Ordinary Concrete Beams Research Articles

The combined effect of load and corrosion on the flexural performance of recycled aggregate concrete beams

AbstractTo investigate the combined effect of load and steel corrosion on the flexural performance of recycled aggregate concrete beams, considering three types of aggregate replacement ratios (i.e., 0%, 50%, and 100%) and four levels of load (i.e., 0, 0.2, 0.4, and 0.6), 12 beams were designed for accelerated corrosion test and four‐points bending test. The load was applied to beams by using a designed loading device before the accelerated corrosion test. After the accelerated corrosion test, four‐point bending test was conducted to measure the flexural performance of beams. The results showed that, with the increase of load level applied to beams before accelerated corrosion test, the number of bending cracks on the bottom of corroded beams after four‐points bending test decreased, while the average spacing of bending cracks increased. The effect of aggregate replacement ratio on the average spacing of bending cracks was more significant than that of steel corrosion. Yield moment capacity and ultimate moment capacity of corroded beams had a strong linear relationship with the maximum mass loss of tensile reinforcement, and both of which decreased with the increase of load level and aggregate replacement ratio. For every 1% maximum mass loss of the tensile reinforcement, the reduction of ultimate moment capacity of beams was approximately 4–6 times larger than that of ordinary concrete beams. The degradation model for ultimate moment capacity of corroded beams proposed in this paper had satisfactory prediction accuracy.

Experiment and Analysis of Mechanical Properties of Lightweight Concrete Prefabricated Building Structure Beams

Recent years have witnessed that the prefabricated concrete structure is in the widespread use of building structures. This structure, however, still has some weaknesses, such as excessive weight of components, high requirements for construction equipment, difficult alignment of nodes, and poor installation accuracy. In order to handle the problems mentioned above, the prefabricated component made of lightweight concrete is adopted. At the same time, this prefabricated component is beneficial to reducing the load of the building structure itself and improving the safety and economy of the building structure. Nevertheless, it is rarely found that the researches and applications of lightweight concrete for stressed members are conducted. In this context, this paper replaces ordinary coarse aggregate with lightweight ceramsite or foam based on the C60 concrete mix ratio so as to obtain a mix ratio of C40 lightweight concrete that meets the engineering standards. Besides, ceramsite concrete beams and foamed concrete beams are fabricated. Moreover, through three-point bending tests, this paper further explores the mechanical properties of lightweight concrete beams and plain concrete beams during normal use conditions. As demonstrated in the results, the mechanical properties of the foamed concrete beam are similar to those of the plain concrete beam. Compared to plain concrete beams, the density of foamed concrete beams was lower by 23.4%; moreover, the ductility and toughness of foamed concrete were higher by 13% and 3%, respectively. However, in comparison with the plain concrete beam, the mechanical properties of the ceramsite concrete beam have some differences, with relatively large dispersion and obvious brittle failure characteristics. Moreover, in consideration of the nonlinear deformation characteristics of reinforced concrete beams, the theoretical calculation value of beam deflection was given in this paper based on the assumption of flat section and the principle of virtual work. The theoretically calculated deflection values of ordinary concrete beams and foamed concrete beams are in good agreement with the experimental values under normal use conditions, verifying the rationality and effectiveness of the calculation method. The research results of this paper can be taken as a reference for similar engineering designs.

Flexural strength of Glass fiber reinforced polymer concrete beam with artificial Fine aggregate

Reinforced concrete Structures with usual steel reinforcements pose a serious threat in aggressive climate factors due to the increasingly rapid concern of corrosion. Because of their resistance to corrosion, high strength-to-weight ratios, and ease of handling, Glass Fiber Reinforced Polymer (GFRP) bars are becoming the emerging technology of the future. Another major issue is scarcity of river sand for making concrete. Hence a research was carried out on concrete mix with artificial M sand for partial fragment of river sand and GFRP bars replacing conventional steel reinforcement.Consequently, an attempt was explored on flexural strength of M40 grade concrete beam reinforced with GFRP (glass fiber-reinforced polymer) reinforcement and mixed with artificial sand or M sand as fine aggregate. A comparative analysis was made between tensile strength of GFRP reinforcement and conventional reinforcement, flexural behaviour of rectangular conventional concrete beam and concrete beam using M sand reinforced with GFRP reinforcement. From the test result, it was found that the beam with combination of GFRP and M sand is achieving 12% higher flexural strength than ordinary conventional concrete beam and withstanding higher deflection.

