Decrease In Shear Strength Research Articles

Microstructural characteristics and mechanical properties of IC10 superalloy and (CoCrNi)94Al3Ti3 MEA joint brazed using NiCrSiB filler

This study focuses on the brazing of IC10 Ni 3 Al-based superalloy to (CoCrNi) 94 Al 3 Ti 3 medium-entropy alloy (MEA) using a NiCrSiB filler metal. The microstructure of the brazed joint was comprehensively investigated, and the forming mechanism of the joint was elucidated. The mechanical properties and fracture behavior of the joint were evaluated. The diffusion of boron from the filler to substrates led to the diffusion-affected zone (DAZ), and the M 3 B 2 - and M 5 B 3 -type boride were precipitated with the coherence of (3 1 0) BCT //(2 0 0) FCC (M 3 B 2 ) and (0 0 2) BCT //(2 0 0) FCC (M 5 B 3 ) adjacent to the IC10 and MEA substrate, namely the DAZ I and II respectively. In addition, the edge dislocation reduced the mismatch between the M 3 B 2 boride and the γ matrix. The isothermal solidification zone (ISZ) was formed near the DAZ when the liquidus temperature reached the brazing temperature due to the diffusion of boron and Si and the dissolution of substrates. The formation of ISZ was effectively activated at high brazing temperatures (1090, 1120, and 1150 °C). The athermal solidification zone (ASZ) was detected in the joint brazed at adopted temperatures, which mainly dominated by eutectic reactions and driven by cooling. The ASZ decreased shear strength of the defect-free joint, and readily accelerated initiation and propagation of cracks. The maximum shear strength of 554 MPa was obtained when the joint was brazed at 1120 °C for 10 min. The fracture mainly occurred in the ASZ (semi-cleavage), and passing through the DAZ (semi-cleavage) and ISZ (dimples). • The brazing of IC10 and (CoCrNi) 94 Al 3 Ti 3 MEA was achieved using a NiCrSiB filler. • The M 3 B 2 - and M 5 B 3 -type borides in the DAZ exhibited coherent with the matrix. • The microstructural evolution and mechanical properties were evaluated. • .

Experimental and Mechanical Behavior of Rubber-Sleeved Group Studs

The group studs used in precast steel-concrete composite bridges can reduce the volume of cast-in-place concrete, consequently accelerating the construction process and improving the construction quality. However, the small spacing of the studs in the group studs may result in a decrease in shear strength and ductility, and a nonuniform distribution of shear force at the root of the studs. Hence, rubber-sleeved group studs, whose studs are wrapped by a rubber sleeve at the root, are proposed to redistribute the shear force at the steel-concrete interface and improve the ductility of the shear connector. In this study, four push-out tests were conducted to demonstrate the composite mechanism of rubber-sleeved group studs. Results show that the rubber-sleeved group studs exhibit better ductility than ordinary group studs. Finite element models verified using the test results were also established for parametric analysis. The mechanism analysis shows that the concrete compression regions around stud roots are sufficiently utilized. Based on the parametric analysis, designing suggestions for rubber-sleeved group studs were provided.

NOVEL METHOD OF BREAKING DOWN RUBBER MOLECULES USING PEPTIZER AND THE PROPERTIES OF RESULTANT NATURAL RUBBER SOLVENT-BASED ADHESIVE

The huge cost of energy associated with the breaking down of high molecular weight rubber during adhesive production has placed a demand for alternative processing technology. In this study, the use of benzoyl peroxide as a peptizer to lower the molecular weight of natural rubber has been reported. The properties of natural rubber-based solvent adhesive produced by mechanical mastication and peptizer were also compared. Natural rubber (NR) was masticated in a two-roll mill at 80oC for 30 mins and was processed into adhesive using xylene as solvent. Similarly, adhesives were formulated by chemical break down of the heavy natural rubber molecules using benzoyl peroxide as peptizer. The peptizer loading was varied from 0.2 – 1.0 parts per hundred rubber (phr) of rubber at 100oC in a water bath while other compounding additives were kept constants for all samples under study. The adhesives produced were subjected to the following test: viscosity, lap shear test, T-peel test and drying time test. Other properties studied are weathering resistance, heat resistance and effect of moisture on the adhesives bond on different substrates. The result shows that the viscosity of the adhesives increases with increasing peptizer loading and the masticated sample has a viscosity slightly lower than that of 0.8phr and 1.0phr peptizer loading. Furthermore, T-peel test shows that 0.4 phr peptizer loading has a better average T-peel strength for the bonds while the masticated sample had the least average T-peel strength when compared with all samples. The sample with 1.0phr peptizer loading had the least decrease in shear strength while the 0.2 peptizer loading had the maximum decrease in shear strength. Finally, the FT-IR spectra shows similarities in spectra but with difference in the intensity of the peaks, indicating the ability of the benzoyl peroxide to effectively oxidize the natural rubber as compared with the mechanical masticated sample. The peak of 1080 cm-1 in the peptized sample indicates a major difference with the spectra of mechanical masticated sample. Generally, the benzoyl peroxide effectively lowered the molecular weight of the natural rubber which is evident in the viscosity, reduced process time and ease of the adhesive formulation.

