Reinforced Concrete Research Articles

Restraint effect of steel bar on early-age shrinkage of steel bar-mortar composites

Time-space-dependent stress and strain distribution within steel bar-mortar composites is key for shrinkage and cracking prediction of Reinforced-Concrete (RC) members. A novel system was designed to investigate the restraint of steel bars on the early-age shrinkage while digital image correlation was also employed to analyze spatial strain distribution. The measured restraint degree increases with the reinforcement ratio and maintains stable after about 36 h. Restraint effects is interfered by micro-cracks, because of which the calculated restraint degree matched the measured one better after being modified by a coefficient concerning reinforcement ratio. The overall restrained stress shows a three-stage process affected by the bonding evolution. The strain spatially undergoes a three-region distribution along the steel bar induced by the shear transfer and a two-region distribution on the cross-section aligning with the interface gradient. This study demonstrates a quantitative analysis on the steel bars restraint parameters and its evolution.

Experimental and Analytical Evaluation to Strengthened R.C Beams Using Ferrocement Under Torsion

The safety of structures around the globe represents a significant and pressing concern, underscoring the urgent need for the development and implementation of effective rehabilitation methods to ensure their continued functionality. Ferrocement has emerged as a durable method for the restoration of reinforced concrete (RC) structures, demonstrating resilience and versatility in addressing structural damage. A substantial body of research has been conducted to examine the mechanical properties of ferrocement, with a particular focus on its efficacy in reinforcing beams against a range of forces. In light of the limited understanding of the factors affecting the torsional strength of ferrocement-wrapped beams, it is imperative to conduct experimental investigations. The objective of this study is to evaluate and compare the torsional strength, angle of twist and crack development of different wrapping types using both analytical analysis and experimental data. The findings indicate that three-sided wrapping is an effective method for enhancing torsional behaviour, as evidenced by both experimental and analytical results. Furthermore, the utilization of styrene-butadiene rubber (SBR) as a connecting material has been demonstrated to be an effective method for maintaining cohesion across reinforced beams.

Simulation study on static pressure crushing performance of demolished reinforced concrete beams for recycling

A highly efficient, low-carbon crushing technology is urgently needed for recycling demolished reinforced concrete (RC) components. Static pressure crushing (SPC), based on fragmentation theory, is a proposed solution. This paper presents a numerical model and a corresponding quantitative analysis method for the SPC of RC components. The model was developed based on a full-scale crushing application of an RC beam, wherein the failure of concrete and steel was characterized by the traditional finite element method (FEM) and the “erosion algorithm”. A volume reduction-based crushing ratio was suggested and proven feasible for the quantitative evaluation of SPC. Subsequently, the effects of component length, boundary conditions, and top die shape on crushing performance were numerically investigated. The results show that the established model effectively simulates the crushing behavior of RC beams, influenced by boundary conditions and top die shape. Furthermore, modifying the top die shape can significantly enhance crushing performance. A crushing ratio of 49.8 % was achieved using the cross-shaped top die. This study provides a practical quantitative analysis paradigm for SPC process optimization.

Flexural Behavior of Precast Rectangular Reinforced Concrete Beams with Intermediate Connection Filled with High-Performance Concrete

Precast rectangular reinforced concrete (PRRC) beams are joined on construction sites using concrete in situ to achieve the desired length. Limited research exists on the effect of intermediate connection shapes and the types of infilled concrete on the flexural performance of PRRC beams. This paper presents a comprehensive experimental and numerical investigation into the performance of PRRC beams with various intermediate connection geometries and infilled materials under flexural loading. The study examines rectangular, triangular, and semi-circular intermediate connections, along with the performance of beams infilled with normal concrete (NC), engineered cementitious composites (ECC), ultra-high-performance ECC (UHPECC), and rubberized ECC (RECC). The experimental results indicate that the rectangular intermediate connection exhibits superior performance in terms of strength and energy absorption compared to the triangular and semi-circular shapes. Beams incorporating UHPECC demonstrated the most significant improvements in strength and energy absorption, outperforming those with ECC and RECC for any shape of intermediate connection. Moreover, beams with rectangular connections and UHPECC infill exhibited the most significant increase in energy absorption and ultimate load compared to the beams with ECC and RECC. The ultimate load of the beams with UHPECC and tensile reinforcement bar diameters of 10 mm and 12 mm increased by 13% and 29%, respectively, compared to the control beam. The energy absorption of the beams with tensile reinforcement bar diameters of 10 and 12 mm was found to be 75% and 184% higher, respectively, than the control beam. In addition, an increase in tensile bar diameter was found to enhance both the energy absorption and the ultimate load capacity of the beams, regardless of the type of infill concrete. Beams incorporating UHPECC demonstrated the most significant improvements in strength and energy absorption, outperforming those with ECC and RECC. In particular, beams with rectangular connections and UHPECC infill exhibited an increase in energy absorption and ultimate load of up to 184% and 29%, respectively. UHPC was calculated to be as high as 184%, and 29%, respectively, compared to the control beams. In addition, an increase in tensile bar diameter was found to enhance both energy absorption and ultimate load capacity. Finite element modeling (FEM) was developed and validated against the experimental results to ensure accuracy. A parametric study was conducted to study the effects of various concrete types in triangular and semi-circular connections, as well as the influence of intermediate connection length on semi-circular connections under flexural loads. The findings reveal that increasing the length of intermediate connections increases the ultimate load of the beams.

