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Determination of failure strains is a topic of great interest for the design of composite structures. To evaluate the ultimate strains of a composite, tensile tests have been carried out on specimens with a range of fiber orientations between 0° and 90°. Ultimate tensile strengths obtained present low or moderate dispersion, the average values constituting a good estimation of the failure stress. Values of failure strains obtained present high dispersion for almost all orientations, so it is proposed to take as failure strain threshold the minimum value for each orientation. Finally, the shear behavior of the material has been evaluated. [ABSTRACT FROM AUTHOR]

To understand the shear characteristics of particles more comprehensively, the shear behavior of rigid particles, deformable particles, and breakable particles is investigated in this work. The rigid particles are modeled by the spheropolygon-based DEM. The deformable spheropolygon-based discrete element method is employed to study the shear behavior of deformable and breakable particles. Firstly, the influence of different circularization radii on rigid particles is studied. It is found that with a larger circularization radius, the edges and corners of the particles become less pronounced, and the particle shape approaches a circle, resulting in a smaller shear force. Secondly, the shear characteristics of breakable particles are examined. The experimental results indicate that particle fragmentation primarily occurs during the early stages of the shear process. Additionally, under high tensile strength, the impact of particle fragmentation on the mechanical properties of granular materials can be disregarded. Lastly, a comparison of shear forces is conducted among rigid, deformable, and brittle particles. The results show that particles assumed to be rigid generate the highest shear forces. On the contrary, deformable particles undergo deformation during shear, while brittle particles experience breakage, leading to a relatively loose packing and consequently less shear force. [ABSTRACT FROM AUTHOR]

Geotechnical problem analyses often involve three-dimensional stress conditions. In this paper, a series of drained true triaxial tests were conducted under stress-controlled conditions to investigate the effect of the intermediate principal stress on the mechanical behavior of calcareous sands. All stress paths, characterized by different intermediate principal stress coefficients (b -values) and terminal stress ratios (η ), were maintained on the same deviatoric plane. The experimental results indicate that the deformation behavior of calcareous sands in three-dimensional stress is highly influenced by the b -values, particularly in the intermediate and minor principal directions, leading to notable anisotropy. The deviatoric stress–strain curves show that the deviatoric strain effectively represents the three-dimensional strain behavior of calcareous sands. As the b -value increases from 0 to 1, a simultaneous decrease in the stiffness and volumetric contraction behaviors of calcareous sands has been observed. [ABSTRACT FROM AUTHOR]

Wetting and drying cycles (WDCs) have a significant impact on the shear behavior of discontinuities with different joint wall materials (DDJMs). This influence is crucial for the reasonable evaluation of the long-term stability of soft and hard interbedded rock slopes under water level fluctuations. As the surface topographies of natural discontinuities collected from the field vary, conducting comparative experiments on natural discontinuity specimens with identical surface topographies is challenging. To solve this problem, a 3D surface topography reconstruction technique was employed to obtain DDJM specimens with three types of surface topographies collected from a typical sliding-prone stratum in the Three Gorges Reservoir area, China. A series of experiments, including computed tomography scanning, 3D laser scanning, and direct shear tests, were conducted to investigate the influence of WDCs on the micro- and macroproperties of joint walls, surface topographies, and shear behavior of DDJMs. The experimental results showed that repeated WDC treatments caused the degradation of the microstructures and macroscopic physical properties of the studied joint walls, and the more severely weakened joint wall played a predominant role in reducing the shear strength of DDJMs. The influence of WDCs on the surface topographies of DDJMs was negligible in this study; changes in the shear behavior of DDJMs were closely associated with the weakening of joint walls induced by WDCs; and the impact degree of joint wall weakening on the deterioration of the shear behavior of DDJMs was interactively influenced by and positively correlated with both the joint roughness coefficient and normal stress. These results will contribute to a better understanding of the evolution of the stability of soft and hard interbedded rock slopes induced by water level fluctuations in the Three Gorges Reservoir area and other reservoir regions. [ABSTRACT FROM AUTHOR]

AbstractThe study on precast UHPC-NC composite beams investigated the effects of shear span ratio, stirrup reinforcement ratio, and NC strength on cracking shear force and diagonal crack width. Tests on eight UHPC-NC beams and one RC beam revealed that increasing the shear span ratio reduced the cracking shear force and widened diagonal cracks. U-shaped UHPC formwork enhanced cracking shear force and delayed crack development. While stirrup ratio had minimal impact on cracking force, it helped delay crack growth. A proposed model accurately estimated cracking shear force and maximum diagonal crack width, offering valuable insights for engineering applications. [ABSTRACT FROM AUTHOR]

The large amount of construction waste produced by the construction industry brings severe natural resource consumption and environmental pollution, elevating the awareness of sustainable development. Recycled aggregate concrete, crushed from construction waste, is recognized as an eco-friendly material and the current optimal solution for the environmental problem. The interface shear failure between substrate recycled coarse aggregate concrete (RAC) and overlay natural aggregate concrete becomes vital for structural safety. In order to study the direct shear performance, a total of 19 specimens were designed to carry out the direct shear test with different replacement ratios, interface types and curing ages. The whole process and failure mode were recorded. The relationships between the shear capacity and deformation, ductility, damage evolution, and energy dissipation were evaluated and discussed. The results demonstrate that the RAC component in the interface was the weak line in the shear plane, accelerating the damage evolution. In the early curing stage, the replacement ratio had a slight influence on the shear properties. Increasing the recycled aggregate replacement ratio from 0 to 100% improved the normalized strength ratio by 8.94% and 14.62%, respectively, for curing ages of 3 days and 7 days. A regression equation was proposed to predict the shear strength, accounting for the curing ages. With the increase in the replacement ratio, the ductility and energy dissipation gradually enhanced. [ABSTRACT FROM AUTHOR]

The impact of treated waste crushed brick on shear behavior regarding reinforced concrete beams (RCBs) has been the primary focus of the presented work. A total of 12 concrete beams of 240 mm in height, 1100mm in length, and 130mm in width were used for that purpose. A total of 3 Normal Concrete Beams (HNCB) and 3 Solid Normal Concrete Beams (SNCB) comprise 6 Normal Concrete Beams (NCB) models. In addition, there are 3 Hollow Recycled Brick Concrete Beams (HRBCB) and 3 Solid Recycled Brick Concrete Beams (SRBCB) among the 6 Recycled Brick Concrete Beams (RBCB) models. The obtained crushed brick from building demolition wastes is incorporated in the concrete mixes at these percentages of 0%, and 50% as a replacement by the weight of coarse aggregate. Samples have been tested for bending at four points. The maximum deflection happened at mid-span of the beam. In the test, diagonal cracking load, as well as ultimate shear strength, were assessed to examine the behavior of the beam concrete with the waste material. The purpose of this experiment has been to ascertain how crushed brick affected the mechanical characteristics of RCBs. Furthermore, the outcomes demonstrate that the addition of crushed brick enhanced the mechanical characteristics of samples and enhanced shear behavior regarding the concrete beams made of crushed brick in comparison to control samples. The findings contribute to the understanding of the mechanical behavior and failure mechanisms of such beams and provide valuable insights into the potential use of recycled brick aggregates in structural applications. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GC) is an innovative and sustainable type of composite resulting from the chemical reaction between waste materials containing and alkaline activators. The researchers have been focused to reduction of the greenhouse‐gas release, especially during the production of cement. Although numerous studies have been conducted on alkali‐activated cement or GC at the material level, there is limited research in the literature on the structural performance of reinforced GC members. The aim of this study is to investigate the effect of fiber combination on the shear and flexural performance of RC beams with maximum and minimum reinforcement ratio. To investigate the shear and flexural behavior of GC beam, four‐point and three‐point tests were performed on 12 GC with hybrid fibers, 4 GC with trio fibers, and 2 GC fiber‐free as references beams. The test parameters were the combination of fibers (steel, glass, carbon, and basalt), the longitudinal reinforcement ratio, and loading type. The key test results include the load‐deflection behavior, characteristics of the cracks, the effect of fiber type on the shear and flexural performance, ductility and stiffness properties, microstructure, the strain in the concrete, and the bars and code predictions. The test results showed that as expected, reducing the longitudinal reinforcement ratio decreased the strength, but the decrease in strength was tolerated by using different types of fibers. The use of trio fibers in beams under bending increased the strength capacity, considerably. Finally, the capacity prediction performance of current codes, that is, GB50010, EuroCode‐2, TS500, and ACI318, were also examined, and the calculations resulted that the current code equations had a percentage error of approximately 25% and 82% on average for flexural and shear, respectively, although EuroCode‐2 equations performed slightly better. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study on the investigation of microscopic mechanism governing the interaction of woven geotextile and angular sand employing the 3D discrete element method (DEM). The surface texture and tensile properties of the geotextile were simulated using overlapping spherical particles, and the angular sand was simulated using rigid blocks. The DEM models were fully calibrated based on previous experimental data. The shear and dilation zones of sand near the interface were quantitatively determined based on particle displacement gradients. Analysis of contact forces was conducted to explain the microscopic mechanism behind the macroscopic strength evolution. The influence of geotextile surface roughness on the shear strength of the geotextile-sand interface is also discussed. The results show that the failure mode of the woven geotextile-sand interface is a combination of particle sliding failure along the geotextile surface and shear failure of the sand within the shear zone above the interface. There is a rapid redistribution of contact forces prior to reaching peak shear resistance, and the average normal contact force within the shear zone remains relatively constant after the peak shear stress is achieved. A completely developed shear zone stabilizes soil deformation, typically after achieving the peak shear resistance. • The thickness of the stabilized shear zone decreases as the normal stresses increase. • The shear zone is completely developed after the peak shear resistance is reached. • Contact forces are rapidly redistributed prior to reaching peak shear resistance. • The evolution of shear strength is caused by interparticle sliding in the shear zone. [ABSTRACT FROM AUTHOR]