Effects of Solder Powder Particle Size and Substrate Surface Finish on Degradation Properties of Solder Joints

In this study, the degradation characteristics of solder joints composed of powder-size Sn-3.0Ag-0.5Cu and the substrate surface finish are compared. Reflow is performed at a N2 ambient to apply an organic solderability preservative (OSP), electroless nickel/immersion gold (ENIG) substrates, and solder pastes of Type 6 (5-15 ㎛) and Type 7 (2-11 ㎛). Subsequently, a thermal shock test (TST) is performed for 1,500 cycles at a temperature of -40 ℃ to 125 ℃ (dwell time of 10 min) to analyze the deterioration characteristics. After N2 reflow is performed, the void content of the OSP substrate/solder joints is higher than that of the ENIG substrate/solder joints, and the shear strength of the ENIG substrate/solder joints is higher than that of the OSP substrate/solder joints. After 500 TST cycles, the shear strength at the OSP substrate/Type 7 solder joints does not decrease, whereas the shear strength at the ENIG substrate/Type 7 solder joints decreases by approximately 25%. Cross-sectional analysis shows that Cu6Sn5 and (Ni,Cu)3Sn4 intermetallic compounds (IMCs) emerged in the OSP and ENIG interfaces, respectively. The increasing rate of IMC thickness at the Type 7 solder joints is higher than that at the Type 6 solder joints. Fracture analysis shows that the OSP and ENIG joints fractured in the solder and solder/IMC interfaces, respectively. The IMC of the OSP and ENIG joints exhibit scallop and needle shapes, respectively. The ENIG joints fractured at the solder/IMC interface because of a stress concentration in the needle-type IMC. After 1500 TST cycles, the shear strength of all samples decreases by more than 50%. Cross-sectional analysis shows a crack at the solder joints of all samples after 1,000 cycles. The decrease in shear strength is caused by these cracks.

Shear behaviour of 3D nonpersistent jointed rock-like specimens: Experiment and numerical simulation

There are many nonpersistent joints in natural rock masses, and they play an important role in the mechanical and failure characteristics of rock masses. To investigate the shear failure behaviour of 3D nonpersistent jointed rock masses, laboratory tests and numerical simulations were conducted in this paper. The 3D nonpenetrating joints are created using a 3D printer, and five persistence ratios are considered. The experimental results show that the shear strength, cohesion and friction angle decrease with increasing joint persistence. A 3D DEM model containing 3D nonpersistent joints is established considering the joint persistence. The flat-joint model and smooth-joint model are used to model rock-like materials and prefabricated joints, respectively. The numerical results are consistent with the laboratory results in both shear strength parameters and failure characteristics. Combined with numerical results, the crack initiation, propagation and coalescence on 3D nonpersistent joint specimens were analysed at the microscale.

Displacement Back Analysis of Reservoir Landslide Based on Multi-Source Monitoring Data: A Case Study of the Cheyiping Landslide in the Lancang River Basin, China

Landslides that occur in the littoral zone of a reservoir can directly damage the hydraulic structures and threaten the lives and property around the reservoir. Due to the spatial variability and heterogeneities of rock mass, a limited amount of data obtained from laboratory and in situ tests cannot comprehensively characterize the mechanical properties of rock and soil masses. Therefore, displacement back analysis is often performed to determine the mechanical parameters of rock and soil masses. The spaceborne Interferometric synthetic aperture radar (InSAR) has proved to be a powerful tool for geodesy in the measurement of landslide movement. However, InSAR can only measure the surface motion of the landslide without the subsurface information. This study uses multi-source monitoring data in the landslide displacement back analysis, including surface InSAR and an internal borehole inclinometer. The identified material parameters and finite element simulation are used to predict the landslide deformation. The case study of the Cheyiping landslide located in the Lancang River basin demonstrates the necessity and feasibility of using multi-source monitoring data in landslide displacement back analysis. The Cheyiping landslide is currently in the creep deformation stage. The decrease in shear strength of rock masses due to the rheological deformation and the change in reservoir water level are the internal and external factors leading to excessive landslide deformation. The numerical modeling can accurately simulate the landslide movement using the identified material parameters. By combing multi-source monitoring data and numerical modeling, the reservoir landslide deformation analysis can help evaluate the landslide deformation state and stability, which is vital for reservoir risk mitigation and the sustainable development of hydropower resources.

