Increase In Reinforcement Ratio Research Articles

FLEXURAL BEHAVIOR OF NORMAL AND HIGH STRENGTH CONTINUOUS BEAMS REINFORCED BY GFRP BARS

In the reinforced concrete structures, fiber reinforced polymer (FRP) has been considered an alternative material to steel reinforcement with the advantages of corrosion resistance, non-conductivity, and high strength to weight ratio. This work is devoted to study the flexural behavior of normal and high strength concrete continuous beams reinforced with glass fiber reinforced polymers (GFRP) bars. Ten continuous beams, with dimensions 150 mm wide × 250 mm deep × 2300 mm long consisting of two equal spans were investigated in this study. The beams were divided into three groups according to the compressive strength of concrete (30, 50 and 70) MPa. Each group consists of three beams with different longitudinal reinforcement ratio (ρfmin, ρfb and 1.5ρfb; where ρfmin and ρfb are the reinforcement ratio at a minimum and balanced condition, respectively). The ultimate load, mid-span deflection, cracks size, concrete strains, GFRP reinforcement strains of the tested beams were verified and contrasted. The experimental results indicate that the increase in the longitudinal reinforcement ratio increases the ultimate load by 125% and decreases the crack size and mid-span deflection by 78% and 57%, respectively. The experimental data were compared with the proposed ACI 440.1R-15 and CSA S806-12 equations. the ultimate load were greater than the calculated results according to (ACI 440.1R-15) by (20%) for beams with (ρmin), while beams with (ρb and 1.5ρb) the ultimate load were less than the calculated results by (9%), cracks size were close to the results according to (ACI 440.1R-15) for normal strength beams, while for high strength beams results were less than the results according to (ACI 440.1R-15), while ISIS-Canada 07 showed good agreement for all tested beams.

Metallurgical characterization of mechanically alloyed MoNiAl-WC reinforced Fe matrix composite

Abstract MoNiAl-WC reinforced Fe matrix composites were obtained by mechanical alloying. The effect of various reinforcement ratios on microstructure change, elemental characterization and phase transformation were examined by using optical microscopy, scanning electron microscopy, energy dispersion spectroscopy, X-ray diffraction, elemental surface mapping and a microhardness test. Fe and MoNiAl-WC compound and powder mixtures were synthesized by MA and nanocrystalline solid solution was obtained. The increase in the reinforcement ratio reduced grain size in the structure and increased the carbide ratio. The composite demonstrated excellent metallurgical qualities and interface bonding. Moreover, it was found that the amount of porosities increased with increasing reinforcement. X-Ray analysis showed the formation of NiAl, Al3Ni and WC phases.

Microstructural and Mechanical Properties of Cu-Based Co-Mo-Reinforced Composites Produced by the Powder Metallurgy Method

In this study, 5, 10 and 15 wt.% commercial purity Co-Mo powders are added to Cu powders using the powder metallurgy method. The prepared powder mixtures are shaped under a pressure of 600 MPa in a uniaxial hydraulic a press and then sintered at 1000 °C for 30 min. Scanning electron microscopy is applied for microstructural analysis. In the microstructure analysis, it is seen that as the reinforcement ratio increases, the grain sizes increase, and it is evenly distributed in Cu. A wear test is then carried out. As a result of this test, the weight loss, friction coefficient change and wear diameter change results of the composites are obtained. Abrasion loads are applied at 15, 20 and 25 N for 4000 m. The samples manufactured for the tensile test are subjected to certain loads on a Shimadzu tensile device. As a result of the abrasion and tensile tests, it was determined that the sample reinforced with 5 wt.% Co-Mo has the best mechanical properties.