Bimrocks are characterized by their geotechnically significant blocky structure, presenting complex shear behavior. This study investigates the shear behavior and dilatancy of bimrocks featuring a rock-like matrix, such as conglomerates. The study addresses a gap in current research, which has predominantly examined the shear behavior of soil-matrix bimrocks (bimsoils). Laboratory direct shear tests were performed on idealized models with varying volumetric block proportions (VBPs). The results highlight that blocks exert both positive and negative effects on shear strength, dilation, and block breakage factor (BF), depending on VBP. Results indicate 40% and 60% as critical VBPs, revealing distinct shear strength trends within this range, contrary to the dominant downward trend. Blocks positively impact dilation and BF between 20% and 50% VBP, while negatively affecting them beyond this range. Blocky skeleton inherently promotes stable dilatancy under normal stress increments and intensifies stress dependency of shear strength. Variations in dilation angle concerning normal stress and VBP suggest the potential for characterizing this factor using equivalent strength and roughness, akin to rockfill materials. Indirect assessments of equivalent strength revealed positive effects of blocks when VBP was between 30% and 70%. Lastly, the findings indicate that blocks notably impact pre-and post-peak behaviors by reducing shear stiffness and inducing local hardening phases. This study also discusses the similarities and distinctions in the function of blocks within soil-like and rock-like matrices. It offers new insights into the exact role of blocks in bimrock shear behavior beyond the traditional interpretation through the variation of friction and cohesion. [ABSTRACT FROM AUTHOR]

The interface between soil and concrete in cold climates has a significant effect on the structural integrity of embedded structures, including piles, liners, and others. In this study, a novel temperature control system was employed to conduct direct shear tests on this interface. The test conditions included normal stress (25 to 100 kPa), temperature (ranging from 20 to −6 °C), water content (from 10 to 19%), and shear rates (0.1 to 1.2 mm/min). Simultaneously, the deformation process of the interface was continuously photographed using a modified visual shear box, and the non-uniform deformation mechanism of the interface was analyzed by combining digital image correlation (DIC) technology with the photographic data. The findings revealed that the shear stress–shear displacement curves did not exhibit a discernible peak strength at elevated temperatures, indicating deformation behavior characterized by strain hardening. In the frozen state, however, the deformation softened, and the interfacial ice bonding strength exhibited a positive correlation with decreasing temperature. When the initial water content was 16% and the normal stress was 100 kPa, the peak shear strength increased significantly from 99.9 kPa to 182.9 kPa as the test temperature dropped from 20 °C to −6 °C. Both shear rate and temperature were found to have a marked effect on the peak shear strength, with interface cohesion being the principal factor contributing to this phenomenon. At a shear rate of 0.1 mm/min, the curve showed hardening characteristics, but at other shear rates, the curves exhibited strain-softening behavior, with the softening becoming more pronounced as shear rates increased and temperatures decreased. Due to the refreezing of interfacial ice, the residual shear strength increased in proportion to the reduction in shear rate. On a mesoscopic level, it was evident that the displacement of soil particles near the interface exhibited more pronounced changes. At lower shear rates, the phenomenon of interfacial refreezing became apparent, as evidenced by the periodic changes in interfacial granular displacement at the interface. [ABSTRACT FROM AUTHOR]

This paper presents results obtained from the discrete-element method (DEM) to study the effects of particle shape on the shear behavior and breakage of ballast aggregates. In this study, a series of direct shear tests have been performed on granular assemblies having various shape sphericity and roundness values. A clump-based degradation (breakage) model is incorporated into the DEM simulation to capture the breakage of aggregates during shearing. The results show that the decrease of particle sphericity and roundness results in an improvement in the shear performance of granular assemblies but subsequent exacerbation in particle breakage, which in turn reduces the shear strength and volumetric dilation. The breakage of particles localizes within an inclined band, with the width and inclination angle of the band increasing in assemblies comprising particles of low sphericity and roundness. A micromechanical analysis is conducted to examine the anisotropy of internal structures and particle motions in granular assemblies. It is observed that both the shape of particles and their breakage significantly influence these factors. Through microscopic analysis, a fundamental governing mechanism of particle shape effects on the shear strength and the breakage of granular materials is investigated at the macroscopic scale. [ABSTRACT FROM AUTHOR]

In this study, an experiment was conducted to investigate the shear performance of reinforced concrete (RC) beams strengthened using fabric-reinforced cementitious matrices (FRCM). Four reinforced concrete beams, including a control specimen, were fabricated, and the shear strengthening effect of the FRCM was investigated on eight shear specimens, with the strengthening type and shear reinforcement as key variables. In particular, the digital image correlation (DIC) technique was applied to closely analyze the deformation of reinforced concrete beams subjected to shear forces. The average shear strain–shear stress curve of each specimen was derived, and the contributions of shear and bending to the vertical deflection and the change in the principal strain angle with increasing shear force were analyzed. The experiment results showed that all specimens failed with diagonal cracks within the shear span. In the specimens without shear reinforcement, the shear strength increased by up to 65% according to the FRCM strengthening, while in the specimens with shear reinforcement, only the sided bond strengthened specimen showed a strength increase of 16% compared to the control specimen. Based on displacement data of the DIC, it was confirmed that FRCM strengthening can control the deformation of the RC beam. To evaluate the shear strength of the FRCM-strengthened RC beams, a shear strength model was proposed by considering the contributions of the concrete section, shear reinforcement, and FRCM. The proposed model was capable of reasonably evaluating the shear strength of RC beams strengthened with FRCM, considering the shear contribution of FRCM and bond capacity between FRCM and concrete substrate, in which the shear strength of specimens was underestimated by 28% to 35%. [ABSTRACT FROM AUTHOR]