A New Low-Temperature Solder Assembly Technique to Replace Eutectic Sn-Bi Solder Assembly.

We successfully achieved low-temperature assembly by reflowing the 13.5Sn-37.5Bi-45In-4Pb quaternary eutectic solder paste and the SAC 305 solder ball together at 140 °C for 5 min. The wetting angle of the mixed solder joint is 17.55°. The overall atomic percent of Pb in the mixed solder joint is less than 1%, which can be further reduced or eliminated. Moreover, after aging at 80 °C for 25 days, we observed no obvious decrease in shear strength of the fully mixed solder joint, which is the most advantage of this assembly technique over Sn58Bi solder assembly. The Bi phase segregation at the interface is slowed down compared with Sn-Bi solder joint. This low-temperature assembly is promising to be applied in advanced packaging technology to replace the eutectic Sn-Bi solder.

Experimental Investigation on Failure Mechanisms of HDPE Welded Geocell Junctions under Different Clamping Distances

Geocells are three-dimensional honeycomb-reinforced geotechnical materials composed of strips and junctions. Its junctions can support and transmit forces in several directions. The performance of geocells has a considerable impact on engineering applications. However, the testing program of geocell junctions still lacks standardization, and limited research has been undertaken regarding the failure mechanisms of junctions when subjected to various stress types. In this paper, four test procedures for HDPE welded geocell junctions were performed, including weld tensile, shear, peeling, and splitting strength tests. The influence of tests under different clamping distances (10.5 mm, 25 mm, 50 mm, and 100 mm) was analyzed, and the stress–strain behavior, peak elongation, and peak and residual strength of junctions under various force states were analyzed in detail. Finally, considering the strength and deformation, the slope laying method of geocells was proposed. The results show that the tensile strength and shear strength decrease with the clamping distance, whereas the peeling strength and splitting strength remain essentially unchanged. Under a 100 mm clamping distance, the tensile strength and shear strength are decreased by 4.51% and 14.08%. Geocells spreading vertically along the surface on a subgrade slope are thought to be more reliable, improving the geocell’s service life in slope protection. The test results can be used to improve a standardized geocell junction testing procedure as well as to guide, evaluate, and enhance the quality and application dependability of geocells.

Effect of Oil Contamination on the Behavior of Collapsible Soil

Loessial soil is moisture-sensitive soil susceptible to settle when fully saturated. In this study, efforts were made to investigate the effect of oil pollutants on mechanical behavior of soil. The loess soil was contaminated by 2,4,6,8 and 10% dry weight of lamp oil and gasoline. Atterberg limits, direct shear, unconfined compressive strength (UCS) and scanning electron microscope (SEM) tests were performed to evaluate the behavior of oil-contaminated collapsible soils. The results of Atterberg tests showed that the plasticity of the soil decreased, due to the reduction in the thickness of the absorbed surface layer and double water layer. According to the direct shear test, with increasing contamination up to 10% of lamp oil and gasoline, the cohesion of the soil was decreased from 14.5 kPa to 7.3 kPa and 7 kPa, respectively, which was due to the reduction in soil plasticity and diffuse double-layer. Because of the lubrication of soil particles, the internal friction angle of soil was reduced from 18.5° to 13.6° and 13.9° for 10% lamp oil and gasoline. UCS of contaminated soil increased in low strains due to the apparent cohesion of hydrocarbons and it decreased 31% for gasoline and 53% for lamp oil at high strains due to the softening behavior of the contaminated soil. SEM test revealed that hydrocarbons covered the soil particles and changed the soil fabrication to dispersed skeleton. Generally, collapsible soil contaminated with different lamp oil and gasoline contents showed a decrease in shear strength and UCS with increasing oil content.

Effect of Thermal Aging on the Mechanical Properties of SAC305.

