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A cement‐based material that meets the general goals of mechanical properties, workability, and durability as well as the ever‐increasing demands of environmental sustainability is produced by varying the type and quantity of individual constituents in high‐performance concrete (HPC) and ultrahigh‐performance concrete (UHPC). Expensive and time‐consuming laboratory experiments can be used to estimate the properties of concrete mixtures and elements. As an alternative, these attributes can be approximated by means of predictive models created through the application of artificial intelligence (AI) methodologies. AI approaches are among the most effective ways to solve engineering problems due to their capacity for pattern recognition and knowledge processing. Machine learning (ML) and deep learning (DL) are a subfield of AI that is gaining popularity across many scientific domains as a result of its many benefits over statistical and experimental models. These include, but are not limited to, better accuracy, faster performance, greater responsiveness in complex environments, and lower economic costs. In order to assess the critical features of the literature, a comprehensive review of ML and DL applications for HPC and UHPC was conducted in this study. This paper offers a thorough explanation of the fundamental terms and ideas of ML and DL algorithms that are frequently used to predict mechanical properties of HPC and UHPC. Engineers and researchers working with construction materials will find this paper useful in helping them choose accurate and appropriate methods for their needs. [ABSTRACT FROM AUTHOR]

It is common knowledge that increased temperatures have a negative impact on the axial load‐capacity and stiffness of reinforced concrete (RC) rectangular columns. This is something that is commonly acknowledged. For the purpose of restoring the axial capacity and stiffness of heat‐damaged RC columns, it is absolutely essential to carefully pick a suitable method for strengthening and repairing the columns. This research paper investigates the performance of various strengthening methods, such as the use of carbon fiber‐reinforced polymer (CFRP) jackets with near‐surface mounted (NSM) steel bars and a combination of welded wire mesh (WWM) and CFRP strengthening techniques, for the rehabilitation of RC rectangular columns that have been damaged due to exposure to high temperatures. Specifically, the paper focuses on the performance of these methods in relation to the rehabilitation of RC rectangular columns. There were three groups of tested RC rectangular columns: pre‐heated and unstrengthened, post‐heated and unstrengthened, and post‐heated and strengthened. Over a period of 3 h, 600°C was applied to the heated columns. Both a scheme utilizing a combination of unidirectional CFRP strips and NSM steel bars and another utilizing a combination of unidirectional CFRP strips and WWM were evaluated. Axial compression tests were performed on each column until failure occurred. The experimental test outcomes revealed that exposure to high elevated temperatures led to a decrease in the axial load‐carrying capacity of 38.6% and a decrease of 75.9% in initial stiffness, compared to unheated RC columns. Both strengthening schemes proved effective in restoring and surpassing the initial load‐carrying capacity of undamaged RC rectangular columns by an average of 35%. Notably, the combination of CFRP strips and WWM exhibited superior performance in restoring the initial stiffness of post‐heated RC rectangular columns, representing a novel finding. The strengthening scheme employing WWM and CFRP recovered 61.3% of the lost axial strength caused by high temperature, while the NSM/CFRP scheme restored 34.5% of the lost axial strength. In addition, the utilization of NSM in combination with CFRP strips as well as utilization of the WWM and CFRP systems leads to stiffness enhancement of 52.1% and 123.7%, respectively, when compared to post‐heated and unstrengthened RC columns. However, the study's findings have clearly shown that combination of WWM and CFRP strips is efficient in enhancing the strength of heated and unheated damage RC beams. [ABSTRACT FROM AUTHOR]

This paper investigates the strengthening of non‐ductile reinforced concrete (RC) columns using partial steel‐plate jacketing to enhance ductile capacity. Quasi‐static cyclic loading tests were conducted on three rectangular RC columns with varying shear‐span‐to‐depth ratios, evaluating the effectiveness of steel‐plate jacketing. Results show improved ductile flexural response, high drift capacity, and maintained gravity‐loading capacity under high lateral displacements. A numerical investigation, adopting a multi‐spring fiber section model, predicted cyclic lateral strength, drift ratio, and failure mode, accurately simulating reinforcement behavior and capturing the shear‐strength enhancement due to steel‐plate jacketing. Numerical results demonstrated good agreement with experimental findings. Based on these outcomes, a simple design procedure for retrofitted concrete columns, applicable to design engineers, has been developed and reported in this paper. This study contributes valuable insights into the practical applications of steel‐plate jacketing for non‐ductile RC column retrofitting, offering a comprehensive approach to predicting their seismic performance. [ABSTRACT FROM AUTHOR]

In this paper, a probabilistic methodology based on image analysis is proposed for earthquake‐induced loss estimation in rectangular reinforced concrete shear walls (RCSWs) in compliance with FEMA P‐58. The methodology is developed using a databank of 285 surface crack patterns gathered from the result of experimental research on 99 rectangular RCSWs with wide‐ranging structural and geometric characteristics. For the complexity extraction, three fractal geometry indices of the damaged specimens are taken into consideration. Fragility functions are generated to determine the probability of exceeding a FEMA P‐58 compliant damage state based on the various methods of repair for specific complexity indices. The fragility functions are obtained using four common probabilistic distributions including lognormal, Weibull, gamma, and beta. The fitness of the fragility curves is examined by two goodness‐of‐fit tests, namely the Kolmogorov–Smirnov test and Lilliefors test. Results show that the Weibull is the best‐fitting distribution for the majority of damage states and succolarity possesses the best results in goodness‐of‐fit tests among fractal geometry indices. Empirical loss indices are also derived in this paper aimed at optimizing the goodness‐of‐fits. Finally, the proposed procedure is utilized for a sample specimen from the databank at various damage levels. [ABSTRACT FROM AUTHOR]

The current paper presents an innovative form of the cold‐formed U‐shape steel encasing concrete composite beam (CUCB). The suggested CUCB consists of a cold‐formed U‐shaped steel encasing plain concrete beam which are connected to each other using continuous transversal threaded stud bolts. The experimental program consisted of eight beam specimens tested in the four‐point bending set‐up. One of them was a normal reinforced concrete beam and considered as a reference specimen while the remaining specimens were CUCB specimens without ordinary flexural and shear reinforcement. Four parameters were studied in this paper: (i) the thickness of the U‐shaped steel, (ii) the spacing between the stud bolts, (iii) the arrangement of the bolts, and (iv) the number of the bolt's rows. Results indicated an overall improvement in the load‐carrying capacity and stiffness of most CUCB specimens in comparison with the reference specimen. It was found that the using of three rows of bolts can significantly improve the ductility and toughness of the CUCB specimen in comparison with two rows of bolts. On the contrary, an increase in the bolt spacing entails a decrease in the CUCB specimens' toughness. [ABSTRACT FROM AUTHOR]

Although it has been shown that using recycled concrete aggregate in new structural concrete is economical and sustainable, the use of this material for such applications is still not widespread. One of the reasons is that manufacturers, designers, engineers, owners, and other market players are not familiar with specifying and utilizing this material—although standards are starting to incorporate provisions for recycled aggregate concrete, successful, practical example projects are needed. The current paper describes the results of a partnership between universities and a precast concrete manufacturer of hollow core slabs. Seven hollow core slabs with volumetric replacement ratios of natural aggregate with recycled aggregate from 0% to 60% were tested to failure in both bending and shear, and then undamaged portions of the slabs were subjected to punching shear until failure. The results showed only mild differences in strength, with different replacement percentages of recycled aggregate under the various loading scenarios. Numerical simulations performed in Abaqus demonstrated the feasibility of analyzing recycled aggregate concrete structural elements and provided important insights into their behavior. [ABSTRACT FROM AUTHOR]

