Concrete Beams Research Articles

ANALYSIS OF THE IMPACT OF CROSS-SECTION DAMAGE ON THE STRENGTH AND DEFORMABILITY OF BENT REINFORCED CONCRETE ELEMENTS

The article analyzes defects and damage in reinforced concrete structures, particularly physical, biological, and chemical, with an emphasis on the impact of prolonged operation and aggressive environmental conditions. Research shows that mechanical damage, such as spalling and potholes, significantly reduces the load-bearing capacity of structures and causes complex deformations. Relevant directions in scientific research have been identified, particularly regarding the behavior of damaged reinforced concrete beams under load, which require further development and improvement of methods for assessing residual load-bearing capacity. The article emphasizes the need for additional experimental studies and the use of modern software for more accurate methods of predicting and calculating reinforced concrete structures.

NONLINEAR MODELING AND ANALYSIS OF DAMAGED REINFORCED CONCRETE BEAMS USING ANSYS AND LIRA-SAPR SOFTWARE PACKAGES

This article presents a comparative analysis of the nonlinear behavior of a reinforced concrete beam with damaged reinforcement in the tension zone under a gradually increasing load until failure. The experimental beam, measuring 2100 mm × 200 mm × 100 mm, consists of a 20 mm diameter rebar in the tension zone, two 6 mm diameter rebars in the compression zone, and 6 mm diameter stirrups spaced 75 mm apart for transverse reinforcement. Nonlinear calculations were performed using ANSYS and LIRA-SAPR, with identical initial conditions applied to both models for accurate comparison. The study focuses on key aspects such as result accuracy, ease of use, and time required for nonlinear calculations, including material and geometric nonlinearity. By highlighting the strengths and weaknesses of each software, the research offers insights for engineers and researchers working on complex structural modeling of reinforced concrete.

Numerical Simulation of GFRP-reinforced Rectangular Concrete Beams and Proposed Design Expressions

Rebar corrosion, which has emerged as a primary detrimental factor, significantly impacts the structural performance, durability, and overall serviceability of reinforced concrete (RC) structures. In response to this issue, the growing use of GFRP, which offers superior corrosion resistance compared to steel, highlights the need to compare its performance with traditional steel-reinforced beams. To address this need, this study aims to evaluate the flexural behavior of beams reinforced solely with GFRP rebar and assess their structural performance relative to steel-reinforced beams. To achieve this, finite element models of both steel-reinforced and GFRP-reinforced beams were developed using ANSYS software. The analysis focused on load-bearing capacities, displacement characteristics, and crack patterns, and included the calculation of strain energies corresponding to collapse prevention performance limits. Overall, the study concludes that these modifications enhance design guidelines for GFRP-reinforced beams, offering improved practical applications in structural design. Significant findings include the proposed modification to the minimum reinforcement ratio equation in ACI 440.1R-15 for GFRP-reinforced concrete, the introduction of a suggested strain reduction factor for GFRP rebar, and the revision of the effective moment of inertia equation with coefficients of 0.05 and 0.95. These revisions improved the general performance indicator to 1.17, yielding better results compared to other equations in the literature. The study concludes that these modifications enhance design guidelines for GFRP-reinforced beams, offering improved practical applications in structural design.

Experimental studies of the strength of reinforced concrete beams with a restored protective layer

The article presents the results of experimental studies to assess the strength of reinforced concrete beams with varying degrees of destruction of the protective layer of the working longitudinal reinforcement, followed by its restoration with a repair mixture. The test results of three series of prototypes, three samples in each series, are presented. Within the series, prototypes were made with the same longitudinal reinforcement, and the samples in each series differed in the degree of destruction of the protective layer of the longitudinal working reinforcement in the transverse bending zone. The samples were tested as freely supported beams loaded in the span by two identical concentrated forces. The results obtained made it possible to evaluate the role of longitudinal reinforcement, depending on the degree of destruction of its protective layer, in ensuring strength, forming a stress-strain state and the nature of destruction of reinforced concrete beams of rectangular cross-section in transverse bending zones.

