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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]

In this study, concrete canvas (CC) layers were used as a novel method to strengthen reinforced concrete (RC) beams because of their flexibility, rapid installation, fast curing, and rapid strengthening. Due to the importance of the CC mechanical properties, various combinations of cement including ordinary (OPC) and High Alumina (HAC), as well as silica fume, were investigated to determine the optimal mixture for strengthening RC beams. The results indicate that substituting 75% of HAC with OPC significantly boosted flexural strength by 33%, and increased tensile strength in the warp and weft directions by 25% and 21%, respectively. The study examined six RC beam specimens in a four‐point flexural test, assessing their flexural properties, ductility, cracking behavior, and energy dissipation. The number of CC layers and the bonding method, which involved either the conventional externally bonded reinforcement (EBR) technique or the externally bonded reinforcement on grooves (EBROG) technique were studied. The experimental results revealed the superiority of the EBR method over the EBROG technique due to the uniform bond between CC and the concrete surface. Using the EBR technique, improvements of 35% and 51% were observed in the load‐carrying capacity of the beams strengthened with one and two CC layers, respectively. It is while for the beam with an improved loading capacity of 51%, the crack width decreased from 5.3 to 2.1 mm, and the energy dissipation increased by three times compared to the control specimen. Theoretical analysis also was performed to calculate the load‐carrying capacity of the RC beams strengthened with CC layers. [ABSTRACT FROM AUTHOR]

In this study, we designed six polypropylene fiber‐reinforced concrete (PP‐FRC) beams and three reinforced concrete (RC) beams for experimental studies. Then, we analyzed the effects of incorporating PP fibers on the cracking performance of PP‐FRC beams from the perspectives of load‐displacement response, crack distribution, crack depth, crack width, crack spacing, and deformation coordination. The research results showed that the cracking load and number of cracks were positively correlated with the volume ratio of PP fibers, while the maximum crack width, average crack spacing, and average crack depth were negatively correlated with the volume ratio of PP fibers. Due to the bridging effect of fibers, the PP‐FRC beam body and reinforcement could deform in a coordinated manner within a specific loading range after cracking, which increased the deformation coordination ability between the body and reinforcement. In this study, the cracking mechanism of PP‐FRC beams was investigated. Firstly, the formula for calculating the cracking moment of PP‐FRC beams was derived from the perspective of equivalent bending tensile strength. Then, based on the fiber bridging law and the bond strength between PP‐FRC and reinforcement, theoretical formulas were proposed to predict the average crack spacing and maximum crack width of PP‐FRC beams. Finally, through comparison, it was found that the proposed formulas could be used for characteristic crack prediction. [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]

Many studies have suggested that engineered cementitious composite (ECC) could be a highly efficient and cost‐effective material for enhancing the flexural strength of reinforced concrete (RC) beams. Recently two effective retrofitting configurations using steel and polyvinyl‐alcohol hybrid fiber reinforced engineered cementitious composite (SPH‐ECC) were proposed (Qasim et al., Eng Struct, 2023, 284, p. 115992) and their high effectiveness for enhancing the flexural strength of RC beam was verified experimentally. However, to examine the performance of these strengthening configurations thoroughly by conducting experiments to cover practical ranges of design parameters is deemed to be too expensive and time consuming. In this study, a numerical parametric study of SPH‐ECC strengthened RC beams was conducted by employing a validated finite element (FE) modeling procedure developed by the authors. The effects of four key design parameters including the compressive strength of concrete and SPH‐ECC, the thickness of SPH‐ECC strengthening layer and the area of reinforcement bars embedded in SPH‐ECC layers on the flexural performance of the strengthened beams were studied. Parametric study results showed that the area of reinforcement bars in the SPH‐ECC layers could significantly affect the flexural strength of the strengthened beams. Furthermore, in order to allow engineers to predict the flexural strength of the strengthened beams quickly, two simple but accurate analytical models were also developed for the two strengthening configurations considered. Their reliability and accuracy were then verified and confirmed by comparing with the parametric study results. [ABSTRACT FROM AUTHOR]

The dual‐function retrofitting system that uses the carbon‐fabric reinforced cementitious matrix (C‐FRCM) as both the anode of impressed current cathodic protection (ICCP) system and the structural strengthening (SS) material, that is, an ICCP‐SS system, is investigated. The experimental program mainly focused on the shear behavior of C‐FRCM strengthened reinforced concrete (RC) continuous beam under the dual‐function retrofitting system. The influence of anode polarization on the shear strengthening of RC continuous beams is analyzed. Shear tests were conducted on a total of 14 corroded RC continuous beams to investigate the influence of key parameters, including anode polarization degree of prefabricated C‐FRCM plate, layer of carbon fiber mesh and side‐wrapping. The failure modes, shear capacities, and load‐deflection curves of the shear‐strengthened RC continuous beams are reported. Based on the test results, the applicability of relevant design codes was evaluated and found to provide rather conservative predictions for the shear capacity of the examined C‐FRCM strengthened RC continuous beams. [ABSTRACT FROM AUTHOR]

This article presents a review of state of the art on nonmetallic reinforcement in terms of bending moment redistribution in double‐span elements. The authors present a summary of existing research programs focused on moment redistribution in FRP (Fiber Reinforced Polymer) reinforced concrete (RC). On this basis authors created a database of concrete elements with all the important construction properties of the elements. Gathered data are presented with quantitative analysis of several variables effecting moment redistribution in published articles. In the following publication authors show a research review which includes an analysis of the influence of variable parameters from the point of view of the database, concerning: degrees of longitudinal reinforcement, ratio between degrees of reinforcement in span and over the support, type of reinforcement (FRP/steel/hybrid), concrete class and transverse reinforcement. [ABSTRACT FROM AUTHOR]

Experimental study of reinforced concrete beams without stirrups under impact: performance evaluation and structural response Experiments on reinforced concrete beams without stirrups are often utilized as a simplified basis to calibrate numerical models of reinforced concrete slabs. This paper details an experimental study on the behavior of reinforced concrete beams without stirrups subjected to impact loading. For this study, the 11‐meter‐high drop tower at the Otto Mohr Laboratory of TU Dresden was used to accelerate a cylindrical impactor with a diameter of 100 mm. Compressed air accelerated the impactor to velocities between 2.7 m/s and 25.8 m/s. The impactor masses were 14.22 kg and 21.66 kg, respectively. Data on impactor and support forces, displacements, and accelerations were collected. Digital image correlation supplemented the measurements. The study revealed that the behavior of the beams exhibited different failure modes depending on the impactor velocity and mass. The shear cracks started to form at impactor velocities of approximately 11 m/s, corresponding to the lighter impactor's kinetic energy of 860 J. Furthermore, the formation of a punching cone near the loading point at impactor velocities of around 22 m/s was observed. These findings provide valuable insights for designing and thoroughly assessing the performance of shear‐deficient reinforced concrete beams under impact loading. The results serve as a foundation for enhancing the precision and reliability of numerical models, facilitating further investigations into complex structural systems. [ABSTRACT FROM AUTHOR]