This paper focuses on the applicability of CatBoost models constructed using various optimization techniques for improved forecasting the compressive strength of ultra‐high‐performance concrete (UHPC). Phasor particle swarm optimization (PPSO), dwarf mongoose optimization (DMO), and atom search optimization (ASO), which have been very popular recently, are preferred as optimization algorithms. A comprehensive and reliable data set is used to develop the CatBoost models, which include 785 test results with 15 input features. The performance of the CatBoost models (PPSO‐CatBoost, DMO‐CatBoost, and ASO‐CatBoost) optimized with different algorithms is thoroughly assessed by means of various statistical metrics and error analysis to determine the model with the best forecasting capability, and this model is compared with the models obtained from previous studies. In addition, Shapley additive exPlanations (SHAP) analysis is used to ensure the interpretability of the forecasting models and to overcome the “black box” problem of machine learning (ML) models. The obtained results demonstrate that all CatBoost models outstandingly forecast the compressive strength of UHPC. Among these models, the DMO‐CatBoost model stands out compared to the other models in various performance metrics, such as high coefficient of determination (R2) values, low root mean squared error (RMSE), mean absolute percentage error (MAPE), and mean absolute error (MAE) values, along with a smaller error ratio. In other words, the RMSE, R2, MAPE, and MAE values of the DMO‐CatBoost model for the training set are 3.67, 0.993, 0.019, and 2.35, respectively, whereas those for the test set are 6.15, 0.978, 0.038, and 4.51. Additionally, the performance ranking of the algorithms used to optimize the hyperparameters of the CatBoost model is as follows: DMO > PPSO > ASO. On the other hand, SHAP analysis showed that age, fiber dosage, and cement dosage significantly influence the compressive strength of UHPC. These findings can guide structural engineers in the design and optimization of UHPC, thus assisting them in developing strategies to improve the strength properties of the material. Finally, based on the best forecasting model developed in this work, a graphical user interface has been developed to easily forecast the compressive strength of UHPC in practical applications without additional tools or software. [ABSTRACT FROM AUTHOR]

In typical reinforced concrete design, reinforcement is designed to carry axial forces, but it can also resist transversal forces by dowel action. This is usually neglected for simplicity's sake in the design phase, but it can be accounted for either explicitly in mechanical models or implicitly in empirical relationships. Furthermore, there are cases where the connection between various concrete elements explicitly depends on dowel action, as for example, in connections between precast elements or between two concrete parts cast at different times. On the other side, dowel action can have a negative impact on the fatigue resistance of reinforcing bars subjected to cyclic loading, because of the local stress concentrations near interfaces due to relative movements, either in sliding or in opening of cracks not perpendicular to the bar. For the assessment of the remaining capacity of existing structures, improved models of the behavior are needed, including realistic models of the behavior of concrete, steel and their interfaces. The aim of the present paper is to provide a contribution to a better understanding of dowel action by two test series. The first series focused on the behavior of the dowel: the concrete specimens with the embedded bars were placed in a custom‐made test setup and subjected to monotonic or low stress‐level cyclic actions with a longitudinal and a transversal crack opening component, up to developing the full plastic capacity of the dowel and rupture at the peak of catenary action. The measurement system included tracking the displacement field at the surface of the concrete and the strains in the dowel by optical fibers glued on its surface. The latter measurements allow to derive the internal forces in the reinforcing bar and deformed shape of the bar as well as the contact pressure between the bar and the surrounding concrete. The results show a strong dependency on the test variables: diameter of the bar, imposed crack kinematics and angle between the bar and the crack. The second test series looked more closely at the behavior of concrete underneath the bar, in the presence of a point load introduced at various locations into concrete through a reinforcing bar. A comparison of the test results with existing models shows a general good agreement and some aspects that deserve to be improved. [ABSTRACT FROM AUTHOR]

A novel application of fiber optic sensing aimed at understanding the tensile behavior of post‐installed reinforcing bars in normal‐strength concrete is presented in this paper. To comply with established assumptions of cast‐in reinforcement, such as the uniform bond stress distribution, the design bond strength of post‐installed configurations is limited. In this study, pull‐out tests in confined conditions were conducted using two high‐performance mortars. Cast‐in‐place anchorages were tested for reference. The proposed fiber optic sensors and post‐processing techniques enable to continually measure and evaluate the bond stress distribution and monitor rebar deformation. Compared to cast‐in rebars, post‐installed rebars exhibit significantly higher bond resistance, particularly due to higher bond stresses at the beginning of the embedment length. These results highlight the potential for reducing the embedment length of post‐installed rebar. Moreover, variations in stiffness and bond stress distribution are found to significantly affect the slip and rebar deformation of both cast‐in‐place and post‐installed rebar. [ABSTRACT FROM AUTHOR]

In an era flooded with a multitude of studies investigating the performance of concrete structures retrofitted using fiber‐reinforced polymer (FRP) materials, this review addresses the critical need for a comprehensive overview of the retrofitting of concrete members using near‐surface mounted (NSM)‐FRP composites, aiming to save time and effort while providing engineers and research community with valuable resources relevant to the field. This review focuses on the key factors influencing both the flexural and shear retrofitting processes of reinforced concrete (RC) beams, such as the percentage, type, size and geometry of NSM‐FRP reinforcement, as well as groove design, groove‐filling materials and beam depth. Moreover, the paper explores the failure modes associated with each retrofitting type, for example, debonding failures, shear/flexural failure and rupture of steel or NSM‐FRP reinforcement, to name a few. The review also delves into the bond behavior of NSM‐FRP‐bonded joints, examining factors, such as the bonded length, surface texture of NSM‐FRP reinforcement and type of bonding agent, which would affect the bond behavior and strength of the joints. The failure mechanisms associated with the bonded joints, such as interfacial bond failure, FRP rupture and splitting of the adhesive cover, are also highlighted. Finally, this compilation aims to guide engineers and researchers by offering a critical and comprehensive database for optimal designs, further development and suggesting future research directions. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of enhancing the bending capacity of beams through a cost‐effective and practical approach. Current methods are often expensive, brittle, time‐intensive, or massive. In response, an alternative method is proposed that involves the utilization of post‐tensioned heavy‐duty metal straps wrapped around steel plates anchored to the beams. To evaluate the effectiveness of the method, six large‐scale normal reinforced concrete beams were constructed with a width of 160 mm and a depth of 240 mm, and a clear span of 1900 mm. The testing parameters were the position of the steel plates along the length of the beam and the position of the metal straps along the height of the steel plates. Quantitative results demonstrate a significant enhancement in the load‐carrying capacity of the beams. Compared to the control specimen, the method led to a minimum increase of 40% of load carrying capacity and a maximum increase of 66%. Key influencing factors include the location of the metal straps on the steel plates (120 or 90 mm away from the bottom of the beam) and the position of the steel plates on the face of the beam (650 mm or 350 away from the edge of the beam). Notably, the load‐carrying capacity increases when the metal straps are positioned lower on the steel plates and the plates are placed further away from the center of the beam. Finally, analytical results obtained using VecTor2 software align well with experimental findings. [ABSTRACT FROM AUTHOR]

