Cast Beams Research Articles

Comparative Study on Flexural Behavior of Reinforced Concrete Beams Cast by Using Hydraulic Cement and Ordinary Portland Cement

This paper is a comparative study of the flexural behavior of reinforced concrete beams cast by using hydraulic cement and ordinary Portland cement for construction applications. The main variables used in this research comprise of type of cement, ultimate compressive strength of concretes, and curing time. Two different types of cement, including hydraulic cement and ordinary Portland cement, were used at three different ultimate compressive strengths of 18 MPa, 25 MPa, and 32 MPa with the curing times of 28 and 90 days. The beams' nominal span-to-depth (L/h) ratio is 8.0. The results showed that the reinforced concrete beams cast by using hydraulic cement and ordinary Portland cement had similar flexural behavior and failure patterns. Both types of the reinforced concrete beams exhibit linear elastic behavior up to approximately 80–90% of their maximum applied load. Then, the behavior of the beams is nonlinear in that the deflection increased rapidly with a slight increase in the applied load until reaching their failure. In addition, based on the experimental results obtained from this study, it was found that the ACI design equations are acceptable for predicting the design strength of the reinforced concrete beams cast by using hydraulic cement and the hydraulic cement can be an equivalent substitute for ordinary Portland cement for the reinforced concrete beams used in this study. Therefore, this application of the hydraulic cement is not only the environmentally friendly practices, but also promoting low-carbon society as well.

Use of hybrid fibers and shrinkage mitigating materials in SCC for repair applications

Self-consolidating concrete (SCC) is used to repair structural elements with congested reinforcement or restricted access to placement and consolidation. In addition to adequate flowability, passing ability, filling capacity, and stability, adequate bonding to the substrate and reinforcing bars, low shrinkage and cracking resistance are required for successful repair. This study employs various shrinkage mitigating materials, including expansive agent (EA), coupled use of EA with shrinkage reducing admixture (SRA), and EA with pre-saturated lightweight sand (LWS) to fulfill these requirements. The effect of these materials on the performance of SCC made with a hybrid synthetic (PP) fiber and a hybrid steel-synthetic (STPP) fiber is investigated. The investigation included key fresh and hardened concrete properties and flexural performance of composite beams repaired using these materials. Test results show that the investigated fiber-reinforced self-consolidating concrete (FRSCC) mixtures can secure adequate workability and mechanical properties and low shrinkage, limited to 600 µstrain after 224 days. High EA content (10% by mass of binder) can lead to excessive expansion at early ages resulting in microcracking and drop in mechanical properties. The FRSCC made with 5% EA and 0.5% SRA, by mass of binder (5EA0.5SRA mixture), had superior mechanical properties (50 MPa compressive strength and 36 GPa modulus of elasticity). The cracking potential due to restrained shrinkage of this mixture is very low. The 5EA0.5SRA mixture made with hybrid synthetic fibers is successfully used to repair reinforced concrete beams prepared with various reinforcement ratios in the tension zone. The results indicate a 48% increase in first crack load, 4% gain in peak load, and 33% increase in flexural toughness compared to the monolithic beam cast with the conventional concrete. A comparison between the cracking load and ultimate flexural capacity of the repaired beams with estimated values by ACI 544 reveals the estimated to experimental ratio of 0.36–0.70 for cracking load and 0.56–0.74 for the flexural capacity. This can stem from the promotion of FRSCC concrete by the effect of hybrid synthetic fibers and the development of internally induced stress in the presence of shrinkage mitigating materials and fibers that led to higher mechanical properties and enhanced performance of FRSCC for repair. Reinforced beams repaired using FRSCC made with 0.5% hybrid synthetic fibers and combination of EA-SRA can reduce the steel reinforcement ratio by 21% to 27%, depending on the primary steel reinforcement.