The lifespan of a reinforced concrete (RC) structure can be greatly influenced by the spatial variability of its material characteristics which, in particular, explains the observed or measured reduction of the tensile strength at first crack when the volume under tension increases. This paper discusses the ability of accounting for the spatial variability of the tensile strength of concrete in RC structures using a stochastic finite element (SFE) method based on random field simulations. In this work, the generation of random fields on the concrete tensile strength aims at computing the force corresponding to the first crack occurrence, and the reduced tensile strength of the structure. The method can be applied in particular to large‐sized structures, which show a pronounced size effect, for different types of loading. The method consists of, first, estimating the mean of the random field, using the analytical approach of the weakest link and localization method (WL 2A${2}_A$). Then, the discretized random field is defined on a particular 2D or 3D grid, and it is finally projected on the finite element mesh of the studied structure. The study of the parameters that influence the prediction of the cumulative density functions (CDFs) of the rupture force or the tensile strength is highlighted using experimental series of concrete beams having different volumes and subjected to 4‐point bending loading. Moreover, the SFE method is applied to a RC tie‐beam under tensile loading, characterized by a weak stress gradient, which complicates the prediction of crack positions. [ABSTRACT FROM AUTHOR]

Determination and validation of material parameters for the non‐linear modelling of concrete This article shows that the load‐bearing behavior of concrete and reinforced concrete beams can be successfully simulated using the material models included by default in the widely used ANSYS Mechanical software. The necessary material parameters are determined using laboratory tests. These are tests on concrete cylinders to determine the compressive and tensile strength as well as the modulus of elasticity. The fracture energy is determined on notched beams. This test is then simulated using the Drucker‐Prager model in combination with Rankine yield surfaces and exponential softening. The calculated load‐deformation behavior matches the test curves well when using the experimentally determined material parameters. A comparative calculation with normatively proposed parameters overestimates the fracture energy and thus the load‐bearing capacity of the test specimens. The numerical model is then validated using reinforced concrete beam tests. The model with the experimentally determined material parameters can reproduce the load‐bearing behavior of the test specimens well, but it also becomes clear that appropriate modeling of the bond behavior is important. In this case, the load‐bearing behavior of the beams with spring elements between concrete and reinforcement nodes is best described. Furthermore, it is shown that the use of reduced or fully integrated elements can have a major influence on the simulated softening behavior of concrete. [ABSTRACT FROM AUTHOR]

In order to study the effect of different loading rates on the fracture behavior of fiber‐reinforced polymer (FRP) reinforced concrete, the fracture experiments of FRP‐reinforced concrete beams under different loading rates were carried out. The calculation method of fracture toughness was given by analytic deduction, and the effects of different loading rates on the fracture parameters were analyzed. The experimental results show that there are three critical points in the fracture process of FRP‐reinforced concrete beam, which are the crack initiation load, crack resistance load, and ultimate load points. The effective crack length at the crack resistance load point increases with the increase of loading rate, and the effective crack length at the ultimate load point does not vary as the loading rate. With the increase of loading rate, the elastic modulus and fracture toughness increase gradually, and there is a logarithmic relationship with the loading rate, which has obvious rate correlation. The fracture process zone (FPZ) length of FRP‐reinforced concrete beams gradually decreases with the increase of loading rate. Highlights: There are three critical points in the fracture process of FRP‐reinforced concrete.The calculation of fracture toughness can be given by analytical derivation.Fracture toughness is logarithmically related to the loading rate.Crack length at the ultimate load point does not vary as the loading rate. [ABSTRACT FROM AUTHOR]

A variety of innovative structural solutions have been recently introduced to mitigate damage and expedite the repair of buildings subjected to extreme seismic events, hence contributing to the urgent need for resilient societies. In this context, the present study experimentally and numerically investigates an innovative reinforced concrete (RC) shear wall (SW) structure with replaceable coupling beams (CBs) equipped with hybrid devices. These hybrid devices couple metallic and viscoelastic dampers and aim at satisfying multiple lateral load performances effectively. To assess the seismic performance of the proposed coupled SWsystem and verify the design principle, comparative shaking table tests were performed on two 1/4-scale seven-story SW structure specimens, including a conventional RC coupled SW and the proposed coupled SW with hybrid devices. The tests results indicate the improved performance of the proposed compared with the conventional system in terms of: (1) reduced interstory drifts and story accelerations demand under awide range of seismic intensities, (2) concentrated damage in the hybrid device and minimal damage to the other components contributing to the reparability of the structure. Furthermore, 3D finite element models for the shaking table test specimens were established in OpenSees and validated against experimental response. Successively, a numerical parametric study was conducted by performing non-linear response history analyses under a set of 22 ground motions to investigate the influence of different design configurations of the hybrid device on the peak interstory drifts and peak story accelerations. [ABSTRACT FROM AUTHOR]

Electromagnetic wave velocity in ground‐penetrating radar (GPR) constant offset data can be estimated via the diffraction hyperbola fitting method. This method is applicable when radargrams contain diffraction events (hyperbolic patterns) caused by scatters in the host smaller or equal to the dominant wavelength. An alternative method for velocity estimation, if no intrusive information is available for a direct correlation, requires the collection of multi‐offset data. The method is quite common for broad geophysical applications; however, it seems not to be fully utilized for engineering applications, such as slabs/walls where thickness estimation and depth of the embedded features are critical requirements for structural assessments. This method would also overcome the limitations in velocity calibration in environments with no hyperbolic signal signatures. The aim of this study is to explore multi‐offset high‐frequency GPR applications, specifically the wide‐angle reflection and refraction method, for structural engineering, to understand whether it is feasible, possible limitations, and advantages. Numerical models reproducing reinforced concrete elements and a cavity wall were analysed to understand the wave behaviour and predict the response prior to testing on real cases. The main purpose is to explore how reinforcing bars can affect the velocity spectra derived from semblance analysis and what the response would be in a case of multi‐layered structure with increasing velocity with depth (cavity wall). The comparison with real cases showed that, despite some intrinsic limitations, high‐frequency multi‐offset approach could be part of standard workflow for all those surveys where no other velocity estimation method is feasible. [ABSTRACT FROM AUTHOR]

