Rectangular Reinforced Concrete Beams Research Articles

Machine learning-based adaptive degradation model for RC beams

Reliable seismic damage assessment of structural systems requires analytical models that are able to capture the cyclic deterioration of components. In this paper, an adaptive-updated degradation model (AUDM) for reinforced concrete (RC) beams is proposed based on the machine learning approach. The proposed model is capable of updating its constitutive parameters from the embedded artificial neural networks, based on the analysis results derived from the previous step. It offers the possibility for generating deterioration without constructing empirical equations, updating the hysteretic shape as the accumulation of damage, and accounting for the effect of variable shear-flexural interaction in nonlinear analysis. The details of the proposed model, including the backbone curve, the hysteretic behavior and the cyclic deterioration rule, were first described. An experimental database consisting of 100 cantilever rectangular RC beams under cyclic loading was collected from the existing literature to identify the constitutive parameters in the proposed model. Artificial neural networks for predicting the constitutive parameters in the proposed model were developed and trained based on the identified data, which was then embedded into the open-source computational platform OpenSees to implement AUDM. The accuracy of the proposed model over the existing commonly-used degradation model is revealed in OpenSees based on the test results of RC beams under cyclic loading. It was found that the proposed AUDM was shown to be superior to the existing degradation models in terms of the lateral bearing capacity, the dissipated energy, the cyclic deterioration and the hysteretic shapes under different failure modes, with the relative error of energy dissipation capacity in the range between −0.19 and 0.19 and the maximum root square error for strength deterioration less than 0.259.

Performance of Reinforced Concrete Beams Strengthened with Carbon Fiber Reinforced Polymer Strips.

Carbon fiber reinforced polymers (CFRP) have shown considerable potential in the repair and rehabilitation of deficient reinforced concrete (RC) structures. To date, several CFRP strengthening schemes have been studied and employed practically. In particular, strengthening of shear damaged RC members with CFRP materials has received much attention as an effective repair and strengthening approach. Most existing studies on strengthening shear-deficient RC members have used unidirectional CFRP strips. Recent studies on strengthened T-beams demonstrated that a bidirectional CFRP layout was more effective than a unidirectional layout. As such studies are limited, in this study, the feasibility of bidirectional CFRP layouts for the shear strengthening of rectangular RC beams was experimentally evaluated. Bidirectional layout details with CFRP anchors as well as rehabilitation timing were considered and investigated. The test results showed that the members with a bidirectional CFRP layout carried less shear strength capacity than those with unidirectional layouts for the same quantity of CFRP material. Nevertheless, the bidirectional CFRP layout allowed for a uniformly distributed stirrup strain compared to the unidirectional CFRP layout at the same load level, which increased the efficiency of the transverse reinforcement. Additionally, the shear contribution of CFRP material according to the CFRP strengthening timing was verified.

Experimental Research on the Flexural Performance of RC Rectangular Beams Strengthened by Reverse-Arch Method

Carbon fiber-reinforced polymer (CFRP) reinforcement technology has been widely used in the reinforcement of reinforced concrete (RC) beams. At this stage, high prestressed CFRP board reinforcement is often used in actual reinforcement. However, most reinforced bridges are designed for a long time, and the design value of the protective layer is low, and it is impossible to achieve a large prestressed tension. Therefore, this paper proposes the reverse-arch method to paste the CFRP board and apply low prestress to strengthen the symmetrical RC beam. Through the three-point forward loading test, the cracking load, ultimate load, crack width, mid-span deflection, strain and failure mode of a reverse-arch method-pasted CFRP board-reinforced beam, a directly pasted CFRP board-reinforced beam and an unreinforced beam are compared. The results show that the load-bearing capacity and stiffness of the test beam can be improved by pasting CFRP plates with anti-arch method, but the ductility of the test beam is reduced. Compared with the unreinforced beam, the maximum cracking load and ultimate load are increased by 56% and 63% respectively. The reverse-arch method can produce low prestress, improve the stiffness and bearing capacity of members, and has a good prospect of engineering application.

