Flexural Strength Of Beams Research Articles

Bending Behavior of Concrete Beams Using Geotextiles in Tensile Areas

Geotextile is made of permeable geosynthetic. Geotextile s are formed from synthetic fibers based on polymers that have high mechanical properties in tensile strength, trapezoidal tearing strength, and puncture resistance. Therefore, researchers want to increase the use of Geotextile as an added material in the tensile area of concrete blocks. The test objects used are 9 pieces of 150mm×150mm×600mm beams. The results of the research were that the addition of woven Geotextile s and non-woven Geotextile s on concrete blocks increased, for woven Geotextile s by 21.593% of beams without using Geotextile s and non-woven Geotextile s of 17.058% of beams without using Geotextile s. So the use of Geotextile s on concrete blocks can improve quality because the value of the flexural strength of beams using Geotextile s is greater than beams without using Geotextiles.

A Study on the Effect of Hollow Tubular Flange Sections on the Behavior of Cold-Formed Steel Built-Up Beams

This paper deals with a study conducted on flexural behavior of cold-formed steel built-up I-beams with hollow tubular flange sections. There were two types of test sections, namely, built-up sections that were assembled with either stiffened or unstiffened channels coupling back-to-back at the web and a hollow tubular rectangular flange at the top and bottom of the web to form built-up I-beam. The flexural behavior along with the strength and failure modes of the built-up sections was examined using the four-point loading system. Nonlinear finite element (FE) models were formulated and validated with the experimental test results. It was observed that the developed FE models had precisely predicted the behavior of built-up I-beams. Further, the verified FE models were used to conduct a detailed parametric study on cold-formed steel built-up beam sections with respect to thickness, depth, and yield stress of the material. The flexural strength of the beams was designed using the direct strength method as specified in American Iron and Steel Institute (AISI) for the design of cold-formed steel structural members and was compared with the experimental results and the failure loads predicted from FE models. Since the results were not conservative, a new customized design equation had been mooted and delineated in the study for determining the flexural strength of cold-formed steel built-up beams with hollow tubular flange sections.

Empirical relationships between compressive and flexural strength of concrete containing recycled asphalt material for pavement applications using different specimen configurations

The flexural strength of pavement concrete is generally deduced by testing beams or by applying empirical equations. In this investigation, concrete mixtures were manufactured, incorporating 0, 20, 50 and 100% Reclaimed Asphalt Pavement (RAP), by weight, as a replacement for natural aggregates. The compressive strength was measured using cubic specimens and the flexural strength was measured for three types of specimens; beam, semicircular (SCB) and modified beam. This study proposes logarithmic and power equations that allow the estimation of the flexural strength of a concrete mix that incorporates RAP as a function of its compressive strength. Linear or power models are proposed to predict beam flexural strength from SCB specimens and a logarithmic model for modified beam specimens. Statistical analyses show that the proposed prediction models can be considered sufficiently accurate and their use is justified.

A flexural design methodology for composite heterogeneous and homogeneous UHPC bridge beams prestressed with bonded strands

A non-iterative flexural design methodology for composite, heterogeneous, and homogeneous ultra-high performance concrete (UHPC) bridge beams prestressed with bonded strands is presented. One key feature of the proposed methodology is the development of closed-form equations for calculating strain in concrete at the most extreme compression fiber at the ultimate limit state, εc, as a function of various parameters. Separate formulations for predicting εc are provided for homogeneous and composite cross-sections. The predicted concrete strain, together with the maximum usable tensile strain for UHPC, εtu, at the most extreme tension fiber are used to calculate cross-sectional curvature and the distribution of strains and stresses. Force equilibrium is then used to determine the depth to the neutral axis and the nominal moment capacity of the beam. The flexural failure mode for the majority of beams considered is a fiber tension controlled failure. From a beam flexural strength perspective, the compressive strength of the deck or top flange for composite and heterogeneous beams, respectively, does not need to exceed 28 MPa. Any excess compressive strength will remain either unutilized or will result in marginal or negligible increases in moment capacities. The magnitude of the cracking strength of UHPC plays an important role in the contribution of UHPC to the moment capacity of the beam and determines whether this contribution is higher or smaller than that provided by the prestressing strands. The strand stress at the ultimate limit state, fps, varied from 1688 MPa to 1743 MPa and was past the linear elastic branch of the assumed stress-strain curve. The parameter that had the highest influence on fps was εtu. The proposed methodology is validated using test data as well as results from validated nonlinear finite element models and strain compatibility analysis.