Flexural behavior of reinforced geopolymer concrete beams with recycled coarse aggregates

Geopolymer recycled aggregate concrete (GRAC) is a new green construction material, which uses geopolymer as the binder and recycled concrete as aggregates. To compare the flexural performance of GRAC and ordinary recycled aggregate concrete (RAC) beams, static loading tests were conducted on seven GRAC beams and three RAC beams. The effects of the replacement ratio of recycled aggregates (RAs), the replacement patterns, and the reinforcement ratio on the flexural behavior of GRAC beams are evaluated. The test data show that the replacement ratio has no significant effect on the cracking pattern, failure mode, or bending capacity of GRAC beams, but the replacement pattern does have an effect. Under a given replacement ratio, replacing only the larger fraction of natural aggregates (NA) with RA improves the concrete strength and crack resistance of both RAC and GRAC beams, compared to that using same replacement percentage for all fractions. Due to the lower elastic modulus and strength of GRAC prepared in this study, the GRAC beams have lower height of neutral axis and greater deflection than RAC beams at the same load level and possess slightly lower cracking load, bending capacity, and ductility. The bending capacity of GRAC beams can be predicted by the formulas proposed for ordinary reinforced concrete beams in the Chinese code GB50010-2010, ACI 318-11, or BS EN 1992-1-1:2004 codes, but the safety margin is generally lower than that of ordinary reinforced concrete beams.

Flexural performance of reinforced concrete beams made by innovative post-filling coarse aggregate process

Concrete made by post-filling coarse aggregate process could reduce the cement content greatly compared with traditional concrete placement method. Thus, it not only lowers the production cost of concrete through lower usage of cement but also reduces the CO2 emissions to the environment. In this paper, the compressive and tensile strength of post-filling coarse aggregate concrete with different post-filling ratios (PFRs) (0%, 10%, 15%, 20%, 25%, 30%) and concrete strength grades (C30, C40, C50) were first studied. Then the flexural performance of nineteen concrete beams with different concrete strength, post-filling ratios, reinforcement ratios was investigated. The experimental results showed that the compressive strength and elastic modulus of the post-filling coarse aggregate concrete increased with the increase of the post-filling ratio of coarse aggregate, reaching the peak value at the filling ratio of 20%. It indicated that there was no obvious difference in the failure mode as well as middle-span deflections between post-filling coarse aggregate concrete (PFCC) beams and ordinary concrete (OC) beams. Ductile failure was observed for all nineteen specimens. Results demonstrated that the cracking load, yield load, and ultimate load of the post-filling coarse aggregate concrete beams all reached the peak value at the post-filling ratio of 20%. In addition, the theoretical predictions of cracking loads and ultimate load carrying capacities matched the experimental results in satisfactory agreement.

Experimental Study on Seismic Behaviour of Angle Steel Connections with Concealed Corbel of Fully Assembled Frame Beam and Column

A method of “concealed corbel angle steel and bolt” is proposed to connect beams and columns of assembled frame. To study the seismic performance of the connection is designed an ordinary concrete beam specimen and three in the form of assembly connection specimens. The hysteretic curve, skeleton curve and ductility coefficient of cast-in-place specimen and angle steel connection specimen with concealed corbel are analysed by low cycle repeated load test. The influence of the angle steel thickness and the additional rib on the specimen in the assembly connection scheme is discussed. The test results show that: compared with ordinary cast-in-place concrete specimens, the assembly connection specimens have higher bearing capacity under the action of low-cycle reciprocating load. The hysteretic curves of the assembly and connection specimens were relatively full, and the displacement ductility coefficient was greater than 3.0, indicating that the assembly and connection specimens had good ductility. Increasing the thickness of the Angle steel and the additional ribs can improve the bearing capacity of the specimens. In particular, increasing the thickness of the Angle steel can significantly improve the bearing capacity of the specimens assembled and connected and reduce the damage of dark corbel before loading.

Feasibility Analysis of Replacing Partial Longitudinal Steel Bars with Layered Steel Fibers

In order to study the feasibility of replacing part of longitudinal reinforcement with layered steel fibers, four-point bending tests were carried out on a group of ordinary recycled concrete beam and three groups of layered steel fibers recycled concrete beams. The cracking moment and ultimate moment, ductility and energy dissipation, deformation and deflection of the experimental groups with lower contents of steel fibers and higher reinforcement ratio and the experimental groups with lower reinforcement ratio and higher contents of steel fibers were compared and analyzed. The results show that it is feasible to replace some longitudinal bars with layered steel fibers when considering cracking moment, ultimate moment, elastic stage and working stage with cracks of load-deflection curve, while it is not feasible when considering ductility, energy dissipation and post-yield stage of load-deflection curve.