To improve shear capacity, as well as reduce on-site casting and steel consumption, a novel Y-shaped perfobond rib (Y-PBL) shear connector with ultra-high-performance concrete (UHPC) grout was proposed. The shear behavior of the Y-PBL shear connector was investigated by six groups of pushout specimens. Their failure modes, load–slip curves, load–separation curves, strain analysis, and shear transfer mechanisms were discussed. Subsequently, finite-element analysis (FEA) models were established to study the effect of parameters on the shear behavior of the Y-PBL shear connector, as well as to compare the shear capacity contributions with straight-shaped PBL (S-PBL) shear connectors. Analytical models were proposed to predict the shear capacity of the Y-PBL shear connector. The results reveal that the proposed Y-PBL shear connector has superior shear capacity and stiffness. The contribution of the perforating rebar is minor compared with the end-bearing effect of UHPC. The analytical predictions agree well with the experimental and FEA results. This study can be used to guide the design and application of the Y-PBL shear connector in steel-concrete composite bridges. [ABSTRACT FROM AUTHOR]

In cold and arid saline areas, the mechanical properties of soils are usually significantly affected by some complicated conditions, especially the coupled effects of the freeze–thaw–dry–wet (F–T–D–W) cycles and soil salinization. This study experimentally investigated the effect of F–T–D–W cycles on the shear performances and microstructures of silty clay that was salinized during wetting processes. Three types of soil samples with different dry densities were designed: (1) silty clay samples without salt (Category Ⅰ); (2) silty clay samples with salt (Category Ⅱ); and (3) silty clay samples that were salinized during wetting processes (Category Ⅲ). Direct shear and scanning electron microscopy (SEM) tests were carried out, the variations in the shear strength, surface deterioration, and shear parameters (e.g., cohesion and internal friction angle) were analyzed, and the degradation mechanism was revealed. The results show that the F–T–D–W cycles and soil salinization significantly affect the shear strength of soils, especially for the samples with low dry densities. The shear strengths of soil samples with and without salt (Categories Ⅰ and Ⅱ) decrease as the F–T–D–W cycles increase. Besides, the cohesion of soil samples increases with dry density and declines with the F–T–D–W cycles due to the appearance of cracks and bond failure among soil particles. In addition, there is a threshold number of F–T–D–W cycles to significantly reduce the cohesion of soil samples, and the threshold numbers for soil samples Categories Ⅰ and Ⅱ are six and three, respectively. The repeated expansion and shrinking of soils accelerate the damage to the soil structure, which results in a decrease in cohesion and interparticle force. However, when the concentration of salt solution in soils exceeds the saturation concentration, a new denser soil skeleton is formed by the soil particles and surrounding salt crystals, which improves the shear strength of the soil samples. This study could provide deep insights into the shear performance and microstructures of silty clay exposed to F–T–D–W cycles. [ABSTRACT FROM AUTHOR]

As the connecting component of I-beam and UHPC, the stud is the basis of the cooperative work of each component, and is crucial to the stability and safety of the structure. To further study the shear behavior of studs in I-beam-UHPC composite structures, the push-out test was carried out by numerical simulation. The numerical simulation is in line with the load-relative slip curve and failure mode obtained by the experiment, verifying the accuracy of the numerical model. On the basis of verifying the model, the influences of the diameter, height and ultimate tensile strength of the stud on the relative slip curve, shear strength, yield strength and shear stiffness of the stud are studied. The findings indicate that a stud with a diameter of 22 mm exhibits a shear strength 156% greater than that of a stud with a diameter of 10 mm. Additionally, the yield strength increases by 135%, and the shear stiffness by 160 kN, highlighting the significant impact of stud diameter on shear resistance. When the ratio of length to diameter is less than 2.7, the shear strength of the stud increases with the height of the stud. The shear strength of a stud with a length-to-diameter ratio of 2.7 is 35% higher than that of a stud with a ratio of 1.5. The ultimate tensile strength of the stud ranges from 360 to 510 MPa, with only an 11 kN increase in yield strength, indicating that the ultimate tensile strength has a limited influence on shear properties. As the height of the stud decreases, its ultimate tensile strength gradually increases, bringing the numerical model closer to the predicted values. For shorter studs with higher ultimate tensile strength, the finite element simulation results are closer to the predicted values.Article Highlights: The numerical model can be used to study the shear properties of I-beam-UHPC composite structures. Increasing the diameter of the stud can improve the shear resistance of the stud. The higher the height of the stud, the lower the shear efficiency. When the height of the stud is smaller and the ultimate tensile strength is larger, the finite element model is closer to the predicted value. [ABSTRACT FROM AUTHOR]

Ferrochrome slag aggregate concrete (FCSAC) incorporated with fly ash offers multiple benefits over FCSAC alone and natural aggregate concrete (NAC) in terms of durability and environmental impacts, without sacrificing essential strength. However, structural behavior of fly ash-based FCSAC is poorly understood due to lack of investigations. This study examined shear performance of 16 full-scale reinforced concrete beams. FCSAC was prepared using 100% FCS coarse aggregate and fly ash as fractional cement replacement (0%, 20% and 30%). To completely comprehend the shear resistance mechanism of FCSAC, eight beams were built without shear reinforcement and eight with it. NAC and FCSAC (without fly ash) were considered as the reference beams. Existing design guidelines and fracture mechanics approaches were verified to predict shear capacity of FCSAC beams. The findings of the study revealed that fly ash incorporated FCSAC beam exhibited fewer cracks and higher shear capacity (about 7%) than NAC beam, but lower strength (about 8%) than FCSAC without fly ash beam. Shear provisions outlined in CSA provisions and fracture model by Gastebled and May could be adopted for FCSAC (with or without fly ash) beams without risk. This research demonstrates that fly ash-based FCSAC can be utilized safely for structural purposes. [ABSTRACT FROM AUTHOR]

The rapid development of aerospace electronics towards lightweight and miniaturized designs has put forward higher requirements for the reliability of device interconnection. It is crucial to study the effects of space radiation and thermal cycle environments on the performance of micro-solder joints. This study uses experimental and simulation methods to study the comprehensive effects of electron irradiation and thermal cycling on the mechanical and electrical properties of Sn-3.0Ag-0.5Cu (SAC305) micro-solder joints. The results show that the combined effect of electron irradiation at a dose of 100 Mrad(Si) and 200 thermal cycles causes the operating temperature of the resistor in the sample to increase while severely reducing the shear strength of the solder joint. Two fracture modes, brittle and plastic, are observed in solder joints during the shearing process. As the number of thermal cycles increases, the proportion of plastic fracture increases. The combined effects of electron irradiation and thermal cycling exacerbate the deterioration of the shear strength of solder joints, with the shear strength of solder joints with brittle fractures decreasing by 28.00% and those with plastic fractures decreasing by 23.34%. [ABSTRACT FROM AUTHOR]

In this study, an experimental program was conducted to investigate the shear behavior of beams made of high-strength and lightweight cementitious composites (HS-LWCCs) containing hollow glass microspheres and carbon nanotubes. The compressive strength and dry density of the HS-LWCCs were 87.8 MPa and1.52 t/m3, respectively. To investigate their shear behavior, HS-LWCC beams with longitudinal rebars were fabricated. In this test program, the longitudinal and shear reinforcement ratios were considered as the test variables. The HS-LWCC beams were compared with ordinary high-strength concrete (HSC) beams with a compressive strength of 89.3 MPa to determine their differences; the beams had the same reinforcement configuration. The test results indicated that the initial stiffness and shear capacity of the HS-LWCC beams were lower than those of the HSC beams. These results suggested that the low shear resistance of the HS-LWCC beams led to brittle failure. This was attributed to the beams' low elastic modulus under compression and the absence of a coarse aggregate. Furthermore, the difference in the shear capacity of the HSC and HS-LWCC beams slightly decreased as the shear reinforcement ratio increased. The diagonal compression strut angle and diagonal crack angle of the HS-LWCC beams with shear reinforcement were more inclined than those of the HSC beams. This indicated that the lower shear resistance of the HS-LWCCs could be more effectively compensated for when shear reinforcement is provided and the diagonal crack angle is more inclined. The ultimate shear capacities measured in the tests were compared with various shear design provisions, including those of ACI-318, EC2, and CSA A23.3. This comparison showed that the current shear design provisions considerably overestimate the contribution of concrete to the shear capacity of HS-LWCC beams. [ABSTRACT FROM AUTHOR]