Dapped‐end beams are frequently used in roofing and flooring systems of precast reinforced concrete buildings as well as in bridge constructions. Due to design flaws, deterioration, and construction mistakes, they may have unsatisfactory structural performance. Past experimental studies investigated the effectiveness of post‐tension strengthening techniques applied to dapped‐end beams, revealing them as effective solutions, even though a limited range of influencing parameters were considered. This paper numerically investigates the performance improvement provided by post‐tension interventions applied to dapped‐end beams. Numerical models were built through a refined FEM software simulating two experimental tests found in the literature. After the models' calibration, a post‐tension intervention was designed and implemented in the models, considering the level of prestressing as the main intervention's parameter. Afterwards, the behavior in the post‐intervention condition was analyzed to find changes in the failure modes and highlight the performance improvement concerning cracking phenomena and ultimate load‐bearing capacity. It is found that the level of tendons' prestress significantly improves the cracking load, which increases almost linearly with respect to it. Conversely, the significant gain in terms of ultimate load‐bearing capacity (up to 53%) shows only slight variations when the prestress level changes. Finally, accounting also for the reduction of deformation capacity for high prestressing levels, practical suggestions are provided regarding the optimal post‐tension choice. [ABSTRACT FROM AUTHOR]

This paper describes the structural aspects of the Wieselburg Bridge collapse in Austria. The original design and reinforcing details for this integral concrete bridge are discussed. The collapse of the bridge is re‐constructed based on forensic documentation of the failure. The results of structural analysis carried out using material properties obtained after failure are compared to the shear capacity obtained from various models and from test results from literature. The results are used to explain the cause of failure of the integral bridge under dead load. [ABSTRACT FROM AUTHOR]

The Metro Tunnel is a Victorian Government funded infrastructure project which will create a new end‐to‐end rail line from Sunbury in the west to Cranbourne/Pakenham in the south east, with bigger and better trains, next generation signaling technology and five new underground stations. This article provides a detailed summary of the structural fire testing requirements for the platform tunnel side wall and arch lining in the Metro Tunnel's State Library and Town Hall stations. Contrasted to building fires, tunnel fires are more significant within a few minutes due to the confined space which can cause concrete spalling and jeopardize the bearing capacity of the tunnel, which is a significant concern to designers. The catastrophic European tunnel fire events in 1999 and 2001 led to the development of innovative regulations and recommendations, including guidelines endorsed by the European Federation of National (EFNARC 132F r3:2006) and Efectis R0695:2020. This paper explains the methodology taken to design the fire rated concrete test for the platform tunnel side wall and arch lining in the State Library and Town Hall stations of Melbourne's Metro Tunnel Project for structural stability for the period of a serious fire event. For the first time, uniaxial loading (500T) was applied to five large‐scale flat concrete panels (1800 × 1800 × 400 mm) which are normally unloaded during fire exposure and exposed to the RABT ZTV (rail) fire curve. The first testing program investigated the influence of polypropylene dosage in the concrete mix design and its effect on the magnitude and severity of concrete spalling. The results indicated that the recommended 2.0 kg/m3 polypropylene dosage requirement as specified by Eurocode is conservative. Concrete mix designs with a stable aggregate and the correct curing regime can mitigate spalling at significantly lower polypropylene dosage rates. The water pooling effect was evident during the fire testing and the surface cracking that developed was vertical to the surface, allowing for the release of the pore water pressure build‐up. [ABSTRACT FROM AUTHOR]

An innovative assembled stiffener‐plate PEC beam‐column joint (SP‐PEC) is proposed to improve better constructability. In this paper, 12 PEC beam‐column joint specimens were subjected to quasi‐static cyclic tests. The design parameters included the thickness of the stiffener‐plate (equal‐stiffness thickness at load standard combination, full‐stiffness thickness of the cross‐section, and 120% of full‐stiffness thickness of the cross‐section) and the beam‐column connection with or without the stub beam. The results revealed that the assembled SP‐PEC beam‐column joint exhibited better seismic performance than the conventional PEC beam‐column concrete joint. The strength degradation coefficients of SP‐PEC beam‐column nodes are all greater than 0.92, and the stiffness decreases slowly. The specimens had good bearing capacity, deformation ability, energy dissipation capacity, and stiffness under a reasonable stiffener‐plate thickness. Then, the bearing capacity calculation formulae of the novel joint with certain prediction accuracy were proposed. Besides, the finite element models of the test specimens were established in ABAQUS and validated against the test results. Finally, further investigations of the SP‐PEC joint configuration by finite element analysis and engineering design recommendations for the assembled SP‐PEC beam‐column joint were provided. [ABSTRACT FROM AUTHOR]

In this paper, a numerical critical shear crack model, in which the shear‐flexural coupling effect is considered and the full process of stress and strain is captured, is proposed to evaluate the post‐peak behavior of reinforced concrete (RC) and steel fiber reinforced concrete (SFRC) beams. The shape of critical shear crack is identified by combining the modified compression field theory considering the bridge effect of steel fibers and the section analysis method. Based on the shape of critical shear crack, the shear capacity of beam members is provided by the shear tension zone and the shear compression zone. The shear capacity of the shear tension zone is calculated by the modified compression field theory and that of the shear compression zone is determined by multiaxial strength criterion of concrete. The vertical displacements caused by the flexure deformation and shear deformation are deduced by the moment area method and integration of shear strain. To verify the proposed numerical approach, a test database of 486 RC beams and 313 SFRC beams was established to predict the shear strength, and the force‐displacement relationships of twelve beam members are used to validate the feasibility for full process analysis. The stochastic analysis of beams with different failure modes is conducted via GF‐discrepancy‐based point selection method and probability density evolution method. The limitation between different failure modes is defined according to the degradation percent of shear capacity and it is taken as threshold value of failure domain, and the failure probability analysis indicates that the designed flexure beam member suffered severe degradation of shear capacity, resulting in a significant decline in safety probability. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive comparison between conventional reinforced concrete (RC) and steel fiber‐reinforced concrete (SFRC) slabs. Twenty‐two‐way rectangular RC and SFRC slabs are designed with varying dimensions, aspect ratios, and boundary conditions, following verified international standards to compare the steel quantities in a unique study. SFRC slabs with larger aspect ratios and discontinuous edges required significantly higher steel percentages than square slabs, as the random three‐dimensional distribution of steel fibers suited the load distribution pattern of square slabs. To further conduct a detailed design and economic feasibility case study on a realistic building model, two 12‐story buildings are computationally designed with RC and SFRC alternatives. The results indicate that SFRC slabs required approximately 25% more steel than RC slabs due to the uniform distribution of steel fibers throughout the section. Project cost and time estimates were conducted based on standard productivity manuals and cost databases in two distinct economies, India and the USA. Despite the higher steel requirements, the 12‐story SFRC building showed time savings of 34.1 days (5.44%) and cost savings of 4.88% and 1.27% when constructed in the USA and India, respectively. The results are compared with limited available data in literature. In conclusion, the study suggests that SFRC slabs in multi‐story buildings could be more economically favorable in countries with higher labor costs. [ABSTRACT FROM AUTHOR]