Many electronic products are subjected to heat for long periods, depending on their operations. Thus, it is expected that the physical and mechanical properties of electronic elements, including the soldering joints, will be affected. In this study, the impact of thermal aging time and temperature on the microstructure and mechanical properties of 96.5Sn–3.0Ag–0.5Cu (SAC305) was investigated. The samples used were SAC305 solder balls attached to copper pads. The research began by examining the microstructure of the aged samples at 150 °C for 100 and 1000 h. Then, this was compared to the microstructure of the same samples without thermal aging. Then, five groups of 10 samples were prepared from a shear stress–shear stain experiment. The first group was as produced, the second group was aged for 2 h, the third group was aged for 10 h, the fourth group was aged for 100 h, and the fifth group was aged for 1000 h. All groups were aged at a temperature of 150 °C. An Instron testing machine was used to plot a shear stress–shear stain curve until the ball was completely sheared off the pad. The mechanical properties, including the ultimate shear strength, the ultimate energy used to shear the ball, and the total energy used to shear the ball at all thermal aging times were then estimated. The results of this study indicated the formation of a layer of Cu6Sn5 over the copper pad, which thickened with thermal aging time. Furthermore, the ultimate and total shear strengths decreased with thermal aging time. The same procedure was repeated to assess the ultimate shear strength at 100 °C. The decrease in ultimate shear strength was more severe with increasing thermal aging temperature.

Influence of Lateral Multistage Unloading Intensity on Mechanical Properties of Reconstituted Coastal Soils Containing Silty Particles

The unclear understanding of the mechanical behavior of soil under unloading conditions is a significant reason for the frequent occurrence of accidents and difficulties in the deformation control of foundation pit engineering in coastal areas. This paper discusses the effect of multistage unloading intensity on the mechanical properties of reconstituted coastal soils containing silty particles through a series of laboratory tests, namely, the CU triaxial, bender-element, and permeability tests. Results indicate that, with an increase in unloading intensity, the shear strength and stiffness parameters decrease, while permeability slightly increases. The effect of unloading intensity on the mechanical properties of silt and mucky silty clay is more pronounced. Additional consideration should be given to the effect of a single excavation depth on the mechanical properties of fine-grained soil in foundation pit engineering in order to ensure the stability of the surrounding soil and the safety of adjacent structures.

The State of Pore Fluid Pressure and 3‐D Megathrust Earthquake Dynamics

AbstractWe study the effects of pore fluid pressure (Pf) on the pre‐earthquake, near‐fault stress state, and 3‐D earthquake rupture dynamics through six scenarios utilizing a structural model based on the 2004 Mw 9.1 Sumatra‐Andaman earthquake. As pre‐earthquake Pf magnitude increases, effective normal stress and fault shear strength decrease. As a result, magnitude, slip, peak slip rate, stress drop, and rupture velocity of the scenario earthquakes decrease. Comparison of results with observations of the 2004 earthquake support that pre‐earthquake Pf averages near 97% of lithostatic pressure, leading to pre‐earthquake average shear and effective normal tractions of 4–5 and 22 MPa. The megathrust in these scenarios is weak, in terms of low mean shear traction at static failure and low dynamic friction coefficient during rupture. Apparent co‐seismic principal stress rotations and absolute post‐seismic stresses in these scenarios are consistent with the variety of observed aftershock focal mechanisms. In all scenarios, the mean apparent stress rotations are larger above than below the megathrust. Scenarios with larger Pf magnitudes exhibit lower mean apparent principal stress rotations. We further evaluate pre‐earthquake Pf depth distribution. If Pf follows a sublithostatic gradient, pre‐earthquake effective normal stress increases with depth. If Pf follows the lithostatic gradient exactly, then this normal stress is constant, shifting peak slip and peak slip rate updip. This renders constraints on near‐trench strength and constitutive behavior crucial for mitigating hazard. These scenarios provide opportunity for future calibration with site‐specific measurements to constrain dynamically plausible megathrust strength and Pf gradients.