Study on the shear behavior of RC beams strengthened by CFRP grid with epoxy mortar

In this paper, an experimental and theoretical study on the shear behavior of rectangular reinforced concrete (RC) beams strengthened by CFRP grid with epoxy mortar was investigated. Based on the test parameters including the reinforcement ratio of CFRP grid, the shear span-to-effective depth ratio and the concrete strength, six beam specimens were prepared and carried out to reveal the their strengthening mechanism and performance improvement. In addition, a prediction model of shear capacity of strengthened beams was proposed for more reasonable prediction. The research results indicated that the shear capacity and crack patterns of RC beams strengthened with CFRP grid in shear can be effectively improved. There was a substantial influence on the shear strengthening effects under the same reinforcement ratio of CFRP grid, as changing the shear span-to-effective depth ratio and concrete strength, which should be paid more attention. A novel shear model was proposed to evaluate the shear capacity of CFRP grid-strengthened RC beams, and this proposed model appeared as a good predictor of shear capacity with sufficient accuracy and smaller dispersion, when compared to other four existing models.

Investigations on fracture in reinforced concrete beams in 3-point bending using continuous micro-CT scanning

This study explores a fracture process in rectangular reinforced concrete (RC) beams subjected to quasi-static three-point bending. RC beams were short and long with included longitudinal reinforcement in the form of a steel or basalt bar. The ratio of the shear span to the effective depth was 1.5 and 0.75. The focus was on the load–deflection diagram and crack formation. Three-dimensional (3D) analyses of the size and distribution of pores and cracks were carried out with an X-ray micro-computed tomography system SkyScan 1173 of high resolution that is a very valuable non-destructive tool for studying a 3D material interior. The tomography system was connected with a quasi-static loading machine ISTRON 5569 to continuously follow fracture changes without loading breaks. The beams failed in shear due to a diagonal shear crack that was steeper with basalt reinforcement. The shear strength and flexural strength of RC beams with steel reinforcement were higher by about 10% than of RC beams with basalt reinforcement. The deflection corresponding to the maximum load of RC beams was higher by about 20–25% in RC beams with basalt reinforcement due to its lower basalt modulus of elasticity. The final volume of cracks in beams reinforced with basalt bars was higher by about 9–20% than in concrete beams reinforced with steel bars due to a higher beam deflection whereas the maximum crack width in concrete beams reinforced with basalt bars was higher by about 20–40% than in concrete beams reinforced with steel bars. The critical shear crack in RC beams with basalt reinforcement was wider by about 20–40% and steeper by about 10–45% as compared to concrete beams with steel reinforcement. The relationship between the crack volume and beam deflection was bi-linear. Both, aggregate breakage and crack branching occurred during beam bending.

Finite element analysis of rectangular RC beams strengthened with FRP laminates under pure torsion

AbstractComposite materials have attracted wide attention in strengthening of structural members. In this study, the behavior of rectangular reinforced concrete (RC) strengthened with fiber reinforced polymer (FRP) laminates under pure torsion was investigated numerically and validated by existing data from literature. Various practical strengthening configurations were considered and the efficiency of them was illustrated. Concrete damage plasticity constitutive model was used and required parameters was drawn. Good agreement in terms of torque–twist behaviors of RC beams strengthened with FRP laminates before and after cracking was found. Reasonable steel and FRP reinforcement responses as well as crack patterns were achieved and the failure modes of all the specimens were modeled correctly. A parametric study was carried out and parameter such as number of FRP plies, concrete compressive strength, and FRP strip orientations were considered. The results showed that the torsional capacity could improves by increasing the number of FRP plies and concrete compressive strength. Moreover, no significant change in the torsional capacity of RC beams when it was strengthened with a 45° or with a 90° FRP laminate was observed.