The verification of dapped‐end beams degraded by corrosion is a problem, especially for existing bridges in service. This paper proposes a nonlinear finite element (NLFE) modeling procedure and a simple strut‐and‐tie based procedure for predicting the response of dapped‐end beams subjected to chloride corrosion. Firstly, the finite element modeling strategy, based on the adoption of multilayer shell elements and the PARC_CL 2.1 crack model is described. Then, the degradation effects on concrete, rebars, and steel‐to‐concrete interaction are defined as a function of the propagation period of corrosion. In particular, the effects of corrosion on the reinforcement are modeled by applying a reduction of tensile strength that considers for both the reduction of cross‐section and the ultimate strain caused by pitting. Concrete splitting cracking due to volume expansion during rust formation is modeled by reducing the mechanical properties of concrete. Corrosion effects in steel‐to‐concrete interaction are modeled by applying a bond strength decay to the spring elements connecting corroded rebars—modeled with truss elements—and concrete multilayer shell elements. The proposed finite element procedure is used to study two scenarios based on different spatial distributions of corrosion‐prone areas. Subsequently, a simplified analytical approach based on the strut‐and‐corroded tie method—called S&CT method—is proposed and compared with the finite element outcomes. Finally, the validations of the two proposed methods are presented with respect to a corroded dapped‐end beam, showing that corrosion of rebars affects the resistance mechanisms of the dapped‐end beam, by reducing both resistance and ductility. The proposed simplified analytical S&CT method provides conservative and safe results compared to the numerical NLFE model and to experimental data. [ABSTRACT FROM AUTHOR]

Breakthrough technology of ultra‐high‐performance concrete (UHPC) introduced in the 1990s exhibits several exceptional mechanical properties that are advantageous in elements of bridge applications. Extensive research has aimed to industrialize UHPC and develop design models. This paper investigates several design models for shear, including a unified approach with that of conventional concrete based on the modified compression field theory (MCFT). An experimental database of UHPC prestressed concrete girders subjected to shear failure is compiled to evaluate model accuracy and a reliability study is conducted to establish appropriate safety factors. The analysis demonstrates that the proposed MCFT‐based model aligns well with experimental results, exhibiting a suitable level of conservatism for design. A reliability assessment of a typical prestressed girder designed according to Canadian Standards Association building and bridge loadings is performed, resulting in a structural reliability evaluation against a target reliability index. The study recommends specific strength reduction and safety factors for design approaches using UHPC. [ABSTRACT FROM AUTHOR]

Hybrid fiber‐reinforced cementitious composites (HyFRCC) consisting of polyethylene (PE) and carbon fiber (CF) have potential for use in advanced composite materials by integrating high mechanical performance with smart functions based on electrical properties. However, an evaluation of the electrical and fracture properties of HyFRCC has not yet been reported. An orthogonal experimental design was used to investigate the effect of the water‐to‐binder (w/b) ratio and volume fraction of PE and carbon fiber on the electrical properties and fracture behavior of HyFRCC in this paper. The results show that the w/b ratio plays a major role in controlling the electrical resistivity of HyFRCC. The larger the amount of hybrid fibers added, the higher the w/b ratio needed. In particular, the PE fiber must not exceed 1.5 vol% to obtain HyFRCC with low electrical resistivity. Carbon fiber has a significant effect on the initial fracture toughness of HyFRCC, while PE fiber determines its unstable fracture toughness. A hybrid fiber system containing 1.0 vol% PE fiber and 0.5 vol% carbon fiber at a w/b ratio of 0.35 was used to reach a compatible electrical property and fracture behavior of HyFRCC. The results of this work provide a novel approach for designing and developing multifunctional cementitious composites, which would be a promising building material for structural strengthening and protection of steel corrosion as well as structural health monitoring. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymer (FRP) reinforced ultra‐high‐performance concrete (UHPC) structural elements have become increasing popular in research and industry communities. In this paper, uniaxial tension tests were conducted to study the effects of fiber type, fiber length, and fiber content on tensile behavior of FRP grid reinforced UHPC plates (FGRUPs). Additionally, the microstructure analysis of specimens was conducted using scanning electron microscopy. Test results reveal that carbon FRP (CFRP) grid can substantially enhance the tensile performance of UHPC under tension: (1) the FGRUPs exhibit a post‐crack strain‐hardening behavior while the UHPC plates exhibit a post‐crack strain‐softening behavior; (2) the FRP grid enhances the cracking stress of UHPC specimens (except for plates with 1% basalt fibers) and the stiffness of the second segment of the stress–strain curve, and substantially enhances the ultimate tensile stress UHPC specimens. Also, the cost‐effectiveness analysis indicates that plates containing 1% of 12 mm length PE fibers have a highest cost efficiency index. Finally, a modified tensile stress–strain model for FGRUPs is proposed and verified. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on the development of a cost‐effective, high‐performance fiber reinforced concrete (HPFRC) for the construction of a 60 m‐span U‐girder roadway bridge without stirrups in the webs, meeting the design requirements of fck ≥ 100 MPa and the post‐cracking flexural strength fR3k ≈ 8–10 MPa. The main objective of this research is to develop a F5 workability class HPFRC that meets the specified design criteria without exceeding 2.5–3.0 times the cost of a C70/85. To achieve this goal, the concrete mix was obtained using 500 kg/m3 of cement and 50 kg/m3 of silica fume. This mix was investigated with nine different combinations of fibers and fiber contents, resulting that 80 kg/m3 of 4D‐fibers (lf = 60 mm) provided the optimal fR3k without compromising workability and cost. Subsequently, an extensive experimental campaign was conducted to cast the U‐girder following the conventional casting techniques involving casting prismatic samples, L‐shaped and rectangular‐shaped panels to represent different parts of the U‐girder. Innovative techniques were used to study the effect of different waiting times between concrete pours. Results from the testing of the prismatic specimens evidenced the need of stitching by means of a poker vibrator planes between successive concrete layers. Furthermore, the study of the panels evidenced that a waiting time of 90 min allows the HPFRC to achieve enough bending and compressive strength to bear internal vibration of the element without liquefying and, at the same time, avoiding cold joints. The results confirm the applicability of the developed HPFRC for the structural element under study following conventional casting techniques. [ABSTRACT FROM AUTHOR]

Chemical prestressing was developed during the 1960s; however, and due to technical difficulties at that time, the technology was not considered as an alternative to conventional prestressing; instead, it was only used as a shrinkage compensating method. Still, recent development in concrete technology encouraged several researchers to revisit this technology, where significant achievements were made. This paper aims to present a state‐of‐the‐art review about the recent development in the chemical prestressing technology. This includes reviewing existing field applications, existing types of expansive additives, influence of different expansive additives, influence of curing methods, mix proportioning, mechanical properties, and structural behavior. Furthermore, a thorough discussion was performed and suggestions were made for future researchers to help further contribute to the development of this prestressing technology. It was concluded that although the chemical prestressing technology seems very promising, more research is required before using it in practical applications. [ABSTRACT FROM AUTHOR]