Summary: Reinforced concrete (RC) shear wall buildings with unreinforced masonry (URM) infilled moment frames are common in India and neighboring countries. This study assesses the influence of the URM infills on their seismic performance. Fully infilled, open first‐storied, and bare frame versions of a 25‐story shear wall building are considered. Multiple stripe analysis is conducted at five return periods to estimate their performance. Fragility functions for the collapse prevention limit state, which is based on seven engineering demand parameter exceedance thresholds, are generated and compared. The presence of infills (full or partial) is observed to have an overall positive effect on the performance of the RC frame‐shear wall buildings. The performance of the open first‐story building was comparable to that of the fully infilled building. The ratio of story shear carried by the moment frames and shear walls is studied at all return periods to understand the variation in frame shear wall interaction with increased damage for each building. In the case of buildings with infills, the frames carry a higher proportion of story shear at lower return periods. For all three buildings, the fraction of story shear carried by moment frames increases along the height of the building. [ABSTRACT FROM AUTHOR]

Cold‐formed steel (CFS) products are extremely versatile and can be used in multiple applications. Recent experiments tests by the authors have shown that mobilising composite action within systems comprising cold‐formed steel beams and lightweight concrete is feasible and can lead to substantial improvements in structural performance. However, their behaviour subjected to elevated temperatures has yet to be investigated; this is, therefore, the focus of the present study. The results of two tests on CFS‐LWC beams at ambient and elevated temperatures are reported. A numerical modelling study using fire dynamics simulator (FDS) software is then described in which the temperature development was successfully replicated. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation into the flexural and cracking behavior of corroded reinforced concrete continuous beams with 11‐month wet–dry cycles strengthened by anodic polarized carbon‐fabric‐reinforced cementitious matrix (C‐FRCM) plates. The failure modes and flexural bearing capacities were discussed. The influences of the layer of carbon fabric mesh and complete carbon fiber‐reinforced polymer (CFRP) wrapping as end anchorage on the strengthening effectiveness were explored. The complete crack development patterns were captured by a digital image correlation system, and the results showed that the C‐FRCM system can provide satisfactory crack width control, as proved by the reduced crack spacing and the maximum crack width. The flexural capacities of the strengthened beams were effectively enhanced and the debonding failure can be eliminated through complete CFRP wrappings. Moreover, the design recommendations were proposed based on the estimation of the crack development as per related design guidelines. [ABSTRACT FROM AUTHOR]

This paper presents the experimental study and finite element modeling of the flexural behavior of concrete beams reinforced with reused steel bars as longitudinal reinforcements. The experimental program and results of eight reinforced concrete (RC) beams constructed with and without reused steel bars are described in detail. The replacement percentages of brand‐new bars with reused steel bars in the tested beams were 50% and 100%. The reused steel bars were coated with and without epoxy. Steel fibers with fractions of 0.5% and 1.0% of the concrete volume were added to the concrete mixes. The load‐deflection relationship, ductility index, toughness, and failure modes of the tested beams are presented and discussed. It is shown that utilizing reused steel bars decreases the ultimate load of RC beams but increases their deflection at the ultimate load compared with the control beam. Increasing the steel fiber ratio increases the ultimate load and the deflection at the ultimate load of RC beams incorporating reused steel bars. However, the zinc‐rich epoxy used to coat the reused steel bars does not affect the behavior of the beams. Three‐dimensional nonlinear finite element (FE) models of the tested beams were developed using ABAQUS and validated against the test results. The developed FE models are capable of accurately simulating the experimentally observed behavior of RC beams with reused steel bars. [ABSTRACT FROM AUTHOR]

The goal of this study is to propose a robust method for the analysis and design of recycled aggregate reinforced concrete (RAC) beams. For this purpose, a machine‐learning framework, named, GA‐XGBoost was designed. A comprehensive dataset of 276 tests of RAC beams was compiled from available literature for training, validating, and testing the models. The results confirmed that the proposed models can offer a precise tool for failure mode classification and capacity prediction of RAC beams. For the design framework, a Generative Adversarial Network for tabular data was utilized to produce synthetic data. These synthetic data can provide options for the selection of design variables. In this framework, the design variables are selected by specifying the design constraints, the objective function to be optimized, and validating the capacity requirements using the developed GA‐XGBoost models. Lastly, a web application was developed to make the proposed GA‐XGBoost models appropriate for practical design. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) concrete beams reinforced by carbon fiber reinforced polymer (CFRP) grid reinforced engineering cementitious composite (ECC) have excellent flexural performance and corrosion resistance in marine environments. However, the lack of a reliable theoretical model for predicting the flexural behavior of the hybrid beams makes it challenging apply them in the practical engineering. To address this issue, a series of numerical models were established to investigate the effects of key parameters on the flexural behavior of the hybrid beams, including the peak load, the neutral axis height, and the sectional stress distribution. Subsequently, based on the influence of the failures of different materials on the flexural performance of the hybrid beam, the loads of four feature points were calculated in the theoretical model to predict the entire load–displacement curve. Finally, the application range of the theoretical model was given based on the neutral axis height. The results showed that the cover thickness of the ECC, the GFRP reinforcement ratio and the cross‐sectional area of the CFRP grid were the key factors affecting the flexural performance of the hybrid beams. The theoretical model established in this study can predict the load–displacement curve accurately and can provide a reference for the subsequent design of the hybrid beams. [ABSTRACT FROM AUTHOR]

The positive effect of fiber‐reinforced concrete (FRC) on shear capacity of reinforced concrete beams is well presented in many experimental studies since 1970s. However, as the main effect of fibers is in the cracking stage, it increases the complexity to analyze such structures numerically. With the increased availability of nonlinear finite element analysis software, structural designers are encouraged to use them to solve complex structural problems. In such cases, understanding and correct definition of material laws in cracked stage of FRC structures are crucial. A blind competition was organized by fib WG 2.4.2 to address this issue. It revealed that the numerical predictions of almost all of the participants overestimated the shear capacity of a T‐beam subjected to bending. The aim of the current study is to demonstrate critical aspects in the definition of input parameters of FRC analysis. A comprehensive parametric analysis is performed considering tensile softening law, shear stiffness, and shear strength definition in cracked stage as well as shrinkage effects. The results suggest that most important aspect is the correct definition of tensile softening law, which should correspond to the lower bound of residual strength obtained by standard notched prisms tests according to EN 14651 or even smaller. [ABSTRACT FROM AUTHOR]

Fibers are mixed within reinforced high‐strength recycled aggregate concrete (RHRAC) beams to improve their flexural performance. This study experimentally and analytically investigates the effect of using RAC combined with polyvinyl alcohol fiber (PVAF) and steel fiber (SF) on the flexural performance of RHRAC beams. A total of 11 RHRAC beams (150 × 300 × 2600 mm3) are manufactured and subject to four‐point flexural testing. The parameters of the concrete are investigated, including the volume content of the PVAF and SF. The experimental results show that SF increases the flexural strength of RHRAC beams more than PVAF does. Conversely, the effect of PVAF on deformability is more significant than that of SF. In addition, the positive influences of hybrid fiber (PVAF and SF) on the crack load, flexural capacity, and deformation capacity are superior to those of single‐mixed PVAF or SF. Three different specifications are used to calculate the flexural capacity of the test beams, among which, JGJ/T465‐2019 is the most reliable. [ABSTRACT FROM AUTHOR]