Investigation of various concrete materials to simulate seismic response of RC structures

This paper focuses on the performance evaluation of several concrete models in reinforced concrete (RC) structures subjected to seismic loading. Despite many studies conducted on implementing different characteristics of concrete in constitutive models, there is an essential need for investigating the ability of these models in predicting the behavior of structures in seismic applications. In this paper, several developed plasticity-based constitutive models with the combination of fracture and continuum damage models are investigated for application in seismic loading conditions. Damage-based isotropic and anisotropic models and smeared cracking approach have been applied as complementary components of plasticity-based concrete models. Robustness assessment of various developed plasticity and damage, or plasticity and smeared crack concrete models are evaluated using a finite element based software, LS-DYNA and employing five concrete models as indicators of desired constitutive models, including MAT 084, representative of plasticity and smeared crack model, and MAT 159, MAT 072R3, MAT 272, and MAT 273, representatives of plasticity and different tensile/compressive damage models. This paper studies the cyclic behavior of structural components, including RC rectangular and T-shaped beams, short and slender columns, lightly and highly reinforced squat and slender shear walls, with and without boundary elements. The minimum number of parameters available in most of the experimental researches is used in the simulation of concrete models. Based on the analysis results, the strengths and weaknesses of five selected concrete models to predict the key characteristics of cyclic behavior of RC structures, including initial stiffness, peak strength, strain at peak strength, failure mode, stiffness degradation, and pinching are discussed. Some recommendations are also provided for modeling the RC structures.

Torsional behavior of solid and hollow concrete beams reinforced with inclined spirals

Enhancing the torsional capacity of reinforced concrete (RC) beams while maintaining reasonably economic and efficient cross-sections poses a practical challenge in the design of such elements. Thus, developing and testing economically viable reinforcing techniques for enhancing the torsional capacity of RC beams is a significant aspect. Among these techniques is the continuous spiral reinforcement system that has shown promising results in enhancing the torsional capacity of rectangular RC elements.In this study, the role of continuous rectangular spiral stirrups, as a transverse reinforcement with a controllable pitch (P) and inclination angle (θ), in enhancing the torsional behavior of rectangular solid and hollow RC beams has been investigated experimentally. The applied torque was directed to lock the spirals for all specimens. The experimental program of this investigation included testing of ten specimens of normal strength RC beams; two of which were solid with closed and spiral rectangular stirrups. While the rest of specimens were hollow specimens included one beam reinforced by closed stirrups and seven beams reinforced by rectangular spiral stirrups with different reinforcing ratios. Different variables were considered to develop a wide range of the beams’ reinforcing scenarios. This includes stirrups type (conventional closed stirrups and rectangular spiral stirrups), inclined stirrups ratio, pitch, inclination angle and finally the longitudinal reinforcement ratio. In addition, a three-dimensional finite element model using ANSYS-15.0 was developed to examine the capability of the model to capture the observed torsional behavior of the experimentally tested beams.The obtained results showed that using inclined spiral rectangular stirrups in reinforcing RC solid and hollow beams greatly enhanced the torsional capacity by about 16% and 18%, respectively compared to using the conventional closed stirrups. Moreover, the results showed that using that technique leads to higher twist- angles, more ductile failure and increased strain energy by about 27% and 16% for solid and hollow beams, respectively. Lastly, the comparison between the results obtained from numerical model and experimental results showed good agreement and thus the numerical model can be used to extend the experimental work for investigating different reinforcing schemes.

Experimental and Analytical Investigations of the Use of Groove-Epoxy Anchorage System for Shear Strengthening of RC Beams Using CFRP Laminates.