Improvement of Flexural and Shear Strength of RC Beam Reinforced by Glass Fiber-Reinforced Polyurea (GFRPU)

The Glass Fiber-Reinforced Polyurea (GFRPU) which is the composite by the elastic polyurea and milled glass fiber have the mechanical characteristics to enhance tensile strength as well as ductility. It must be reinforcement materials in repair and retrofit applications for strengthening structural capacity and has a merit of simple construction of spray coating to prevent the debonding from concrete surfaces unlike the existing strengthening methods such as Fiber-reinforced polymer (FRP) or steel plate. This work compares the improvement degree in load-carrying capacity as well as flexural ductility of RC beam reinforced externally by polyurea or GFRPU. Seven specimens of four reinforced concrete (RC) beams for evaluating flexure-resisting capacity and three beams for shear-strengthening capacity are tested. The mechanical behavior and characteristics of the specimens reinforced by local and global reinforcement method classified according to strengthened area are compared. It is shown that the polyurea- or GFRPU- reinforcement leads to the enhancement in the load-resisting capacity up to 8~11% and flexural ductility within the range of 8.41~13.9 times of the non-reinforced beam. And the global reinforcement method has more improvement in the shear- and flexure-resisting capacity than the local method. It is also observed that the GFRPU can be more effectively utilized in enhancing the structural shear-resisting capacity than the flexure-carrying capacity. Doi: 10.28991/cej-2021-03091662 Full Text: PDF

Microbial induced calcium carbonate precipitation study using Bacillus subtilis with application to self-healing concrete preparation and characterization

This study aimed to develop novel bacteria-based self-healing concrete by microbial induced calcium carbonate precipitation mechanism. A group of spore-forming bacterium related with gen Bacillus subtilis were selected for cultivation at elevated pH solution. The derived alkali-resistant Bacillus subtilis M9 was applied for biomineralization test whereas the precipitate mineral was calcium carbonate in calcite phase according to X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) results. With B. subtilis M9 as the healing agent, the self-healing concrete beam specimens were then prepared by incorporating polyvinyl alcohol fibers. Air-entraining agent was utilized to yield micro pores in cement paste mixture to provide ecological niches for microbe. 3-point-bending test was conducted to form 0.3-mm-width cracks on the beam bottom. After 28 days curing, the micro cracks were autonomously healed with calcium carbonate precipitation fillings due to the bacteria metabolic activity. The sequent SEM tests implied that calcite is the dominant mineral phase with some bacterial imprints on the crystal surface. Furthermore, flexural strength of the sealed beam subjected to repeated bending was enhanced by about 14% compared to residual flexural strength. The beam flexural strength recover was realized by remediation of the cracks in matrix as well as repairing of fiber–matrix interface bond.

Behavioral Investigation of Reinforced Concrete T-Beams with Distributed Reinforcement in the Tension Flange

Current design codes and specifications allow for part of the bonded flexure tension reinforcement to be distributed over an effective flange width when the T-beams' flanges are in tension. This study presents an experimental and numerical investigation on the reinforced concrete flanged section's flexural behavior when reinforcement in the tension flange is laterally distributed. To achieve the goals of the study, numerical analysis using the finite element method was conducted on discretized flanged beam models validated via experimentally tested T-beam specimen. Parametric study was performed to investigate the effect of different parameters on the T-beams flexural behavior. The study revealed that a significant reduction in the beam flexural strength with increasing deflection is encountered as a sizable percentage of reinforcement is distributed over the wider flange width. The study recommended that not more than 33% of the tension reinforcement may be distributed over an effective flange width not wider than ℓn/10. This result confirms and agrees well the ACI 318 limit on the effective width to be less than ℓn/10.

Flexural strength of concrete-galvalume composite beam under elevated temperatures

In this paper, the elevated temperature on a concrete-galvalume composite beam's flexural strength based on the numerical and experimental methods is investigated. The strategy is to perform modeling and simulation of the flexural test based on finite element method (FEM) at room temperature and validate its results by using experiments at the same temperature. With material constants and boundary conditions set-up provided from the validation, we model and simulate the same flexural tests for the composite at higher temperatures. The study concludes that the flexural strength of the beam decreases at higher temperature. Additionally, it was shown that cracking moments is very sensitive to the temperature fluctuation and the failure modes are sensitive with respect to the elevated temperature.