Precast segmental beams made of fibre-reinforced geopolymer concrete and FRP tendons against impact loads

In the open literature, there is no investigation into the impact behaviour of prefabricated segmental concrete beams (PSCBs) cast with low CO2-emission fibre-reinforced geopolymer concrete (GPC), reinforced with non-corrodible basalt fibre-reinforced polymer (BFRP) reinforcement, and post-tensioned with carbon FRP (CFRP) tendons. This research, hence, aims to close this existing gap of knowledge. The primary goals are to investigate the effect of dispersed fibres on the impact response of PSCBs and to compare the performance of CFRP versus steel tendons. The experimental results reveal that the PSCBs fail due to excessive joint openings that lead to concrete spalling and flying concrete debris. The inclusion of dispersed fibres in the concrete postpones crack development, reduces reinforcement strain, and effectively mitigates concrete spalling and stiffness degradation of the beams. While fibres show limited influence on the deflection response of PSCBs, as the deformation of segmental beams is predominantly governed by joint openings with no fibres bridging across the joints, they play a crucial role in preventing severe damage during impact events. The impact response of beams post-tensioned with CFRP tendons is analogous to those with steel tendons. Notably, both the CFRP tendon and BFRP reinforcement remain intact even when the beam fails under impact loads. This implies that CFRP tendons and BFRP reinforcement can be successfully employed in constructing durable and sustainable segmental GPC beams capable of withstanding impact loading. A high-fidelity numerical model of PSCBs made of GPC and FRP tendons and reinforcement subjected to impact loads is also developed, for the first time, to supplement the discussions of experimental findings.

Experimental Validation of Dynamic Response of Small-Scale Metaconcrete Beams at Resonance Vibration.

Structures and their components experience substantially large vibration amplitudes at resonance, which can cause their failure. The scope of this study is the utilization of silicone-coated steel balls in concrete as damping aggregates to suppress the resonance vibration. The heavy steel cores oscillate with a frequency close to the resonance frequency of the structure. Due to the phase difference between the vibrations of the cores and the structure, the cores counteract the vibration of the structure. The core-coating inclusions are randomly distributed in concrete similar to standard aggregates. This mixture is referred to as metaconcrete. The main goal of this work is to validate the ability of the inclusions to suppress mechanical vibration through laboratory experiments. For this purpose, two small-scale metaconcrete beams were cast and tested. In a free vibration test, the metaconcrete beams exhibited a larger damping ratio compared to a similar beam cast from conventional concrete. The vibration amplitudes of the metaconcrete beams at resonance were measured with a frequency sweep test. In comparison with the conventional concrete beam, both metaconcrete beams demonstrated smaller vibration amplitudes. Both experiments verified an improvement in the dynamic response of the metaconcrete beams at resonance vibration.

Flexural Strength and Modulus of Elasticity of Concrete Beam Cast with Binary Blending of Recycled Concrete Aggregate and Marble Dust

This research paper presents the combined effect of recycled coarse aggregates and marble dust on the flexural strength and modulus of elasticity of concrete. Use of the waste materials in concrete leads to sustainable development; and is the need of the day. Recycled aggregates were processed from demolishing waste and ensured by sieve analysis for well-graded concrete. Marble dust was used as cement replacement from 2.5% to 10% in increments of 2.5%. Recycled aggregates were used in equal dosage with conventional aggregates. A total of five batches of beams and cubes were cast using normal mix concrete. The curing of the specimens was done for 28 days. Ultrasonic pulse velocity testing was done to evaluate the modulus of elasticity. The same was also evaluated using an empirical equation of ACI and from the literature. A comparison of the results shows that both UPV testing and numerical equation by ACI can comfortably be used for evaluation of the modulus of elasticity of recycled aggregate concrete. Beams were tested under central point load for flexure. Comparison of flexural strength and deflection with control concrete shows that a 5% dosage of marble dust as cement replacement along with 50% replacement of conventional coarse aggregates with coarse aggregates from demolishing waste is optimum as with this replacement level residual flexural strength is 88% and the deflection is only 5% more than control concrete and less compared to the maximum approximate deflection allowed by ACI-31.