Experimental and Numerical Analysis of High-Strength Concrete Beams Including Steel Fibers and Large-Particle Recycled Coarse Aggregates

In order to study the performances of high-strength concrete beams including steel fibers and large-particle recycled aggregates, four different beams have been designed, tested experimentally and simulated numerically. As varying parameters, the replacement rates of recycled coarse aggregates and CFRP (carbon fiber reinforced polymer) sheets have been considered. The failure mode of these beams, related load deflection curves, stirrup strain and shear capacity have been determined through monotonic loading tests. The simulations have been conducted using the ABAQUS finite element software. The results show that the shear failure mode of recycled concrete beams is similar to that of ordinary concrete beams. The shear carrying capacity of high-strength concrete beams including steel fibers and large-particle recycled coarse aggregates grows with an increase in the replacement rate of recycled coarse aggregates. Reinforcement with CFRP sheets can significantly improve the beam’s shear carrying capacity and overall resistance to deformation.

Experimental Study on the Fracture Parameters of Concrete.

This study aimed to determine the influence of the volume fraction of steel fibers on the fracture parameters of concrete. Fifty notched steel-fiber-reinforced concrete (SFRC) beams and ordinary concrete beams with 100 mm × 100 mm × 515 mm were cast and tested via a three-point bending test. Among them, the type of steel fiber was the milling type (MF), and the volume fraction of steel fiber added was 0%, 0.5%, 1%, 1.5% and 2%, respectively. The effects of the steel fiber volume fraction (VF) on the critical stress intensity factor (KIC), fracture energy (GF), the deflection at failure(δ0), the critical crack mouth opening displacement (CMODC) and the critical crack tip opening displacement (CTODC) were studied. Through the analysis of test phenomena and test data such as the load-deflection (P-δ) curve, load-crack mouth opening displacement (P-CMOD) curve and load-crack tip opening displacement (P-CTOD) curve, the following conclusions are drawn: with the increase of the steel fiber volume fraction, some fracture parameters increase gradually and maintain a certain linear growth. The gain ratio of the fracture parameters increases significantly, and the gain effect is obvious. Through this law of growth, the experimental statistical formulas of fracture energy and the critical stress intensity factor are summarized.

Strengthening and Repair of Self Compacting Concrete Beams( Dept.C )

While there is abundant research information on ordinary concrete beams strengthening or repairing with FRP, relatively little data on the behavior of self-consolidating concrete (SCC) is available. Carbon Fiber Reinforced Polymers laminates (CFRP) was investigated for strengthening and repairing SCC and high strength self compacting concrete (HSSCC) beams subjected to one midpoint load in in order to compared to beams made of normal concrete (NC) and normal high strength self compacting concrete (NHSSCC) at the same conditions respectively. To demonstrate the concept, this paper presents results of a laboratory investigation of 24 beams (150x200x1600 mm) on the behavior of self compacting concrete strengthening and repairing with one layer of CFRP laminate and subjected to one midpoint load, including the effect of using 8 different mixes to study the effect of mix proportions on rapped CFRP beams behavior. Test results showed that the addition of CFRP laminate to the tension surface of the beams demonstrated significantly improvement in stiffness and ultimate load capacity of beams. The response of control and strengthened beams were compared and evaluated by experimental and theoretical calculations. It was observed that ductility indexes of SCC and HSSCC beams were more efficient than NC and NHSC respectively. Load carrying capacity of control, strengthening and repairing self compacting concrete beams was closed to traditional concrete beams (about 90-95%). The paper also highlighted the crack pattern of all cases of beams which indicated more distribution and smaller crack amplitude for strengthened beams with respected to the control beams.

Experimental Study on Carbon Fiber Concrete Beams

The influence of the length of carbon fiber on the deflection and strain of carbon fiber concrete beams was studied by testing the flexural capacity of the normal section of four carbon fiber concrete beams. The results show that the length of carbon fiber has a certain influence on the strength of reinforced concrete beams. The failure deflection of fiber concrete beams increases with the increase of the length of carbon fiber. Carbon fiber can improve the brittle failure of concrete beams. No matter how long the carbon fiber is, the cracking load and ultimate load of CFRC beam are not different from that of ordinary concrete beam.