Ductility is one of the most important requirements of RC design besides other requirements such as strength and stiffness. In recent years, concrete beams with a large amount of tensile reinforcement ratio (ρ) have been required in large projects, such as high‐rise buildings and bridges. Using high (ρ) increases the strength and stiffness of the beams and leads to a decrease the ductility. This paper aimed to investigate the effect of using steel fibers reinforced concrete (SFRC) layer in compression zone on the flexural behavior of over‐reinforced concrete beams. Partial replacement of concrete with SFRC layer in compression zone was used to avoid the brittle compression failure of concrete. For this purpose, 12 over‐reinforced concrete beams with a span of 1300 mm and a cross‐section of 120 mm × 180 mm were cast and tested under a three‐point loading. The first beam was used as a reference beam and others as strengthened beams using SFRC layer. The effects of thickness and length of strengthening layer, (ρ), volume fractions of steel fibers, and strengthening methods on flexural performance of tested beams were investigated. The flexural capacity, failure modes, crack patterns, load–deflection relationships, load–strain relationships, ductility index, and toughness were evaluated. The results showed that the suggested technique (SFRC layer in the compression zone) is an effective technique to increase ultimate load, ductility, and toughness by up to 35.72%, 121.01%, and 349.16%, respectively, compared to the reference beam. Furthermore, the failure mode changed from brittle to ductile failure. Also, one of the main advantages of this technique is allows to increase of (ρ) up to 8.55% (4.15ρb) without needing the compressive reinforcement. The results of this study indicate that the using SFRC layer in the compression zone is an appropriate and economical method to provide high flexural capacity and ductility over‐reinforced concrete beams. [ABSTRACT FROM AUTHOR]

Summary: The objective of this study was to study the effect of load details of successive explosions on the blast behaviors of reinforced concrete (RC) beams. First, the effect of the successive loading of two identical explosions was discussed by considering the influences of standoff distance, charge mass on the failure states, and structural responses (displacement and support reaction force). And keeping the total TNT charge mass of 1 kg unchanged, the effect of loading numbers was investigated by loading two 0.5 kg TNT successively and a single 1 kg TNT on RC beams, respectively. Besides, the successive loading of two different explosions was also considered by investigating the effects of loading sequences and the first explosion induced pre‐damage on the ultimate accumulated damage of RC beams. At last, based on the reaction force and displacement responses, a nonlinear relationship between the dynamic residual load‐carrying capacity and the accumulated residual displacement was obtained to assess the damage states of the tested beams. The results show that the local failure range along the beam span direction (length of peeling‐off and length of spallation) caused by the first blast load did not apparently increase when the damaged beams were subjected to another blast load. With the increase in explosion numbers, depth of compressive crushing increases gradually. At the same stand‐off distance (from 0.25 to 0.45 m), due to the damage accumulation effect, successive loading of two 0.5 kg TNT can trigger more severe local failure but smaller accumulated residual deflection to beams than the single loading of a 1 kg TNT. Besides, when two different blast loads are loaded on tested beams, the loading sequence of the larger one first and then the smaller one (1 kg TNT/0.5 kg TNT at h = 0.45 m) can trigger larger damage to beams than the opposite loading sequence (0.5 kg TNT/1 kg TNT at h = 0.45 m). And for the beams subjected to a smaller blast load first and then a larger one, a stiffer behavior may be triggered by the second blast load on the beam after the first loading of the smaller blast load due to the residual strain in longitudinal reinforcement. Furthermore, based on the nonlinear relationship between residual load‐carrying capacity and residual displacement, the accumulated damage of RC beams was divided into mainly four phases. [ABSTRACT FROM AUTHOR]

Point cloud can provide rich 3‐D geometric information of structures, and it has been widely investigated for generating digital functional models, such as finite element (FE) model and building information model (BIM). However, for the existing digital models, how to maintain and update the new local geometric changes on the existing digital models has not been sufficiently studied. Therefore, this research presents a method to update the local 3‐D geometric changes on digital functional models using point cloud processing and surface cut. The proposed pipeline starts from processing the point cloud of the local structural change for reconstructing the local surface mesh. After that, the surface mesh is aligned to the corresponding location of the existing digital model by point cloud registration. Then, the geometry updating can be achieved by cutting the digital model with the generated surface mesh. To validate the proposed geometry updating method, two case studies were performed on damaged concrete beams with their intact FE models. The results show that the 3‐D geometry changes caused by the damage on the edge and vertex can be successfully updated with high resolution on the existing digital models. The results demonstrate the feasibility of integrating the proposed method into structural health monitoring (SHM) systems for further analysis. [ABSTRACT FROM AUTHOR]

Summary: This study investigates the flexural performance and degree of composite action (DCA) of precast concrete sandwich panels (PCSPs) with four types of connectors. Five full‐scale specimens were designed, and 4‐point bending tests were performed. The specimens included four PCSPs utilizing glass fiber reinforced polymer (GFRP) truss connectors, steel truss connectors, concrete rib connectors, and GFRP pin connectors, respectively, along with a solid panel (SP). The results indicated that the flexural performance and DCA provided by the four types of connectors followed an ascending order as follows: GFRP pin‐type connectors, GFRP truss connectors, steel truss connectors, and concrete rib‐type connectors. Moreover, the study presented a novel method for calculating DCA, namely, the neutral axis method, which was compared with the displacement and strain methods. The reasonableness and accuracy of the neutral axis method in calculating DCA during the linear elastic stage were verified. Results indicated that the neutral axis method provided more precise and reasonable DCA that closely matched the experimental results compared with the displacement and strain methods. Additionally, the neutral axis method was simpler to calculate DCA and had a broader range of applications. Finally, the study provided recommendations for the optimal application scenarios of each calculation method. [ABSTRACT FROM AUTHOR]

Summary: The present study deals with introducing a novel approach toward estimating the effective width of flanged reinforced concrete shear walls (FRCSWs). Due to the paucity of studies in assessing the effective width of nonrectangular sections, this paper aims at proposing efficacious formulations for the effective width estimation of short, squat, and slender T‐ and U‐shaped reinforced concrete (RC) shear walls subjected to the simultaneous action of the axial and lateral loading. To this end, at first, FRCSWs are simulated in the flanged shear wall numerical laboratory (FlashLab) program, which utilizes the finite element Abaqus software to analyze the walls. Thereafter, employing the developed numerical models, an extensive parametric investigation is conducted for a wide range of the key parameters. General expressions have then been developed to estimate the effective width of flanged RC shear walls invoking the evolutionary polynomial regression (EPR) analysis in conjunction with the genetic algorithm (GA). To assess the capability of the established equations in predicting the effective width of flanged sections, R‐factors have been calculated for all the cases examined in this study, which ranged between 0.78 and 0.94. Furthermore, a comparison has been made among the results attained through the proposed methodology and those obtained using the conventional design codes. It was revealed that the relative error obtained employing the proposed formulations is less than that of the corresponding values of the design codes by approximately 30% on average. The superiority of the established framework stems from consideration of the following: (1) influential parameters, (2) effective width variations at different performance levels, (3) loading direction, and (4) type of the wall in the effective width calculation process. [ABSTRACT FROM AUTHOR]