Structural behavior of beams cast using normal and high strength concrete containing blends of ceramic waste powder and blast furnace slag

In general, the use of ceramic waste powder (CWP) in concrete production is limited to few percentages (i.e., less than approximately 10–15% of Portland cement), given the resulting decrease in concrete strength and durability. This paper seeks to assess the relevance of blending CWP with blast furnace slag (BFS) to foster pozzolanic reactions and reinstate the drop in strength and structural performance of reinforced concrete (RC) members. Two categories of normal- and high-strength concrete (NSC and HSC) mixtures possessing 34 and 71 MPa compressive strengths are tested in this program. The RC beams measured 2-m in length and were differently configured by steel reinforcements to assess the flexural and shear strengths as well as the bond to embedded spliced rebars. Regardless of the steel configuration, results showed that the structural properties curtail when the concrete mixtures are prepared with 10% CWP replacement rate. This was attributed to a dilution effect and higher CWP porosity that detrimentally alter the concrete microstructure and strengths. The drop in flexural, shear, and bond strengths was found to be fully restored with the use of ternary binder composed of 55% cement, 35% BFS, and 10% CWP. Such results are in line with the improved concrete strength and durability, revealing the relevance of blending CWP with BFS to foster synergistic effects and reinstate the structural properties of NSC and HSC beams. Findings of this work can increase the CWP added-value for the construction industry, while reducing the cement carbon footprint.

Flexural behaviour of High-performance concrete beams under Cyclic loading conditions

Flexural behaviour of high-performance concrete (HPC) was affected by various parameters and plays a vital role in the strength of concrete. Present study aims in deciphering the role of cyclic loading on HPC reinforced with steel fibers. The study was carried out by casting of beams with hooked end steel fiber reinforced concrete with various grades (M60, M80, M100) and with admixtures (GGBS and Silica fume). Cast beams were studied for compressive strength, tensile strength, and flexural strength under cyclic loading. The study shows that there was a significant increase in compressive strength of HPC mixed with 1.0% of steel fiber. Flexural strength was found to be comparatively higher (upto 15% for all grades) for 1.25% steel fiber mixed HPC. Direct tensile strength is found to be higher than split tensile strength. Addition of steel fiber in HPC beam under cyclic loading, resulting in delayed or late development of cracks with decreased crack size.

Experimental investigation on influence of hybrid fibers in flexural behavior of reinforced concrete beams

Addition of fiber is a promising solution, to enhance the flexural behaviour of reinforced cement concrete [RCC] beams. It improves the peak load, ductility and energy absorption characteristics of RCC. Ineffective mono fibers in the concrete perform very effective, when combined through the hybridization and contribute towards the strength. Fiber hybridization offers appreciable improvement in fresh and hardened properties of concrete. To achieve optimum performance, synergetic effect of fibers is more important. Incorporation of two fibers in concrete matrix, bridges the cracks effectively. Hence to investigate the effect fiber hybridization in the flexural performance, RCC beams were cast, experimented and the results were compared with the control beams. In the present study, it is intended to evaluate and compare the impact of steel and basalt fibers in mono form and hybrid form, on the flexural parameters such as first crack load, load response behaviour, ductility, crack width and flexural strength of RCC beams. To evaluate the mechanical properties of M40 grade fiber reinforced concrete, volume fractions chosen were 0.25%, 0.5% and 0.75%. Comparatively addition of basalt fibers with steel fibers, improves synergetic response to a considerable extent. From overall assessment of the mechanical properties, it was established that the combination of basalt and steel fibers at 0.25% and 0.75% respectively, produced optimum results. Optimum volume fraction of fibers identified is used in the casting of RCC beams. Wherever possible, flexural parameters were cross checked, with Indian Standards.

Experimental investigation of dimensional ratio effects on shear capacity of high-performance cementitious composites deep beams

Deep beams are generally used as main load-bearing beams or pile caps which are very common in high rise buildings. The span to height ratio of beams is an essential parameter in their flexural and shear behaviors . The usage of composite concretes conjuncture with fibers enhances the deep beams to overcome the relative brittleness and fragility of concrete and its low energy absorption. In this paper, the experimental research on eight deep reinforced concrete beams cast and replaced with high-performance cementitious composites was carried out. Two group specimens with 2% steel fiber and without fiber, the same height, and similar reinforcement details, and also different span to height ratios from 0.75 to 2 were considered and tested with the three-point flexural method. The experimental ultimate shear strength was compared with the predicted value in different codes. The test results indicated that the load-bearing capacity of deep-beam specimens was increased up to 84.8% with the same dimension when replacing conventional concrete with cementitious composites containing 2% of steel fiber. • New relations suggested to determine the ultimate capacity of deep beams made from cementitious concrete with fiber. • An experimental study was conducted regarding the shear behavior of deep beams using this material, might be a sort of innovation. • Extra work on structural aspects and applying this material and the behavior of deep beams made from this material are of high importance.