Internal curing of recycled aggregates concrete

Curing is essential to achieve durable concrete. Internal curing is defined as water provision inside concrete to achieve curing internally instead or in addition to the commonly used external water spraying. Generally, internal curing results in reducing water consumption, improving concrete homogeneity and reducing surface cracking. In this work, recycled concrete aggregates is utilized as the medium for water supplements to provide internal curing, due to its high water absorption compared to virgin aggregates. Different percentages of locally available recycled coarse and fine aggregates were utilized in designing different concrete mixes with water/cement ratios of 0.4 and 0.6. Resulting, concrete mixes were tested for their workability, unit weight, air content, compressive strength, flexural strength of beams and slabs, shrinkage and freeze and thaw resistance. It was found that the use of recycled aggregates in general slightly reduce mechanical properties due to its inferior properties. Its use, however, for internal curing improve properties such as delay of cracking, freeze-thaw resistance, and dynamic modulus of elasticity. It was recommended, therefore, to use 50% recycled aggregates for internal curing as this will improve properties in addition to the well-known sustainability benefits of both internal curing and utilization of recycled materials that are also discussed in the paper.

Experimental and Analytical Study on Behaviour of Flexural Beams using Blast Furnace Slag

The study presents the experimental and analytical behavior of flexural beams by replacing coarse aggregate with that of blast furnace slag. The basic objective of this study was to identify alternative source of good quality aggregate because the natural stone quarries are depleting very fast due to rapid pace of construction activities in India .The effect of replacing natural coarse aggregate by slag on the compressive strength of cubes, split tensile strength of cylinders and flexural strength of beams are evaluated in this study. Use of slag – a waste industrial by product of iron and steel production provides great opportunity to utilize it as an alternative to normally available aggregate. The test results of concrete were obtained by adding slag to coarse aggregate as a replacement of stone aggregate in various percentages of 0%, 20%, 40%, 60% and 100%. All specimens were cured for 28 days before testing. From the study it has been observed that the blast furnace slag aggregate could be a good replacement of stone aggregate.

Sandstone cutting waste as partial replacement of fine aggregates in concrete: A mechanical strength perspective

Construction activities are progressing rapidly across the globe due to the demand for concrete and its constituent materials especially fine and coarse aggregates. The large quantity of concrete production is causing an acute shortage of natural sand. Nowadays researchers are finding ways by exploring better alternatives of river sand in the form of manufactured sand as well as crushed rock sand. Sandstone cutting waste are sand-sized grains of mineral obtained from sedimentary rocks. This research aims to find the mechanical properties of concrete containing sandstone cutting waste collected from Bayana in Rajasthan state in India with the replacement of natural river sand. The study was carried out by opting three different w/c ratios i.e. 0.35, 0.40 & 0.45 and concrete mixes were designed as per IS10262: 2009. The effect of sandstone cutting waste was investigated both for fresh concrete attributes i.e. slump & density as well as hardened Concrete attributes i.e. compressive strength of cubes, the flexural strength of beams & split tensile strength of cylinders along with abrasion resistance in concrete cubes along with microstructural studies of hardened concrete by scanning electron microscope(SEM), optical microscope(OM). A comparison study was also carried out with control mix concrete having 0% sandstone cutting waste and further river sand was replaced with sandstone cutting waste using replacement level of 10%, 20%, 30%, 40%, 50% & 100% along with optimum levels in between. It was observed that sandstone cutting waste can be utilized in the production of structural concrete as partial replacement of river sand up to 10% replacement level using w/c ratio of 0.35 & up to 30% replacement level using w/c ratio of 0.4 & 0.45.

The Corrosion Probability and Flexural Strength of an RC Beam under Chloride Ingress Considering the Randomness of Temperature and Humidity.

The load capacity of reinforced concrete structure will decrease by chloride ingress in coastal region. In this paper, the corrosion probability and flexural strength of a typical reinforced concrete beam design under the influence of temperature and humidity was obtained by the Monte Carlo method. The relationship between flexural strength, temperature, relative humidity, and geometric parameters was established. The annual average temperature and relative humidity were treated as random variables together with the geometric size and concrete compressive strength. The corrosion probability and flexural strength in a wave splashing zone, coastal atmospheric zone, and offshore atmospheric zone were calculated. The results show that the corrosion probabilities of the three regions are obviously different. When the standard deviation of temperature is less than 1.5 °C, the temperature can be treated as a constant in the calculation of the concrete cracking probability in the wave splashing zone. A binary logistic regression formula was given to predict whether the randomness of temperature and humidity should be considered in the offshore atmospheric zone. When the standard deviation of the temperature is less than 1 °C, the temperature randomness has no significant effect on the flexural strength of beams in the wave splashing zone. The flexural strength distribution conforms to the normal distribution in the early stage of service and the Weibull distribution after concrete cracking.