Reinforced concrete deep beams in bridges and other critical infrastructure are subjected to millions of load cycles during their service life. At the same time, they typically work with high shear and develop critical diagonal cracks. The cyclic loading across the cracks results in fatigue damage of the shear‐resisting mechanisms, which needs to be taken into account in the assessment of existing structures, and in particular in members with small amount of shear reinforcement built according to early design codes. To aid the development of advanced assessment approaches for such structures, this paper presents five large‐scale fatigue tests of deep beams with a stirrup ratio of 0.134%. The beams are preloaded to develop complete diagonal cracks, and then are subjected to cycles with different minimum and maximum load. The focus is placed on detailed crack measurements, needed for the development of crack‐based assessment approaches. The crack data is analyzed with the help of the two‐parameter kinematic theory to quantify important deformations. It is shown that the fatigue across the shear cracks is associated mainly with degradation of aggregate interlock and progressive damage in the critical loading zones. It is also shown that as the maximum load is decreased, the fatigue life increases, and the failure mode can switch from shear to flexure. [ABSTRACT FROM AUTHOR]

Most of the Italian infrastructures have been built since the mid‐twentieth century. Prestressed concrete (PC) has been widely used, especially for bridges and viaducts. These structures have proved effective over time, but their performance could be affected by degradation phenomena (i.e., corrosion of the tendons and residual prestressing) or construction defects (i.e., grouting of the ducts), which need to be accurately modeled. This paper focuses on the flexural response of two reduced‐scale, posttensioned, PC bridge girders, prestressed with two different jacking forces and tested under four‐point bending configuration. Four multidimensional numerical models were developed to simulate the experimental behaviors of the selected specimens, using two alternative computational strategies, namely, the finite element method (FEM) and applied element method (AEM). Three FEM modeling were considered, ranging from one‐dimensional lumped‐plasticity models to two‐dimensional and three‐dimensional (3D) spread‐plasticity models. Besides, 3D AEM models were developed into another software package. The accuracy and the computational costs of the two numerical strategies are discussed in this paper. Also, the main features of each numerical modeling technique are addressed, including comparisons between numerical and experimental global response data as well as the statistical characterization of the model error. Based on these different features, the authors also suggest the most suitable numerical strategy for future studies on PC girders. [ABSTRACT FROM AUTHOR]

As a sustainable concrete material, hemp and recycled aggregate concrete (HRAC) is produced by partial replacement of natural coarse aggregates (NCA) with recycled concrete coarse aggregates (RCA) and industrial hemp fibers. The objective of the reported research was to investigate the structural performance of reinforced concrete beams prepared with HRAC and designed to fail in flexure, shear, or bond splitting modes of failure, and to compare that performance with companion control beams cast with conventional concrete. The significance stems for the fact that no previous research is reported on mixtures using such a combination of hemp fibers and RCA. Test results indicated that HRAC beams with 0.75% volumetric percentage hemp fibers and 50% RCA replacement had comparable peak load capacities to the control beams with no RCA and no fibers, with ±4% difference for all tested modes of failure. Additionally, the fracture energy of the HRAC beam was higher than the control beam by 3.6%, 17.9%, and 14.4% for the flexure, shear, and bond modes of failure, respectively. Moreover, a life cycle analysis (LCA) was considered to compare HRAC mix with conventional concrete mix in terms of the environmental aspects. LCA results indicated that HRAC is a sustainable concrete, specifically with respect to structural performance and lower environmental impact. [ABSTRACT FROM AUTHOR]

Silica, a principal component of waste glass powder (GP) reacts with calcium hydroxide to form the hydration products, and the process is affected by the fineness of GP and the percentage of cement replaced. This study investigates the structural behavior of concrete incorporating GP in reinforced concrete members by 0%–25% (by weight) replacement of cement with GP along with 0%–0.45% addition of glass fibers (GFs). The compressive and tensile strengths, strength activity index (SAI), and failure mode of treated concrete mixtures have revealed the optimum values as 15% replacement of cement with GP with 0.3% of GF. In the second stage of experiment, reinforced concrete beams were cast at various percentages of GP and GF to investigate the load–deflection response. It was observed that the beam specimen treated with GP exhibited considerably less mid‐span deflection (14.8 mm) at failure as compared to the control beam (with no GP and GF) which failed at 29.4 mm. The beam specimen treated with GP only showed significant degradation in stiffness after the peak load due to the fact that a part of GP remains unreacted and acts as a filler. Moreover, the beam specimen cast at optimum percentages of GP (15%) and GF (0.3%) showed large mid‐span deflection and higher failure load as compared to the control beam. These results suggest that the partial replacement of cement with GP should be accompanied by the addition of fibers to avoid unwanted brittle responses of GP concrete, with the additional advantage of reducing the non‐biodegradable waste. [ABSTRACT FROM AUTHOR]

The reinforced concrete (RC) beams could be upgraded in shear using steel and fiber‐reinforced polymer (FRP) having several shapes (bars, strips, or sheets). Using near‐surface mounted (NSM) Glass FRP (GFRP) bars is still limited compared to carbon FRP (CFRP) elements as shear reinforcement. Moreover, using reinforced high‐strength concrete layers (HSCL) as NSM shear strengthening for the RC beams is still limited. Herein, three RC beams internally reinforced in shear using different shear areas (without, 100 mm stirrups apart, and 200 mm stirrups apart) were experimentally tested as reference beams (CB). Other eight beams strengthened in shear using NSM HSCL, and bars were experimentally tested. Moreover, an extended finite element (FE) simulation was implemented through a verified FE model to study the effect of other NSM aspects on shear‐strengthened beam response. The results explained that, regardless of the internal stirrups area and external NSM characteristics, the shear‐strengthened beams showed higher load efficiency than the corresponding CB. The NSM upgraded shear beam had slightly higher load efficiency than the un‐strengthened beam having the same steel area as internally shear stirrups. Moreover, increasing the internal shear stirrups decreased the total efficiency of the NSM shear strengthening and the internal stirrups regardless of the NSM characteristics. Furthermore, the NSM HSCL was more efficient than the corresponding NSM bars in increasing the load capacity and stiffness of the shear‐strengthened beams. The reported analytical model predicted well the shear capacity of the tested beams. [ABSTRACT FROM AUTHOR]