Effects of the alumina reinforcement ratio on the corrosion properties of iron based composite materials

Abstract Iron based composite materials reinforced with various ceramic particles are used in operating conditions requiring features such as high hardness, strength and wear resistance. The composite materials may be subject to corrosion depending on the working environment. In this study, the corrosion properties of iron based composite materials produced by powder metallurgy, containing carbon and different amounts of alumina reinforcement were investigated. In the materials production, 0.5 wt.-% carbon and 1, 3 and 5 wt.-% alumina powders were added to the iron powders as reinforcement. Followed by mixing, one-way cold pressing and sintering, respectively, both iron based carbon and alumina reinforced composite samples were obtained. The electrochemical corrosion properties of iron based composite materials containing various amounts of alumina reinforcement were investigated in a 3.5 wt.-% NaCl environment and the effects of the reinforcing material ratio on the corrosion behavior of the composite material were determined. It was determined that with an increase in the alumina reinforcement ratio, the corrosion rate of the material increases and the corrosion resistance decreases.

Experimental study on seismic behavior of precast beam‐column connections under cyclic loading

AbstractPrecast concrete structures have satisfactory performances in quality control and construction progress. This article experimentally studied the seismic behavior of a type of precast beam‐column connection. Three full‐scale specimens are designed with different longitudinal reinforcement ratios and details of connections. Precast beam‐column connections are systematically investigated focusing on their failure modes, hysteretic and skeleton curves, strength, ductility, stiffness degradation, and energy dissipation capacity. Test results show that the shear panel damage becomes more serious, and the ductility drops dramatically by 32.3% with the increased reinforcement ratio. Moreover, with the change from service holes to reserved grooves, the ductility of the specimen increases evidently, and the energy dissipation capacity fully developed, increasing by 24.0%. Furthermore, influences of reinforcement ratio and detail of construction on the trend of stiffness degradation showed to be not significant. Research findings could provide guidelines for the popularization and application of this type of precast beam‐column connection in reinforcement concrete frame structures.

Mechanical behaviour of ECC ring beam connections under square local compressive loading

To reduce the damage degree and ensure the connection zone have a sufficient local compressive strength for safely transferring the axial load from the concrete filled steel tube (CFST) column, a novel through-beam engineered cementitious composite (ECC) ring beam connection is proposed. To investigate the local compressive behaviour of the ECC ring beam connections, fifteen ring beam connections with different matrix types, width factors, height-to-width ratios and reinforcement ratios were tested under square local loading. According to the test results, the ECC ring beam connections showed higher load carrying capacity and ductility than the reinforced concrete (RC) ring beam connections. It was found that decreasing the height-to-width ratio and increasing the reinforcement ratio evidently improved the peak load of ECC ring beam connections. Test results also showed that increasing the width factor resulted in a significant increase in the displacement ductility for connections with a large height-to-width ratio. The height-to-width ratio showed a positive influence on the ductility for connections with a large width factor. Additionally, increasing reinforcement ratio could significantly increase the ductility. These test results point to the great potential of the use of ECC in the ring beam connections where the connection will be subjected to large axial load.

Experimental and theoretical investigation of steel-reinforced bamboo scrimber beams

A novel steel-reinforced bamboo scrimber beam is proposed in which steel bars or prestressed steel bars are embedded in a bamboo composite material. The flexural performance of the reinforced bamboo beam with different reinforcement ratios and different levels of prestressing forces was investigated by a four-point bending test. The results show that both reinforced beams and prestressed reinforced beams fail due to rupturing of the bottom tensile bamboo fibers; no significant yielding failure occurs in the top compression zone. The ultimate bearing capacity of the reinforced beams increases with an increasing reinforcement ratio and prestressing, and the influence of the prestressing is inferior to that of the diameter of the reinforced bars. The flexural stiffness at the serviceability limit state of the reinforced beams increases linearly with an increasing reinforcement ratio and can be enhanced by up to 36.80% compared with that of control beams. The prestressing reinforcement has an insignificant influence on the initial flexural rigidity of the bamboo scrimber beams but accommodates effective upper reverse bending deflection for reducing the actual bending displacement. The calculation methods for the flexural rigidity and bearing capacity are presented by considering the cross-sectional strain and stress distribution of the reinforced beams, and the proposed models are found to provide accurate predictions for both reinforced and prestressed reinforced bamboo beams. Steel-reinforced bamboo scrimber beams can thus be used for long-span, heavy-load bamboo structural engineering.