Study on shear behavior of reinforced coral aggregate concrete beam

Reinforced coral aggregate concrete beam and reinforced ordinary aggregate concrete beam with different concrete type, concrete strength, and steel type were designed in this study to investigate their shear behavior. The shear behavior of reinforced coral aggregate concrete beam was tested, the failure mode and deflection behavior were studied, and the calculating model for the ultimate shear capacity ( Vcs) of reinforced coral aggregate concrete beam was proposed. Results showed that the failure mode of reinforced ordinary aggregate concrete beam and reinforced coral aggregate concrete beam were basically the same. As the concrete strength increases, the normal section cracking load ( Vcr), inclined section Vcr, and Vcs of reinforced coral aggregate concrete beam increased gradually. Furthermore, Vcr and Vcs of reinforced coral aggregate concrete beam were as follows: 316 stainless steel > common steel > zinc-chromium coated steel > new organic coated steel. For the coral aggregate concrete structure in ocean engineering, in order to prolong its service life, the use of new organic coated steel was suggested. At the same time, the influence of high-strength coral aggregate concrete and stirrup corrosion was comprehensively considered and the calculation model for the Vcs of reinforced coral aggregate concrete beam was presented and was then verified.

Effect of waste rubber particles on the mechanical performance and deformation properties of epoxy concrete for repair

The article conducts the compressive, flexural, spilt, deflection and strain experiments on epoxy concrete with added fine, medium and coarse rubber particles respectively at 5%, 10%, 15%, 20% and 25%. Medium sized rubber particle is selected for further study in a composite beam test in which rubber epoxy concrete serves as a repair material to “glue” two ordinary concrete short beams, as well as a bond tensile strength test. A deformation compatibility parameter is introduced to measure two strains for indicting the composite beam’s deformability. It is found that, meanwhile keeping an adequate interfacial strength needed as a repair material, rubber in epoxy concrete help increase deformability, which is beneficial to compensate the rigidness of epoxy concrete.

Fractal Characterization of Non-Uniform Corrosion of Steel Bars in Concrete Beams after Accelerated depassivation and Seven-Year Natural Corrosion.

In this work, the non-uniform corrosion characteristics of steel bars in stressed reinforced concrete beams after accelerated depassivation and seven-year outdoor natural corrosion is analyzed using fractal theory. 3D laser scanning and 3D reconstruction technology are applied to collect the cross-sectional area along the steel bars and obtain the corrosion curves. The non-uniformity of corrosion is analyzed by fractal dimensions which is calculated by variation method. The results indicate that the initial loading level and loading zone have some influence on non-uniform characteristics of steel bars. For an ordinary concrete beam, the increase of load can cause a reduction of fractal dimension of corrosion curves by 5%, which indicates the non-uniformity of corrosion will increase with the increase of load level. The fractal dimension in the bending zone is lower than that in the tension–shear zone, which indicates that corrosion is more non-uniform in bending zone. However, the loading level and loading zone have a slight influence on corrosion level, and the maximum difference of corrosion level caused by load is merely 0.23%. Furthermore, the corrosion level increases with the decrease of fractal dimension, suggesting that the non-uniformity of corrosion increases with the growth of corrosion level. The incorporation of slag powder can help reduce the non-uniformity of corrosion, but the influence on reduction of the corrosion level is about 0.25%. For concrete structures under marine environment, application of slag powder is a good method to slow down the corrosion and reduce the non-uniformity of corrosion.

Research on Design of Vibration Comfort of Large Span Roof Based on structural scheme

This article focuses on the layout of three types of large-span floor slabs with ordinary concrete ribbed beams, restressed beams, and box-shaped slabs combined with specific engineering projects. By using finite element software, the vibration comfort of the three kinds of structural schemes was evaluated from the aspects of structural dynamic characteristics, jump load response and so on. The analysis results show that the common ribbed beam system can meet the vibration comfort requirement of the slab under reasonable plane layout. Restressed beam system has little effect on the frequency of natural vibration of the floor slab. The box beam system can increase the natural vibration frequency of the vertical vibration of the floor and improve the vertical vibration performance of the floor.