Ultra‐high performance concrete (UHPC) prefabricated beams are competitive in accelerated bridge construction. However, their broader application has been hindered by limited large‐scale tests and inaccurate design methods. To fill this gap, the authors conducted an experimental investigation on the shear and flexural performance of UHPC pi‐beams using two full‐scale specimens. One specimen was a precast UHPC beam, while the other was a composite beam with a normal concrete slab on the UHPC beam. The primary focus was on crack propagation, ultimate capacities, and failure modes. To complement the experimental findings, the extended finite element method (XFEM) was developed as a numerical approach. Nevertheless, relying solely on XFEM to understand real structural behavior is prone to misinterpretations. Moreover, the shear and flexural capacities were evaluated using existing codes and compared with the experimental results. The comparisons revealed that the predictions of shear capacities were at least 15% lower than the experimental values, whereas the flexural capacities showed acceptable agreement. To address this, the authors introduced the limit equilibrium method, leading to a more accurate prediction of shear capacity for UHPC beams with a deviation of <2%. [ABSTRACT FROM AUTHOR]

To study the influence of the defects on the flexural behavior of laminated T‐beams, full‐scale beam tests of three reinforced concrete laminated T‐beams with incomplete bonding and one non‐defective reinforced concrete laminated T‐beam were conducted under monotonic loading. The results showed that the failure modes and crack patterns of the defective beams were similar to those of beams without defects. However, horizontal cracks appeared in these defects. Although the peak loads of the four specimens were relatively close, the difference in the maximum deflection was distinct. The deflection span ratio of each specimen exceeded 1/17, and the displacement ductility ratio exceeded 15. The results indicate that internal defects have only a slight influence on the flexural capacity of laminated beams but significantly influence their ductility. [ABSTRACT FROM AUTHOR]

Iron tailings have been extensively studied as mineral admixtures and as coarse and fine aggregates. However, few studies have been conducted on the mechanical properties of iron tailings concrete structures. Using iron tailings powder as an mineral admixture, and iron tailings gravel and sand as coarse and fine aggregates, respectively, the flexural behavior of full iron tailings concrete (FITC) beams was investigated experimentally. Compared with conventional concrete (CC) beam, we showed that the crack‐resistant, yield, and ultimate moments of FITC beams are similar to those of the concrete strain of FITC beams, which is in good agreement with the plane section assumption before cracks appear. The low elastic modulus of FITC makes the deflection of three FITC beams larger than that of a CC beam. The current design code of China is appropriate for calculating the load‐carrying capacity of FITC beam; however, the deflection calculation formula should be modified. [ABSTRACT FROM AUTHOR]

Following the recent collapse of a cable‐stayed bridge in Genoa, Italy, an interest has arisen to understand if it would have been possible for unknown localised material deterioration and/or decrease in prestress levels to introduce noticeable changes in the dynamic behaviour of RC stays. As such, in this study we start by reviewing past research work, experimental and analytical, on the effects that prestress level may or may not have on the dynamic response of RC beam elements. We then review also available analytical formulations used to determine the natural frequency of vibration of prestressed beams, and, subsequently, complete the preliminary investigation on the effects of prestress levels, and local damage, through the analysis of finite element models of prestressed beams and stays. The comparison of analytical and numerical estimations with results obtained from an in‐situ dynamic characterisation campaign on a RC bridge stay is also undertaken. In the second part of the study, we explicitly consider the Morandi bridge case‐study, for which finite element models of the stays alone, as well as of the full bridge, are developed and analysed. The obtained results are then also compared with the observations made in pre‐collapse in situ dynamic characterisation endeavours. All results obtained and discussed lead to the conclusion that, most regrettably, dynamic characterisation endeavours do not have the capability of providing insight on possible localised material deterioration or partial reduction of the average state of compression in this type of structural elements. [ABSTRACT FROM AUTHOR]

Structural health monitoring is the process of implementing a continuous damage detection strategy to optimize the inspection and maintenance schedules of bridges, and extend their lifespans. One of the main challenges of automated damage detection is the lack of data on damaged states, which makes it difficult to validate new approaches in the research and development stage. To alleviate this problem, a monitoring campaign on a two‐span test bridge with defined defects is conducted and documented in this article. The bridge is a steel‐concrete composite structure with a length of 30 m, with two primary steel girders and a segmented concrete deck. The recorded data capture the long‐term ambient data from 18 test days and changing environmental conditions, as well as the short‐term ambient data and dynamic load tests from four damage scenarios with well‐defined damage extents. A mobile measurement system with numerous sensors is used for data acquisition. A shaker is placed on the bridge to excite white noise. The main goal of this article is to document the experimental procedure and perform preliminary plausibility checks on the measured data. First results demonstrate that system response data and environmental conditions are recorded reliably and that environmental effects significantly affect the long‐term measurements. Therefore, a suitable data set is provided as open‐source data for future studies on data normalization and automated damage detection. [ABSTRACT FROM AUTHOR]

Dowel action of the longitudinal reinforcement in RC beams without and with small amounts of shear reinforcement is typically considered a constant shear contribution determined from the splitting strength of the concrete cover. However, in a recent experimental investigation by the authors, it was shown that the shear force transferred by dowel action for beams without shear reinforcement should be determined from the dowel displacement and a linear elastic model and a rigid plastic dowel model. This article is aimed at extending this model to also cover members with small amounts of shear reinforcement. To that aim, a novel approach to calculate the shear force carried by dowel action of the longitudinal reinforcement in both beams with and without shear reinforcement is presented. The model is derived by establishing an equilibrium of work between the internal stored elastic or dissipated plastic energy and the external work performed by the shear force in the dowel. Additionally, a method to determine the displacement of the dowel from DIC measurements is presented. For the remaining shear‐transfer actions, reasonable constitutive models from the literature are adapted. On the basis of DIC measurements, the shear force carried by each of the shear‐transfer actions is calculated for 16 shear tests of beams without and with small amounts of shear reinforcement. The sum of shear force carried by each of the shear‐transfer actions is shown to predict the applied shear force fairly well, from the development of the critical shear crack until failure. Additionally, it is shown that for beams with shear reinforcement below the minimum requirements according to the current design standards, the shear capacity is governed by aggregate interlock, residual tensile stresses, and the inclination of the compression chord. While for beams with shear reinforcement above the minimum requirements, the shear capacity is governed by the shear reinforcement and dowel action. [ABSTRACT FROM AUTHOR]