The shear stirrups and bend-up reinforcement in ultra-high-performance concrete (UHPC) beams could potentially be excluded due to the superior mechanical properties of UHPC. This paper reports the new findings of an experimental research into the factors that influence the shear behavior of non-stirrup UHPC beams. Fourteen beams were tested in shear, comprising twelve non-stirrup UHPC beams and two normal concrete (NC) beams reinforced with stirrups. The test variables included the steel fiber volume content (2.0%, 1.5%, and 0%), the shear span-to-effective-depth ratio (1.2, 1.8, 2.0, and 3.1), beam width (150 mm and 200 mm), and beam height (300 mm, 350 mm, and 400 mm). The results demonstrated that the steel fiber volume content had a significant influence on the shear behavior of the non-stirrup UHPC beams. The failure modes of the beams without steel fibers were typically brittle, whereas those reinforced with steel fibers exhibited ductile failure. The shear resistance of the beams could be significantly enhanced by the addition of steel fibers in the concrete mix. Furthermore, the post-cracking load-bearing performance of the beams could also be markedly improved by the addition of steel fibers. In addition, the shear span-to-effective-depth ratio had a considerable impact on the failure mode and the ultimate shear strength of the tested beams. The contribution of steel fibers to the shear capacity of the UHPC beams was observed to increase as the shear span-to-effective-depth ratio increased. The French standard formulae tended to overestimate the contribution of steel fibers, and the calculation results were found to be more accurate for UHPC beams with a moderate shear span-to-effective-depth ratio (around 2.0). Moreover, the French standard formulae demonstrated greater accuracy at a larger beam height for calculating the contribution of UHPC matrix. [ABSTRACT FROM AUTHOR]

AbstractThe integration of cutting-edge materials and computational methods is now essential in contemporary engineering, especially in sectors where a deep comprehension of the mechanical behavior of reinforced composite materials is crucial. In this context, steel matrix composites, enhanced with reinforcing elements like TiB2, have garnered attention due to their potential for superior mechanical properties and wide-ranging applications. This article explores an innovative computational framework based on the Representative Volume Element (RVE) concept to examine the elastoplastic properties of a ferritic steel matrix reinforced with ceramic particles (TiB2). The finite element analysis (FEA) is performed with periodic boundary conditions (PBCs) to apply the specified loading to the RVE. As a first endeavor, the developed multi-faceted approach provides a broader perspective on shear behavior and the elastoplastic composite’s properties of Fe-TiB2 for various reinforcement volume fractions. Then, the focus of this study lies in its application to the deep-drawing process, a critical manufacturing operation with significant implications in industries such as automotive and aerospace. The established approach for homogenizing elasto-plastic Fe-TiB2 composites is applied to analyze the influence of reinforcement variation on several critical aspects during the deep-drawing process, including formability, forming force, Von Mises stress distribution, and logarithmic strain. [ABSTRACT FROM AUTHOR]

In order to fully utilize the advantages of stud and perfobond leiste (PBL) connectors, a new composite shear connector was proposed in which the studs were welded to the H‐beam of the PBL shear connectors. In addition, to further improve the durability performance of the structure, steel‐fiber‐reinforced polymer composite bars (SFCBs) were used to replace steel rebars as penetrating rebars. In this study, the shear behaviors of SFCBs‐reinforced composite shear connectors were investigated by push‐out tests. The effects of the number of studs, the number of holes, and the type of penetrating rebars on the failure mode, load–slip curve, and shear behavior of the composite shear connectors were analyzed. The specimens' failure modes were mainly shearing the studs and crushing the concrete. Increasing the number of studs and holes has resulted in an increase of at least 7.47% in the shear resistance and 12.36% in the stiffness. SFCB had little effect on the shear resistance and reduced the stiffness but could improve ductility, with a maximum improvement of 11.49%. Additionally, a finite element model was established for parametric analysis. The results showed that the diameter of the SFCB and hole had a significant impact on the shear resistance. An equation for calculating the shear resistance based on the contributions of various components has been established that was applicable to composite shear connectors and has good accuracy and applicability. [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]

A growing body of research has shown that reversed cyclic shear loading of reinforced concrete (RC) causes effects that are not accounted for in monotonic behavioral models. Notable among these effects are a reduction in shear strength and significant plastic offsets. This paper presents the General Crack Component Model, a rational, mechanics‐based model that explicitly considers the constitutive behavior of cracks in RC. Cracked RC is treated as a series–parallel system of bonded and unbonded regions, where the crack interfaces have both crack closing hysteresis and a kinematic contact constraint. Validation was performed using data from monotonic and reversed cyclic experiments on panel elements, and has shown that this analytical model is able to accurately capture the salient features of reversed cyclic shear behavior. [ABSTRACT FROM AUTHOR]

A few research studies are available on the behavior of reinforced concrete (RC) box section beams with fiber‐reinforced polymer bars (FRP) and FRP stirrups. Consequently, the behavior of these beams needs to be investigated. This article studies experimentally, numerically, and analytically the effect of some variables on the behavior of RC box section beams. This article investigates many variables, such as the shear span‐to‐total depth ratio, the flexural FRP reinforcement ratio, and the FRP vertical and horizontal web reinforcement ratio. The experimental program consists of nine simply supported reinforced concrete box section beams. The numerical models using the nonlinear finite element program ANSYS V.15 are carried out. The results are compared to the experimental results using load‐deflection curves, crack patterns, failure loads, and failure modes. The shear capacities based on Egyptian ECP 208‐2019 and ACI 440‐2015 codes are compared to each other and to the experimental results. The findings show an adequate agreement between the experimental, numerical, and analytical results for the range of the studied parameters. The results reveal that increasing the shear span‐to‐depth ratio by 50% decreases the carrying capacity, toughness, and displacement ductility by 2%, 28%, and 12%, respectively. The increase in main FRP reinforcement rebars by 20% increases the carrying capacity and toughness by 59% and 62%, respectively. Increasing vertical FRP stirrups by 79% increases the failure load and toughness by 26% and 15%, respectively, and displacement ductility increases only by 0.8%. The increase in horizontal FRP stirrups by 79% increases the failure load, toughness, and displacement ductility by 33%, 8%, and 4%, respectively. Both Egyptian and American codes are conservative in some cases and unconservative in others, while the numerical results are unconservative. [ABSTRACT FROM AUTHOR]