Reinforced concrete (RC) beams strengthened in shear with carbon fiber reinforced polymer (CFRP) laminates as externally bonded reinforcement (EBR) usually fail due to debonding. This paper presents an experimental and analytical investigation on the use of groove-epoxy as an anchorage system for CFRP plates and sheets bonded on both sides of shear deficient RC beams. The aim of this study is to assess the effectiveness of using groove-epoxy in enhancing the shear capacity of RC beams. Nine rectangular RC beams were strengthened with CFRP plates and sheets with groove-epoxy anchorage systems of different groove widths and tested under four point bending. It is observed that the RC beams strengthened with the groove-epoxy anchorage system showed an increase in the shear-strength over the unstrengthened control beam up to 112 and 141% for plates and sheets, respectively. Also, the increase of shear-strength contribution of the groove-epoxy system to that of CFRP without grooves ranged between 30–190% for CFRP plates and between 40–100% for CFRP sheets. Generally, the contributions of groove-epoxy on shear-strength decreased with the increase of groove width. Moreover, shear strength prediction models, based on modifications of the ACI440.2R-17 shear model, were developed by incorporating groove factors as a modifier to the FRP shear-strength contribution. The developed models predicted the experimental shear-strength of the tested RC beams with a good level of accuracy, with an average mean absolute percent error (MAPE) = 3.31% and 6.68%, normalized mean square error (NMSE) = 0.072, 0.523, and coefficient of determination R2 = 0.964, 0.691, for plates and sheets, respectively.

FRP shear contribution prediction for U-wrapped RC T-beams using a soft computing tool

The reinforced concrete (RC) T-beam is relatively stronger in shear than the rectangular RC beam, represents the most realistic condition and has more implications in the construction industry. However, no study encompassing a large number of results of tests conducted on the RC T-beams externally shear strengthened with fiber-reinforced polymer (FRP) has been found. Therefore, the current study targets to calculate the contribution of externally bonded FRP towards the shear capacity of RC T-beams by means of a soft computing tool i.e. adaptive neuro-fuzzy inference system (ANFIS). A total of 148 sets of data collected from the literature and used for the training and testing of the ANFIS model. A comparative study between the ANFIS predictions and the obtained experimental outcomes has revealed that the ANFIS forecasts are in fine agreement with the experimental outcomes. Additionally, evaluation of the efficacy of the current ANFIS model has been done by comparing the ANFIS predictions with the predictions of seven broadly utilized design guidelines. On the basis of the comparison of different performance measures, it has been deduced that the efficacy of the current ANFIS model is superior to the considered design guidelines. A parametric study has also been done to explore the impact of the combined effect of the two input parameters on the FRP shear contribution.

Experimental Investigation of Reinforced Concrete Beam with Openings Strengthened Using FRP Sheets under Cyclic Load.

In this study, the cyclic behavior of reinforced concrete (RC) beam with openings strengthened using carbon fiber-reinforced polymers (FRPs) was experimentally investigated. Seven rectangular RC beams were cast and strengthened through external bonding of carbon fiber-reinforced polymer (CFRP) sheets around the beam web opening with different orientations to evaluate the maximum resistance, secant stiffness, strength degradation, ductility, energy dissipation capacity and behavior of the specimens’ failure mode under cyclic load. One solid beam without an opening (i.e., control specimen) and six beams constructed with circular web openings typically located in the middle of the beam and adjacent to the supports were used in the experiments. Among the six specimens with opening configuration, two beams were unstrengthened, and the remaining four specimens were strengthened with two layers of FRP sheets with vertical and inclined scheme orientation. Numerical studies were performed on ABAQUS software, and finite element modelling analysis results were verified through experiments. Results demonstrated that the use of FRP sheets has a significant effect on the cyclic behavior of RC beams, thereby improving the maximum strength and ultimate displacement to approximately 66.67% and 77.14%, respectively. The validated finite element models serve as a numerical platform to apply beneficial parametric studies, where the effects of opening size and bond length are investigated.

