Flexural Strength Of Beams Research Articles

Experimental and analytical investigation of bracket moment connection for precast concrete beam-to-composite column joints

In large industrial buildings, precast prestressed concrete beams and composite columns are appealing to achieve longer span and higher story height, with temporary supporting and scaffolding minimized. To facilitate field erection of moment connection between precast beams and composite columns, a bracket connection transferring beam loads to the column by connecting the beam to a composite bracket attached to the column has been developed. Since precast beams are lap-spliced and integrated with the bracket by concrete engagement at the interfaces, the connection performance depends on beam lap length and load transfer details (i.e., concrete shear keys). In this study, the seismic performance of precast prestressed concrete beam-to-composite column joints with the bracket connection was experimentally and analytically investigated. Cyclic loading tests were conducted on four full-scale specimens with different beam lap lengths and load transfer details. For the specimens with a longer beam lap length, the bracket connection successfully transferred the beam flexural strength to the column with the connection barely damaged. The governing failure mode was beam flexural yield occurring at the bracket end. However, for the specimen with a shorter beam lap length, relative slips at the interfaces of the beam and bracket occurred and thus the strength was governed by the bracket connection. Excellent ductility satisfying the acceptance limit of special moment frame in AISC 341 was achieved in all specimens. The load transfer at the bracket connection through concrete shear keys and other details were further investigated through finite element analysis. Design models to predict the connection strength were proposed and the validity of the models was verified through comparisons with the tests and analyses.

Numerical Study of GFRP-reinforced Concrete Beams with Straight and Hooked-end Bar Lap Splices

Glass fibre-reinforced polymer (GFRP) has been increasingly used as the main reinforcement in concrete structures due to its durability and resistance to corrosion. However, there is a lack of data regarding the bond behaviour of GFRP bars with 180-degree hooked ends used in flexure concrete elements. To investigate the effects of the hooked ends of GFRP bars on the bond strength with concrete, beams reinforced with GFRP bars with straight and hooked-end lap splices at the midspan were modelled using ABAQUS/Standard software. The finite element models were validated using the experimental results of four full-size concrete beams. Two beam specimens had straight-end bars, while the other two had hooked-end bars. Sensitivity analysis was performed to find the proper values for model verification, such as dilation angle and mesh density. According to the outcomes of the parametric study conducted in this research, changing the length of the bar lap splices in the range of 15 to 40 times the bar diameter had a negligible effect on the beam’s overall behaviour. Increasing the number of reinforcing bars from 3 to 5 increased the beam flexural strength by about 33%, whereas increasing the diameter of the bars from 10 to 20 mm doubled the beam strength.

Flexural behavior of circular rubberized concrete-filled double-skin steel tubular beams: Experiments

The study aims to assess the impact of RuC on twelve concrete-filled double-skin steel tube (CFDST) specimens. The research explores key variables, including outer tube slenderness ratio, hollow ratio, and rubber replacement ratio. Rubber particles replace natural aggregates at replacement ratios (ρνr) of 0%, 15%, and 30% by mass. The experimental findings are comprehensively discussed, encompassing member flexural capacity, confinement effects, ductility, energy dissipation, and failure mechanisms. The findings reveal that replacing normal concrete (NC) with RuC leads to a reduction in beam flexural strength ranging from 5.0% to 18.1%, depending on ρνr and outer tube diameter. In contrast, RuC members exhibit an increase of up to 70% in ductility and 27.7% in energy dissipation compared to members with NC, depending on rubber content. Increasing the outer tube thickness proves to be an effective method for mitigating strength reduction due to rubber replacement. Specifically, elevating the outer tube thickness from 3.6 mm to 4.5 mm results in strength enhancements of 17.0%, 19.0%, and 23.7% for beams with NC, 15%RuC, and 30%RuC, respectively. Furthermore, the results are applied to assess existing design models and to suggest modifications that offer improved strength estimations for a broad spectrum of rubber replacement ratios.