A new type of UHPC‐NC (normal concrete) structure in the negative moment zone was proposed to improve the bearing capacity of the connection structure in the negative moment zone of prefabricated prestressed concrete (PC) beam bridges. First, the distribution characteristics of the crack, cracking load, ultimate moment, and ductility coefficient of the new structure were obtained by the 1:4 scale model tests. The feasibility of the connection structure is verified. Then, the value ranges of critical structural parameters affecting the bearing capacity of the connection structure based on the plane section assumption analysis, including the reasonable thickness of the UHPC layer, the reinforcement ratio of the longitudinal tensile reinforcement, and the diameter of the reinforcement, are obtained. At the same time, based on the verification of the finite element model, the influence of crucial research parameters on the bending capacity of the connection structure is obtained by using the finite element method. Finally, a theoretical method for the bending moment capacity of the connection structure of the UHPC‐NC structure is proposed, considering the high ductility characteristics of UHPC materials. The average relative error between the calculation results and the finite element method is within 7.2%, which verifies the reliability of the calculation method in this paper and provides a reference for its design and engineering application. [ABSTRACT FROM AUTHOR]

This paper presents a rational approach for describing the cracking behavior of fully‐ and partially restrained fiber reinforced concrete members co‐reinforced with conventional reinforcement subjected to an axial force imparted by shrinkage. The proposed analytical model extends the approach developed by Gilbert for fully restrained reinforced concrete members to account for the post‐cracking strength offered by the fibers at each of the cracks as the concrete ages and dries. The effects of partial end‐restraint are also studied to gain a clearer understanding of the mechanism of direct tension cracking caused by restrained shrinkage and the factors affecting it. [ABSTRACT FROM AUTHOR]

The flexural behavior of beams strengthened with GFRP bars and high‐performance fiber‐reinforced concrete (HPFRC) was investigated in this paper. The four‐point flexural response of one reference beam and four beams strengthened with high‐performance fiber‐reinforced concrete was investigated by experimental research and theoretical calculation. The experimental and theoretical data (strain, load, etc.) are discussed. Parameters varied included the strengthening scheme (bottom‐side strengthening and three‐side strengthening) and the type of high‐performance fiber‐reinforced concrete (engineered cementitious composite [ECC] and ultra‐high‐performance concrete [UHPC]). The results showed that the cracking load and ultimate load of beams strengthened with UPFRC material were 31.3%–170% and 9.6%–20.7% higher, respectively, relative to the reference beam. Beams with three‐side strengthening (without interfacial debonding) had higher ultimate load, smaller crack width, and better durability relative to beams with bottom‐side strengthening. The UHPC layer was more effective in increasing the ultimate bearing capacity, and ECC strengthening layer was more effective in inhibiting cracking development of beams. Based on the experimental results, a model was proposed to predict the ultimate bearing capacity of beams strengthened with high‐performance fiber‐reinforced concrete, which could provide good agreement between the experimental and predicted results. [ABSTRACT FROM AUTHOR]

This paper presents the findings of a large‐scale experimental study that focus on assessing structural behavior of reinforced concrete (RC) cantilever slabs with carbon/epoxy fiber‐reinforced polymer (CFRP) composite strips using a near‐surface‐mounted (NSM) approach. The NSM/CFRP system evaluated in this study was implemented in strengthening the shoulders of the Slide Canyon Bridge in California, USA. The experimental phase is divided into two main parts: (i) determining the design parameters for NSM, including the bondline strength through pull‐out tests, and (ii) conducting a practical evaluation of the bending behavior of original and retrofitted RC cantilever slabs, each with varying NSM reinforcement and three different development lengths. Results of this study indicated that the use of NSM‐CFRP has a considerable benefit in that it significantly improves ductility and changes the failure mode of the unstrengthened RC slab from the typical brittle shear‐based failure mode to a more ductile flexural‐based failure mode. The large‐scale slab specimens' performances, which had different development lengths, showed little variance, except for the slab specimen with a development length of 457.0 mm that exhibited an appreciable flexural stiffness as compared to other specimens evaluated in this study. In order to simulate the serviceability and ultimate behavior of the RC slab specimens, linear and nonlinear finite element analyses were performed. A satisfactory agreement between numerical and experimental results was achieved especially at load level prior the initiation of large‐size cracks. [ABSTRACT FROM AUTHOR]

In this paper, the concept of steel fiber reinforced concrete (SFRC)‐plastic columns was explored and discussed. Plastic served as a 3D printed formwork that remained in place. Five different column cross‐section shapes, based on Cesaro fractal iterations, were created and filled with steel fiber reinforced mortar. After curing, the specimens were loaded and load‐strain characteristics were recorded, with a focus on destruction characteristics and energy dissipated up to 6.0% strain. The results showed that columns with fractal‐based cross‐sections had smooth destruction with significant formwork deformation. All columns exhibited highly quasi‐plastic behavior. The results demonstrate the feasibility of replacing traditional formwork and concrete with a more automated 3D printed plastic and SFRC solution. Future research should focus on large‐scale columns and other structural elements. [ABSTRACT FROM AUTHOR]

In this paper, the ordinary reinforced UHPC T‐shaped beam, steel plate reinforced UHPC T‐shaped beam and prestressed UHPC T‐shaped beam were compared by conducting the flexure test. The vertical displacement, crack development, strain change, and crack resistance were discussed. The steel plate reinforced UHPC T‐shaped beam shown better cracking resistance and mechanical properties. Based on the research, the multi‐scale finite element model of the steel plate reinforced UHPC T‐shaped beam was established, and the influence parameters were analyzed. The beam height, steel plate thickness and web thickness shown great influence on the ultimate bearing capacity of the beam. The bearing capacity calculation formulas of the steel plate reinforced UHPC T‐shaped beam based on the plastic strengthening model of the steel were proposed. The calculation results shown good agreement with the test value. [ABSTRACT FROM AUTHOR]

The paper describes the authors' contribution to the evolution of numerical simulation of concrete structures based on the nonlinear finite element method. The formulation of constitutive relations for concrete material is a keystone of this approach, whereas cracking is the dominant feature. Two distinct methods of crack modeling were developed, namely, the discrete and the smeared crack models. Blind prediction benchmarks of the experimental tests are used for model verification. Application of the numerical simulation in the design of concrete structures is supported by the global safety format, where the uncertainty sources, due to the material and the resistance model, are considered. A structural assessment of a prestressed reinforced concrete viaduct is shown as an example of application. [ABSTRACT FROM AUTHOR]

The paper presents the results of an original experimental program that was focused on punching shear behavior of flat slabs supported by rectangular columns with a column rectangularity index cmax/cmin = 1.0, 4.33, and 6.33 and slabs supported by elongated columns that were loaded by four different load patterns. Seven isolated flat slab specimens with a thickness of 200 mm were tested until their failure. An effect of the column geometry and the way of the flat slab loading on punching shear capacity of slab‐column connections were investigated. The obtained experimental results were confronted with predictions carried out with the design provisions from code of practice EC2 (2004), ACI 318‐19, and prEC2 (2021) and the original Critical Shear Crack Theory (CSCT) (2008) model developed by Muttoni. Experimental results confirmed an effect of column rectangularity on punching shear resistance when a value of shear strength ratio Vtest/Vmodel was below one in the specimens with cmax/cmin > 2. The highest punching resistance was achieved in slab specimen with loading pattern x/2y where x is an axis along the column dimension cmax. The lowest capacity was achieved with a loading pattern 9x/y where 90% of the load flew perpendicular to the axis "y" parallel with cmin. The most accurate and balanced predictions provided CSCT (2008) model. [ABSTRACT FROM AUTHOR]