Numerical study on flexural behaviour of sulphate corroded RC beams strengthened with ultra-high-performance concrete

Ultra-high-performance concrete (UHPC) has found extensive application in the strengthening of existing reinforced concrete (RC) structures; however, limited knowledge exists regarding its use in RC structures exposed to sulphate attacks. This study developed a non-linear finite element analysis (FEA) model to predict the flexural behaviour of sulphate corroded RC beams strengthened with UHPC jackets. The FEA model, validated with experimental results, was extended to examine UHPC configurations and thicknesses. Evaluation included ultimate load capacity, serviceability state, and stiffness. Crack patterns, load-deflection behaviour, and strain distribution were analysed for strengthened beams at their respective ultimate loads along the mid-span cross-section height. FEA results showed diverse configurations significantly enhanced the load-carrying capacity of sulphate corroded RC beams by 54.5-88.6%. Strengthened beams exhibited a 64% increase in flexural moment capacity, with notable improvements in cracking and post-cracking stiffness. Strain distribution analysis revealed UHPC strengthening increased strain values, emphasising UHPC jackets’ substantial role in resisting stresses and enhancing flexural behaviour. As expected, the three-sided UHPC configuration outperformed two-sided and bottom-side ones. Increasing UHPC thickness proved most effective in bottom-side strengthening, followed by three-sided, with a lesser effect in two-sided strengthening. Theoretical predictions from the suggested flexural moment capacity calculation aligned well with FEA results.

Performance evaluation of indented macro synthetic polypropylene fibers in high strength self-compacting concrete (SCC)

Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0–1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread.

An interpretable machine learning approach for predicting the capacity and failure mode of reinforced concrete columns

During seismic events, reinforced concrete (RC) columns play a crucial role in maintaining buildings’ structural integrity. This motivated engineers and practitioners to search for key parameters that influence the load-carrying capacity and failure mechanisms of such columns. However, the complexity and nonlinearity of seismic effects along with the intricate nature of RC columns as a composite system challenge the capabilities of analytical and empirical approaches to accurately capture the response of RC columns. Subsequently, the present study utilizes Machine Learning (ML) techniques to identify the failure modes and predict the corresponding capacities of RC columns based on both their geometrical and material properties. Decision trees and different ensemble methods were employed to predict both the columns’ failure mode and ultimate capacity. A multivariate dataset consisting of 486 cyclically loaded rectangular and circular columns was used to develop and validate the models. In addition, different embedded variable selection techniques were employed to evaluate the significance of input parameters in predicting the performance of columns. Moreover, partial dependence plots and accumulated local effects were employed to uncover the interrelationships between the input features and the modelled outputs. The developed models yielded an average accuracy of 90% and 95% for predicting the failure mode and ultimate capacity of RC columns, respectively. Given such high accuracy, it can be inferred that, ML techniques have the potential to provide efficient and reliable prediction tools to support seismic design and assessment decisions - mitigating seismic risks and empowering resilience planning in the face of extreme events.