Hooking Effect on Flexural Strength and Toughness of Steel Fiber-Reinforced Concrete Beams

Hooking Effect on Flexural Strength and Toughness of Steel Fiber-Reinforced Concrete Beams

The comparative study of epoxy and bacterial injections for cracked concrete beam flexural strength

Cracks in concrete beams can significantly affect the performance of reinforced structures. To repair cracks in concrete, Traditional crack repair methods typically involve epoxy injection, but studies have suggested that epoxy may not fully restore the original strength. Therefore, concrete structure repair requires the development of new and more efficient materials. This study focuses on investigating the potential of Bacillus megaterium, a bacterium known for its self-healing properties in concrete. This bacterium has the capability to precipitate minerals like calcium carbonate, which can fill the cracks and increase the strength of concrete. Testing is carried out on reinforced concrete beams with existing cracks, sized at 100 mm x 100 mm x 500 mm. The specimens are divided into two groups, one repaired with epoxy injection and the other with bacterial injection, with varying additions of 10% and 15%. The research results show that the injection process with the addition of 15% bacteria is able to restore approximately 99.72% of the initial strength of the concrete beams. The results of this research contribute to the development of improved repair techniques that can restore the flexural strength of cracked concrete beams and extend the service life of concrete structures.

Effects of Mud Content on the Setting Time and Mechanical Properties of Alkali-Activated Slag Mortar.

High mud content in the sand has a negative impact on cement mortar but there is little research on Alkali-activated slag (AAS) mortar. In order to explore the impacts of mud content in the sand on the performance of AAS mortar, this paper used sand that contains silt, clay, and a mixture of silt and clay; tested the setting time of AAS with different mud contents of 0%, 2%, 4%, 6%, 8%, and 10%; and measured the unconfined compressive strength and beam flexural strength of 3 d, 7 d, and 28 d AAS mortar specimens. The microstructure of AAS mortar with different kinds of mud was observed by scanning electron microscope (SEM), the elemental composition of the hydration product was tested by energy dispersive spectroscopy (EDS), and the AAS interaction mechanism with different kinds of mud was analyzed. The main conclusions are: the higher the mud content in the sand, the shorter the initial setting time and the longer the final setting time of AAS, mainly because the mud in the sand affects the hydration process; mud content above 4% causes a rapid decrease in the compressive and flexural strengths of AAS mortar, mainly because the mud affects the hydration process and hinders the bonding of the hydration product with the sand. When there is no mud in the sand, the main hydration product of AAS is dense calcium-alumina-silicate-hydrate (C-A-S-H) gel. When the sand contains silt, the hydration product of AAS is loose C-A-S-H gel. When the sand contains clay, the hydration products of AAS contain C-A-S-H gel and a small amount of sodium-aluminum-silicate-hydrate (N-A-S-H), and needle-like crystals. Loose gel and crystals have a negative effect on the AAS mortar strength.

Effects of Borax, Sucrose, and Citric Acid on the Setting Time and Mechanical Properties of Alkali-Activated Slag.

The setting time of alkali-activated slag (AAS) binders is extremely short, while traditional retarders of Portland cement may be invalid for AAS. To find an effective retarder with a less negative impact on strength, borax (B), sucrose (S), and citric acid (CA) were selected as potential retarders. The setting time of AAS with different admixtures dosages of 0%, 2%, 4%, 6%, and 8%, and the unconfined compressive strength and beam flexural strength of 3 d, 7 d, and 28 d AAS mortar specimens were tested. The microstructure of AAS with different additives was observed by scanning using an electron microscope (SEM), and the hydration products were analyzed by energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), and thermogravimetric analysis (DT-TGA) to explain the retarding mechanism of AAS with different additives. The results showed that the incorporation of borax and citric acid could effectively prolong the setting time of AAS more than that of sucrose, and the retarding effect is more and more obvious with the increase in borax and citric acid dosages. However, sucrose and citric acid negatively influence AAS's unconfined compressive strength and flexural stress. The negative effect becomes more evident with the increase in sucrose and citric acid dosages. Borax is the most suitable retarder for AAS among the three selected additives. SEM-EDS analysis showed that the incorporation of borax does three things: produces gels, covers the surface of the slag, and slows down the hydration reaction rate.

