few have been related to RC beams strengthened in shear using EB-FRP composites. In addition, the analytical models that have been reported so far have failed to address and encompass all the factors affecting the contribution of EB-FRP to shear resistance because they have mostly been based on experimental studies with limited scopes. The aim of this paper is to build an extensive database of all the studies using finite element analysis (FEA) carried out on RC beams strengthened in shear with EB-FRP composites and to evaluate their strengths and weaknesses through various studied parameters. [ABSTRACT FROM AUTHOR]

For the current problem of detection of grouting defects in posttensioned prestressed concrete members, the paper takes a single-layer arrangement of prestressed pipes as the object of study. The influence law of the main factors such as pipe material, defect size, defect critical surface location, and prestressing reinforcement location on the results of the impact-echo method for detecting concrete grouting defects was studied. Firstly, the ABAQUS finite element software was used to simulate these factors to obtain the influence law on the detection results, and a modal test was conducted to verify them. The results show that the impact-echo method can effectively test the location of defects and the degree of burial depth, and the pipe material influences the test results, and the impact of corrugated metal pipe is smaller and more accurate than the PVC pipe. In addition, the greater the plate thickness frequency drift rate, the larger the transverse size of the defect, so the plate thickness frequency drift rate and the measured defect depth are combined to quantitatively determine the depth of the defect. [ABSTRACT FROM AUTHOR]

To reveal the global picture and emerging evolution trends with sufficiently large literature data of RC structure's service life prediction, especially the time to corrosion initiation, the scientometric analysis on the corresponding evolution trends was performed by using visualization software CiteSpace and VOSviewer in this paper. First, the application of CiteSpace and VOSviewer and retrieval strategy for data collection were described. And then, information visualization analysis was carried out based on the papers related to RC structure's service life evaluation from publications number evolution, journal distribution, and authors' contribution. Finally, document cocitation network, cooccurring keywords network, and timeline view of keywords network were conducted to discuss the research hotspots on time to corrosion initiation evaluation of reinforcement. Research results reveal that the number of publications on RC structure's service life evaluation reached its peak in 2011. Besides, Structural Safety is the journal that makes the most significant contributions, and Professor Li CQ is the author with the most contribution score. Moreover, the knowledge body of the time to corrosion initiation prediction consists of six clusters; the high-citation articles in this field mainly focus on the multiple-parameters model and probabilistic reliability method. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) slab is an important component in civil construction and protection engineering, and its dynamic response under impact loading is a complex mechanical problem, especially for two or multiple continuous impact loads. In this paper, a series of drop hammer impact tests were carried out to investigate the dynamic response of RC slabs with two successive impacts. The time history of impact force and the failure characteristic of the slab surface were recorded. Moreover, four influence factors, including slab thickness, reinforcement ratio, impact location, and drop hammer height have been discussed. Besides, a 3D numerical model based on the finite element method (FEM) was established to expand the research of constrained force, deflection, and vertical stress of an RC slab. The results show that increasing the slab thickness and reinforcement ratio can improve the impact resistance of an RC slab. The impact point location and drop hammer height have a great influence on the dynamic response of the RC slab. In addition, the RC slab will have more obvious damage under the second impact, but the dynamic response becomes weaker. It may be because of the local damage in the concrete caused by the first impact that would weaken the propagation of vibration. [ABSTRACT FROM AUTHOR]

In this paper, a series of model tests about the trapezoidal filling structures filled with tire reinforced concrete particles has been conducted to study their stability and the ultimate bearing capacity. The effects of the reinforcing tire slices on the global stability and ultimate bearing capacity of the model were investigated, the results show that the tire slices reinforcement can reduce the total settlement of the trapezoidal filling structure, and the ultimate bearing capacity of the reinforced trapezoidal filling structure with tire slices is obviously improved. Among them, the settlements of crushed concrete particles reinforced with bottom layer, top layer, and two layers (both bottom layer and top layer) waste tire slices are 11.5%, 37.7%, and 46.2% less than that of unreinforcement, respectively. Compared with unreinforcement, when the top layer of the model is reinforced with tire slices, the Earth pressure values at the top layer and the bottom layer are reduced by 21.1% and 22.7%, respectively; the Earth pressure values at the top layer and the bottom layer are reduced 6.3% and 14.3%, respectively, when the bottom layer of the model is reinforced with tire slices, and the Earth pressure values at the top layer and the bottom layer are reduced 23.4% and 32.9%, respectively, when the two layers of the model are reinforced with tire slices. The sliding surface of the pure concrete particles filled trapezoidal structure is continuous and runs through the whole trapezoidal filling structure slope; the sliding zone of reinforced trapezoidal filling structure with tire slices decreases with the laying of tire slices. [ABSTRACT FROM AUTHOR]