Effect of longitudinal steel reinforcement ratio on deflection and ductility in reinforced concrete beams

This search report is an experimental result on load –deflection relationship of various ratios of longitudinal reinforcement for six simply supported reinforced concrete beams. All specimens’ dimensions are (200×300×1750mm) and they were tested under two-point loading. Concrete compressive strength was (37.0-40.7 MPa). The variables studied in this work were tensile steel ratio (0.46-3.0%), bar diameter (12, 16 and 25mm) and number of bars (2 or 3 bars). It is concluded that for low reinforcement values (ρ < 0.013), an increase in ρ is sharply reduced the ductility index μ d . However, this effect decreases with increase in ρ values. All beams exhibit insufficient displacement ductility (less than 3) when reinforced with ρ/ρ b > 0.4. The increase in longitudinal steel ratio using 2 bars is more significant than when using 3 bars in yield and ultimate strengths of specimens as well as the deflection values at yield load, but the deflection values have gradual decrease at the ultimate load as a result of ductility decrease. It was concluded that the increase in longitudinal reinforcement ratio causes an increase in yield and ultimate strength of beams, these increments are compatible with the steel ratio i.e. by increasing the ρ by 50% the strength is increased about this ratio. As well as, the decreasing in ductility compatible with increasing the ρ by 50% the ductility decreased in about 50% on average.

Numerical and theoretical research on flexural behavior of steel-UHPC composite beam with waffle-slab system

Based on the experimental study on six steel-UHPC composite beams with waffle slab (SUCBWS), a three-dimensional finite element model was proposed to analyze the flexural behavior of SUCBWS. Then the applicability of finite element model was validated against the experimental results. A subsequent parametric study was performed to investigate the effects of yield strength of steel, ratio of rib height to upper panel thickness, transverse reinforcement ratio and layout of ribs on the flexural behavior. Results show that the reduction of thickness of upper panel for waffle slab will significantly weaken its integrity and increase the risk of longitudinal splitting failure by comparing with reducing the number of ribs. The waffle slab with low ribs should be adopted as the bridge deck. The increase of transverse reinforcement ratio has little effect on improving the ultimate flexural capacity, while it is obvious for improving the ultimate deformation capacity. The minimum transverse reinforcement ratio of 0.5% is suggested. The contribution of ribs is small for flexural capacity but is large for ensuring ultimate deformation capacity. Finally, the calculation method of ultimate flexural capacity was proposed. The comparison of theoretical, experimental and numerical results revealed the good accuracy of predictions indicating that the actual behavior of SUCBWS was reasonably reflected by the calculation method.

Seismic Performance of Various Piles Considering Soil–Pile Interaction under Lateral Cycle Loads for Integral Abutment Jointless Bridges (IAJBs)

The flexural pile foundation is used in integral abutment jointless bridges (IAJBs) in practical engineering to effectively dissipate the horizontal reciprocating deformation induced by the ambient temperature or earthquake loadings. Various types of flexural piles including the H-shaped steel pile (HP), prestressed concrete pile (PC), prestressed high-strength concrete pile (PHC) as well as the reinforcement concrete pile (RC) have been implemented in IAJBs. However, there is a lack of comprehensive studies on the flexural deformation and seismic performances of these piles. In order to investigate and compare their mechanical behaviors and seismic performances, a low-cycle pseudo-static test on several different types of piles was carried out. The test results indicated that the plastic hinge location of piles moved to a deeper pile depth with the increase of reinforcement ratio, buried pile depth and prestressing level, which led to better pile–soil interaction. The crack resistance of a concrete pile was improved as the reinforcement ratio and prestressing level increased. Moreover, the rectangular pile had a better soil–pile interaction and energy dissipation capacity than the circular pile. The inflection point of the pile deformation shifted deeper as reinforcement ratio, buried pile depth and prestressing level increased, which improved the effective length and horizontal deformation capacity of piles. The H-shaped steel pile showed a better elastic-plastic deformation capacity, ductility and energy dissipation capacity as compared to the concrete pile. Moreover, the pile having a higher bearing ratio sustained larger lateral loads whereas the surrounding soil was subjected to higher loads. Finally, new seismic design criteria of three-stage seismic fortification and five damage level for the concrete piles of IAJBs were proposed.