Seismic fragility and risk assessment of Reinforced Concrete bridges undergoing elastomeric bearing deformations induced by landslide

The paper presents a study on the seismic fragility of Reinforced Concrete (RC) bridges isolated by elastomeric bearing devices subjected to differential displacements induced by slow-moving landslides. The seismic behaviour of isolated bridges is ruled by the performance of elastomeric bearings to reduce and dissipate earthquake actions. These bridges are subjected to service loads that usually are accounted for in design, but possible additional actions from the surrounding environment, such as landslides affecting substructure components, can seriously undermine the seismic response. The paper describes a practical approach to investigate the seismic fragility and risk of RC bridges isolated by elastomeric bearings, which may undergo early deformations induced by the differential displacements of substructure components. On the basis of previous existing studies, the proposed methodology is based on numerical modelling accounting for landslide-induced substructure displacements and proper modifications on the constitutive law and hysteretic response of the elastomeric bearings. Subsequently, after establishing specific limit-states, nonlinear time history analyses of the seismic response are used to estimate fragility curves and risk indicators. The study points out that it is possible to quantify the influence of landslide-induced effects on seismic fragility and risk by using only two numerical models, in order to provide decision support to transportation authority responsible for ensuring the safety of bridges and road networks. The proposed approach has been tested on a real-life case study, the Santo Stefano Viaduct in Italy, which was subjected in the past to relevant deformations of the elastomeric bearings due to an active landslide phenomenon.

Carbon-Storing Structural Material Based on Wastewater-Cultivated Chlorella Sorokiniana

Microalgae cultivation is a promising technology for carbon sequestration and wastewater remediation. It is economically and logistically critical to find viable applications for the large quantities of produced biomass. In current research, a structural material is developed by using nearly 100% Chlorella sorokiniana. The otherwise non-cohesive microalgae cells are first surface-activated and then compacted under a relatively high pressure. The resulting material is a dense solid, stronger than typical steel-reinforced concrete in flexural tests. The processing procedure is simple and fast, and the setup is scalable. This technique may be useful for next-generation green construction and provide a use-case for sustainable microalgae biomass.

Retrofitting performance of precast UHPC jackets and NSM GFRP bars in pre-damaged RC columns with deficient lap splices

Fiber-reinforced polymer (FRP) jackets and the near surface-mounted (NSM) technique have been widely used to improve the seismic performance of intact reinforced concrete (RC) columns with deficient lap splices. For damaged lap-spliced RC columns, use of ultra-high-performance concrete (UHPC) jackets is more powerful in eliminating the bond splitting failure and recovering the stiffness than FRP jackets. This study proposed an L-shape precast steel-reinforced UHPC (PR-UHPC) jacket to improve the retrofit performance of conventional cast-in-place (CIP) and precast UHPC jackets. Further, PR-UHPC jackets were combined with NSM GFRP bars to develop an innovative method. Cyclic loading tests were performed on three three-fourths scaled deficient lap-spliced RC columns. One intact column was directly retrofitted with PR-UHPC jackets, while the other two were first damaged and then retrofitted with PR-UHPC jackets and the combination of PR-UHPC jackets and NSM GFRP bars, respectively. To investigate the effects of UHPC details and NSM bar types, a previous study on lap-spliced RC columns retrofitted with CIP plain UHPC jackets and NSM steel bars was incorporated. The test results indicate that the retrofitted columns failed with rebar fracture, and plastic hinge shifting was prevented. The peak load, effective yield stiffness, and ultimate drift ratio of the retrofitted columns were 29∼50 %, 37∼39 %, and 126∼165 % higher than those of the unretrofitted columns, respectively. NSM GFRP bars outperformed steel bars in terms of residual drift ratio control. The numerical model well predicted the cyclic behavior by addressing the pre-damage effect and the actual confinement of PR-UHPC jackets. The parametric study revealed that the increase of PR-UHPC jacket width effectively improved the strength and stiffness, while the pre-damage degree had a minor effect. The recommended UHPC jacket height for the present columns was 2.5 times the plastic hinge length. Finally, a design method was developed for the UHPC jacket width.