Stability of fiber-reinforced shotcrete (FRS)-rock interface under high-and-variable temperature conditions during high geothermal tunnel construction is related to the safety of tunnel support. The rough rock specimen preparation method and the high-and-variable temperature conservation model were proposed based on the tunnel environment. In the present work, direct shear tests were conducted on composite specimens of FRS and rock, which were subjected to high-and-variable temperature curing (with initial curing temperatures of 46, 57, and 71 °C) and different levels of normal stress (0.5, 1.0, and 2.0 MPa). The characteristics of roughness surface changes before and after shear were analyzed based on industrial type optical surface scanning. The acoustic emission (AE) of the shear process of the combined test and the microscopic characteristics of the concrete under high-and-variable temperature curing conditions were investigated. The main findings are as follows. (1) The curing temperature, normal stress, and roughness exert significant influences on both the shear strength and failure mode of the interface between rock and FRS. Shear strength was reduced by 36% and shear displacement by 30.7% at an initial curing temperature of 71 °C compared to 46 °C at an interface height of 0.35 mm and a normal stress of 1 MPa. The interface protrusion height of 0.35 mm and the initial curing temperature of 46 °C increased the normal stress from 0.5 to 2.0 MPa, the shear strength increased by 65%, and the shear displacement increased by 28%. The shear strength increased by 28%, shear displacement decreased by 39%, and the number of AE events at the peak shear stress increased by a factor of 11 for specimens with a normal stress of 0.5 MPa, an initial curing temperature of 46 °C, and a bulge height of 3 mm relative to 0.35 mm. (2) The post-peak evolution of shear stress can be categorized into four types: fast drop, fast drop followed by rebound, fast then slow drop, fast then slow drop with fluctuations. (3) Shear failures at the interface and on the rough rock surface primarily occur on the concrete side, and the influence of the initial curing temperature on the failure mode weakens with increasing roughness and normal stress. (4) The inclusion of alkali-resistant glass fiber (AR-GF) mitigates the detrimental effects of high temperature on concrete and concurrently enhances the shear strength of the interface between rock and FRS. These research findings can provide valuable insights and support for the investigation, design, and construction of FRS support systems in high-temperature underground engineering projects. Highlights: The rough rock specimen preparation method based on 3D scanning and 3D engraving and the high-and-variable temperature curing model were proposed. Shear mechanics and acoustic emission characteristics of the shotcrete-rock interface after high-and-variable temperature curing were investigated. The rough surface analysis method based on industrial surface scanning was proposed to study the characteristics of rock rough surface changes. The effect of initial curing temperature on the shear strength of the shotcrete-rock interface decreases with increasing normal stress and roughness. [ABSTRACT FROM AUTHOR]

Soil biocementation through microbially induced carbonate precipitation (MICP) is a promising technique for improving soil behavior in a nondisruptive manner, particularly for rehabilitation and retrofitting applications. Previous studies characterizing the shear behavior of biocemented soils have concentrated on poorly graded sands, whereas research on well-graded gravelly soils, which are extensively used in shallow geotechnical structures, has been lacking. Mohr–Coulomb strength parameters have been predominately employed to interpret the macromechanical effects of biocementation, but the previously reported findings show significant contradictions. In this study, a well-graded aggregate, representative of commonly used well-graded gravelly soils, was biocemented and subjected to monotonic drained triaxial compression. The test results show remarkable improvements in shear behavior, with the observed changes in stress–strain responses, strength and stiffness development, and stress dilatancy agreeing with those reported for biocemented sands as well as conventional cemented soils. Relatively low cementation levels can effectively rectify the mechanical performance caused by poor compaction to that seen at optimal levels, demonstrating the feasibility and potential of biocementation for improving soils of this type. Detailed analysis of the results reveals the decisive role of cementing bonds and their degradation in causing behavioral changes at different shearing stages. The theories of bonded structure and force-chain evolution are used to explain the preyielding observations, while an analytical approach capable of quantifying the evolution of different strength components is presented for postyielding macromechanical characterization. Conversely to the inference drawn from the strength parameters, the largest improvement is found in the frictional rather than the dilative and cohesive components of strength. Further analysis reveals the commonality of the macromechanical effects of biocementation, density, and confinement, and a unique relationship between macromechanical composition and peak stress ratio emerges. [ABSTRACT FROM AUTHOR]

The red stratum soft rock, contained extensively in the deep soil–rock mixture (SRM) backfill area of southwest China, exhibits significant water-disintegrating properties that greatly impact the foundation's bearing capacity and deformation failure in this region. This study introduced the large-scale triaxial test to investigate the mechanical deformation characteristics of clay-red stratum soft rock mixture before and after wetting. Simultaneous, combined with the results of test, the law of water disintegration of red stratum soft rock was revealed, and its effects were analyzed in detail. The results show that: (1) Wetting intensified the crushing of rock blocks, resulting in the reduction of shear strength and critical strain of the samples, the decrease of critical internal friction angle and secant modulus, and the significant increase of the relative crushing rate of rock blocks; (2) The most significant increase and decrease of the content before and after the test occur in the particles with the particle size of 0.5–2 mm and 20–40 mm, respectively; (3) Wetting-induced breakage of the red stratum soft rock mainly occurs during the first two hours after encountering water; (4) An increase in confining pressure exacerbates the influence of wetting. Additionally, based on the theory of non-linear elasticity, with the assuming that the reduction of secant modulus causes the wetting deformation, a theoretical calculation model of the wetting axial strain was proposed. Through comparing the calculated results with the measured values obtained by using the "double-line method" and "single-line method" test, it is found that the calculation method can accurately predict the wetting axial strain of SRM and be used for quantitative analysis of wetting deformation. [ABSTRACT FROM AUTHOR]

The weakened shear behavior of sandstones induced by hydrofracturing fluids significantly affects the activation of natural fractures during hydraulic stimulation in hydrocarbon and geothermal exploitations. This paper presents an experimental study of characterizing the sandstone joints treated by water-based fracturing fluid (WFF) and acid mixture solution (AMS) treatment that simulate rock joint–hydrofracturing fluid interactions in deep reservoirs during short shut-off times on wells after hydraulic fracturing. Three-dimensional (3D) optical scanning method coupled with 3D rigid engraving was utilized to create replicas of natural rock joint surfaces, and direct shear tests were conducted to probe the shearing behavior of untreated and WFF/AMS-treated replicas with three different roughness levels and under two high normal stresses of 15 and 30 MPa. Microindentation and X-ray diffraction were then performed to investigate the degradation of mechanical properties and potential alterations in composition and microstructure of the hydrofracturing fluid-treated joint surfaces. The results indicate that short-term interactions between the hydrofracturing fluids and sandstone can lead to a reduction in mechanical properties and frictional resistance of the joint surface, ultimately weakening its shearing properties. The decline in mechanical properties observed in the AMS-treated sample is attributed predominantly to the dissolution of QFC (quartz, feldspar, and calcite) and swelling of clay minerals. For the WFF-treated sample, clay mineral swelling and the residual guanidine gum on the joint surfaces remain the primary factors contributing to the reduction in shearing resistance. At high normal stresses of 15 and 30 MPa, joints with different roughnesses exhibit asperity shearing off as the dominant mechanism. Furthermore, an increase in joint roughness leads to a higher friction angle on the joint surface. However, higher normal loads could result in a reduction in apparent cohesion. The results of this study provide valuable insights into the interactions between hydrofracturing fluids and sandstone, as well as the behavior of natural fracture activation during hydraulic fracturing. [ABSTRACT FROM AUTHOR]

The use of synthetic materials with high corrosion resistance in a concrete matrix yields structures that are more durable and suitable for use in aggressive environments, eliminating the need for frequent maintenance. Examples of such materials include glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars (FRP). Due to the low modulus of elasticity of these bars, concrete elements reinforced with FRP longitudinal rebars tend to exhibit cracks with wider openings and greater depths compared to those reinforced with steel rebars, which diminishes the element's shear resistance. The addition of discontinuous fibers into the concrete aims to maintain stress transfer across the cracks, thereby enhancing the shear capacity and ductility of FRP-reinforced structures. This study evaluates the impact of fiber addition on the shear resistance of concrete beams reinforced with FRP rebars. An experimental investigation was conducted, focusing on the partial and complete substitution of stirrups with polypropylene macro fibers in concrete beams reinforced with FRP longitudinal rebars and stirrups. This research examined beams reinforced with glass (GFRP) and basalt (BFRP) fiber-reinforced polymer bars. For the initial set of beams, all stirrups were replaced with synthetic macro fibers. In the subsequent set, macro fibers were added to beams with insufficient stirrups. Although the complete replacement of GFRP and BFRP stirrups with polypropylene macro fibers did not alter the brittle shear failure mode, it did enhance the shear resistance capacity by 78.5% for GFRP-reinforced beams and 60.4% for BFRP-reinforced beams. Furthermore, the addition of macro fibers to beams with insufficient stirrups, characterized by excessive spacing, changed the failure mode from brittle shear to pseudo-ductile flexural failure due to concrete crushing. In such instances, the failure load increased by 18.8% for beams with GFRP bars and 22.8% for beams with BFRP bars. [ABSTRACT FROM AUTHOR]

To improve the shear capacity and repair shear cracks in prestressed concrete box girders, a novel strengthening method utilizing Polyvinyl Alcohol-Engineered Cementitious Composite (PVA-ECC) was proposed and studied. The integrated method consisted of section enlargement with PVA-ECC and decentralized prestressing using prestressed steel strands, which were embedded in the PVA-ECC after being prestressed and bonded. Field investigations were conducted to study and evaluate the effectiveness of this method under random traffic loads using health monitoring systems. Additionally, based on engineering practices, three finite element models (unreinforced box girder, box girder with strengthened side web only, and box girder with strengthened entire web) representing different construction sequences were established to investigate changes in shear behavior before and after strengthening. Finite element analyses were conducted under various loading conditions, and the results showed that the stress response of the webs decreased by approximately 30–40 % after strengthening. Additionally, the deflection of the top slab decreased by approximately 25–35 %. The results from monitoring data and finite element analyses demonstrated that the proposed strengthening method effectively enhanced the shear performance of the box girder webs. This research can provide a reference for strengthening and evaluating existing prestressed concrete box girders.