The present paper proposes a mechanical model for the prediction of the response of slender reinforced concrete beams with corroded transverse and longitudinal reinforcements. The proposed model is based on the Modified Compression Field Theory and is able to predict the load–displacement curve of members subjected to monotonic displacement‐controlled tests up to their peak load. The corrosion‐damage effects are considered by means of an effective width of the beam and by means of reduced values of both cross‐sectional area and strain capacity of steel bars. The accuracy of the model is evaluated by comparison with results of tests reported in the literature. Moreover, a simple relation is suggested for the estimate of the shear strength of reinforced concrete beams with low values of the effective geometric percentage of (corroded) stirrups. [ABSTRACT FROM AUTHOR]

Since reinforced concrete members suffer from different types of loads during their service life, the steel bars embedded in reinforced concrete members can be easily corroded in chloride‐laden environment. To investigate the influence of combined effect of load and steel corrosion on the flexural stiffness of recycled aggregate concrete (RAC) beams, 12 RAC beams were prepared and tested. The effects of load level (i.e., the ratio of the load applied to beams to the ultimate load) and recycled coarse aggregate (RCA) replacement ratio (i.e., the ratio of RCAs to replace natural coarse aggregates) on the internal force arm coefficient of cracking cross‐section, the elastoplastic resistance moment coefficient of cross‐section, and the strain incongruity coefficient of corroded tensile steel bars were analyzed, and a calculation model for flexural stiffness of RAC beams under combined effect of load and steel corrosion was established. The results showed that when the ratio of bending moment to ultimate bending moment of the pure bending part of beams was within 0.55–0.80 and the average mass loss of tensile steel bars was less than 3.23%, 0.85 could be adopted as the internal force arm coefficient of cracking cross‐section. The elastoplastic resistance moment coefficient of cross‐section was approximately a constant when the corroded RAC beams were in the service stage, while it increased obviously with the load level. There was a strong linear relationship between strain incongruity coefficient and average mass loss of tensile steel bars during the service stage of corroded RAC beams, and the strain incongruity coefficient increased linearly with the load level. The calculated values of the model of flexural stiffness proposed in this paper were in reasonable agreement with the experimental values. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) and prestressed concrete (PC) structural elements need to be designed in order to guarantee large plastic deformations, avoiding any loss in their load bearing capacity. In this framework, the rotation capacity of RC and PC beams has been demonstrated to be a function of concrete mechanical properties, reinforcement characteristics, and of the structural size. On the other hand, Theory of Plasticity as well as the International Standards completely disregard size‐scale effects and ductile‐to‐brittle transitions, leading to an overlook of the strain‐softening behavior of the concrete matrix and of the rotation capacity of RC beams. On the other hand, the Cohesive/Overlapping Crack Model is able to evaluate concrete cracking in tension and concrete crushing in compression, as well as snap‐back and snap‐through unstable phenomena, steel yielding and/or slippage. This Nonlinear Fracture Mechanics model predicts a reduction in the moment versus rotation plastic plateau by increasing the beam depth and/or the reinforcement percentage. The numerical investigations carried out on reinforced and prestressed high‐performance concrete beams having rectangular or T‐shaped cross‐sections highlight the size‐scale effects on plastic rotation capacity that allow to formulate new scale‐dependent upper and lower limits of reinforcement percentage to guarantee a stable and ductile postpeak behavior of reinforced concrete structures. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) is a new type of fiber‐reinforced polymer (FRP) composite material, which has the characteristics of high performance, high toughness, high tensile fracture load, low elongation, low creep, no rust, and safety in use. The good performance of PET can significantly improve the mechanical properties of its components. A total of six reinforced concrete (RC) beams were produced in the test, one of which was a comparison beam, and the other five were reinforced with PET. In the test, the PET reinforcement spacing, number of reinforcement layers, and laying method were used as control variables, and an experimental study on the normal section bending performance of the specimen was performed. The test analyses the failure characteristics, crack width, bearing capacity, and deflection of the specimens under different reinforcement conditions. The test results showed that PET reinforcement can effectively inhibit the occurrence and development of cracks in RC beams and improve the ultimate bearing capacity and ductility of the components. The smaller the PET reinforcement spacing, the higher the ultimate bearing capacity; the greater the number of PET layers, the better the ductility of the specimen. Additionally, the economy, environmental protection, and portability of PET are of great significance for its application in practical engineering reinforcement. [ABSTRACT FROM AUTHOR]

This paper presents an experimental program of the bond behavior of concrete beams reinforced with hybrid fiber‐reinforced polymer (FRP) and steel bars, and the bond behavior between flexural cracks is investigated. Under the static loading, both the slip of steel and glass FRP (GFRP) bars increased significantly after steel yielding, while the slip of steel bars presented a faster increase rate. A method of calculating the bond stress based on test data was proposed, and this method overcame the disadvantage of histogram distribution of the conventional method. An analytical model of calculating the bond stress was proposed, and was verified with the test results. Under the fatigue loading, the bond stress deteriorated more seriously with a higher upper limit of fatigue load. The slip increased rapidly at the initial stage, and remained approximately unchanged with the increase of fatigue cycles, and the slip increased dramatically when the beam was subjected to fatigue failure. After fatigue loading, the yielding strength and ultimate strength of steel bars showed an increase rate less than 5%, while the hardening phase decreased significantly. The ultimate tensile strength of GFRP bars after fatigue decreased in the range of 4.5%–32.3%, and the modulus for elasticity remained unchanged. [ABSTRACT FROM AUTHOR]

Through this study, an attempt was made to produce concrete beams from self‐compacting concrete (SCC) contain expanded polystyrene (EPS) beads as coarse aggregate and waste plastic fibers (WPFs) produced from cutting disposed packing straps in site. The beams were designed according to ACI‐318‐14, where three different reinforcement ratios were chosen for the purpose of checking the conductance of thresholds made of this type of environmentally friendly concrete under bending loads. The use of EPS with WPFs had a significant positive effect in reducing the density of concrete, and the highest percentage of reduction was equal to (38.46%). Using WPFs had a positive effect in increasing the flexural toughness of concrete prisms, and the maximum increment was equal to (180%) compared with these made from the reference mix. The results proved the possibility of producing lightweight concrete from the use of EPS waste and WPFs, three of which are structurally can be classified as lightweight concrete combination of normal weight and lightweight aggregates according to specifications requirements of ASTM330/330M‐14. Reinforced lightweight SCC beams behaved under flexural loads similar to the reinforced concrete beams made from normal weight concrete counterparts under flexural loads. [ABSTRACT FROM AUTHOR]