Shear behavior of reinforced concrete beams with high-strength reinforcements after high temperatures

This paper investigates the effect of steel reinforcement configured with different strengths after different high temperatures on the shear performance of the test beams, a total of 20 reinforced concrete (RC) beams, through experiments, numerical analyses and theoretical studies, in order to understand the key factors affecting the shear performance of the beams. The test revealed that the mechanical properties of concrete and steel reinforcement showed a trend of increasing and then decreasing after high temperatures. Increasing the stirrup ratio and stirrup strength can significantly improve the crack resistance and shear capacity of the beams, as well as the deformation performance of the beams. The residual shear strengths of test beams with high-strength stirrups after exposure to high temperatures are significantly greater than those of ordinary reinforced concrete beams. Specifically, the shear capacity of beams with high-strength stirrups after exposure to 800°C increased by 23.7 % compared to ordinary beams, and the mid-span deflection performance increased by 28.7 %. The stresses in the shear span region of the test beams after high temperature were more concentrated at the diagonal and the number of cracks was significantly reduced. In this paper, a simplified formula for calculating the residual shear capacity of RC beams after room and high temperatures is proposed, which can well predict the test results.

Development of data-driven models to predict seismic drift response of RC wall structures: An application of deep neural networks

This research aimed to develop data-driven models using deep neural networks (DNNs) that can rapidly predict the seismic drift responses of reinforced concrete (RC) wall structures in building frame systems, aiming to overcome the challenges of costly seismic performance evaluation of building structures. A total of 46 RC wall structures ranging from four to 40 stories were analyzed and subjected to 1,000 ground motions including far-field, near-field-pulse, and near-field-no-pulse types. Two input sets were investigated initially. The first input set comprises peak ground acceleration (PGA), spectral accelerations at 1 s–6 s with 1-s intervals, and the first five natural periods of the wall structure. The second input set contains PGA and spectral accelerations at the first five natural periods of the wall structure. The DNN model developed based on the first input set demonstrated superior accuracy achieving an R2 value of 0.880, and slightly outperformed other reputable machine learning models. To enhance the applicability of the developed model, the ground motion type was incorporated as an additional variable to the first input set, which led to an R2 value of 0.869. Ultimately, two DNN models, one based on the first input set and the other considering the ground motion type, were proposed in this study. Finally, the two models were applied to quickly predict seismic drift responses of a new 24-story RC wall structure, and the predicted results were then utilized to efficiently construct the fragility function. The findings highlight the potential of DNNs as an efficient solution to address complex and costly challenges in the earthquake engineering domain.

Strengthening of RC Beam with GFRP Composites in Shear N. B. Bhopale

The rehabilitation, repair and strengthening of existing reinforced concrete (RC) structures is essential due to factors such as aging, steel reinforcement corrosion, construction/design defects, increased service loads demand, seismic events, and advancements in design guidelines. Fiber-reinforced polymers (FRP) are now being recognized as a promising material for the rehabilitation of such structures, through strengthening or repairing. In buildings and bridges, RC sections are commonly found in the form of beams and girders. Shear failure of RC beams is particularly due to its sudden occurrence without warning. Therefore, the utilization of externally bonded (EB) FRP composites for shear strengthening of RC beams has gathered popularity as a structural enhancement technique, primarily due to advantages of FRP composites, such as high strength-to- weight ratio and exceptional corrosion resistance. In addition, FRP repair systems give a cost-saving choice to traditional repair methods and materials. A study was performed to analyse the shear characteristics of RC beams enhanced with continuous glass fiber-reinforced polymer (GFRP) sheets. Reinforced concrete beams externally bonded GFRP sheets subjected to failure using a symmetrical two-point concentrated static loading system. The experimental data obtained included load, deflection, and failure modes of each beam, along with the effect of the number of GFRP layers on the beams The failures observed in strengthened beams typically commence with the debonding of the FRP sheets, followed by brittle shear failure. The shear capacities of these beams were higher than that of the control beam.

Seismic performance investigation of new buckling-restrained steel plate for resilient rocking column foot joint

Seismic damage-controllable components and design approaches are crucial for achieving the seismic resilience and post-earthquake recovery of building structures. To improve the seismic resilience of reinforced concrete (RC) frame structures, this study proposed a novel assembled replaceable rocking column foot joint. The column foot joint is composed of a concrete foundation, short steel-tube concrete column in the center, and four new buckling-restrained steel plates (BRSPs) on the periphery. A detailed design method for the BRSPs was developed, and six BRSP specimens were designed with different core weakening forms and thicknesses. The specimens were cyclically tested and the failure mode and hysteresis behavior were examined. The test results confirmed that the proposed BRSPs exhibit satisfactory energy-dissipation capacity and achieve damage control. The refined numerical models were developed using ABAQUS and verified using the test results. Parametric analyses were conducted for the BRSPs to examine the influence of core plate thickness, gap size, and restraint plate thickness. A numerical analysis model of the column foot joint was established, and the influence of the axial compression ratio and BRSP bearing capacity on the seismic performance of the column foot was investigated. This study provides a reference for the construction of resilient RC frame structures.