Bimrocks are characterized by their geotechnically significant blocky structure, presenting complex shear behavior. This study investigates the shear behavior and dilatancy of bimrocks featuring a rock-like matrix, such as conglomerates. The study addresses a gap in current research, which has predominantly examined the shear behavior of soil-matrix bimrocks (bimsoils). Laboratory direct shear tests were performed on idealized models with varying volumetric block proportions (VBPs). The results highlight that blocks exert both positive and negative effects on shear strength, dilation, and block breakage factor (BF), depending on VBP. Results indicate 40% and 60% as critical VBPs, revealing distinct shear strength trends within this range, contrary to the dominant downward trend. Blocks positively impact dilation and BF between 20% and 50% VBP, while negatively affecting them beyond this range. Blocky skeleton inherently promotes stable dilatancy under normal stress increments and intensifies stress dependency of shear strength. Variations in dilation angle concerning normal stress and VBP suggest the potential for characterizing this factor using equivalent strength and roughness, akin to rockfill materials. Indirect assessments of equivalent strength revealed positive effects of blocks when VBP was between 30% and 70%. Lastly, the findings indicate that blocks notably impact pre- and post-peak behaviors by reducing shear stiffness and inducing local hardening phases. This study also discusses the similarities and distinctions in the function of blocks within soil-like and rock-like matrices. It offers new insights into the exact role of blocks in bimrock shear behavior beyond the traditional interpretation through the variation of friction and cohesion.

The damage of rock joints or fractures upon shear includes the surface damage occurring at the contact asperities and the damage beneath the shear surface within the host rock. The latter is commonly known as off-fault damage and has been much less investigated than the surface damage. The main contribution of this study is to compare the results of direct shear tests conducted on saw-cut planar joints and tension-induced rough granite joints under normal stresses ranging from 1 MPa to 50 MPa. The shear-induced off-fault damages are quantified and compared with the optical microscope observation. Our results clearly show that the planar joints slip stably under all the normal stresses except under 50 MPa, where some local fractures and regular stick-slip occur towards the end of the test. Both post-peak stress drop and stick-slip occur for all the rough joints. The residual shear strength envelopes for the rough joints and the peak shear strength envelope for the planar joints almost overlap. The root mean square (RMS) of asperity height for the rough joints decreases while it increases for the planar joint after shear, and a larger normal stress usually leads to a more significant decrease or increase in RMS. Besides, the extent of off-fault damage (or damage zone) increases with normal stress for both planar and rough joints, and it is restricted to a very thin layer with limited micro-cracks beneath the planar joint surface. In comparison, the thickness of the damage zone for the rough joints is about an order of magnitude larger than that of the planar joints, and the coalesced micro-cracks are generally inclined to the shear direction with acute angles. The findings obtained in this study contribute to a better understanding on the frictional behavior and damage characteristics of rock joints or fractures with different roughness.

The scarcity of comprehensive data on the shear properties of reinforced GP‐concrete beams without shear reinforcement has hindered their widespread use, mainly due to challenges in predicting their shear performance. This study examines the influence of incorporating up to 15% waste glass powder (GP) with two separate particle size categories: GP‐A (55 to 135 μm) and GP‐B (finer than 55 μm) as a cement replacement on the 180‐day shear performance of reinforced concrete beams with varying cement content and without stirrups. To accomplish this, a total of 14 beams were used, all sharing identical dimensions measuring 200 mm × 250 mm × 2000 mm. The aforementioned parameters were investigated for their effects on the shear performance of beams, including crack patterns, modes of failure, load–deflection behavior, and strength capacities at different loading stages. Furthermore, this investigation explores the applicability of the most commonly used design codes of practice for predicting the shear strength of reinforced GP‐modified concrete beams. These codes are typically employed to design the shear strength of reinforced conventional concrete shallow beams without shear reinforcement. The study's findings indicate that the impact of GP particle size on the shear performance of beams with the same GP content is almost negligible. Additionally, the study found that incorporating GP into concrete beams does not have any negative effects on their cracking load capacity, shear strength, or flexural cracking load capacity. In fact, it can even improve the latter. A comparison of experimental results with predictions from the design codes revealed that both the CEB‐FIP (1990) equation and the ACI equations provided safe estimates of shear strength for the tested beams. However, the CEB‐FIP (1990) equation yielded predictions with a lower mean, standard deviation, and coefficient of variation compared with the ACI equations, suggesting a higher level of accuracy in its estimates. The findings affirm the suitability of GP‐concrete as a viable alternative in concrete structures specifically engineered to withstand shear forces. [ABSTRACT FROM AUTHOR]

Direct shear tests have been extensively conducted on undulated soil-structure interfaces, but there has been limited research on ice-rich debris-rock interface (IDRI). Glacier bedrock often experiences abrasions and erosions, leading to undulated rock surfaces. To investigate the damage evolution, shear deformation, and strength characteristics of undulated IDRI, a series of cryogenic direct shear tests were conducted out under different undulations, normal stresses, temperatures, and volumetric ice contents. Interestingly, the results reveal that increasing undulation leads to a decrease in brittleness, shear stiffness, peak shear stress, and cohesion, while the peak displacement and internal friction angle increase. A shear strength model was proposed, showing an exponential relationship between shear strength and undulation. The shear strength parameters, including peak shear stress, cohesion, and internal friction angle are more sensitive to undulation at lower temperatures. The number of shear fractures on the interface increases with higher undulation and the possible reasons for this phenomenon were discussed. Based on the test results, a disturbed state concept model that combines linear and nonlinear characteristics is developed to describe the shear stress-displacement relationship at the interface. [ABSTRACT FROM AUTHOR]

Glacier collapses can occur due to shear failure at the ice-rich debris–rock interface (IDRI). To examine the shear behavior of IDRI, shear tests were conducted on artificial IDRI specimens with varying ice contents (40%, 65%, and 90%), normal stresses (150, 250, 350, 450, and 550 kPa), and temperatures (−1, −3, −5, −7, and −9 °C). Our findings reveal that temperature has the most significant impact on both peak and residual shear strength, followed by normal stress and ice content. As the temperature increases from −9 to −1 °C, the peak and residual shear stress decreased by 62.5%–78%. Notably, for IDRI with the lowest ice content (40%), the residual shear stress is highly influenced by normal stress. We have developed an improved Mohr–Coulomb strength criterion of IDRI in which the cohesion and internal friction angle are determined by ice content and temperature. Furthermore, we propose a novel constitutive model, based on the disturbed state concept, to describe the shear behavior of IDRI. This model combines a spring model and a hyperbolic model. We also discuss the mechanisms through which ice content and temperature influence the shear deformation modes and shear strength of IDRI. [ABSTRACT FROM AUTHOR]