Size Effect on the Rheological Shear Mechanical Behaviors of Different Joints: A Numerical Study

Under the condition of constant external stress, the displacement and stress of the joint will be adjusted continuously with time, resulting in the creep phenomenon, that is, the continuous increase of the strain with time, which further causes the damage of the jointed rock mass. In order to study the size effect of joint shear rheological mechanical properties, this paper conducted shear rheological numerical simulations on nonpenetrating and penetrating joint models established in Particle Flow Code (PFC) and analyzed the effect of specimen size on the rheological and shear mechanical behavior of the model. The results show the following: (1) For the rheological direct shear test, the instantaneous shear displacement of the joint increases continuously as the size increases, showing a significant positive size effect. (2) For through-type joints, only the cohesion shows a certain size effect, and the shear strength and friction angle have a nonobvious relation with specimen size. (3) For anchored through-type joints, the increase of the model size leads to a decrease in shear strength, while the friction angle-size effect of joints is not remarkable.

Study on Deformation Characteristics of Loess Ultrahigh-Fill Slope Based on Large-Scale Undisturbed Soil Centrifugal Model Tests

Taking the loess high-fill project of Lv Liang airport in China as the research object, large-scale centrifugal tests were carried out to investigate the deformation characteristics of the collapsible loess ultrahigh-fill slope under natural moisture content and saturated state by using a joint model of undisturbed loess and remolded loess. The results show that the consolidation deformation of the collapsible loess ultrahigh-fill slope is the main factor causing its deformation. The post-construction deformation amount and deformation rate are large in the early stage, and the relationship between the post-construction deformation and thickness of filling body is linear. When the water content of soil increases due to infiltration, the consolidation of the filling body and the collapse of the undisturbed foundation loess will cause settlement and deformation of the slope. The slope may crack along the soft zone formed when the water infiltrates. When failure occurs, the sliding surface will pass through the collapsible soil layer. The contact surface between the collapsible loess layer and the adjacent soil layer is part of the sliding surface, and the contact surface with a relatively low strength will be damaged first. When the strength difference between adjacent soil layers is large, the upper soil layer on the slip surface shows a typical translational sliding mode. The slip surface is approximately arc-shaped, and there is a transition layer with a specific thickness between the slip surface and contact surface. The water content of the high-fill slope has a great influence on the post-construction settlement of the slope crest and slope stability. The post-construction settlement of the slope crest increases with the increase in the water content of the filling body, and the stability coefficient of the slope decreases with the increase in the water content of the filling body. In the saturated state, the sliding force of soil increases, the shear strength decreases, and the stability of high fill slope decreases. Therefore, it is necessary to strengthen the inspection of the rationality of drainage system design in slope construction to ensure slope safety.

Thermoelectric and mechanical characterization of the utilization of FeTe as an electrode for iodine-doped PbTe

In addition to the thermal and electrical characteristics of the thermoelectric material, the energy conversion efficiency of TE devices is influenced by other factors including the interface resistance, which in turn is affected by chemical changes or mechanical failure. We have investigated the use of FeTe as an electrode for iodine-doped PbTe. The telluride of iron has CTE and work function values that match well with those of PbTe. The FeTe/PbTe contact was determined as ohmic in nature with low resistance. Contact resistance and shear strength values were determined over aging times of up to 400 h at 573 K and were found to be nearly unchanged.In contrast, samples in which Fe was used as electrode showed significant decrease in shear strength and a significant increase in joint resistivity over the same aging conditions. From the electrical and thermal characterization, the conversion efficiency of the FeTe/Pb1.0004Te0.997I0.003/FeTe single leg was determined as 4.678% for Th = 673 K and Tc = 300 K.

Assessment of the Effect of Diagonal Reinforcement Quantity on Seismic Behavior of Coupling Beams

ABSTRACT The aim of this study was to scrutinize the seismic behavior of coupling beams according to the quantity of diagonal reinforcement. Four specimens with different diagonal reinforcement quantities were tested with reversed cyclic loading. The shear strength and deformation capacity of coupling beam specimens were compared to those from ACI 318–19 and ASCE 41–17, respectively. With a decrease in diagonal reinforcement, shear strength and chord rotation capacity of diagonal reinforced coupling beams (DRCBs) diminished. An empirical equation to calculate the minimum quantity of diagonal reinforcement was proposed to satisfy the limiting deformation capacity using regression analyses with test data of 45 collected DRCB specimens.