Influence of Specimen Width on Crack Propagation Process in Lightly Reinforced Concrete Beams

Models used to study the fracture process of concrete are often considered 2D, ignoring the influence of specimen width. However, during the fracture process in pre-cracked concrete beams, the crack length varies along the thickness direction, especially in reinforced concrete. To study the influence of specimen width on reinforced concrete fracture behavior, a 3D numerical method was used to simulate the crack propagation processes of lightly reinforced concrete beams based on Fracture Mechanics. Nonlinear spring elements with different stress-displacement constitutive laws were employed to characterize the softening behavior of concrete and the bond-slip behavior between the steel bars and concrete, respectively. It is assumed that the crack begins to propagate when the maximum stress intensity factor at the crack tip along the beam width reaches the initial fracture toughness of concrete. To verify the validity of the proposed method, the completed crack propagation processes of lightly reinforced concrete three-point bending notched beams were simulated, and the calculated load-crack mouth opening displacement curves showed a reasonable agreement with the experimental data. Moreover, the impact of the 2D reinforced concrete beam model on the crack propagation process was analyzed. The results indicate that at the initial loading stage, the external load P obtained from the 2D model is significantly larger than the result from the presented 3D model.

Carbon fiber reinforced polymer (CFRP) laminates: flexural strengthening method for prestressed concrete beams with anchorage loss

Abstract Post-tensioning (PT), a method of pre-stressing, involves the use of high-strength steel strands/ tendons to reinforce concrete or other materials. On the contrary, Carbon Fiber-Reinforced Polymers (CFRP) are lightweight, high-strength materials with used to strengthen concrete structures by adhering the polymer to the concrete element. Challenges with post-tensioned elements include reverse curvature of the post-tensioning strands, tendon misplacement, and frequent damage in the anchorage and dead-end zones. These difficulties frequently cause bulging of the surrounding concrete, even at lower stress levels, and can lead to concrete bursting when tension exceeds certain threshold. This study investigates into the potential of CFRP strengthening technique to improve the flexural capacity of post-tensioned concrete beams with anchorage loss. Through an experimental program, the study compares the performance of control beams to those reinforced with different layers of CFRP. The results of this study demonstrated that there was a significant increase in flexural capacity, ranging from 45.31% to 78.62% for single layers and 87.17% to 153% for double layers of CFRP sheet. Additionally, the research examines how different levels of prestressing and CFRP wraps influence crack formation and delamination patterns of carbon fiber, with promising results. It was also noted that optimal usage of CFRP fibers and tendons is found to be critical. The study suggests exploring alternative fiber types and orientations for future study.

Reactive powder concrete beam design using a mathematical software to reduce costs

AbstractReactive powder concrete is widely recognized for its remarkable mechanical characteristics and resilience, rendering it an ideal option for structural uses that include heavy loads. However, the intricate interaction of numerous material and geometric aspects makes constructing reactive powder concrete beams extremely difficult. By using MATLAB to provide an optimized design framework for beams, this research tackles these issues. Particle swarm optimization and evolutionary algorithms are two of the advanced techniques used in the study to solve the optimization problem. It also includes constraints other one as structural requirements and material limitations. Results demonstrate that MATLAB-based optimization facilitates effective design, lowering costs and material consumption, with potential for more applications in the building sector.

Experimental study on the shear behaviour of high-strength lightweight concrete beams incorporating graphene oxide.

Graphene oxide (GO) has achieved significant progress in the material behaviour of cement-based materials. However, research on its structural behaviour in high-strength lightweight concrete (HSLWC) structures is limited, which restricts its engineering applications. This study focused on investigating the effects of low contents of GO on the shear behaviour of HSLWC beams. A total of four HSLWC beams with GO contents of 0, 0.01, 0.03 and 0.05% (by weight of cement) were designed to observe failure modes, load‒deformation curves, shear capacities, crack behaviour and load‒strain curves under four-point loading by a 300 kN servo loading device. The results revealed that all the beams exhibited shear compression failure. GO improved the shear capacity of the HSLWC beams, and this strengthening effect increased with increase in GO content. When the content of GO was 0.05%, the ultimate load of the beam reached a maximum, which was 39.2% greater than that of the control beam. GO can endow the HSLWC beams with a certain degree of ductility. In addition, a modified JGJ 12-2006 model was proposed to predict the shear capacity of HSLWC beams containing different GO contents on the basis of a comparison of typical models. This study can provide exploratory engineering practice for evaluating and designing GO-reinforced HSLWC structures.