Due to the extraordinary mechanical properties of ultra-high-performance concrete (UHPC), the shear stirrups in UHPC beams could potentially be eliminated. This study aimed to determine the effect of beam height and steel fiber volume content on the shear behavior of non-stirrup UHPC beams under a larger shear span–depth ratio (up to 2.8). Eight beams were designed and fabricated including six non-stirrup UHPC beams and two comparing stirrup-reinforced normal concrete (NC) beams. The experimental results demonstrated that the steel fiber volume content could be a crucial factor affecting the ductility, cracking strength, and shear capacity of non-stirrup UHPC beams and altering their failure modes. Additionally, the height of the beam had a considerable effect on its shear resistance. French standard formulae were more accurate for the UHPC beams with larger shear span–depth ratios, PCI-2021 formulae greatly overestimated the shear capacity of UHPC beams with larger shear span–depth ratios, and Xu's formulae were more accurate for the steel fiber-reinforced UHPC beams with larger shear span–depth ratios. In summary, French standard formulae were the most suitable formulae for predicting the shear capacity of UHPC beams in this paper. [ABSTRACT FROM AUTHOR]

In recent decades, loess landslide events have attracted increasing attention in the South Jingyang tableland. To elucidate the mechanical mechanism of landslide initiation in the region, this work collected undisturbed loess and paleosol samples taking from the Q2 strata in the South Jingyang tableland. A range of direct shear tests were carried out to explore the strength evolution law of shear zone soil subjected to a varying initial moisture content. In addition, soil water characteristic curves (SWCCs) were also charted and used for predicting the unsaturated shear strength. The findings show that the basic physical properties of the paleosol are different from those of loess due to their different pedogenic environments. The normal stress level and initial moisture content jointly determine whether the shear behavior is strain hardening or strain softening. The shear strength and strength parameters evidently diminish with an increasing initial moisture content, and cohesion contributes to the vast majority of strength attenuation. Paleosol samples possess higher values in shear strength and strength parameters than loess samples due to their stronger inter-particle cementation. The predictive formulas of unsaturated shear strength for undisturbed loess and paleosol are proposed, respectively, based on the Vanapalli model, and the calculated values of the strength prediction model are in perfect agreement with the experimental values. [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]

Clay-rich rocks such as mudstone have a great affinity for water due to the formation of a diffuse double layer around the negatively charged minerals. This makes the behavior of this rock type unique when exposed to different temperatures. Therefore, the tensile, compressive, and shear mechanical behaviors of mudstone were investigated under the coupling effect of temperature and confining pressure. Results indicated that the mudstone can sustain a temperature of up to 500 °C without the appearance of thermal cracks. By increasing the temperature from room temperature (RT) to 500 °C, the mechanical properties improved due to thermal expansion that causes the closure of pre-existing micro-cracks. Tensile strength increased by about 92.3% after thermal treatment at 500 °C, while the tensile modulus of elasticity (ET) increased from 14.2 GPa under RT to 16.1 and 20.5 GPa after thermal treatment at 250 and 500 °C, respectively. The compressive behavior of the mudstone was greatly influenced by the coupling of temperature and confining pressure. Comparing between initial (T = RT and σ3 = 0.0 MPa) and extreme (T = 500 °C and σ3 = 10 MPa) conditions in this study, compressive strength, axial and transverse moduli of elasticity increased by about 150%, 59%, and 148%, respectively. However, Poisson's ratio decreased from 0.387 to 0.248, indicating an increase in the brittle behavior of the mudstone between initial and extreme conditions. Regarding shear behavior, the linear Mohr–Coulomb criterion was in good agreement with test data to represent the shear behavior of the mudstone before and after thermal treatment. A little reduction of about 4% in the peak friction angle was observed after thermal treatment at 500 °C, while the cohesion increased by about 47%. This indicates a significant improvement in the peak shear strength of the mudstone with increasing temperature. The experimental findings of this study offer valuable insights into the mudstone behavior when exposed to thermal effect. The obtained parameters play a critical role in the governing equations that describe how the rock material responds to thermal effect in terms of compressive, tensile, and shear behavior. Highlights: Clay-rich rocks such as mudstone have unique behaviour under thermal effect. The influence of coupling temperature and confining pressure was considered. Tensile strength and modulus of elasticity were measured as temperature function. Compressive behavior including elastic moduli and Poisson's ratio was investigated. The shear behavior of intact mudstone versus temperature effects was analyzed. [ABSTRACT FROM AUTHOR]

The shear behavior of basalt fiber–reinforced polymer-reinforced seawater–sea sand concrete (BFRP-SSC) beams was investigated experimentally. The effects of several factors, including stirrup diameters (8, 10, and 12 mm), stirrup spacings (100, 125, and 150 mm), and shear span-to-depth ratios (1.55, 1.95, and 2.35), were considered. The results demonstrated that the shear mechanism of the diagonal section of BFRP-SSC beams could be explained using the arch truss model. Moreover, the shear span-to-depth ratio significantly influences the shear capacity, bending stiffness, diagonal crack width, and shear failure mode of beams, with diagonal compression failure occurring in beams with a ratio of 1.55 and shear compression failure occurring in beams with a ratio between 1.95 and 2.35. In addition, the actual shear capacities of 72 BFRP-reinforced concrete (BFRP-RC) beams were compared to the results obtained by five design provisions. Correction coefficient of shear span-to-depth ratio, modification to stirrup spacing, correction equation of stirrup strain, and shear contribution coefficient of stirrups were proposed to modify the shear equation in ACI 440.1R-15. The results of the modified shear equation showed a good agreement with the actual shear capacities of beams. The findings of this research have theoretical significance for the design and practical application of BFRP-SSC beams in marine construction. [ABSTRACT FROM AUTHOR]

Corrugated web girders with plate flanges have been widely applied in buildings and bridges due to the large shear capacity of the corrugated web (CW). However, experiments on corrugated web girders with tubular flanges are limited. Accordingly, this paper explores, through four full-scale small-size experimental tests used on buildings, the shear behavior of a type of girder formed with a CW, concrete-filled tubular flange, and bottom flat plate flange (CWGCFTF) with different CW thicknesses, wavelengths, and concrete strengths. Based on the imprecise results of one current test, a novel simple support device is proposed to improve the accuracy of the shear test of the CWGCFTF. The test results also show that the shear ratios of the tubular flange to the entire cross-section range from 15–18% when the loading reaches that of the corresponding shear stress to 80% of the shear yield strength of the CWs. Moreover, local buckling appears at the top surface of the steel tube with the CW shear buckling failure of the CWGCFTF under the shear tests. At the end, a theoretical equation of the shear ratio of the CW to the whole cross-section is derived, and a shear yield strength equation of the CWGCFTF is proposed and verified by comparisons with the test results. [ABSTRACT FROM AUTHOR]

This study focuses on using various machine learning (ML) models to evaluate the shear behaviors of ultra-high-performance concrete (UHPC) beams reinforced with glass fiber-reinforced polymer (GFRP) bars. The main objective of the study is to predict the shear strength of UHPC beams reinforced with GFRP bars using ML models. We use four different ML models: support vector machine (SVM), artificial neural network (ANN), random forest (R.F.), and extreme gradient boosting (XGBoost). The experimental database used in the study is acquired from various literature sources and comprises 54 test observations with 11 input features. These input features are likely parameters related to the composition, geometry, and properties of the UHPC beams and GFRP bars. To ensure the ML models' generalizability and scalability, random search methods are utilized to tune the hyperparameters of the algorithms. This tuning process helps improve the performance of the models when predicting the shear strength. The study uses the ACI318M-14 and Eurocode 2 standard building codes to predict the shear capacity behavior of GFRP bars-reinforced UHPC I-shaped beams. The ML models' predictions are compared to the results obtained from these building code standards. According to the findings, the XGBoost model demonstrates the highest predictive test performance among the investigated ML models. The study employs the SHAP (SHapley Additive exPlanations) analysis to assess the significance of each input parameter in the ML models' predictive capabilities. A Taylor diagram is used to statistically compare the accuracy of the ML models. This study concludes that ML models, particularly XGBoost, can effectively predict the shear capacity behavior of GFRP bars-reinforced UHPC I-shaped beams. [ABSTRACT FROM AUTHOR]