Several efficient applications of ultrahigh‐performance fiber‐reinforced concrete (UHPFRC). Among them are UHPFRC jackets utilized for strengthening or permanent formworks of the steel reinforcing normal strength concrete (NSC) columns since UHPFRC jackets could enhance the compressive strength and other properties of the NSC column. However, the efficiency of a UHPFRC jacket simultaneously depends on its thickness and the added steel fiber volume fraction. The paper aims to explore the interaction effect of UHPFRC jacket thickness and steel fiber volume fraction on the behavior of UHPFRC jackets confining the NSC core under compressive load. The circular ultrahigh performance concrete jacket filled inside with the normal strength concrete, named NSC‐UHPFRC column specimen, is tested under loading on the NSC core. UHPFRC jacket thickness of 18‐49 mm with three adding steel fiber volume fractions was conducted for the experimental study. The investigation and analysis of the effect of the UHPFRC jacket and the steel fiber volume fraction on compression behaviors of NSC‐UHPFRC columns proceeded after the compressive strength test results were validated using Richart's model. This comprised a review of various parameters such as specimen failure pattern, stress–strain relationship, and ductile indices. The Weibull distribution was employed to explain the interaction effect on the variation in the experimental results. Finally, an interaction model was proposed and used to discuss the interaction effect of UHPFRC jacket thickness and steel fiber volume fraction and the optimum condition of the compressive strength of the NSC‐UHPFRC columns. [ABSTRACT FROM AUTHOR]

The development of fragility curves is an important step in seismic risk assessment within the scope of performance‐based earthquake engineering. The goal of this work is to use machine learning methods (regression‐based tools) to forecast the large‐span precast parking structural responses and fragility curves. This study proposes five predicting models based on machine learning to evaluate the seismic performance of the large‐span precast parking structures, including: neural networks, genetic algorithm‐based neural networks, support vector machine, decision tree and random forest. A database that includes 453 numerical synthetic results was used to train and test the machine learning models. The seismic performance of large‐span precast parking structures were predicted using the constructed machine learning models. Finally, the sensitivity analysis of input parameters was conducted. From this paper we can conclude that: (1) the genetic optimization‐based neural networks' predicting model has the most accurate predictive ability for seismic fragility estimation and (2) the structural responses and the fragility curves of parking structures are related to the differences of the stiffness of the connectors and the number of floors, of which the stiffness of the connectors should be given special attention. [ABSTRACT FROM AUTHOR]

In this paper, the flexural stiffness of the reinforced concrete (RC) beams reinforced with high‐strength steel bars after exposure to different elevated temperatures was investigated experimentally and theoretically. The effects of the elevated temperature (room temperature, 200°C, 400°C, 600°C, 800°C, and 1000°C), high‐temperature duration time (0 h, 1 h, and 2 h), and steel bar types (HRB600 and HRB500) on the load–deflection response, load–stiffness response, and crack distribution of tested beams were investigated. The results showed that when the temperature is below 600°C, the effect of high temperature on the stiffness reduction of high‐strength RC beams is not significant, while the beams reduced the stiffness when the exposure temperature reached 800°C and 1000°C, regardless of the type of the steel bars. The elevated temperature accelerated the development of the deflection of RC beams, and the bending stiffness of the RC beams decreased more severely as the increase of duration time. By using appropriate degradation factors, the residual stiffness of the beams was predicted well by the analysis calculation method and the effective inertia moment calculation method, for example, the prediction accuracy is over 91% and 85.8% for the cases under and over 800°C, respectively. However, for the beams at 1000°C, a correction coefficient (0.652) was applied to improve the accuracy of the calculative stiffness of the HRB600 RC beams at the service load stage. [ABSTRACT FROM AUTHOR]

To enhance the mechanical and constructional performance of the ultra‐high performance concrete (UHPC) beams, the steel plate placed at the bottom surface of the UHPC beam is utilized to replace the ordinary steel rebars. In this paper, four 3.2 m UHPC T‐shaped beams with different reinforcement patterns of ordinary steel rebars and external steel plate were fabricated and comparatively tested under flexure loading. Their damage patterns, load versus deflection behavior, flexural capacity, load versus strain behavior, moment versus curvature behavior, stiffness, and crack development were investigated. The flexural experiments indicated that the external steel plate, positioned at the bottom surface of the UHPC members, could resolve the difficulty of installing ordinary steel rebars in slender UHPC components and improve its constructional performance. Compared with the inside steel rebar reinforcement, the employment of the steel plate at the bottom surface of the UHPC beam can effectively increase the distance from the neutral axis to the tensile reinforcement at the serviceability and ultimate states, thereby improving its flexural capacity and stiffness. Additionally, the configuration of the external steel plate was beneficial to reduce the tensile stress level of the tensile reinforcement and limit the opening of UHPC crack width, and thus their crack resistance can be effectively enhanced. Moreover, increasing the thickness of the steel plate or rebar ratio can also significantly improve the flexural capacity, stiffness, and cracking resistance of UHPC beams. [ABSTRACT FROM AUTHOR]

The bond behavior between reinforcement and concrete has a significant influence on the load‐bearing behavior and serviceability of the composite material. This paper focuses on the characterization of the bond behavior between fine‐grained concrete and mineral‐impregnated carbon‐fiber reinforcement. In this study, the influence of different bond lengths on local bond behavior was experimentally investigated. To predict the bond stress along the bond length, an analytical bond stress‐slip model was specified, and its model parameters were determined based on the experimental tests using an iterative approximation approach. Based on the defined bond stress‐slip model, a numerical bond model was developed and adjusted for the first time. A three‐dimensional (3D) finite element analysis (FEA) allows the simulation of the local bond stress along the bond length. Finally, the results of the 3D FEA were compared with the results of the experimental investigations to validate the developed numerical model. [ABSTRACT FROM AUTHOR]

To realize the prefabricated structure of special‐shaped concrete‐filled steel tubular (CFST) column frame and enhance the level of indoor room utilization, this paper proposed a novel prefabricated frame with special‐shaped CFST columns and H‐shape steel beams connection with side plate. To investigate seismic behavior of this prefabricated frame structure, a 2‐story and 2‐bay CFST frame specimen was fabricated and tested under reversed cyclic loading. The failure mode, hysteresis behavior, degradation of lateral stiffness and bearing capacity, ductility and energy dissipation were analyzed. Experiment results indicated that failure mode presented strong columns and weak beams. Hysteresis curve of frame showed fully shuttle‐shaped. The mean story drift angle was 1/36 at ultimate stage. Equivalent viscous damping coefficient was 0.038–0.464. The bearing capacity degradation was relatively gentle, but the overall stiffness degradation was more obvious. It suggested that the frame had proper seismic and energy dissipation property. After the test, the seismic property of test frame was further investigated through the numerical simulation approach. The failure mode and skeleton curve obtained from the simulation were nearly consistent with test results, indicating that numerical analysis results were precise and with high reference meaning. [ABSTRACT FROM AUTHOR]