Flexural performance of reinforced concrete beam made with waste foundry sand as fine aggregate

PurposeThe structural behavior of reinforced concrete (RC) beams made with waste foundry sand (WFS) was examined in this study by using investigational data. Five RC beams were tested in this present work, four beams with varying WFS content and one beam with natural aggregates. The factors considered for studying the flexural performance of RC beams were WFS content (10%, 20%, 30% and 40%), 15% Ground Granulated Blast Furnace Slag (GGBS) is used as supplementary cementitious (SCM) content for all beams and tension reinforcement ratio (0.95%). The crack pattern of the RC beams with WFS (RCB1, RCB2, RCB3 and RCB4) was similar to that of referral beam–RCB0. The RC beams made with WFS (RCB1, RCB2, RCB3 and RCB4) show lesser number of cracks than referral beam–RCB0. It is observed that RCB1 beam shows higher ultimate moment carrying capacity than other RC beams. A detailed assessment of the investigational results and calculations based on IS: 456-2000 code for flexural strength exhibited that the present provisions conservatively predicts the flexural strength and crack width of RC beams with WFS and 15% GGBS. It is suggested that 10% WFS can be used to make RC beam.Design/methodology/approachIn this present work, four RC beams made WFS and one RC beam made with natural aggregates. 15% GGBS is used as SCM for all RC beams. After casting of RC beams, the specimens were cured with wetted gunny bags for 28 days. After curing, RC beams like RCB0, RCB1, RCB2, RCB3 and RCB4 were tested under a four-point loading simply supported condition. An assessment of investigational results and calculations as per IS: 456-2000 code provisions has been made for flexural strength and crack width of RC beams with WFS and 15% GGBS. The crack pattern is also studied.FindingsFrom this experimental results, it is found that 10% WFS can be used for making RC beam. The RCB1 with 10% WFS shows better flexural performance than other RC beams. RC beams made with WFS show lesser number of cracks than referral beam–RCB0. IS: 456-2000 code provisions can be safely used to predict the moment capacity and crack width of RC beams with WFS and 15% GGBS.Originality/valueBy utilization of WFS, the dumping of waste and environmental pollution can be reduced. By experimental investigation, it is suggested that 10% WFS can be used to make RC structural members for low cost housing projects.

Experimental evaluation of flexural behavior of High-Performance Fiber Reinforced Concrete Beams using GFRP and High Strength Steel Bars

Substitution of only steel rebar with fiber-reinforced polymer (FRP) or in combination with steel rebar has been recommended to reduce corrosion effects in steel rebar. This paper has pursued the impact of hybrid concrete beams reinforced with High Strength Steel Bars (HSS) and Glass Fiber-Reinforced Polymer Bars (GFRP) manufactured employing High-Performance Fiber-Reinforced Cementitious Composites (HPFRCC) instead of conventional concrete through experimental tests. Seven concrete beams including conventional concrete and HPFRCC in three separate groups, having identical compressive strengths and longitudinal steel reinforcement ratios, have been tested following respected codes and regulations to supply sufficient development lengths using GFRP headed bars, under four-point loading tests. The first and second groups, each represented one conventional concrete beam and an HPFRCC model with GRFP or HSS; the third group included three HPFRCC beams using GRFP and Steel rebar to assess flexural behavior of beams under different reinforcement ratios. Experimental results indicated that HPFRCC beams demonstrated improvements in their load capacity, flexural strength, bending stiffness, ductility, and energy absorption compared to similar conventional concrete beams. Also, in hybrid beams compared to steel reinforced concrete beams both cast with HPFRCC, the more the effective reinforcement ratio of both single and hybrid bars increased, the more ductility was improved between 37 and 88 percent. Displacement ductility of hybrid beams having effective reinforcement ratios up to 1.35 and 1.25 times more than the balance ratio was increased 23 and 37.5 percent, respectively. Energy absorption for HPFRCC beams reinforced only with GFRP or steel rebar was increased 31 and 250 percent compared to identical conventional concrete beams, respectively. In hybrid compared to GFRP reinforced beams both cast with HPFRCC, the more effective reinforcement ratio increased, the more energy absorption was increased in a range of 51 up to 174 percent. Therefore, it can be concluded that using the hybrid of GFRP and HSS bars result in up to 30 percent improvement in flexural strength because of the effective performance of GFRP after steel rebar yielding and ductility increase due to HSSs yielding.