Experimental investigation on seismic performance of mechanical joints with bolted flange plate for precast concrete column

The conventional assembled monolithic grouted sleeve connection of column–column joints continues to require in situ grouting, which has certain disadvantages, including the necessity of wet construction. Compared with cast-in-situ columns, its seismic performance is relatively insufficient in terms of deformation and energy dissipation capacity. In this paper, a new type of precast concrete column–column joint and its corresponding column base joint with a steel jacket for confining the concrete core and bolted flange plate is proposed to achieve rapid erection. Six specimens are tested at a high axial compression ratio and cyclic reversed loading, including three precast column–column joints with bolted flange plate, one column base joint with bolted flange plate, one grouted sleeve connection joint, and one cast-in-situ column. This study focuses on the effects of the ratio of longitudinal reinforcement to the gap between the steel jacket and upper concrete on seismic performances. Test results indicate that this new joint is reliable, and all failure modes involve the flexural failure of the precast upper column. The influence of tensile reinforcement on the out-of-plane deformation of the flange plate is minimal. Compared to the cast-in-situ column, the column with a flange plate connection has a more gradual crack development, a slightly higher resistance, an improved ductility, and a better energy dissipation capacity. With the increase in longitudinal reinforcement ratio, the confining effect of the steel jacket on the concrete core becomes more distinct. The gap between the steel jacket and upper concrete could effectively delay the compressive damage on the concrete surface. Finally, considering the confining effect of the steel jacket, the flexural capacity of the proposed precast column is determined using the fiber model. The predicted results approximate the test values and are all within the safe range.

Experimental investigation and numerical analysis of RC beams shear strengthened with FRP/ECC composite layer

Five Reinforced Concrete (RC) beams strengthened with Basalt Fiber Reinforced Polymer (BFRP) grid in conjunction with Engineered Cementitious Composite (ECC) were tested along with one conventional RC beam for reference to investigate their performance improvement, particularly in shear capacity, due to strengthening. The test results highlighted that the failure modes of the tested beams were dominated with shear-compression failure in the shear/bending moment regions and concrete crushing in the compression part of the pure bending zone. A good bonding performance between the BFRP-ECC composite and concrete substrate was exhibited during the testing process, which can effectively suppress the propagation of diagonal cracks in the shear/bending moment regions. The shear capacity of strengthened RC beams was greatly improved with the increase of BFRP grid reinforcement ratio. Moreover, the reinforcement effect of this strengthening technique was much more effective with the increase of shear-span ratio of the tested RC beams. Furthermore, finite element analyses based on ABAQUS/Standard software were conducted to provide analytical estimations of the shear capacity of the strengthened RC beams. The analytical results revealed that the predicted values agree very well with the test data, which can effectively predict the shear capacity of RC beams strengthened with BFRP-ECC composite.

Crack development and calculation method for the flexural cracks in BFRP reinforced seawater sea-sand concrete (SWSSC) beams

In this paper, the bending test of ten seawater sea-sand concrete (SWSSC) beams were carried out. The reinforcement bars employed were steel bars, basalt fiber-reinforced polymer (BFRP), and glass FRP (GFRP) bars. The beam performance in the service stage, such as crack development, was mainly analyzed. Based on the current codes and gathered data, the equation for predicting the maximum crack width of FRP-RC beams under short-term loading was proposed. The results showed that the crack width and deflection of the FRP-beams were larger compared with those of steel-beams. An increase in reinforcement ratio or section depth notably improved the beam stiffness, thereby reducing the deflection and crack width. The application of small diameter reinforcements was beneficial to decrease the crack width without compromising the beam deflection. Based on the test results, the average bond coefficient was 1.13, which was in good agreement with the value of 1.0 provided by CSAS806-12 for ribbed reinforcements. The proposed formula of crack width calculation can be applied as a guideline for the estimation of crack development during the service of SWSSC beams.