In order to investigate the shear behavior of coral aggregate reinforced concrete beam (CARCB), the different concrete strength, steel types affect the shear behavior of CARCB was studied, the calculation formula of shear capacity (Vcs) and numerical analysis model of CARCB was proposed. The results show that: All kinds of CARCB have inclined section suitable reinforcement failure, the failure law of CARCB and ordinary aggregate reinforced concrete beam (OARCB) was basically the same. Considering stirrups corrosion and nonlinear mechanical properties characteristic of coral aggregate concrete (CAC), the Vcs calculation formula of CARCB was proposed, and its applicability in C25 ∼ C60 CARCB was verified, its accuracy was 26% and 34% higher than GB50010–2020 and JGJ/T 12–2019, respectively. A numerical analysis model suitable for describing the shear behavior of CARCB was proposed based on K&C (Karagozian & Case) theory, and its applicability in C25 ∼ C60 CARCB was verified, it was found that this model can well describe the whole process of CARCB inclined section failure, and the errors between simulated and measured values of Vcr, Vcs and midspan deflection are 0∼18%. In addition, the Vcs obtained by the numerical model is 3% more accurate than the calculation formula, indicating that the numerical model can effectively distinguish the variation law of shear behavior of CARCB.

Carbon fiber-reinforced polymer (CFRP) is attractive to serve as reinforcements for concrete structures under harsh environmental conditions. Previous studies show that strip-shaped CFRP stirrups are satisfactory to replace conventional steel stirrups for concrete beams under shear, but the shear resistance mechanism of the strip-shape CFRP stirrups is not well understood. To fill this research gap, this study conducts a comparative analysis to examine the effects of different types of stirrups (CFRP or steel) on the distribution of shear cracks and the variation in shear resistance components of concrete beams with varying shear span-depth (a/d) ratios. A digital image correlation (DIC) technique is employed to capture the shear crack development of the beams. The results demonstrate that the strip-shaped CFRP stirrups (designed based on the principle of equal stiffness with steel stirrups) effectively restrain the propagation of individual shear crack, particularly at a large shear span (a/d=3.5). This enhanced crack restraint leads to a notable reduction in crack width and a significant increase in shear resistance component by 37.5% in the ultimate state when the strip-shaped CFRP stirrups are employed, compared to their steel stirrup counterparts at the same a/d ratio. These findings can facilitate the design and applications of concrete beams with CFRP stirrups.

The investigation into the impact of dry and wet cycles as well as prolonged immersion on the shear properties of bolted rock joints can facilitate comprehension of the mechanism behind shear damage in anchorage rock slopes located within dam sites, which is crucial for conducting long-term stability analyses of such slopes and ensuring safe operation of hydropower plants. In this study, the sandstone from the Three Gorges reservoir area was collected and utilized to made into bolted rock joint specimens, which underwent 12 cycles of wetting and drying as well as 180 days of immersion before undergoing direct shear tests to investigate the degradation of their mechanical properties. The test results indicate that both treatments for water deterioration can significantly reduce the peak shear strength of bolted sandstone joints. The shear deformation characteristics of bolts also vary with the decrease in rock mass strength. As the number of wet and dry cycles, as well as immersion time, increases, the plastic hinge length of the bolt gradually extends. The surface roughness of the joint has an impact on the fracture mode of the bolt. In a flat joint, the fracture section of the bolt exhibits a certain inclination angle, indicating a damage mode where positive and shear stresses act in concert; whereas in a rough joint, the fracture section of the anchor rod shows almost zero inclination angle and is damaged under positive stress. Finally, an attempt was made to apply the conclusions of this paper to engineering by conducting a time-varying reliability analysis of the generalized anchored slope model. The results obtained have significant guidance for evaluating the long-term stability of anchored slopes in hydropower projects.

Strengthening reinforced concrete (RC) columns utilizing advanced composites, including fiber-reinforced polymer (FRP), polyethylene terephthalate (PET) FRP, and engineered cementitious composite (ECC) has attracted extensive efforts for decades. Remarkable achievements have been made in understanding the performance of the retrofitted RC columns that failed in the strengthened area. However, localized strengthening may force failure to shift outside the retrofitted zone, and these cases are rarely reported in literature. This paper focuses on the seismic performance of shear-critical RC columns that failed outside the strengthened zone. The main test parameters considered are the axial compression force (ACF) ratio and the strengthening materials used (ECC, carbon FRP (CFRP)-ECC, or PET-ECC). The results indicate that the failure mode and failure zone depend on the strengthening conditions. Weak strengthening (ECC only) will not result in a shift of the failure zone but strong retrofitting combinations do (CFRP-ECC and PET-ECC). Although the shear failure shifted to the unstrengthened zone, strengthening can still significantly improve ductility, energy-dissipation capacity and stiffness. A larger ACF can change the failure modes from shear to flexural or from shear-flexural to shear-compression. Shear strength models with and without considering the ductility-based reduction effects are evaluated.

The large amount of construction waste produced by the construction industry brings severe natural resource consumption and environmental pollution, elevating the awareness of sustainable development. Recycled aggregate concrete, crushed from construction waste, is recognized as an eco-friendly material and the current optimal solution for the environmental problem. The interface shear failure between substrate recycled coarse aggregate concrete (RAC) and overlay natural aggregate concrete becomes vital for structural safety. In order to study the direct shear performance, a total of 19 specimens were designed to carry out the direct shear test with different replacement ratios, interface types and curing ages. The whole process and failure mode were recorded. The relationships between the shear capacity and deformation, ductility, damage evolution, and energy dissipation were evaluated and discussed. The results demonstrate that the RAC component in the interface was the weak line in the shear plane, accelerating the damage evolution. In the early curing stage, the replacement ratio had a slight influence on the shear properties. Increasing the recycled aggregate replacement ratio from 0 to 100% improved the normalized strength ratio by 8.94% and 14.62%, respectively, for curing ages of 3 days and 7 days. A regression equation was proposed to predict the shear strength, accounting for the curing ages. With the increase in the replacement ratio, the ductility and energy dissipation gradually enhanced.

The interface between soil and concrete in cold climates has a significant effect on the structural integrity of embedded structures, including piles, liners, and others. In this study, a novel temperature control system was employed to conduct direct shear tests on this interface. The test conditions included normal stress (25 to 100 kPa), temperature (ranging from 20 to −6 °C), water content (from 10 to 19%), and shear rates (0.1 to 1.2 mm/min). Simultaneously, the deformation process of the interface was continuously photographed using a modified visual shear box, and the non-uniform deformation mechanism of the interface was analyzed by combining digital image correlation (DIC) technology with the photographic data. The findings revealed that the shear stress–shear displacement curves did not exhibit a discernible peak strength at elevated temperatures, indicating deformation behavior characterized by strain hardening. In the frozen state, however, the deformation softened, and the interfacial ice bonding strength exhibited a positive correlation with decreasing temperature. When the initial water content was 16% and the normal stress was 100 kPa, the peak shear strength increased significantly from 99.9 kPa to 182.9 kPa as the test temperature dropped from 20 °C to −6 °C. Both shear rate and temperature were found to have a marked effect on the peak shear strength, with interface cohesion being the principal factor contributing to this phenomenon. At a shear rate of 0.1 mm/min, the curve showed hardening characteristics, but at other shear rates, the curves exhibited strain-softening behavior, with the softening becoming more pronounced as shear rates increased and temperatures decreased. Due to the refreezing of interfacial ice, the residual shear strength increased in proportion to the reduction in shear rate. On a mesoscopic level, it was evident that the displacement of soil particles near the interface exhibited more pronounced changes. At lower shear rates, the phenomenon of interfacial refreezing became apparent, as evidenced by the periodic changes in interfacial granular displacement at the interface.