Experimental study on seismic behavior of RC beams with corroded stirrups at joints under cyclic loading

Corrosion of stirrups can be a major factor in the degeneration of seismic behavior for reinforced concrete (RC) structures. In this work, low-cycle loading tests were conducted on six rectangular RC beam specimens at joints with different stirrups corrosion levels. The failure modes, hysteretic curves, skeleton curves, stiffness degradation curves, ductility factor, energy dissipation and bearing capacity of RC specimens are compared and discussed. Meanwhile, the influence of corrosion cracks on mechanical properties of members was also investigated. Experimental results show that with an increase of stirrup corrosion level, the energy dissipation capacity and plastic deformation capacity dropped significantly. For specimens with a lower corrosion level of stirrups, though, the energy dissipation reduced gradually and the ductility factor increased slightly, indicating that slight corrosion of stirrups improved the ductility of specimens. However, the energy dissipation and ductility coefficient declined remarkably as the stirrup corrosion level increased. Compared with the uncorroded specimen, the ductility factor and energy dissipation decreased observably, by 22.5% and 34.5%, respectively, for specimen with stirrup corrosion level of 15.4%. Furthermore, the failure modes gradually changed from ductile bending failure to brittle failure as the corrosion level of stirrups continuously increased. The disadvantageous influence of stirrup corrosion degree larger than 15.4% in RC structures should be considered in their seismic analysis.

Repair of Severely Damaged Reinforced Concrete Beams with High-Strength Cementitious Grout

High-strength cementitious materials such as high-performance concrete are extensively used for retrofit of reinforced concrete (RC) structures. The effectiveness of these materials is increased when mixed with steel fibers. A commonly used technique for strengthening and repair of RC beams consists of applying high-performance fiber-reinforced concrete jackets around the beam perimeter. This paper investigates the jacketing method for repairing severely damaged RC beams. Four 2 m (6 ft 63/4 in.) long rectangular RC beams, 200 × 300 mm (8 ×12 in.) were initially cast and loaded until failure based on three-point bending tests. The four beams were then repaired by thickening the sides of the damaged RC beams using a commercially available high-strength shrinkage grout with and without steel fibers. Strain and deformation were recorded in the damaged and repaired beams to compare structural performance. It is shown that the flexural strength of the repaired beams is increased and the crack pattern under loading is improved, proving that the proposed repair method can restore the resistance capacity of RC beams despite the degree of damage. A method for repair is proposed and an analytical investigation is also performed to understand the structural behavior of the repaired beams based on different thickening configurations.

Experimental and numerical investigation of shear performance of RC beams strengthened with FRP using grooving method

In this paper, enhancement in the shear capacity of reinforced concrete (RC) members strengthened with carbon fiber –reinforced polymer (CFRP), using grooving method (GM) through externally bonded reinforcement in groove (EBRIG), was first investigated by laboratory tests. To achieve it, Eight RC rectangular beams were constructed, and interaction between externally applied CFRP sheets and internal steel stirrups was investigated. The specimens, with dimensions of 200 × 300 × 2000 mm (width × height × length), were tested under four-point bending and their failure mechanisms were briefly compared. The specimens were then further examined by a numerical tool for validating against experimental results. Outcomes inferred that vertical utilization of EBRIG technique enhanced shear capacity of the beams with and without stirrups by an average of 37% and 71%, respectively. Diagonal utilization of EBRIG method angled at 45° increased the shear capacity about 60% and 95% in the strengthened beams with and without stirrups, respectively. Results indicated that by increasing stirrup spacing, the effective strain of CFRP fibers increased. Results also showed that ductility of strengthened beams without stirrups decreased compared to control specimens, while ductility of strengthened beams with stirrups increased. Furthermore, modeling the cohesive layer for the CFRP-concrete interface revealed a good estimation of load-deflection behavior compared with the experimental results. Numerical results also demonstrated that bonding stresses of the interface layer reached higher values in strengthened specimens with stirrups compared to specimens without stirrups.