BALOK LAMINASI KOMBINASI BAMBU PETUNG ( DENDROCLAMUS ASPER ) DAN BAMBU ATER ( GIGANTOCHLOA ATTER ) SEBAGAI BAHAN KONSTRUKSI ALTERNATIF

One form of innovation in the use of bamboo as a construction material to replace wood is laminated beams or what is known as glulam glued laminated timber, which is the manufacture of artificial boards/beams using a lamination method that uses adhesive for the process of joining bamboo. The aims of this study were: (1) to determine the compressive strength of laminated petung bamboo (Dendroclamus asper), ater bamboo (Gigantochloa atter) and the combined laminated petung and ater bamboo, (2) to determine the flexural strength of laminated petung bamboo (Dendroclamus asper), bamboo ater (Gigantochloa atter) and laminated combination of petung and ater bamboo, (3) to determine the equivalence of laminated beams with wood from the results of the flexural strength test, (4) to determine the equivalence of laminated beams with wood from the results of the compressive strength test. Based on the classification of wood in Indonesia according to the Indonesian Timber Construction Regulations (PPKI) 1961. The results of this study indicate that: (1) The average compressive strength of petung bamboo is 14.44 MPa, the average compressive strength for ater bamboo is 12.96 MPa, and the combined compressive strength results get an average of 13 .33 MPa. (2) The average value of flexural strength is 167.323 MPa for petung bamboo, the flexural strength results for ater bamboo get an average of 139.043 MPa, the combined beam flexural strength results get an average of 169.680 MPa. (3) Based on the results of the study, the flexural strength of petung bamboo laminated beams was equivalent to class I wood, ater bamboo was equivalent to strong class II wood, the combination of petung bamboo and ater bamboo was equivalent to class I wood. (4) Based on the results of the compressive strength study of bamboo lamisani beams petung is equivalent to class I wood, ater bamboo is equivalent to class II wood, the combination of petung and ater bamboo is classified as class I wood.

Seismic behavior of reinforced concrete beam-column joints with unstressed steel strands fully or partially used for beam longitudinal reinforcement

Five beam-column joint specimens: three exterior and two interior specimens were subjected to cyclic loading to investigate the effectiveness of using unstressed Grade 1860 MPa steel strands as full/partial replacement for the conventional Grade 420 MPa deformed bars as beam longitudinal reinforcement. The study also developed a special hooked anchorage detail to anchor the steel strands in the joint region. The test specimens failed by beam plastic hinge formation near the column face as intended in design, with drift capacities between 5.12% and 7.57%. However, the full (100%) and partial (50%) replacement of deformed bars by strands led to a 58% and 28% decrease in average relative energy dissipation. Despite this, the full/partial replacement of deformed bars by strands as beam longitudinal reinforcement resulted in enhanced reentering capabilities. Fracture of longitudinal steel strands observed in the beam plastic hinge region at the end of the test indicated the effectiveness of the special hooked anchorage detail in allowing steel strands to develop their capacity. Further, the flexural strength of the beams of test specimens was evaluated through a detailed moment-curvature analysis, which predicted the beam flexural strength with high accuracy and less variation (mean = 1.01, standard deviation = 0.02). After that, beam flexural strengths were evaluated following the ACI 318–19 procedure modified to include the proposed bilinear strand model, which produced conservative estimates of beam flexural strength (mean = 1.15) suitable for design. Also, the procedure to estimate the beam's probable flexural strength is presented. Finally, required modifications to the conventional seismic design procedure were proposed to incorporate the use of strands as beam longitudinal reinforcement.

Impact of Polymer Coating on the Flexural Strength and Deflection Characteristics of Fiber-Reinforced Concrete Beams

Liquid polymers (LP) have become an important structural material used in the construction industry in the last decade. This paper investigates the viability of using commercially available LPs as a coating material to improve the flexural strength of fiber-modified concrete beams. The scope included preparing rectangular prism concrete beams with a concrete mixture including fly ash and fiber and coating them with four different liquid polymers at a uniform thickness following the curing process while one set of samples was maintained under the same conditions as a control group without coating. In addition, cylindrical samples were prepared to determine the compressive strength of the concrete mixture. Following the curing process in an unconfined open-air laboratory environment for another 28 days, concrete samples were tested to determine the flexural strength and deflection characteristics under center point loading equipment. The results revealed that all four coating types enhanced both the flexural strength and the average maximum deflection of the beams compared to the control group. While the enhancement in the flexural strength changed approximately between 5% and 36% depending on the coating type, the improvements in average maximum deflections varied between 3.7% and 28.4%.