Investigation of Wear Behavior of Particle Reinforced AL/B4C Composites under Different Sintering Conditions

In this study, the effects of different sintering conditions of boron carbide reinforced to aluminum matrix powder on microstructure, density and wear resistance by a mechanical alloying method were researched. Powders produced by mechanical alloying for eight hours at the atrial shaft were compressed with a cold isostatic press die under 350 MPa to obtain cylindrical composite specimens. The raw samples were sintered in high purity argon at 600, 625, 650 °C for 90 minutes. The wear behavior of the Al/B4C metal matrix composite was studied using a pin-on-disk wear tester. Under favorable conditions, it has been observed that reinforced boron carbide wear can be reduced by more than two decades. Various investigations have been made to relate this improved wear performance to reinforcement ratios. Aluminum abrasion test results showed that different types of abrasion occurred and that the abrasion resistance was increased by the change of the bubble rate. In the experimental studies that were carried out, it was observed that wear resistance increased with the proportion of boron carbide reinforced directly by the weight, and especially with a 15% B4C ratio depending on the increased reinforcement ratio.

Investigating the synergistic effect of CNT + MLG hybrid structure on copper matrix and electrical contact properties of the composite

In this study, carbon nanotubes (CNTs) and multi-layer graphene (MLG) were mixed and reinforced into copper matrix at the rates of 1, 2 and 10 vol.%. Thus, the synergistic effect of CNT $$+$$ MLG hybrid structure on copper matrix was investigated and the usability of the obtained composite as an electrical contact material was examined. In addition, changes in the properties of the composite were demonstrated with the changes in amounts of CNTs and/or MLGs in Cu matrix. In this study, both reinforcements and composites were produced under laboratory conditions. The electrical conductivity, abrasion properties, and hardness of the produced composites and their usage as electrical contact material were investigated. The obtained results were compared with previous studies, and their reasons were revealed. The electrical conductivity of the obtained composite increased first to a certain reinforcement amount with the increasing CNT $$+$$ MLG hybrid reinforcement rate and then decreased. However, the electrical conductivity of the composite reinforced with only CNTs or MLGs at the same rate was found to be higher than CNTs $$+$$ MLGs reinforced composite. The abrasion resistance of CNT $$+$$ MLG hybrid-reinforced copper matrix composite showed an increase with increasing reinforcement ratio. The increase in the amount of MLGs in the composite caused an increase in the abrasion resistance of the composite. This situation can be said to be caused by the lubricant property of MLGs. CNT $$+$$ MLG hybrid-reinforced copper matrix composites were used as an electrical contact material in an experimental set-up, and this material loss in these materials and the damages on the surfaces after 20,000 turn on/off were investigated. It can be asserted that the electrical contact properties of the composite improved with increasing amount of MLGs. MLGs distributed rapidly the heat generating during the operation of the contact and weakened the mechanical effects during the on/off states of the contacts due to their lubricant properties which helped to reduce the damage on the contact materials.

Analysis of polymeric composite materials for frictional wear resistance purposes

This research is about manufacturing brake pads from a polymeric composite material composed of domestic materials, which are cheaper and available in the market. An unsaturated polyester is used as the basic material. Styrene–butadiene rubber and montmorillonite clay materials available in the market are used as the fillers. The Kevlar fibers, the nylon, and the steel fibers are used as reinforcing materials to improve the mechanical properties. The Shore hardness, compressibility, thermal conductivity, impact, and wear resistance tests have been implemented. The results show that the hardness, compressive, and impact resistance of the samples increase with the increase of the reinforcement ratio by Kevlar fibers, nylon fibers, and steel fibers. The rate of wear decreases with the increase of reinforcement ratio. The thermal conductivity decreases with an increase in the reinforcement ratio by Kevlar fibers and nylon fibers while the thermal conductivity increases with an increase in the reinforcement ratio by Kevlar fibers and steel fibers. Compared to the commercial brake pads, high strength, high wear resistance, high impact resistance, high hardness, high compressive strength, low thermal conductivity, and low-cost brake pads have been proposed.