Crystalline admixture (CA) has been extensively utilized as the commercial product for improving the performance associated with strengthening self‐sealing of cracks or decreasing the permeability of concrete. However, few researches characterizing the restrained shrinkage and cracking potential of concrete with CA at early age. This paper aimed to expand the limitation by means of the experiments including mechanical properties test and restrained ring test on high‐strength concrete (HSC) with CA from Xypex. The proportion of CA was 0%, 0.5%, 1.0%, and 1.5% by the mass of cement. The incorporation of CA enhanced the compressive and splitting tensile strength as well as modulus of elasticity tested in this paper. A significant increase was observed in free and restrained shrinkage of HSC with CA. Although incorporation of CA ameliorated the stress relaxation, residual stress in restrained concrete ring developed rapidly with the incorporation of CA due to the significant increase in restrained shrinkage at early age. Restrained concrete ring with CA demonstrated a higher stress rate, which implied a higher cracking potential. When CA proportion increased from 0% to 0.5%, 1.0%, and 1.5%, a higher cracking potential was revealed through calculation, and restrained concrete ring exhibited earlier cracking age. Caution should be exercised with the application of such CA in concrete mixtures under restrained conditions. [ABSTRACT FROM AUTHOR]

The restraint of lateral reinforcement can effectively improve the bearing capacity and deformation capacity of confined concrete columns. Generally, the behavior of confined concrete column under axial compression and lateral cyclic loading is a complex process and has been the subject of numerous studies dating from last century. This paper presents a review to summarize and discuss the investigations of concrete columns confined by lateral reinforcements under axial compression and lateral cyclic loading with the aim of obtaining a clear understanding on the mechanism and performance of confined concrete column. In this paper, a test database of confined concrete columns under axial compression and lateral cyclic loading is established, presented, and evaluated. The detailed provisions of confined concrete columns from current codes are concluded and it is found that these codes neglect the beneficial effect of lateral reinforcement on shear bearing capacity of confined concrete columns under lateral cyclic loading. Additionally, the stress–strain models and development of lateral reinforcement strain/stress in confined concrete columns under axial compression are mainly presented and discussed. Moreover, theoretical and experimental studies on seismic behavior of confined concrete columns are evaluated, including compression‐flexure calculation, shear bearing capacity, ductility, energy dissipation capacity, and other detailed requirements. Furthermore, main influential factors of confined concrete columns under axial compression and lateral cyclic loading are discussed, respectively and it is founded that the synergy work of longitudinal and lateral reinforcement, and the deformation coordinated relationship between lateral reinforcement and core concrete significantly affect the bearing capacity and deformation capacity of confined concrete columns. Therefore, further studies are suggested to optimize and quantify the strength grade combination relationship between lateral reinforcement, longitudinal reinforcement, and concrete to achieve economical design and construction. [ABSTRACT FROM AUTHOR]

Basic magnesium sulfate cement (BMS) is a new type of magnesium cementitious material, which has similar advantages with magnesium oxychloride cement, such as lightweight, fast setting, high strength, wear resistance, and is not easy to absorb the moisture. It can widely replace magnesium oxychloride cement in the field of building insulation materials. In addition, the BMS has 2.5 times the flexural strength of Portland cement of the same strength grade, and its durability and reinforcement protection performance is similar to Portland cement, which also has a good application prospect in the field of civil engineering. The preparation and hydration process of BMS is reviewed in this paper. The microstructure and properties of BMS, magnesium oxychloride cement and magnesium oxysulfate cement are comparatively analyzed. The effects of content and activity of α‐MgO in the magnesium materials, the type of blending solution, the α‐MgO/MgSO4 ratio, the type and dosage of chemical admixture on the microstructure and properties of BMS were clarified. This paper is helpful for the application of BMS in civil engineering. [ABSTRACT FROM AUTHOR]

Openings in flat slabs near to columns are often needed to supply the building with utilities. The presence of these openings can lead to a decrease of the punching resistance which is related to (i) the reduction of the control perimeter, (ii) the stress concentrations at the edges of the openings, (iii) the reduction of the unitary shear resistance caused by increased flexural deformations, and (iv) the moment transfer in the slab connection in case of unsymmetrical openings. The effect of the openings on the punching shear resistance is strongly related to the geometry, the location, the number, and the size of the openings. To quantify the strength reduction due to the openings, current code approaches account for a reduction of the control perimeter defined by radial lines from the centroid of the column to the edges of the opening. Even though slabs with opening have been investigated since the 1960s, available experimental evidence on the behavior of slabs with openings without shear reinforcement is scarce and some effects are neglected in current design codes. Eurocode 2 and fib Model Code do not consider the effect of unsymmetrical openings leading to moment transfer in the slab‐column connection. ACI 318:2019 recommends considering these cases as free edges; however, additional information is necessary to perform the analysis. The present paper analyses a database of 68 flat slab specimens with openings according to ACI 318:2019, current Eurocode 2 (EN 1992‐1‐1:2004), the draft for the second generation (prEN 1992‐1‐1:2021), fib MC 2010:2013, and the Critical Shear Crack Theory. This paper proposes a new approach and a new definition of the control perimeter to improve the prediction of the punching shear resistance of slabs with openings based on the results of the database, the previous studies, and the linear‐elastic analyses of the shear force distribution along the control perimeter. [ABSTRACT FROM AUTHOR]

Cement used in structural concrete accounts for 60% of all cement. Thus, the amount of CO2 emission by cement in structural concrete in a year is about 5% of the amount emitted by mankind. However, the Life Cycle Assessment (LCA) of structural concrete emits CO2 not only at the product stage but also at the use stage after construction. In this paper, carbon neutrality is viewed from an economic point of view. Then a rough indicator is presented to grasp the CO2 emissions of structural concrete. This paper also shows that LCA of structural concrete should consider not only the materials but also the maintenance phase. And low‐carbon technologies currently in use is introduced. Then the need for multi‐cycle structural concrete with a circular economy is presented. Moreover, it is estimated that CO2 emissions due to disasters in the use stage could be enormous. The carbon neutrality of concrete is not a risk but an opportunity for us. [ABSTRACT FROM AUTHOR]

Corrosion of posttensioned bridges raises great concern, since the only way to safely assess the condition of the tendons is through destructive evaluation. In this scenario, this paper presents the results of an extensive literature review on reported cases of corrosion of posttensioned bridges and few prestressed structures. The aim is to increase knowledge about the structural consequences of possible corrosion‐induced failure mechanisms. The cases were rated according to the increasing severity of the observed damage and consequent interventions as follows: ordinary maintenance is effective, extraordinary maintenance is necessary, and maintenance is insufficient or absent. It was found that most corrosion‐sensitive structures were segmental and box section beam bridges. Most cases required extraordinary maintenance. Warning signs were often observed. The damage was mainly ascribed to design and execution mistakes that facilitated the ingress of external chlorides causing corrosion. The paper concludes with a discussion of the consequences for structural safety. [ABSTRACT FROM AUTHOR]

When shear cracking occurs in existing reinforced concrete deep members, engineers are faced with the challenge of determining the safety of the members. This paper presents a crack‐based assessment approach that utilizes the Two‐Parameter Kinematic Theory (2PKT) as a framework for the assessment of lightly reinforced concrete deep beams. The paper presents three assessment approaches with progressively increasing levels of approximation (LoAs). The first level of approximation (LoA I) involves using the 2PKT in a predictive manner for situations where the crack shapes are unknown, LoA II improves upon LoA I by incorporating more detailed modeling of the strain in the transverse reinforcement at the location of the critical cracks, and LoA III includes the details of LoA II but also uses the detailed crack geometry as an input in the assessment. Each of the LoAs is presented and compared with experimental data from a 4‐m deep beam test in the literature. The shear carrying mechanisms determined from the kinematic model are evaluated and compared across LoAs. Finally, the paper utilizes LoA III to study the size effect in shear for deep beams. The results quantify the influence of aggregate interlock on the size effect in shear critical deep beams. [ABSTRACT FROM AUTHOR]