A novel posttensioning technique using nickel‐titanium‐niobium (NiTiNb) shape memory alloy (SMA) wires for the repair of reinforced concrete beams was evaluated numerically. A finite element model of a reinforced concrete beam was developed within a damage mechanics framework to simulate concrete cracking and subsequent posttensioning. The predicted yield and ultimate moment capacities of the simulated posttensioned beams were up to 14% less than the corresponding experimental results. Cumulative discrepancies in the assumed material models led to the conservative model results. The effects of concrete tensile damage, SMA reinforcement ratio, SMA‐concrete interaction (bonded vs. unbonded), and the effective prestress on the service and ultimate behavior of the posttensioned beam were evaluated. Partial loss of prestress in the SMA due to elastic shortening of the concrete was insignificant (<3%) because of the relatively low elastic modulus of the SMA. Increasing the SMA reinforcement ratio by three times increased the yield moment of the posttensioned beam by 99%. Reducing the effective SMA prestress to 80% of the initial prestress to account for the possible losses resulted in a decrease in the yield moment by up to 7.8%. [ABSTRACT FROM AUTHOR]

This paper addresses the stress field of reinforced concrete (RC) beam–column joints retrofitted with haunches. Design of such solution currently assumes internal forces evaluated by the so called β‐factor approach, which was originally conceived targeting the enhancement of steel moment‐resisting frames. Extension to RC is subsequent as it emerges from the literature survey. The analytical model is first critically rediscussed. Inconsistencies of the adopted structural scheme, with respect to the actual mechanical behavior, may lie on the compatibility conditions which are imposed between the haunch and concrete beam (or column). In this regard, two‐dimensional finite element models (FEM), using linear‐elastic materials, are employed to study the stress field of two benchmark specimens derived from literature. A partial validation is carried out against experimentally derived internal forces. Results show that, for haunches with extended flat plates and stiff diagonals, compressive diffusion affects the entire haunch region. Consequently, beam's kinematic hypothesis of linear strains is no longer valid. The predicted joint shear demand resulted underestimated by β‐factor approach by 50%. Since 2D FEM may be not efficient for many practical circumstances, an application of Strut‐and‐Tie is alternatively proposed. Finally, both the limitations and possible extensions of the proposed approaches are stated transparently. [ABSTRACT FROM AUTHOR]

A reliable crack width assessment is a basic part of the sustainability control of the reinforced concrete structures subjected to corrosion degradation. The uncertainty of the concrete cracking model based on a finite element method and nonlinear fracture mechanics is investigated. The parameters of numerical model, such as the finite element mesh size and amount and arrangement of reinforcement are the subject of a case study. The uncertainty of the crack width model is verified on the experimental data from the tests of reinforced concrete beams. The constitutive model of crack propagation is based on the smeared cracks. The effects of numerical discretization as well as dimensional simplification are shown. [ABSTRACT FROM AUTHOR]

The paper presents the Structural Health Monitoring system installed on the posttensioned concrete road bridge over the Odra River in Poland. The bridge superstructure has a form of the 5‐span box girder with skewed supports, built using the cantilever method. During operation of the bridge (since 2010) many cracks arrived in the superstructure, mainly within the main bridge span with a length of 140 m. Therefore, as a part of a complex diagnostic process, the monitoring system were incorporated for assessment of the bridge performance and for observing further propagation of damage. The implemented monitoring system utilizes Fiber Bragg Grating (FBG) technique for measuring of strains, changes of cracks width and angular displacements of concrete box girder for various operating conditions of the structure including effects of regular road traffic, environmental influences and rheological phenomena. The paper presents applied testing and measuring procedures as well as results of the monitoring. Conclusions regarding effectiveness of the applied testing method in identification of the bridge condition are formulated and discussed. [ABSTRACT FROM AUTHOR]

Bangladesh is connected through bridges and many of them are experiencing damages due to the aging of concrete, weathering effect, or excessive loading. Repair and retrofitting of those bridges are becoming inevitable to make them operational. In this study, the damages of a concrete bridge have been investigated through non‐destructive tests and numerical methods. A repair and retrofitting strategy for the damaged girders has been developed using epoxy injection, shrinkage‐compensated micro mortar, and externally bonded Carbon Fiber Reinforced Polymer (CFRP) sheets. The micro mortars are injected inside the large cracks and damaged portions of the girders. The flexural zones of the girders were strengthened using U‐shaped CFRP sheets. Field load tests are also conducted to determine the achieved improvement from the repair strengthening work. Dynamic accelerometers, digital probes, and linear variable differential transformers (LVDT) were attached to determine the actual deflections of the girder before and under loading. Finite Element models (FEM) are developed to validate the field data and determine the shear and flexural resistance of the retrofitted girders. The outcomes show that the retrofitted bridge satisfies the design requirements of the AASHTO‐LRFD guidelines. [ABSTRACT FROM AUTHOR]

The possibility to measure strains continuously using distributed fiber optic sensors (DFOS) offers enormous potential for structural health monitoring. Cracks can be automatically detected, localized and crack widths calculated. To address the relevant questions of choosing the right DFOS and appropriate application technique for monitoring existing structures, two 4 m long reinforced concrete beams were loaded under service loads in a 4‐point bending test. The DFOS were either bonded directly to the smooth concrete surface or along a groove. For comparison, another DFOS was integrated into the specimen. It is demonstrated that with the used adhesive, a good strain transfer from the specimen to the DFOS can be ensured even with subsequent installation. In order to detect all cracks with high reliability, robust DFOS with a monolithic cross section should be preferred for the practical use. The accuracy of crack width measurement was verified through Reference measurement via digital image correlation. For the monolithic DFOS, all measurement deviations were within the tolerance range of ±0.05 mm. With layered sensing cables, significant misinterpretations occurred due to strongly damped strain curves. [ABSTRACT FROM AUTHOR]

The ways of designing and building steel girder bridges with a composite concrete deck vary much between different parts of the world. A bridge system with twin steel I‐girders or a concept with multiple (more than two) girders can be used. The design and use of details and secondary systems also vary a lot. In order to give horizontal stabilization and distribute horizontal loads, bracing between the I‐girders bracings are often used. Although not so common, the bracing can also be used to distribute vertical loads between the main girders. To describe and to analyze the possible impact from using a lateral bracing, this paper describes the design of a curved bridge in Guatemala City and its challenges. The new Bridge over the Pinula River is designed as a steel‐concrete composite bridge with multiple steel girders with a concrete deck on top and has lateral bracing between the girders. The bridge is used as a case study to analyze the impact from a lateral bracing system on the vertical load distribution between the longitudinal girders. The bridge was designed with lateral bracing between the top flanges along the whole bridge and with bracing between the lower flanges near the supports. The case study shows that the distribution of eccentric vertical loads between the longitudinal girders can be improved by using lateral bracing between the lower flanges for multiple girders. In some cases, it may not be beneficial to use lateral bracings along the whole bridge length, like for example this bridge. In this case due to the governing design cases in the construction stages where these bracings influenced the torsional stiffness of the bridge in such way that an unfavorable distribution of the support reactions between the six girders at some supports was achieved. [ABSTRACT FROM AUTHOR]