Numerical Evaluation of the Steel Plate Energy Absorption Device (SPEAD) for Seismic Strengthening of RC Frame Structures

In this paper, a new strengthening technique is proposed: the Steel Plate Energy Absorption Device (SPEAD) system, which is intended to increase the flexural strength of beam and column members in RC frame structures. In this way, while permitting calibration of the strength increase in the beam to comply with the strength hierarchy criteria needed for a proper seismic behaviour it can provide additional energy absorption. A numerical evaluation of the SPEAD system is carried out by means of a refined 3D model built with an advanced nonlinear finite element program. The SPEAD system has been virtually applied (through finite element analyses) to an RC external beam–column joint, representative of typical existing RC buildings, and the numerical results are compared to those of a specimen that was not upgraded and subjected to the same experimental tests. The SPEAD upgraded model provided a strength increment of about 50% with also a strong reduction of bond-slip effects in the joint panel region. This latter, in turn, provided a beneficial increase of ductility. Based on the positive results from numerical simulations, a design method is also provided.

Experimental study of deflection of steel fibre reinforced concrete beams: comparison of different design codes

The flexural behaviour of steel fibres reinforced concrete (SFRC) beams is investigated using digital image correlation (DIC) technique. The deflection and curvature of the tested RC beams have been analysed by DIC technique. The experimental results in terms of deflection and other results found in the literature are compared against the predicted values using the design codes (ACI318, Eurocode 2, Russian code SP 52-101 and CAN/CSA-S806). The outcome of this study indicates that the flexural strength of beams reinforced with steel fibres is 1.15–1.25 higher than that of beams without steel fibres. Also, the deflections of SFRC beams are 15–30% higher than those of beams without steel fibres. Moreover, this study shows a good agreement between the theoretical deflections calculated by design codes and the experimental deflections for SFRC beams given by the present results. On the other hand, the codes’ predictions are found to underestimate the deflections, with an average error about 1.31 for beams without steel fibres. When using a reduced modulus Ecr equals to Ec/1.4 for high strength fibre reinforced concrete (HSFRC) beams, the ACI318 and Eurocode 2 results are found to safely predict the deflections up to load equal to 75% of the ultimate load for the HSFRC beams.

Effects of tensile reinforcing steel ratio and Near-Surface-Mounted bar development length on the structural behavior of strengthened RC beams

Abstract The use of near-surface mounted (NSM) Glass fiber reinforced polymer (GFRP) bars is one of the most popular and effective techniques for strengthening reinforced concrete (RC) beams. This paper presents an experimental research program to study the flexural strengthening of RC beams comparing two areas of bottom tensile reinforcing steel and three development lengths of NSM GFRP bars. The beam test results indicated that the beam flexural strength increased up to 110% and 58% for the cases of low and high tensile reinforcing steel ratios, respectively. The effect of the tensile reinforcing steel area on the critical value of the development length of NSM GFRP bars was also investigated. It was found that decreasing the axial stiffness ratio, reduced the strengthening efficiency and the critical development length of the NSM GFRP bars. Finally, a 3D Finite Element (FE) model using ANSYS was constructed and was validated using the experimental results. Good agreement was seen between experimental and FE model results.

Impact of Reinforcing Bar Characteristics on Flexural Strength of Beams

Reinforced concrete (RC) frame members under seismic loading are likely to experience large inelastic deformation, therefore, sufficient ductility Brittle mode enhancements must be avoided to enhance the potential for energy dissipation. These components are satisfied and satisfied after the earthquake. The event depends to a large extent on the nature of the materials used in its manufacture. That is, steel and concrete. This research is concerned with Strengthen steel in bending behavior until failure. When the capacity design for the reinforced concrete buildings or structures is sufficient real capacity does not exceed the actual design capabilities. In addition, RC member is a large inflexible deformation is expected to produce sufficient seismic dissipation. Because of the ability to bend. The post-productivity performance of RC members is mainly controlled by steel rods, which have some special characteristics. Performance requirements strength of yield, strength of tension and elasticity the steel manufacturing method. Thirty years of bending test Reinforced concrete beam was observed using carefully controlled steel bars. The reliable bending behavior and YS and UTS values must be within a narrow range around the value used design Members. If these values are greater than the specified value, they may cause a crisp cut failure instead of more bending and perfect bending failure modes.