Seismic performance of precast short-leg shear wall using a grouting sleeve connection

Precast shear wall structures have been widely used in recent years due to their advantages of energy saving, environmental protection and efficient construction etc. The validity and reliability of connection methods are the key to ensure the performance of structures. In order to study the seismic behavior of precast short-leg shear wall connected with the grouting sleeve, a cast-in-place shear wall (OSSW) and a precast short-leg shear wall (PSSW) were designed and produced in this paper, respectively. The seismic indexes were obtained by low-cyclic reversed loading, such as failure mode, hysteretic behavior, stiffness degradation and energy dissipation capacity etc. The test results indicate that the failure of the specimens are controlled by bending instead of shear, but there is a noticeable difference in the cracking distribution between the two types of specimens. The bearing capacity of each feature point of PSSW is close to that of OSSW and the ductility and energy dissipation capacity of PSSW are slightly lower than that of OSSW. The data of test also reveal that the reinforcement bars connected by grouting sleeves are reliable before yielding, but the bonding strength between grouting material and the connecting reinforcement bar in the sleeve decrease after yielding. In addition, the finite element numerical simulation of PSSW is carried out to study the influence of longitudinal reinforcement ratio on the seismic indexes. With the increase of longitudinal reinforcement ratio, the bearing capacity and energy dissipation performance of PSSW are gradually enhanced. but the ductility of the specimen is reduced.

Strengthening unreinforced masonry walls using natural hemp fibers

This paper presents an experimental setup to study the effectiveness of using natural hemp fibers for enhancing the out of plane flexural capacity of unreinforced masonry walls. Wall specimens are constructed using normal-weight hollow concrete masonry units, and then hemp fiber fabrics are externally applied for strengthening. Performance of the hemp reinforced wall units is gauged by examining the flexural capacity, ductility, and failure modes of the wall specimens. A sensitivity analysis is conducted to investigate the effects of different strengthening configurations on the capacity of strengthened wall sections. Experimental results show that both the flexural capacity and ductility of the walls increase with an increase in reinforcement ratio.

Influence of Reinforcement Bars on Concrete Pore Structure and Compressive Strength.

In this research, the influence of reinforcement bars on concrete pore structure and compressive strength was experimentally investigated. Concrete samples with two mixture ratios and nine reinforcement ratios were provided. Tests were conducted on concrete pore structure and compressive strength at three ages (3 d, 7 d, and 28 d). It was found that reinforcement bars changed the concrete pore structure. In terms of size, the pore structure of concrete increased with the increase of reinforcement ratio. At the same age, concrete compressive strength in reinforced concrete specimens saw a gradual reduction when reinforcement ratio increased. A formula was proposed to calculate the compressive strength of concrete in reinforced specimens according to the strength of unreinforced concrete.

Direct tensile behaviors of steel-bar reinforced ultra-high performance fiber reinforced concrete: Effects of steel fibers and steel rebars

Based on strengthening the structural performance of ultra-high performance fiber reinforced concrete (UHPFRC), a steel-bar reinforced ultra-high performance fiber-reinforced concrete (R-UHPFRC) is presented in this study. To provide more information about the direct tensile behaviors of R-UHPFRC member, several dogbone-shaped R-UHPFRC specimens are tested, with the experimental variables including the volume content of steel fiber and the reinforcement ratio of steel rebar. The effects of the fiber volume fraction and reinforcement ratio of steel bars on the direct tensile properties of R-UHPFRC are evaluated using multiple performance parameters, including load-deformation relationship, tension-stiffening behavior, tensile stiffness and damage pattern. Test results indicate that there is minimal difference in overall load-elongation responses of R-UHPFRC specimens with an increasing fiber volume fraction. The variation in the reinforcement ratio of the steel bar, by contrast, has significant influence on the tensile responses of R-UHPFRC specimen, especially the peak strength and hardening modulus increases considerably with a growing reinforcement ratio as compared to non-reinforced UHPFRC specimens. Importantly, the tensile strain values of R-UHPFRC with rebars are significantly higher than the counterparts of UHPFRC without rebars, and this rising trend is even more pronounced when the reinforcement ratio increases. Further, the use of R-UHPFRC with combined reinforcements is beneficial to extend the strain hardening capacity of UHPFRC itself. Even, a desired post-peak ductility can be achieved by a rationally designed reinforcement ratio of steel bars. The increased reinforcement ratio of steel rebars transfers the tensile failure pattern of the R-UHPFRC members from a single, localized crack into multiple localized cracks.