Highly reliable Cu[sbnd]Cu low temperature bonding using SAC305 solder with rGO interlayer

The immoderate growth of intermetallic compounds (IMCs) and the transformation of benign IMCs to malignant IMCs are the main causes for the decrease of the mechanical properties and reliability in the CuSn joints. In this study, a 14 nm thickness reduced graphene oxide (rGO) interlayer was directly prepared between Cu and Sn-3.0 Ag-0.5 Cu (SAC305) solder to inhibit the immoderate growth of IMCs and malignant IMCs formation at the bonding interface. The highly reliable CuCu bonding was realized at 150 °C under the external pressure of ~8.3 MPa. The bonded samples were aged at 150 °C for 0 h–72 h for reliability tests. After aging for 72 h, the thickness of the IMCs layer at the Cu/rGO/solder interface decreases by more than 30%, and the average projected area of IMCs grains decreases by more than 80% compared with that at the Cu/solder interface. Furthermore, the decreasing rate of shear strength with rGO interlayer is lower than that without rGO interlayer for long time aging. For the Cu/rGO/solder bonding structure, after 72 h aging, the shear strength is higher and the contact resistance is lower compared with the Cu/solder bonding structure. For this low temperature bonding process using the rGO interlayer, the immoderate growth of IMCs at the bonding interface was inhibited, which can delay the decrease of shear strength due to aging of the bonding interface.

Abnormal Shear Performance of Microscale Ball Grid Array Structure Cu/Sn–3.0Ag–0.5Cu/Cu Solder Joints with Increasing Current Density

The shear performance and fracture behavior of microscale ball grid array structure Cu/Sn–3.0Ag–0.5Cu/Cu solder joints with increasing electric current density (from 1.0 × 103 to 6.0 × 103 A/cm2) at various test temperatures (25 °C, 55 °C, 85 °C, 115 °C, 145 °C, and 175 °C) were investigated systematically. Shear strength increases initially, then decreases with increasing current density at a test temperature of no more than 85 °C; the enhancement effect of current stressing on shear strength decreases and finally diminishes with increasing test temperatures. These changes are mainly due to the counteraction of the athermal effect of current stressing and Joule heating. After decoupling and quantifying the contribution of the athermal effect to the shear strength of solder joints, the results show that the influence of the athermal effect presents a transition from an enhancement state to a deterioration state with increasing current density, and the critical current density for the transition decreases with increasing test temperatures. Joule heating is always in a deterioration state on the shear strength of solder joints, which gradually becomes the dominant factor with increasing test temperatures and current density. In addition, the fracture location changes from the solder matrix to the interface between the solder matrix and the intermetallic compound (IMC) layer (the solder/IMC layer interface) with increasing current density, showing a ductile-to-brittle transition. The interfacial fracture is triggered by current crowding at the groove of the IMC layer and driven by mismatch strain at the solder/IMC layer interface, and the critical current density for the occurrence of interfacial fracture decreases with increasing test temperatures.

Study on the Effect of Moisture Content and Dry Density on Shear Strength of Silty Clay Based on Direct Shear Test

Silty clay is a kind of clay with more powder group than sand group, and its shear strength is mainly influenced by moisture content, dry density, and particle gradation. In this study, the deformation characteristics of silty clay under different normal pressure conditions were investigated from the perspective of control variables through indoor direct shear experiments. The results of the study show that with the same guaranteed moisture content, it can be seen from the fitted curves that with the increase of dry density, the arrangement of soil particles becomes more compact, the cementation between soil particles is strengthened, the shear strength increases, the occlusal friction increases due to the change of arrangement between soil particles, and the angle of internal friction and cohesion are relatively larger; in addition, when the dry density is the same, with the increase of moisture content, the soil becomes softer, and the form of water in the soil particles changes. In addition, when the dry density is the same, as the moisture content increases, the soil becomes softer, the presence of water between the soil particles changes, resulting in the weakening of the occlusion between the soil particles, the shear strength decreases, and the cohesion and the angle of internal friction relatively decrease.

Shear strength of steel fibre RC beams under repeated loads

The purpose of this work was to examine the possibility of employing steel fibres rather of standard shear strengthening, on the shear strength, crack widths and distribution, and flexural strength in concrete beams under repeated loading. When adding steel fibres, it leads to the modification of many properties of concrete, especially tensile strength. Simply supported concrete fibrous reinforced beams without web reinforcement have the dimensions of (2100 × 150 × 300) mm with three different volume fractions (0, 0.5, and 1.0) % of steel fibres under monotonic and repeated shear loading were analyzed using ABAQUS software. A repeated load was applied on the analyzed beam by two points of loading and for ten cycles up to failure. The results indicate decrease in the ultimate shear strength and an increase in the number and widths of the crack under repeated load compared with the results of a monotonic load. The results show that the deflection under repeated load was higher than deflection under monotonic load.