Machine learning-based models for FRP shear contribution of wrapped reinforced concrete beams

Machine learning-based models for FRP shear contribution of wrapped reinforced concrete beams

A Review of the Shear Design Provisions of ACI Code and Eurocode for Self-Compacting Concrete, Recycled Aggregate Concrete, and Geopolymer Concrete Beams

A Review of the Shear Design Provisions of ACI Code and Eurocode for Self-Compacting Concrete, Recycled Aggregate Concrete, and Geopolymer Concrete Beams

Experimental Studies of Low-Reinforced Concrete Structures Containing Inter-Bay Construction Joints Strengthened with Prestressed Basalt Composite Reinforcements and External Transverse Reinforcements

During the long-term operation of main run-of-river head powerhouses for hydroelectric power plants, technical changes that deteriorate the operational properties of their reinforced concrete structures can occur. Therefore, in order to substantiate the application of prestressed basalt composite reinforcements to strengthen reinforced concrete hydraulic structures in operation, a set of computational and experimental studies was carried out, taking into account their characteristic features. After 4 years of ageing, the serviceability and reliability of the beams with prestressed basalt composite reinforcements were demonstrated through stabilisation of the prestress losses and the values obtained for bearing capacity, deflection, and the width of the opening of the inter-bay construction joints and the deformations of the metal reinforcements and the basalt composite reinforcements. The bearing capacity of the investigated reinforced concrete beams reinforced with external transverse reinforcements was increased 1.4–2.5 times over that of the variants reinforced with longitudinal prestressed basal composite reinforcements. Furthermore, in this study, the impacts of static loads and seismic effects with a magnitude greater than 8 on the run-of-river hydroelectric power plant powerhouse were calculated based on dynamic design theory. Regarding applications to hydroelectric power plant structures and constructions, for which it is not always possible to determine the location of compressed or tensile zones during their operation nor under seismic action, our research results are suggestive of a reasonably positive effect.

A numerical investigation of the structural behavior of reinforced concrete beams fully or partially encased with UHPC layers in flexure

Weakness in the structural facilities appears due to design faults, poor construction, usage change, maintenance lack, material defects, and environmental conditions. Therefore, strengthening structures becomes necessary for deteriorated concrete and enhancing aging concrete elements to achieve satisfactory performance perfectly. This study numerically investigated the structural behavior of conventional concrete beams reinforced with Ultra-High Performance Concrete (UHPC) layers on different sides. The arrangement of UHPC layers, bonding method between traditional concrete and UHPC, layer thickness, and reinforcement ratio were examined using Abaqus software. The interface between the UHPC layer and conventional concrete sustains compressive, tensile, and shear stresses, which cause weak resistance to the stresses at the contact surfaces. Therefore, the simulation of contact face in Abaqus needs a proper numerical model relying on practical methods. However, using the bonding models available in Abaqus is crucial for reaching logical results comparable to the practical ones. The practical bonding approaches are highly consequential, such as roughening surfaces by sandblasting to attain a firm connection between the contact surfaces, which permits using a surface-based tie constraint for simulation. Further, epoxy resin conducts as a thin coating between contact surfaces, making it possible to simulate via a cohesive surface. The results proved that increasing the area encased by the UHPC layer improves load capacity further and reduces the deflection at the maximum load. Surrounding the beam on whole sides with a UHPC raises load capacity by 108 % and reduces deflection by 46 %. Adding a UHPC layer to the beam delays crack initiation and reduces their number and spacing. Increasing the UHPC layer thickness or reinforcement ratio enhances the load capacity of the beam at cracking and the ultimate state.

INVESTIGATION ON CORROSION AND FLEXURAL BEHAVIOUR OF REINFORCED CONCRETE USING MARINE SAND

Traditionally, the construction industry relies on both manufactured sand (known as MF-Sand) and river sand as primary constituents for fine aggregates. However, in response to the dwindling supply of river sand, the contemporary preference is firmly in favor of MF-Sand. This research focuses the utilization of meticulously cleaned marine sand (referred to as MR-Sand) as a superior substitute for MF-Sand, aiming to curtail the reliance on and depletion of river sand, a finite natural resource. The objective of this research is to examine the mechanical property of flexural performance of Reinforced Cement Concrete (RCC) Beam and durability study of concrete using corrosion test in which washed MR - Sand as a fine aggregate in partial replacement of MF-Sand from 20% to 60%. The physical and chemical characteristics of treated and untreated marine sand are compared with a view to better comprehending the features of MR and MF-Sand. Experimental research works have been carried out to look into the corrosion test and flexural strength in order to better understanding the strength and durability attributes of concrete. The values for flexural strength, ultimate load, load-deflection, load-strain, and crack pattern have been compared for the RCC beam specimens MF100, MR20, MR40 and MR60. The findings indicate that 60% of MR-Sand possesses the desired properties of strength and durability of concrete. Additionally, Finite Element Analysis is carried out using the ABAQUS software to further validate the experimental findings of load-deflection, load carrying capacity, crack pattern and flexural strength.