A Study on the Flexural Behaviour of Geopolymer Lightweight Eco-Friendly Concrete Using Coconut Shell as Coarse Aggregate

This paper presents the flexural behaviour of concrete containing ground granulated blast furnace slag (GGBS) as a binder, manufactured sand (M-sand) as a fine aggregate, and coconut shell (CS) and crushed stone aggregate (CSA) as coarse aggregates. Alkaline activator sodium hydroxide with 10 molarity and sodium silicate were used in a weighing proportion of 1 : 2.5 to produce structural grade concrete. Out of 12 beams cast, 6 were used to study geopolymer coconut shell concrete (GPCSC) beam behaviour and 6 were used to study geopolymer conventional concrete (GPCC) beam behaviour. Data presented include cracking behaviour, ultimate moment capacitates, deflection behaviour, ductility ratio, and end rotation of the beam. Laboratory investigations show encouraging results, and it can be summarized that coconut shell has good potential as a coarse aggregate for the production of structural grade geopolymer lightweight coconut shell concrete.

Characteristics Investigations of Dry Bamboo Ash Fractional Replaced Cement with in M25 Grade Concrete

Most bamboos are used in-house ceiling, Ornament works behavior science of earliest culture regulations. If fresh and dry stages bamboos are equally important, of construction works. Green stage bamboos working process of interlocking formations woodworks and dry stage bamboos are working in support for centering for slabs, tunneling or varies constructional purposes. These papers say about dry bamboos ash to use the sub stained to mixed the partially replaced within 53 grades of cement. In 20, 30, and 40%. And constituent of mixing ratio is M25 grade of concrete (1:1:2). And its process of proper casting of cubes, beams and cylinders to put in to the test analysis for strength, absorption tastings machines and these each types of test result are higher values. Because its better constituent DBA ash mixed with cement substance identical strength attained the concrete cubes, cylinders and beams. And its improved concrete strength and highly interlocking ability of friction bonding into the coarse and fine aggregate of the concrete. And same time its high workability.

Contribution of lightweight self-consolidated concrete (LWSCC) to shear strength of beams reinforced with basalt FRP bars

To date, the shear contribution of lightweight self-consolidating concrete (LWSCC) members reinforced with basalt fiber-reinforced polymer (BFRP) bars (LWSCC-BFRP) has not yet been investigated. Therefore, the anticorrosion properties of BFRP bars combined with the advantages of LWSCC motivated this research to assess the behavior of such members under shear. Eight beams cast using LWSCC and normal-weight concrete (NWC) reinforced with BFRP or steel bars were prepared and tested up to failure. The specimens had a total length of 3100 mm and concrete cross section of 200 mm in width and 400 mm in depth. The influence of two different types of BFRP bars of comparable quality and commercially available (sand-coated basalt and helically grooved basalt) on shear capacity was assessed. The tested beams included five beams reinforced with BFRP bars, one beam reinforced with steel bars, and two beams constructed using NWC for comparison purposes. The experimental results indicate that the adoption of LWSCC allowed for decreasing the self-weight of the reinforced concrete (RC) beams (density of 1800 kg/m3) compared to NWC. Test results show that the concrete shear capacity of the LWSCC beams increased as did the axial stiffness of the longitudinal BFRP reinforcing bars. The test results were compared with the shear capacities predicted using the provisions in several standards. Using a 0.75 concrete density reduction factor in the CSA 2012 shear equation to consider the influence of concrete density yielded a more accurate value for the concrete shear capacity. In addition, using a 0.8 concrete density reduction factor in the ACI 2015 design equation yielded an appropriate degree of conservatism compared to the NWC beams.