Penggunaan Bambu Sebagai Struktur Rumah Tinggal Modern Ramah Gempa

Bamboo material can be applied to structural and decorative elements of modern and minimalist architecture. Use bamboo as structural element, among: 1) as reinforcement structural column, bamboo diameter of 12 cm inserted into the structural column inside iron reinforcement, then cast with concrete. This technique can reduce concrete volume up to 50% than conventional concrete columns, 2) as wall reinforcement, bamboo inserted between the iron reinforcement of the supporting wall, then cast with concrete mortar. This system in addition strengthening walls against the moment forces pressure, can also reduce the volume of concrete. This system can produce walls with a thickness of only 8 cm, much thinner when compared to conventional brick walls 15 cm thick, 3) as reinforcement of concrete slabs, woven bamboo is laid horizontally as a partial replacement for concrete reinforcement iron. This system aims to significantly reduce the amount of iron on the slab, which will reduce construction costs. Science and technology application activities for lecturers of the Department of Civil Engineering, Politeknik Negeri Padag regarding the use of bamboo as earthquake strength for modern residential structure have been carried out at Panti Asuhan Khusus Anak Mentawai, Jl.Purus 4 Padang, on Sunday, August 20, 2023. This activity provides knowledge and adds insight for orphanage children, will finish their education in high school, about alternative materials to replace wood and concrete that are cheaper. So later it is hoped that if they are entrepreneurial or involved in the construction world use of bamboo.

Finite Element Analysis of Shear Performance for Reinforced Concrete T-Beams by Polymer Bars Strengthened with Carbon Fiber Using Embedded Through Section Technique

The purpose of this research presents the research results obtained from a numerical simulation using the ABAQUS/CAE version 2019 finite element software. This study tested the shear behavior of T-beams made of reinforced concrete (RC). The structure is reinforced with a carbon fiber reinforced polymer (CFRP) bar embedded through a section (ETS). The numerical validation approach implicated using numerical analysis on the experimental data collected from twelve reinforced concrete (RC) T-beams divide into two groups each group include reference beam, the field of numerical analysis was expanded to encompass the examination of many aspects, such as the impact of the diameter of CFRP bars. The main objective of this project is to create a computational model that accurately transcribes the complex nonlinear properties inherent in beams. This work conducts a comparative investigation of computational and experimental models, with a specific focus on their load-deflection features and cracking patterns. The study found that the average ratio of ultimate load to deflections in numerical model simulations for beams was 1.011, whereas in experimental testing it was 0.928. The research findings establish a clear correlation between the diameter of CFRP bars and the stiffness of a beam, assuming a constant angle of inclination and spacing.

Finite Element Analysis of Reinforced Concrete Beams Strengthened with Hybrid Fiber Reinforced Polymer Systems using ANSYS

Background: Existing reinforced concrete (RC) structures can deteriorate over time due to aging, poor construction design, natural disasters, etc. In recent years, fiber-reinforced polymer (FRP) composite materials are becoming a preferred choice for concrete construction repair due to their durability, high strength, and corrosion resistance. This study aimed to study and analyze the properties of the constituent materials to identify any weaknesses and potential improvements. Methods: The present study investigated the effectiveness of flexural strengthening of RC beams using a hybrid grouping of glass-FRP (GFRP) and carbon-FRP (CFRP) unidirectional laminates. ANSYS finite element analysis (FE) software was used to investigate the failure modes of the beams and the stress-strain parameters. The impact of adopting two different grades of reinforcing bars in RC beam modeling was also contrasted in the study. Results: Comparisons between the finite element analysis and experimental literature results were made. Based on the test findings, it could be concluded that retrofitted beams perform better than non-retrofitted beams. According to experimental results, the HY14 sheet enhanced beam had a 188.46% higher ultimate load than the unenhanced beams. Conclusion: Comparing experimental findings to the conclusions of the numerical analysis, a maximum difference of ultimate load and deflection at mid-span of 3.40% and 4.91%, respectively, were used to assess the accuracy of the results.