Flexural Performance Evaluation of Novel Wide Long-Span Composite Beams Used to Construct Lower Parking Structures

Efficient parking structures are urgently required in Korea. The design of parking structures more than 8 m in height is difficult because both fire and seismic resistance must be considered. Existing designs are uneconomical and conservative. However, the design of parking structures less than 8 m in height is relatively simple and there are few restrictions to the construction. It is essential to optimize the design of parking structures less than 8 m in height. Here, we describe novel wide long-span composite beams that reduce the story height of low parking structures. The flexural capacity of seven of the beams was evaluated; all beams were loaded at two points prior to monotonic bending tests. We also performed finite element analysis (FEA) based on the material properties of the test specimens, and compared the results to those of the structural tests. The flexural strength of the wide composite steel beams increased by approximately 20% as the steel thickness rose by 3 mm, from 6 to 9 mm. The rebar shape (triangular or rectangular) did not affect flexural strength. The flexural strength of beams without rebar was 10% less than that of beams with rebar. The FEA and test results were in good agreement. The section plastic moments were free from global and local instability.

Exploratory study on the utilization of recycled wood as raw material for cross laminated timber

Cross-Laminated Timber (CLT) has been gaining interest in recent years as an attractive and environmental-friendly building material. As such, CLT has been used for structural components in building constructions such as apartments, commercial buildings, or offices. CLT predominantly uses newly harvested lumber as a raw material. In this study, however, CLT fabricated using recycled wood was explored for possible utilization in wood structures. The recycled wood was obtained from wooden boxes, wooden pallets, and scrap wood from lumber suppliers, and their mechanical properties were tested. The average tension-parallel-to-grain strength of these recycled woods was 52.2 MPa, while their average compression-perpendicular-to-grain and compression-parallel-to-grain strength were 20.6 and 4.0 MPa, respectively. Four CLT beams of 2 m-length, 100 mm-width, and 130 mm-depth glued with epoxy adhesive were tested to measure their flexural strengths. A set of two CLT beams was loaded on upright and lying positions, and their average flexural strengths were 8.1 and 7.6 MPa, respectively. The effects of lamina lap splices and adhesives on CLT beam flexural strength were studied. Apparently, adding several variations of lap-splices and adhesives has marginal impact on CLT beam flexural strength.

Effect of Shear Reinforcement on Flexural Strengths of Normal Weight and Palm-Kernel Shell Reinforced Concrete Beams

The focus of this research is to investigate the effect of shear reinforcement on flexural capacities of reinforced Normal Weight Concrete (NWC) and Palm Kernel Shell Concrete (PKSC) beams. Ten beams were cast: five from PKSC and five from NWC. The beams were with shear reinforcement spacing of 50 mm, 100 mm, 150 mm, 200 mm and without shear reinforcement respectively. The beams were loaded with a point load at beam centre, and the results showed that the flexural capacity of the beams decreases as the spacing of the shear reinforcements increases. The ultimate loads of PKSC beams were lesser than that of NWC beams by 9.0%, 7.1%, 14.5%, 21 and 26.8% for shear reinforcement spacing of 50 mm, 100 mm, 150 mm, 200 mm and for beam without shear reinforcements respectively. The deflections of the PKSC beams were greater than that of the NWC, hence the PKSC beams had more plastic rotation capacity than the NWC beams. The study shows that reinforced concrete beams produced from 20% partial replacement of crushed aggregate by PKS have the potential of being used for structural purposes in low cost buildings. Keywords: Palm Kernel Shell Concrete, Normal weight concrete, Palm kernel shell, Deflection, Shear reinforcement.

Seismic design of the double-cell accordion-web reduced beam section connection

The Accordion-Web Reduced Beam Section (AW-RBS) connection consists of a corrugated web, replacing the flat web, within a limited area near the column face, which reduces the beam flexural strength and forces the plastic hinge to form in the corrugated zone. This paper presents a seismic design procedure in the framework of the U.S. design standards for a double-cell AW-RBS connection, which consists of two box sections oriented such that an accordion web is formed within a limited area in the beam. The analytical evaluation of the flexural strength of the beam with a corrugated web was first presented. Then, a step-by-step design method was proposed to size the connection. Quasi-static cyclic tests were conducted on two relatively identical specimens including double-cell AW-RBS connections. A detailed numerical model of a connection with deep beams and columns designed in accordance with the proposed design procedure was developed and a nonlinear analysis was performed to investigate the seismic response of the connection and verify the adequacy of the proposed design method for the beam sizes frequently used in steel moment-resisting frames. The results confirmed the satisfactory response of the double-cell AW-RBS connection under cyclic loading. The stable plastic hinge formed in the reduced area of beams as predicted in design and no yielding was observed in the beam-to-column groove weld. The findings of the numerical simulations confirmed that the AW-RBS connection with deep beams and columns could potentially exceed the plastic rotation limit for ductile moment connections without significant instability and strength degradation.