Nonlinear Finite Element Analysis of Reinforced Concrete Beam-Column Connection with Interface Elements under Cyclic Loading

To study the nonlinear response of corner beam-column junctions with inclusion of the effect of construction joint between the column and the beam cast at different times and subjected to cyclic and repeated loads, a computer program of three dimensional nonlinear finite element analysis, written by Al-Shaarbaf[1], (P3DNFEA)has been extended to account for the effect of construction joints on the behavior and to deal with concrete behavior under cyclic loads.The 20-node isoperimetric brick elements have been used to model the concrete, while the reinforcing bars are modeled as axial members embedded within the brick elements. A nonlinear cyclic behavior model for concrete is developed in uniaxial and multiaxial states of stress. Also, a nonlinear cyclic behavior model for reinforcing bars is presented.In completion, the behavior of concrete under cyclic loads is simulated by an elasto-plastic work hardening model followed by a perfectly plastic response. In tension, affixed smeared crack modeled has been used to simulate the behavior of concrete with a tension-stiffening model to represent the retained post-cracking tensile stresses in concrete. Closing and reopening of cracks during cyclic loading has been taken into consideration.The nonlinear equations of equilibrium have been saved using an incremental-iterative technique based on the modified Newton-Raphson method. The convergence of the solution was controlled by a force convergence criterion. The numerical integration has been conducted by using 27-point Gaussian rule.To represent the shear transfer between two concretes cast at different times, 20-noded interface layer brick elements are used with Fronteddu’s and Millard’s models to represent the aggregate interlock and the dowel stiffness, respectively.Comparison between the results obtained from the finite elements and the available experimental results is made for a corner beam-column junction with inclusion of the effect of a construction joint. Good agreement is obtained. The maximum difference in ultimate load is 3.9%.A parametric study dealing with construction joint is presented by taking various conditions of the junction. These include the axial load on the column, strength of concrete in the second cast.

Flexural Behavior of Reinforced RAC Beams Exposed to 1000°C Fire for 18 Hours

In order to meet the socio-economic demands around the globe, construction industry not only consumes concrete at a very fast pace but also yields huge amounts of construction and demolishing waste. The phenomenon gives rise to environmental issues due to production of concrete ingredients and due to dumping of the waste. Therefore, one of the solutions is the production of green concrete utilizing demolished waste. This research work studies the effect of prolonged fire (18 hours) on the flexural behavior of reinforced concrete–recycled aggregate beams. The beams were using 50% replacement of natural coarse aggregates with demolished concrete. The beam samples were cast as both normal and rich mix concrete and were cured for 28 days. After curing, the beams were exposed to fire at 1000°C in a purpose made oven, followed by testing in a universal load testing machine under central point load. The test results show that the proposed beams (cast with rich mix) exhibited about 22% reduction in flexural strength. The failure mode of the beams was observed as shear failure.

A combined finite difference and finite element model for temperature and stress predictions of cast-in-place cap beam on precast columns

In this study, a combined finite difference and finite element model was developed to predict the temperature development, thermally induced stresses and associated cracking risk in the concrete of a cast-in-place cap beam cast on precast columns of a bridge. The numerical model considers degree of hydration dependent heat rate, Young’s modulus development, strength development and early age tensile and compressive creep behavior. The temperature and stress analyses were performed on two sections of a cast-in-place cap beam (with a cross section of 1.6 m × 2.1 m): one at mid-span of the cap beam and the other on top of the precast column. The results show that the section of the cap beam at the column had high tensile stresses at the mid-sides which exceeded the early age concrete tensile strength when not covered with insulation blankets during construction. Additionally, the use of insulation materials, reduction of initial concrete temperature and proper choice of casting time can significantly mitigate the thermal stress and cracking risk of the cap beam. The model can be conveniently programmed and be a useful tool to help engineers control concrete temperature and take measures to minimize the risk of early-age thermal cracking for cast-in-place pier caps and its connection to a precast column, or other similar concrete members/connections, thus accelerating construction schedules for bridge projects.