Flexural Behavior of RC Continuous Beams Strengthened by Cementitious Composite Materials

Due to their great strain capacity, high tensile strength, and ability to localize cracks, cementitious composite materials are beneficial for strengthening reinforced concrete (RC) members. This paper illustrates the application of cementitious composite materials in the form of precast thin layers to strengthen a double-spanned, full-scale RC beam. Both positive and negative zones were strengthened by the precast layer embedded into the concrete cover. The precast layers have a dimension of 20 mm in thickness and 150 mm in width as that of the substrate beam and were applied by two configurations: plain and reinforced layers. A ductile smooth steel sheet with 2 mm in thickness and 100 mm in width was used inside the reinforced precast layer. The composite action of the precast layer has mutual benefits; the embedded steel sheet localizes the cracks, while the surrounding cementitious composite materials protect the steel sheet from environmental impact. The experimental results showed that the strengthening system has a significant contribution to improve the failure mode and load-carrying capacity. The use of a plain precast layer caused a 6% increase in the ultimate load and a 33% enhancement in the moment redistribution ratio compared to the control beam (CB). Applying the strengthening system with reinforced precast layer shifted the failure mode from rupture failure in the precast layer to delamination without slippage in the embedded steel sheet and matrix, leading to the full tensile capacity of the precast layer. Besides, the yielded and ultimate loads increased by 34% and 41%, respectively, and maximum deflection increased by 36%. In addition, the beam's ductility increased by 36%, and the moment redistribution ratio was enhanced by 49% compared to the CB. Doi: 10.28991/CEJ-2024-010-09-05 Full Text: PDF

Experimental Study on Shear Strengthening of Reinforced Concrete Beams by Fabric-Reinforced Cementitious Matrix.

In this study, an experiment was conducted to investigate the shear performance of reinforced concrete (RC) beams strengthened using fabric-reinforced cementitious matrices (FRCM). Four reinforced concrete beams, including a control specimen, were fabricated, and the shear strengthening effect of the FRCM was investigated on eight shear specimens, with the strengthening type and shear reinforcement as key variables. In particular, the digital image correlation (DIC) technique was applied to closely analyze the deformation of reinforced concrete beams subjected to shear forces. The average shear strain-shear stress curve of each specimen was derived, and the contributions of shear and bending to the vertical deflection and the change in the principal strain angle with increasing shear force were analyzed. The experiment results showed that all specimens failed with diagonal cracks within the shear span. In the specimens without shear reinforcement, the shear strength increased by up to 65% according to the FRCM strengthening, while in the specimens with shear reinforcement, only the sided bond strengthened specimen showed a strength increase of 16% compared to the control specimen. Based on displacement data of the DIC, it was confirmed that FRCM strengthening can control the deformation of the RC beam. To evaluate the shear strength of the FRCM-strengthened RC beams, a shear strength model was proposed by considering the contributions of the concrete section, shear reinforcement, and FRCM. The proposed model was capable of reasonably evaluating the shear strength of RC beams strengthened with FRCM, considering the shear contribution of FRCM and bond capacity between FRCM and concrete substrate, in which the shear strength of specimens was underestimated by 28% to 35%.

Effect of using normal concrete or recycled concrete layer on behavior of repaired projectile bullet damaged reinforced concrete beams

AbstractThis study utilized experimental research to investigate the efficiency of using normal aggregate concrete (NAC) or recycled aggregate concrete (RAC) as a new concrete layer for repairing projectile bullet damage to strengthening reinforced concrete (RC) beams. This study comprised the construction and testing of eight RC beams made of RAC and NAC. They are initially subjected to projectile bullets and after that tested with flexure load to evaluate the effect of using RAC and NAC that was investigated. The findings of test results demonstrate that the repaired specimens with RAC or NAC experienced a higher load capacity than the damaged control specimens. As such, this approach could potentially use to restore RAC or NAC beams were previously damaged by projectile bullets. In addition, the findings of this research indicate that the load capacity of the damaged RC beams that were previously repaired using the NAC layer was higher than the load capacity of the damaged RC beams that were repaired using the RAC layer. The load capacity enhanced significantly of (106%–118%) and (104%–113%), respectively, when NAC and RAC are utilized in repairs. Therefore, using either NAC or RAC concrete is more economical, environmentally friendly, and efficient than demolishing.