A Study on non Destructive Tests and Flexural Strengths of Geopolymer Concrete Using Combination of Different Fine Aggregates

Geopolymer concrete is a new technology that deserves more attention in the rapidly evolving sustainable construction industry. Furthermore, to avoid the depletion of natural resources, by-product waste management technologies are essential. Today, river sand is in short supply. DMS (Dredged Marine Sand), on the other hand, which faces disposal and land acquisition issues, proves to be a viable alternative to river sand. In this paper, a mixture of M-Sand and DMS was used in place of river sand, and non-destructive, Flexural strength of beam by monotonic loading and cyclic loadings were investigated. The findings indicated that DMS has attained flexural characteristics and with regard to cracks, very minor and vertical cracks are observed in all beams as in the case of monotonic loading. Further, they originate from the tension zone

Experimental and statistical investigation of the three-point bending strength of the composite sandwich beams with trapezoidal core

This paper aims to evaluate the influence of graphene nanoparticles and the structural configuration of the core as independent variables on the flexural strength of the composite sandwich beams by combining experimental and statistical methods. Composite sandwich beams with trapezoidal cores were fabricated using carbon fiber/epoxy and vacuum infusion process. Central composite design (CCD), a subset of response surface methodology (RSM), was employed to statistically analyze the main effect of three input variables, core height, core angle, and graphene content on the flexural strength of the beams. The flexural properties of the beams were derived using a three-point bending test. The experimental and statistical results indicated that the maximum bending load was increased by increasing the height and angle of the core, and the optimal mixing percentage of graphene and epoxy was 0.2 to 0.3 weight percentage. In addition, the experimental results were compared with the numerical simulation obtained from ABAQUS finite element software and the numerical results were found to be in good agreement with the experimental results.

Analytical and Experimental Study on Cold-Formed Steel Built-Up Sections for Bending.

In the construction of steel structures, the two most common types of structural members are hot-formed and cold-formed members. This paper mainly describes the analytical and experimental research on the strength and characteristics of CFS bolted built-up sigma sections having different structural arrangements under bending. The cross-sectional dimensions for the parametric study were selected by the sizes available in the market. In this paper, ANSYS workbench software was used to perform FE modeling and observe the local, flexural, and interaction of these buckling. Then, experimental study was performed by varying the arrangement of open section beams between face-to-face and back-to-back, connected using bolts or fasteners different spacings. Further, we conducted bending tests on cold-formed steel built-up members having simple edge stiffeners in the middle. Comparing both analytical and experimental studies, the results indicate that the back-to-back connected built-up beam section provides a flexural capacity higher than the face-to-face built-up section. Moreover, increasing the bolt spacing enhanced the load-carrying capacity of back-to-back sigma section built-up beams. It has also been discovered that the flexural strength of beams is primarily determined by bolt spacing or itsposition.

Seismic behavior of precast concrete beam-column joints with encased steel tube

Concrete-encased-and-filled steel tubular (CEFT) columns can be potentially connected to concrete beams as well as steel beams. This study aims to develop a novel precast concrete (PC) construction method connecting the CEFT columns and PC beams. In the proposed method, partial openings were provided in the steel tube to facilitate bar placing and concrete casting at the joint. To investigate the seismic behavior of the proposed connections, cyclic lateral loading tests were performed for cruciform beam-column joints. The test parameters were the opening dimensions, presence of cross-beams, and beam flexural strength. In all test specimens, the beam flexural yielding occurred with limited shear damage at the joint, attaining the deformation capacity of more than 4% drift ratio. However, due to the lack of concrete integrity and the reduction of effective joint depth, bond-slip of the beam flexural reinforcement was considerable. The overall seismic performance of the test specimens was evaluated by the acceptance criteria of ACI 374.1-05. While the requirements of the strength and energy dissipation were satisfied, the stiffness requirement was hardly met. On the basis of the results, design considerations for the proposed connection method were recommended.