Shear Strengthening of Reinforced Concrete T-Beams by Using Fiber-Reinforced Polymer Composites: A Data Analysis

Many studies have compiled experimental results of fiber-reinforced polymer (FRP) shear strengthened reinforced concrete (RC) beams into databases for the investigation of the effect of different parameters on the efficacy of FRP strengthening schemes. However, these studies are mainly comprised of the results of FRP shear strengthened rectangular RC beams. The RC T-beams are stronger in shear than the rectangular RC beams, represent the most realistic situation, and have more significance in the construction industry. However, no study comprising of a large number of results of FRP-strengthened RC T-beams has been found. Therefore, the present study represents the results of more than 250 tests performed on the shear deficient RC T-beams strengthened with FRP and also the essential material characteristics. It also compares the accuracy of seven widely used design guidelines for the prediction of shear contribution of FRP based on the experimental shear contribution of FRP. This study concludes that the efficacy of the FRP strengthening scheme varies with the adopted strengthening schemes, whereas the predictions of different design guidelines observed to be not promising. However, predictions by fib and TR55 guidelines have good correlation and standard deviation values, respectively, with the experimental results than the other guidelines.

Condition assessment of RC beams using artificial neural networks

In this study, an imaged-based methodology for condition assessment of Reinforced Concrete (RC) road bridge components is presented. The study is divided into experiments on RC rectangular beams and scaled (1:12) T-beams, validation of numerical models for T-beams and training of corresponding artificial neural networks (ANNs). In the experimental work, Digital Image Correlation (DIC) was used as a virtual sensor for data extraction. Rectangular RC beams of size 1800 mm × 150 mm × 200 mm and scaled (1:12) RC T-beams were tested under four-point flexural loading on a 100-ton dynamic testing machine. The experimental stress-strain curves obtained from the compression test on prism specimens at 28 days were used as input data for material model parameters in finite element model (FEM) software SAP2000. To assess the condition of structural components, a local damage index (LDI) was developed. Validation of FEM results with experimental results enables derivation of moment-curvature backbone curve for full-scale bridge girders, which enables further quantification of damage and residual moment capacity of full-scale bridges designed by Ministry of Road Transport and Highways (MoRTH). The correlation between the experiments, simulation and ANN predictions was found to be very satisfactory.

Effective strengthening schemes for heat damaged reinforced concrete beams

Several effective strengthening schemes for enhancing the flexural strength of heat-damaged reinforced concrete (RC), beams are proposed. A series of twenty-eight RC rectangular beams were cast, subject to a temperature of 600 °C for 3 h, strengthened, and then tested in flexure to determine the effect of externally applied carbon and glass fiber reinforced polymeric sheets (CFRP) and (GFRP) respectively, as a method for regaining the beams’ flexural capacity. The load-deflection behavior and the modes of failure of the beams tested are described. The beams strengthened in shear and flexure with CFRP and GFRP sheets applied at the sides and the bottom of the beams in U-shaped jackets or strips showed a significant increase in their flexural strength compared to control and heat damaged ones. They achieved a high percentage of the control beams load carrying capacity, and exhibited a ductile failure characterized by the initiation of typical flexural cracks in the moment zone followed by the occurrence of flexure-shear cracks in the constant shear span. Optimizing the CFRP and GFRP strengthening schemes proposed could provide promising and cost effective repair alternatives for enhancing the flexural capacity of fire damaged RC members.

Structural Performance of Externally Strengthened Rectangular Reinforced Concrete Beams by Glued Steel Plate

This paper examines both flexural and shear behaviour of eight full-scale (2700×160×100-mm) reinforced concrete rectangular beams subjected to one-third point load. Two types of beams were investigated; Type-E and Type-C. Type-E are reinforced concrete rectangular beams strengthened externally by 1.5mm thick structural steel plate glued to the tensile face with epoxy as adhesive while type-C are reinforced concrete rectangular beams without structural steel plate glued to the tensile face. An average concrete strength of 30N/mm2 at 28 days was used. Required internal reinforcement according to BS 8110-1:1997 was provided for the concrete rectangular beams. Before the beams were externally strengthened, the beam surface to be plated was gritted to take off the cement membrane and to open up the aggregates. Epoxy adhesive was applied as a paste to both the plate and concrete surfaces: the two surfaces were then put together and held in place under pressure of 3.84kN/m2 until the glue was cured. The beams were subjected to flexural testing after 28 days, using loading frame. Each of the rectangular beams support at both ends were subjected to one-third point load, deflection readings were recorded using a dial gauge at every 1.82kN increment. At ultimate load, the beams failed by a crack initiated at the bottom fiber of the beams. From the test results, an average flexural and shear strengths of Type-C beams are; 21.91N/mm2 and 1.05N/mm2 respectively, while type-E beams are; 28.91N/mm2 and 1.39N/mm2 respectively. The results of the investigation showed that flexural and shear strengths of reinforced concrete rectangular beam increased when strengthened externally by bonded steel plate. A straightforward analytical procedure was developed to validate the experiment results of type-E and type-C beams, using rectangular stress block for concrete. Experimental average failure load for beams Type-C and Type-E are 22.44kN and 29.60kN respectively while theoretical failure load for Type-C and Type-E beams are 20.86kNand 31.2kN respectively. Generally, there were acceptably fair correlations between analytical and experimental failure loads of Type-C and Type-E beams.