Experimental Study on Cracking Resistance of Recycled Concrete Beams Reinforced with Hybrid Polyacrylonitrile and Recycled Fibers

In order to improve the comprehensive performance of the recycled concrete, reduce the waste of natural resources and environmental pollution, fly ash and recycled concrete aggregates were mixed into the reference concrete group RC0 to partially replace cement and natural coarse aggregates, respectively. The basic mechanical properties of five groups of recycled concrete reinforced with recycled fibers and organic fibers in different combinations were analyzed. In addition, the cracking resistance, failure process and bearing capacity of each group of recycled concrete beams were also studied. The test results and corresponding analysis showed that: the damage process of concrete beams reinforced with hybrid polyacrylonitrile fibers and recycled fibers was basically the same as that of ordinary concrete beams; the development of cracks is more effectively prevented with the increase of the proportion of waste fibers; the use of recycled waste fibers and polyacrylonitrile can significantly improve cracking resistance, deformation resistance, and load carrying capacity of recycled concrete beams.

Bond Behavior of Tension Bar at Lap Splice of SCC Beam

This paper investigates the bond strength of tension lap splice in the ordinary concrete (OC)beam and self-compacted concrete (SCC) beam. A total of six beam specimens were cast for thebending test. Results indicate that the SCC beam and OC beam present similar bond strength at thelap splice of tension bar. Current code for the tension lap splice is available for the SCC beam. Bothof the SCC and OC beams with transverse stirrups could have ductile flexural behavior in the regionof tension lap splicer. Only minor spalling between reinforcing steel and concrete was found underservice loading, such that the corrosion resistance of the tension lap splice in the SCC and OC beamscould be preserved.

Bending mechanical properties research on prestressed airport concrete pavements

To prevent airport pavements from suffering fatigue failure before the end of designed life and to construct high‐grade airport concrete pavements quickly, this study has developed a method which applies the prestressed concrete to airport pavements. A three‐point bending loading scheme has been designed to conduct the bending, flexural strength, and fatigue tests on 96 concrete beams. The results showed that, compared with ordinary concrete beams, the resistance of prestressed concrete beam to bending deformation was greatly enhanced. For the beams subjected to the vertical load with increasing prestressing force, however, the deflection of the beams was decreased by a minor degree while both of their tensile stress and tensile stress area showed a sharp decrease. Moreover, the flexural strength of the concrete showed an evident increased with verified degrees while both the numbers and the width of cracks generated at the bottom of specimens decreased significantly. The average fatigue life of the prestressed concrete beams was extended 3 to 6 times longer than that of the ordinary concrete beams depending on the increasing levels of prestressing force. In general, the bending fatigue life of the prestressed concrete beams follows the two‐parameter Weibull distribution with a correlation coefficient greater than 0.96. Based on this Weibull distribution, a double‐logarithmic fatigue equation among three parameters, that is, the survival rate P, the stress level S, and the fatigue life N has been developed.

Application of HPFRCC on Coupling Beams with Bundled Diagonal Reinforcement

The objective of this study was to develop simple reinforcement details for diagonally reinforced coupling beams; reducing transverse steel by use of high-performance fiber-reinforced cementitious composites (HPFRCCs) and bundling diagonal bars are explored. Four coupling beam specimens with length-to-depth aspect ratios of 2.0 or 3.5 were fabricated and tested under cyclic lateral displacements. The test results revealed that HPFRCC coupling beams with bundled diagonal bars and widely spaced transverse reinforcement (one-half the amount of reinforcement required by current seismic codes.) exhibited excellent seismic performance compared with ordinary concrete coupling beams to bundled diagonal bars and code-required transverse reinforcement.

Cyclic Behavior of HPFRCC Coupling Beams with Bundled Diagonal Bars

Coupled shear walls are efficient in resisting lateral forces induced by winds and earthquakes. However, it is difficult to construct coupled shear walls particularly because current design codes require complex reinforcing details within coupling beams. The objective of this study was to develop simple reinforcement details for diagonally reinforced coupling beams; reducing transverse steel by use of high-performance fiber-reinforced cementitious composites (HPFRCCs) and bundling diagonal bars are explored. Four coupling beam specimens with length-to-depth aspect ratios of 2.0 or 3.5 were fabricated and tested under cyclic lateral displacements. The test results revealed that HPFRCC coupling beams with bundled diagonal bars and widely spaced transverse reinforcement (one-half the amount of reinforcement required by current seismic codes) exhibited excellent seismic performance compared with ordinary concrete coupling beams having code-required distributed diagonal reinforcement and transverse reinforcement.