The stiffness and elasticity of polymer-coated pumice a potential method for reinforcing concrete 3D printing structures

Pumice has been used successfully as a lightweight aggregate concrete replacement (LWAC). Pumice, on the other hand, absorbs a lot of water during the mixing process, which might impair the strength of the concrete. This research examines the influence of coated pumice in concrete mixes on beam flexural strength and stiffness in order to avoid excessive water absorption and acknowledges concrete extrusion-based 3D printing's potential to revolutionize the construction sector. By getting rid of the need for formwork, 3D printing is expected to cut the cost of building civil engineering structures, speed up construction, and make working conditions better. Because of the layer-by-layer additive manufacturing process, it is necessary to alter the way concrete buildings are constructed and strengthened, particularly in areas subject to stress loads. The findings reveal the flexural strength of coated pumice was compared to that of untreated pumice and was found to be 2.58 percent higher. In addition, it also reveals that inclined nails may be utilized in a variety of orientations to provide printing materials with flexural strength.

Numerical investigation on flexural behavior of RC beams with large web opening externally strengthened with CFRP laminates under cyclic load: Three-point bending test

In the current paper, the effect of carbon fiber reinforced polymer (CFRP) laminates on the flexural strength of reinforced concrete beam (RCB) with the web opening in the flexural zone was investigated using a numerical method. The main aim of the current work is to model the reinforced concrete beam strengthen by two shape of CFRP laminates (2layer and U-shape), to observe the influences of CFRP on the flexural strength of the beam. To this end, cyclic loading was applied to investigate the flexural behaviour of the Twelve RC beams under the cyclic loading. All beams kept the same dimensions length, breadth, and depth (2400 × 300 × 200) mm were modeled in the finite elements adopted by ABAQUS software. Steel bars have been used for both flexural strengthening and stirrups. A Three-point bending tests were performed using cyclic loading. Furthermore, the effect of web openings with different sizes (Side length of 40, 60, 75% of the breadth) on the flexural behavior of RC beams was investigated in detail. The flexural strength, local analysis, and ductility of the base beam and CFRP reinforced beam were analyzed. The results of the simulations revealed that the CFRP laminates enhanced the strength of the base beam significantly.

Repercussion of steel slag on SCC with concrete debris and slag aggregate: An analysis of internatel structures over beam element

The paper discusses the experimental study on Self Consolidating Concrete (SCC) made with the fractional replacement of recycled aggregate (RA) and slag aggregate (SA). The SCC rheological properties are evaluated with the use of steel slag (SS) and the effects are studied at ages of 7, 14, 21 and 28 days. The substitution of aggregates made with the SCC (RA25/SA15), SCC (RA20/SA20) and SCC (RA15/SA25) along with steel slag. 30 % of steel slag is chosen as the optimum percentage on grade-M30 concrete. SCC with different percentage of substitutions are tested with slump test, V-funnel, U-box and L-box test. Cube-compressive, cylinder-tensile and prism and beam flexural strength. The results obtained for SCC are analysed and compared with Normal Concrete (NC). The optimum specimen is observed under SEM-EDs analysis for its mineral composition and C-H-S gel formation, which shows not much variation compared to NC. However marginally fair strength is achieved on the SCC with substitutions and certainly there is a room for improvement in strength characteristics.