Structural Performance of Externally Strengthened Rectangular Reinforced Concrete Beams by Glued Steel Plate

This paper examines both flexural and shear behaviour of eight full-scale (2700×160×100-mm) reinforced concrete rectangular beams subjected to one-third point load. Two types of beams were investigated; Type-E and Type-C. Type-E are reinforced concrete rectangular beams strengthened externally by 1.5mm thick structural steel plate glued to the tensile face with epoxy as adhesive while type-C are reinforced concrete rectangular beams without structural steel plate glued to the tensile face. An average concrete strength of 30N/mm2 at 28 days was used. Required internal reinforcement according to BS 8110-1:1997 was provided for the concrete rectangular beams. Before the beams were externally strengthened, the beam surface to be plated was gritted to take off the cement membrane and to open up the aggregates. Epoxy adhesive was applied as a paste to both the plate and concrete surfaces: the two surfaces were then put together and held in place under pressure of 3.84kN/m2 until the glue was cured. The beams were subjected to flexural testing after 28 days, using loading frame. Each of the rectangular beams support at both ends were subjected to one-third point load, deflection readings were recorded using a dial gauge at every 1.82kN increment. At ultimate load, the beams failed by a crack initiated at the bottom fiber of the beams. From the test results, an average flexural and shear strengths of Type-C beams are; 21.91N/mm2 and 1.05N/mm2 respectively, while type-E beams are; 28.91N/mm2 and 1.39N/mm2 respectively. The results of the investigation showed that flexural and shear strengths of reinforced concrete rectangular beam increased when strengthened externally by bonded steel plate. A straightforward analytical procedure was developed to validate the experiment results of type-E and type-C beams, using rectangular stress block for concrete. Experimental average failure load for beams Type-C and Type-E are 22.44kN and 29.60kN respectively while theoretical failure load for Type-C and Type-E beams are 20.86kNand 31.2kN respectively. Generally, there were acceptably fair correlations between analytical and experimental failure loads of Type-C and Type-E beams.

Numerical study using FE simulation on rectangular RC beams with vertical circular web openings in the shear zones

Transverse and vertical openings are usually created in beams made of reinforced concrete (RC) to accommodate the pipes and ducts used in utilities. The decrease in shear strength because of the openings causes problems in current RC beams. This study investigates the impact of various vertical circular web openings alongside the shear-area span of an RC beam on its shear performance. To this end, a model with three finite element (FE) dimensions was developed, primarily for investigating and analyzing the outcome of this case. Using the ANSYS-V15 FE program, 41 beams were analyzed. The findings of the eight investigational beams were compared with results from previously published works. The devised model was tested to ensure its accurate functioning, using outcomes already attained through experiments. The outcomes of the experimental test proved that the newly devised FE model could be used to calculate the RC beams’ shear-load capacity and to accurately predict failure modes. The outcomes revealed that the effect of the vertical-opening diameter on the width of the beam section was greater than the effect of the length of the shear span. Therefore, we concluded that the influence of the opening diameter was greater than the effect of the number of openings.