A novel method was proposed to improve the bond behavior of new-to-old concrete interface, which was beneficial to introduce the fiber-reinforced concrete only at the old concrete interface. This study investigated the effect of the fiber addition, strength grade of new concrete, interfacial angle, and surface treatment types on the bond behavior in terms of the new-to-old concrete through the axial tensile tests. The three-dimensional digital image correlation technique (3D-DIC) and scanning electron microscope were adopted to evaluate the variation of specimen surface strain distributions and microstructure of fiber-reinforced concrete and bond interface between new-to-old concrete. The experimental results indicated that interfacial angle and surface treatment type were significantly promoted bond behaviors, while the specimen cooperating with steel fibers had the highest bond strength. Besides, the maximum strain locations obtained from 3D-DIC method were the same as the location of the specimen failure, which indicated the 3D-DIC method can be adopted to forecast the structural failure. The microcrack strain located in the major crack was decreased with the development of the major crack. Ample crystals and Ca(OH)2 were generated in the interface between the new-to-old concrete to weaken the bond strength. Moreover, this paper provided the mechanics-driven and machine learning method to predict the bond strength. This study provides a new interface bonding method for the fabricated and large span structure to effectively avoid cracking of new-to-old concrete. [ABSTRACT FROM AUTHOR]

The durability of concrete structures can effectively be enhanced by using stainless steel rather than ordinary steel reinforcements under harsh service conditions. Because the basic mechanical properties and stress-strain relationship of stainless steel reinforcements obviously differ from those of ordinary steel reinforcements, the current design codes for reinforced concrete structures are not appropriate for stainless steel-reinforced concrete. On the basis of the research works reported in the past decades, this paper systematically summarizes and analyzes the mechanical properties and corrosion resistance of stainless steel reinforcements, the properties of the bond between stainless steel reinforcements and concrete, the mechanical properties of stainless steel-reinforced concrete members, and the application of stainless steel reinforcements in practical engineering and proposes relevant problems which should be examined further. It is suggested that the design theory of stainless steel-reinforced concrete structures should be further improved to take full advantage of these structures. [ABSTRACT FROM AUTHOR]

This paper treats the vibration characteristics of three different types of asymmetric buildings and investigates the feasibility of applying an innovative vibration-based multicriteria approach-based damage index (MCA-DI) technique to detect the damage. This technique combines a modified form of the traditional modal strain energy method (MSEM) developed by decomposing the mode shapes into lateral and vertical components together with a modified form of the modal flexibility method to define a new damage indicator. Lastly, the dynamic behavior of three asymmetric building instances, including a 10-storey L-shaped structure, a 10-storey setback structure, and a 6-storey reinforced concrete structure with an unsymmetrical distribution of columns, was studied under five different damage scenarios. The results showed that despite different vibration characteristics of these three asymmetric buildings, the proposed method was able to accurately and effectively locate all damages and eliminate the confusion when more than one index is simultaneously used by using only the first a few modes. [ABSTRACT FROM AUTHOR]

The bond-slip damage of the interface between profile steel and concrete is the key point of steel-reinforced concrete structure. This paper is based on the statistical analysis of a large amount of experimental data and the distribution characteristics of bonding stress on the bonding surface of the profile steel and concrete, and the conversion rules between the three parts (chemical bonding force, frictional resistance, and mechanical interaction) of the bond force are obtained. According to the mutual conversion rules of the three parts of the bonding force on the steel-reinforced concrete bonding surface, a mesomechanical model based on the spring-friction block element is established. Taking into account the discreteness of concrete performance on the bonding surface and the randomness of defects, using the stochastic damage theory, a constitutive model of stochastic bonding damage on the steel-reinforced concrete bonding surface is established. The comparative analysis with the results of a large number of steel-reinforced concrete pull-out tests shows that the model can reasonably reflect the damage characteristics of the steel-reinforced concrete bonding surface. [ABSTRACT FROM AUTHOR]

This paper is related to a laboratory program for the shear strength of reinforced concrete corbels (RCC) cast with or without recycled aggregate (RA) by investigating the main parameters affecting the corbels behavior including the replacement aggregate recycling ratio, fcu, and shear span to effective depth ratio a/d. Eight specimens were cast and tested. The obtained results were compared with ACI and EC2 codes. It is found that the ACI code and E2 code give sensibly conservative results when compared with the findings of the present work for all tested specimens regarding RA, concrete strength, and a/d. Also, the experimental results show that the presence of recycled aggregate decreases slightly both cracking and failure loads. Furthermore, the failure load development due to the effect of compressive strength is more effective with the presence of recycled aggregate, and the 50% ratio of RA was the suitable ratio in elaborate crack and failure loads. Finally, the reduction of the span-depth ratio (from 0.50 to 0.35) increases the crack and failure load by 8.1% and 20.2%, respectively, leading to confirm that the corbel strength is much sensitive to decreasing span-depth ratio compared to the associated deflections. [ABSTRACT FROM AUTHOR]