Effect of self-compacting concrete added with concrete debris and steel slag aggregate

Recycled Aggregate (RA) and Slag Aggregate (SA) have been used as alternative course materials in concrete for decades in the building industry in order to achieve sustainability. The use is currently acknowledged as a viable alternative to coarse aggregate, and it is a promising material for reducing the environmental effect of slag waste and concrete debris. The experimental investigation on Self Consolidating Concrete (SCC) created with fractional replacement on RA and SA is discussed in this work. The slump test, V-funnel, U-box, and L-box tests are performed on SCC in its fresh condition with substitutes. The mechanical characteristics are measured at the ages of 7 and 28 days to determine the effective usage level of replacement. Cube-compressive strength, cylinder-tensile strength, prism and beam flexural strength are all tested, and the results are compared to NC and SCC values. According to the results of the tests, the studied values of concrete characteristics with a higher percentage of RA and SA replacement are lower than those of reference mixes. In grade-M30 concrete with W/C optimal, the aggregate replacement is done as a mix of both RA and SA together with steel slag 7 percent as a partial substitution for cement. Microstructure analysis is used to examine the mineral composition and C-H-S gel formation of the specimen with a pretty optimal value. According to SEM-EDs analysis, adding steel slag to the mix results in the formation of additional C-S-H gel, which aids in the attainment of fair strength and compressive strength values that are within the range of slag activity index; however, mineral element subsistence differs from the reference mix. Nevertheless, the findings are adequate for practical use and cost-effectiveness, with acceptable strength attributes.

Effect of 6 Hour Fire on Flexural Strength of RC Beams made with 50% Coarse Aggregates from old concrete: Part 1: Normal mix

Shifting of people from villages/small cities to big cities poses a serious issue of accommodation and other associated infrastructure. For the solution of said issue, demolition of old structures to construct new high-rise buildings is opted. The demolishing waste is an additional problem for the project, particularly due to unavailability of the dumping space in many areas. A method of addressing the issue is by using it in new concrete. This research study presents an experimental investigation to check the effect of a 6-hour fire at 1000◦C on the bending resistance of reinforced concrete beams prepared by replacing 50% conventional coarse aggregate with coarse aggregate from demolished concrete. 24 RC beams of 0.9m × 0.15m × 0.15m size are cast using 1:2:4 mix and 0.54 water cement ratio. To reinforce the beams 2#4 bars in each tension and compression zones are used. Out of 24 beams, 12 are cast with all-natural coarse aggregates to compare the results. After 28-days standard curing, all beams are exposed to fire for 6 hours in purpose made oven. The beams are then left at room temperature for 24-hours followed by testing of all the beams in universal load testing machine with central point loading. Load and deflection are monitored at regular intervals. Comparison of the results with control specimen shows that the proposed beams observed 13.43% reduction in flexural strength which is quite smaller. The beams failed in shear which complies with the failure mode of normal concrete beams. Thus, the proposed material has good fire resistance when used in reinforced concrete beams.

PERILAKU LENTUR PADA BALOK BETON SERAT BESI BERLUBANG MENERUS DI DAERAH TARIK

Concrete beams that receive a positive bending force, at the top will experience a compressive force while at the bottom receive a tensile force. The theory that reinforced concrete is a structural system where the steel or reinforcement in the concrete functions to withstand tension, then the concrete below the neutral line does not receive a compressive force but transmits a tensile force to the reinforcement. This study analyzes and reduces the area in the tensile area by continuously installing 2 inch diameter PVC pipes and adding fiber to the concrete. This reduction in area is expected to reduce weight and material savings without reducing its strength. This research was carried out with a sample of 28 days old concrete blocks with quality f'c = 21.04 MPa with dimensions of 12 cm x 18 cm x 250 cm, with 4Ø10 mm reinforcement with quality fy = 450 MPa. Concrete beams are made in 3 variations in the form of solid beams, hollow beams without fiber, hollow beams with fiber. Each variation has 2 samples. From the test results, all beams experienced flexural cracks which were characterized by cracks perpendicular to the beam axis and flexural strength behavior which the difference was not significant. From the three variations of this beam, it shows that the results of the hollow beam with the addition of fiber have a greater first crack load. The addition of fiber is able to slow down the cracks that occur and contribute to withstand tensile stresses so that the beam still has strength to bear the load even though cracks have occurred. Based on the calculation simulation, in order to equalize the strength of the hollow beam with fiber, the dimensions of the solid beam need to be enlarged so that the solid beam becomes more expensive. This shows that hollow beams with fiber are more economical than solid beams.