Deformation responses of reinforced concrete beams under pure torsion

The experimental programme that is the focus of this report dealt with twelve beams cast in three groups: Normal Concrete (NC), High Strength Concrete (HSC), and Self Compacting Concrete (SCC). The applied loads, resulting torsional moments, angles of twist and longitudinal strains are listed in Tables and presented in graphs, to aid discussion. The results of the practical work revealed that increasing the compressive strength of a section increases the stiffness of a beam, thus decreasing the angle of twist markedly. Increasing the steel fibre content in a section similarly decreases the value of the angle of twist of the beam, as well as resulting in an increase in stiffness. Increasing the compressive strength of a section also increases the stiffness of a beam, thus decreasing the longitudinal strain. While increasing the steel fibre content in a section decreases the value of longitudinal strain on all beams, resulting in an increase in stiffness, the highest improvement (100%) was seen in the HSC group.

Behavior of High Strength Hybrid Reinforced Concrete Deep Beams under Monotonic and Repeated Loading

Introduction:This study presents the experimental and analytical investigation of the behavior of high strength hybrid reinforced concrete deep beams under monotonic and repeated two-point load. The idea of hybrid in this work is different. Two types of concrete were used in beam but not in cross-section. The first type was the Fibrous High Strength Concrete (FHSC) at shear spans for enhancing shear capacity against cracking due to diagonal strut failure (by adding Steel Fiber (SF) in that regions), while the second type was the Conventional High Strength Concrete (CHSC) at the mid-portion between the two strengthened shear spans.Methods:The experimental work included the casting and testing of ten deep beams. Five among the beams were tested under monotonic loading (control beams) and other beams were tested under repeated loading at the level of 75% of ultimate load of control beams. The effect of some selected parameters as the type of load, the hybrid and non-hybrid beams, the compressive strength of concrete (fʹc) (normal and high) and the amount of web reinforcement (ρw) were studied in terms of crack patterns, ultimate load and load versus midspan deflection.Results and Conclusion:From the experimental test results, when beam cast with fibrous with SF of 1% concrete along entire length, the ultimate load of 10.96% increased as compared with hybrid beam. And it was observed to increase as much as 32.78% as compared with beam cast from conventional high strength concrete under monotonic loading. Under repeated loading of 75% control ultimate load, the ultimate load for beam cast with fibrous concrete along entire length increased as much as 15.32% as compared with hybrid beam. And it was seen to increase 36.17% as compared with the beam cast from conventional high strength concrete. The percentage increase in ultimate load of hybrid (SF ratio 1%) deep beam cast with high strength concrete became 97.3% as compared with the identical beam cast with normal strength concrete under monotonic loading and (98.21%) under repeated loading (load 75% control beam load). The percentage increase as ultimate load for hybrid beam cast with SF ratio 1% was 9.62% as compared with hybrid beam with SF ratio 0%. As the web reinforcement increased from 0 to 0.004 and from 0 to 0.006, the percentage increased in the ultimate load as 28.07% and 57.89%, under monotonic loading as 26.14% and 59.09%, under repeated loading.Then, Strut and Tie model (STM) procedures were used to analyze the experimentally tested hybrid deep beams under monotonic loading of the present investigation. Comparison of experimental results was made with corresponding predicted values using the STM procedure presented of ACI 318R-14 Code and with other procedures

COMPARING THE FLEXURAL STRENGTH OF CONCRETE MADE WITH RIVER SAND WITH THAT MADE WITH QUARRY DUST AS FINE AGGREGATE

This work focuses on the 100% replacement of river sand with quarry dust in the production of concrete. Two types of concrete were produced (concrete made with river sand and that made with quarry dust as fine aggregate), the concretes produces were cast into beams and cured for 28 days. The flexural strengths of the concrete beams cast was determine at 28 day strength. At 28 days target strength the maximum flexural strength of concrete made with river sand as fine aggregate is 5.375111N/mm2 and minimum flexural strength is 2.2155N/mm2, for the concrete made with quarry dust as fine aggregate the maximum flexural strength is 2.567 N/mm2. The maximum value of 2.567 N/mm2 for concrete made with quarry dust as fine aggregate is higher than the minimum value of 2.2155N/mm2 for concrete made with river sand as fine aggregate. With this result it shows that quarry dust is a good substitute to river sand in the production of concrete.