Hybrid CFRP‐GFRP sheets for flexural strengthening of continuous RC beams: Experimentation and analytical modeling

AbstractContinuous reinforced concrete (RC) beams cast in place are commonly used in construction; however, there is a notable gap in the literature regarding the performance of continuous RC beams strengthened with fiber‐reinforced polymer (FRP) sheets. Strengthening RC beams with FRP sheets typically leads to reduced ductility and moment redistribution capacity due to the linear stress–strain behavior of FRP materials compared to non‐strengthened RC beams. Addressing this gap, this study explores the feasibility of enhancing the mechanical properties and ductility of strengthened elements through a hybrid approach, combining carbon‐fiber‐reinforced polymer (CFRP) and glass‐fiber‐reinforced polymer (GFRP) sheets. An experimental program was conducted, retrofitting two continuous two‐span RC beams (250 × 150 × 6000 mm) with hybrid CFRP‐GFRP (HCG) sheets. Concentrated loads were applied at the center of each span, and comprehensive data on strains in FRP sheets, longitudinal reinforcements, and crack propagation patterns were recorded and meticulously analyzed. The outcomes demonstrated that employing HCG sheets for strengthening RC continuous beams significantly improves ductility, load‐carrying capacity, and moment redistribution, surpassing the performance of beams strengthened with either CFRP or GFRP sheets. To ensure accurate predictions of the flexural response, an analytical model was developed and rigorously verified using the experimental results. The model takes into account the strain compatibility condition and provides insights into the behavior of continuous RC beams strengthened with CFRP, GFRP, and HCG sheets. This research contributes valuable knowledge to the understanding of FRP sheet strengthening techniques, emphasizing the efficacy of HCG sheets for achieving enhanced structural performance in continuous RC beams.

Innovative friendly-environmental hybrid model of precast reinforced concrete deep beams based on curved hybridization

Innovative friendly-environmental hybrid model of precast reinforced concrete deep beams based on curved hybridization

Experimental investigation of prismatic and non-prismatic reinforced concrete beams

Experimental investigation of prismatic and non-prismatic reinforced concrete beams

A comparative analysis of decision tree on torsional capacity of reinforced concrete beams

A comparative analysis of decision tree on torsional capacity of reinforced concrete beams

Effect of Stirrups Shaped on Shear Capacity of Self-Compacting Concrete Beams Provided by External Steel Plate

The stirrups are the major factor which resists the shear forces and others parameters like as aggregate and dowels are contribute with less than 7% of shear strength.Shear connectors transmit the shear forces in composite beams between steel parts and concrete, therefore these connectors can be used as vertical legs to assistance stirrups in their performance. It was also noted that the change in the Shape of the stirrups does not have a significant effect on the shear capacity, and the decrease in endurance can be compensated by reducing the distance between the stirrups, and it was also noted that the horizontal parts of the stirrups may have a limited and negligible effect, and therefore the stirrups can be replaced by I shaped instead of conventional stirrups therefore the stirrups can be replaced by I shaped instead of conventional stirrup.

Flexural behaviour of normal concrete circular beams strengthened with ECC and stainless steel tubes

The use of laminated fibres for strengthening reinforced concrete beams is challenging owing to bonding and compatibility issues, especially in scenarios where cost effectiveness and long-term performance are important. A novel flexural strengthening technique for normal concrete circular beams (NCCBs) is proposed, using engineered cementitious composites (ECCs) and stainless steel tubes (SSTs). To examine the application of the proposed strengthening method, five NCCBs were fabricated and tested under static loading until failure to investigate the effects of ECC thickness and SST thickness. The test results showed that the strengthening technique greatly improved the failure pattern and the ultimate flexural capacity of the tested NCCBs, and the enhancement increased with an increase in the thickness of the ECC and SST. Using Abaqus software, finite-element models were constructed to simulate the performance of the tested NCCBs. The accuracy of the finite-element modelling was confirmed by comparing the simulations with the experimental results. The validated model was used for a detailed parametric investigation of the effects of the thickness of the ECC and SST on the failure and ultimate bending capacity of the strengthened beams.

Flexural behaviour of self-compacting coconut shell reinforced concrete beam using manufactured sand

Flexural behaviour of self-compacting coconut shell reinforced concrete beam using manufactured sand