Collision on reinforced concrete (RC) piers by moving vessels or vehicles is a significant issue. This paper presents the static and impact behavior of RC piers with different hollow ratios. Three specimens were statically tested to obtain the load-displacement response. Low-velocity collision on eleven RC piers was conducted under the same velocity of 2.42 m/s. The damage process, failure mode, and force response were comprehensively analyzed. The experimental results indicate that the hollow ratio plays a significant role in the failure mode and ultimate load of RC piers under static and impact loadings. For RC piers with a hollow ratio of 0 and 0.4, the global failure dominated the damage process. However, failure of piers with a hollow ratio of 0.6 was governed by the local damage near the loading point. The static load capacities of the RC piers with a hollow ratio of 0.4 and 0.6 were 1.27% and 60.5% smaller than that of the solid pier, respectively. RC piers with a higher hollow ratio or lighter drop weight suffer smaller peak impact force. The increase of the longitudinal reinforcements leads to a promotion of the peak and mean impact force. Furthermore, the numerically predicted failure modes and impact load response show satisfactory agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents the flexural behaviour of concrete containing ground granulated blast furnace slag (GGBS) as a binder, manufactured sand (M-sand) as a fine aggregate, and coconut shell (CS) and crushed stone aggregate (CSA) as coarse aggregates. Alkaline activator sodium hydroxide with 10 molarity and sodium silicate were used in a weighing proportion of 1 : 2.5 to produce structural grade concrete. Out of 12 beams cast, 6 were used to study geopolymer coconut shell concrete (GPCSC) beam behaviour and 6 were used to study geopolymer conventional concrete (GPCC) beam behaviour. Data presented include cracking behaviour, ultimate moment capacitates, deflection behaviour, ductility ratio, and end rotation of the beam. Laboratory investigations show encouraging results, and it can be summarized that coconut shell has good potential as a coarse aggregate for the production of structural grade geopolymer lightweight coconut shell concrete. [ABSTRACT FROM AUTHOR]

The incorporation of sisal fiber into the concrete matrix reduces waste disposal, which has negative environmental impacts. The aim of this study was to perform an experimental investigation on shear strength and microstructure of chemically treated sisal fiber-reinforced concrete (SFRC). In order to accomplish the aim of the study, physical, shear, and mechanical properties of concrete reinforced with chemically treated sisal fiber have been performed. 0.50%, 1.00%, 1.25%, 1.50%, 1.75%, and 2.00% of sodium hydroxide (NaOH) and sulfuric acid (H2SO4) treated sisal fiber were used as an addition to the dry weight average with the help of the American Concrete Institute (ACI) mix design procedure. After the 7th and 28th days of curing, shear strength according to the ASTM D5379M standard and the mechanical properties of concrete have been conducted. For microstructural properties, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were conducted after the concrete was cured for 28 days. Forty-six percent and 20% compressive strength enhancement at the 7th and 28th days of curing was compared to the control mix. Twenty-seven percent enhancement was recorded in the split tensile strength of 1.5% SFRC as compared to the control mix at 28 curing days. A shear strength of 1.5% SFRC was improved by 95% at the 7th curing days and 28% at the 28th curing days as compared to the control mix. As compared to conventional concrete, SFRC shows a denser microstructure. In addition to this, portlandite, quartz, calcium aluminum silicate, and C─S─H crystal are the available phases in the concrete matrix. [ABSTRACT FROM AUTHOR]

In this study, wavelet-based damage-sensitive features are employed to derive the seismic fragility functions/curves for reinforced concrete moment-resisting frames. Two different wavelet transform functions, namely, Bior3.3 and Morlet mother wavelet families, were applied to absolute acceleration time histories of building frames to extract the wavelet-based and refined wavelet-based damage-sensitive features (i.e., DSF and rDSF). The accuracy of seismic assessments and certainty in predicting structural behavior strongly depend on the specific optimal intensity measures selected, reliability of wavelet-based damage-sensitive features, and some such intensity measures as PGA, PGV, PGD, Sa, and Sdi as the conventionally utilized measures to detect the damage state of a structure. These measures were examined against their statistical properties of efficiency, practicality, proficiency, coefficient of determination, and sufficiency to select the appropriate optimal intensity measures, which were then used to drive the fragility curves disclosing the failure or other damage states of interest. For the purposes of this study, three different concrete moment-resisting frames with four-, eight-, and twelve-story building frames were adopted for implementing the proposed approach. The findings demonstrate that the wavelet-based damage-sensitive features (DSFs/rDSF) simultaneously satisfy all the statistical properties cited above. This is evidenced by the low variance and dispersions observed in the frame damage state predictions by the fragility functions derived from the wavelet-based DSF when compared with those derived from the classical fragility analyses such as spectral acceleration at the first mode period of the structure. A final aspect of the study concerns the superior performance and efficiency of the fragility curves derived by the Bior3.3 wavelet-based DSF over those derived from Morlet wavelet-based DSF. [ABSTRACT FROM AUTHOR]