This paper investigated the analytical solution of the bond strength between ribbed steel bar and engineered cementitious composites (ECC). In this method, ECC cover was regarded as a thick‐walled cylinder subjected to the uniform internal pressure which consisted of an elastic uncracked outer ring and a partially cracked inner ring. For the uncracked outer ring, it can be solved by the elastic mechanics theory. To solve the partially cracked inner ring, two key problems that had to be investigated were the crack width and the tensile stress–crack width relationship of ECC. According to the steady‐state cracking mode, the hoop deformation of ECC was expressed by the equal distribution and then the crack width can be determined. Besides, the fictitious crack model in fracture mechanic was introduced to describe the crack propagation process. Then a trilinear model was applied to reflect the tensile stress–crack width relationship of ECC materials, which considered the combined action of aggregate bridging and fiber bridging on the crack surface. Finally, the comparison between the calculation results and experimental results was carried out to prove the validity of the analytic method of bond strength proposed in this paper. Results indicated that the analytical solution and the experimental data fitted in well with each other. Then parameter analyses were conducted based on the analytical method proposed in this paper. [ABSTRACT FROM AUTHOR]

Modulus of elasticity of concrete is one of the important parameters in structural design of Reinforced Concrete (RC) members. For design and analysis purposes destructive/laboratory test are performed, however, for structural health monitoring and forensic investigation non‐destructive tests are preferred. Hence, it is essential to have correlations that can yield accurate results. Standard codes of different nations propose different methodologies for the estimation of modulus of elasticity. Moreover, in available literature no consensus is observed for ideal methodology. In view of this, the present paper experimentally investigates secant modulus of elasticity, initial tangent modulus, P‐wave dynamic modulus and S‐wave dynamic modulus for eight different concrete mixes. The regression analysis is conducted on experimental data and statistical models are proposed for reliable assessment of modulus of elasticity. Further, a correlation between static and dynamic modulus of elasticity is also proposed. Lastly, the experimental results are compared to the results obtained from developed models. It has been discovered that the proposed models accurately predict the modulus of elasticity of concrete. [ABSTRACT FROM AUTHOR]

The use of Recycled aggregate (RA) enhances concrete sustainability. If used on an industrial‐scale, structural verification, and testing will be required to confirm that RA concrete can meet relevant industrial standards and the requirements of manufacturers, especially in the precast‐concrete industry. In this paper, an experimental campaign with the participation of a precast‐concrete manufacturer is reported. The objective is to test a self‐compacting concrete (SCC) mix, designed for structural applications, that contains maximum amounts of 100% coarse RA, in order to establish its compliance with the habitual requirements of precast‐concrete manufacturers. Thus, scaled beams (12 × 24 × 180 and 24 × 24 × 130 cm) were subjected to bending, shear‐bending, shear, and long‐term‐deflection tests. In addition, the performance of that SCC mix in the bending and shear‐bending tests was compared with the performance of an SCC mix of similar compressive strength containing 0% coarse RA. In the failure tests, the experimental results were between 1.5 and 3 times higher than the required values. The elastic behavior of both SCC mixes was also very similar in those tests, regardless of the amount of coarse RA, due to the robust design of the water and superplasticizer content of the SCC, which balanced the decreased flowability and the lower compressive strength of SCC that resulted from the additions of coarse RA. The SCC mix with 100% RA showed a lower load‐bearing capacity after failure and narrow compliance margins with the deflection limits of the long‐term‐deflection test. Even though the SCC mix with 100% RA met all the standard technical specifications of the precast‐concrete manufacturer, reference should always be made to the serviceability limit states that are applicable at the time of the structural design phase. [ABSTRACT FROM AUTHOR]

The structural behavior of concrete hinges under general loading is far from being properly understood, which is to a large extent due to the lack of pertinent experimental data. This paper contributes to filling this knowledge gap by presenting and discussing the results of an experimental campaign on one‐way Freyssinet concrete hinges. Seven large‐scale concrete hinges were tested in the Large Universal Shell Element Tester, which allowed the investigation of their behavior under general loading by all six stress resultants. A combination of digital image correlation and distributed fiber optic measurements allowed a deeper insight into the structural behavior of the specimens. The tested hinges could sustain very high axial stresses exceeding 4.5 times the uniaxial concrete compressive strength, large rotations of over 60 mrad, and shear stresses in transverse and longitudinal directions up to 2.24 times the axial compressive stress. The resistance to bending moments about the strong axis and torques also proved to be significant. A moderate amount of reinforcement crossing the hinge throat considerably increased the shear resistance at low axial stresses and produced a ductile shear behavior. [ABSTRACT FROM AUTHOR]

The dynamic behavior of laced reinforced concrete (LRC) T‐beams could give high‐energy absorption capabilities without significantly affecting the cost, which was offered through a combination of high strength and ductile response. In this paper, LRC T‐beams, composed of inclined continuous reinforcement on each side of the beam, were investigated to maintain high deformations as predicted in blast resistance. The beams were tested under four‐point loading to create pure bending zones and obtain the ultimate flexural capacities. Transverse reinforcement using lacing reinforcement and conventional vertical stirrups were compared in terms of deformation, strain, and toughness changes of the tested beams. The inclination angles of the used lacing reinforcement with respect to the longitudinal reinforcement were 45° and 60°. The lacing reinforcement was efficient and participated actively in resisting the bending moments and shear forces at the same time. For the same diameter of lacing reinforcement, the 60° inclination angle imposed more ductility before failure than beams with lacing reinforcement of a 45° inclination angle. Moreover, the lacing bar diameter was more effective in improving the load‐carrying capacities when using the inclination angle of 45°. A finite element (FE) model was developed and validated using the experimental results based on the measured deformations and strains to conduct a parametric study. The investigated parameters included the effect of the arrangements of the applied loads, laced rebar diameter, inclination angle, tension reinforcement ratio, and concrete strength. [ABSTRACT FROM AUTHOR]

Insufficient research has been done on the mechanical and thermal properties of rubber concrete in the presence of fire. In this paper, we do detailed numerical modeling of the rubber concrete's thermomechanical behavior under dynamic conditions at high temperatures (800°C) using different percentages of rubber aggregate (0%, 10%, 20%, and 30%). The novelty of this work lies in its analysis of the temperature profiles over time in rubber concrete. This analysis is carried out using finite difference models developed with the MATLAB tool to predict thermomechanical parameters such as elastic modulus, thermal strain, tensile strength, and compressive strength. In addition, the dynamic behavior of the rubber concrete under impact loading was predicted, including stress and velocity change as a function of time at elevated temperatures. By the equations of motion and transient conduction, the mathematical model developed is based on density, thermal conductivity, heat capacity, and thermal expansion. The comparison between numerical and experimental results, and the analysis of the influence of the percentage of rubber aggregates on thermomechanical parameters, as well as the influence of temperature on the evolution of stress and velocity as a function of time, have shown the effectiveness of the mathematical and numerical model developed. [ABSTRACT FROM AUTHOR]