In the fragility analysis, researchers mostly chose and constructed seismic intensity measures (IMs) according to past experience and personal preference, resulting in large dispersion between the sample of engineering demand parameter (EDP) and the regression function with IM as the independent variable. This problem needs to be solved urgently. Firstly, the existing 46 types of ground motion intensity measures were taken as a candidate set, and the composite intensity measures (IMs) based on machine learning methods were selected and constructed. Secondly, the modified Park–Ang damage index was taken as EDP, and the symbolic regression method was used to fit the functional relationship between the composite intensity measures (CIMs) and EDP. Finally, the probabilistic seismic demand analysis (PSDA) and seismic fragility analysis were performed by the cloud-stripe method. Taking the pier of a three-span continuous reinforced concrete hollow slab bridge as an example, a nonlinear finite element model was established for vulnerability analysis. And the composite IM was compared with the linear composite IM constructed by Kiani, Lu Dagang, and Liu Tingting. The functions of them were compared. The analysis results indicated that the standard deviation of the composite IM fragility curve proposed in this paper is 60% to 70% smaller than the other composite indicators which verified the efficiency, practicality, proficiency, and sufficiency of the proposed machine learning and symbolic regression fusion algorithms in constructing composite IMs. [ABSTRACT FROM AUTHOR]

This paper presents the numerical analysis of prestressed reinforced concrete (PRC) beams strengthened with near-surface mounted (NSM) carbon fiber reinforced polymers (CFRP). ABAQUS finite element software was used to simulate the existing test beams to investigate the flexural behaviors of PRC beams strengthened with NSM CFRP strips. The finite element model of beams strengthened with NSM CFRP strips was established. The finite element calculation results were compared with the experimental results to verify the accuracy and effectiveness of the model. Based on this model, the influences of concrete strength grade and amount of CFRP strips on the flexural behaviors of directly strengthened beams and the cycle numbers and overload amplitude on the flexural behaviors of damaged strengthened beam were further analyzed, and the load-carrying capacity calculation formula of PRC beam strengthened with NSM CFRP strips was established. The results showed that the simulation results and the theoretical calculation were consistent with the test results. With the increase of concrete strength grade and amount of CFRP strips, the ultimate load of directly strengthened beams increased significantly, with a maximum increase of 21.3% and 23.0%, respectively. When the concrete strength grade exceeded C50, the improvement of the ultimate load was limited. When the overload amplitude was less than 60% of the ultimate load, the cycle numbers (within 500 times) had little effect on the yield load, ultimate load, and deformation. When the overload amplitude was higher than 60% of the ultimate load, the deformation increased, and the ultimate load decreased with the increase of the cycle numbers. The larger the overload amplitude, the smaller the ultimate load, and the larger the deformation under the same cycle numbers. [ABSTRACT FROM AUTHOR]

The shear key in the reinforced concrete open-web sandwich plate (RCOSP) is a block joint that connects with the top chord and the bottom chord. In order to understand the failure mode of the shear key and verify the accuracy of the current algorithm, a total of 9 test pieces are prepared and classified 3 groups were assigned longitudinal reinforcement (LR) ratios of 0.49%, 0.82%, and 1.24%, respectively. The horizontal concentrated static loading under simple support condition is carried out. The test results show that the shear key is horizontally cut and the concrete is pulled apart or crushed along the direction of chord width at the shear key-chords area; the strain level of the concrete and stirrup of the shear key is lower averagely; the development of the horizontal displacement and the strain of the longitudinal bars of the test pieces goes through elastic, elastoplastic, and plastic stages; the ultimate load of the test pieces has almost no relationship with the reinforcement ratio of shear key but is controlled by the degree of crack development in the area where shear key connects with the chords. To avoid the current algorithm overestimating the shear capacity of shear key, the restricted condition of shear section is proposed. The finite element analysis (FEA) further verifies that the restricted condition of shear section proposed in this paper is reasonable and necessary. [ABSTRACT FROM AUTHOR]