Reinforced Concrete Research Articles

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.

Comparison of seismic assessment guidelines using a case study reinforced concrete wall building

There are several seismic assessment standards and guidelines available around the world that can be used to identify vulnerable buildings. The assessment procedures and criteria in these documents are different, and thus, the assessment outcomes for a particular building, if assessed using different standards, can also be different. In this study, provisions of the linear static and non-linear static analysis procedures of three prominent seismic assessment documents, the American Society of Civil Engineers /Structural Engineers Institute standard ASCE 41 (2017) [1], the New Zealand Seismic Assessment Guidelines (2017) [2], and the European Standard EN 1998-3 (2005) [3] (also known as Eurocode 8 Part-3 or EC8-3) are discussed and compared, highlighting some of their similarities and differences. A reinforced concrete (RC) wall building used in FEMA P-2006 (2018) [4] for demonstration of ASCE 41 provisions is taken as the case study building for comparison of the assessment provisions. The linear and non-linear static analysis procedures specified in the three documents are applied to the case study building and the assessment outcomes are compared. The assessment results are found to vary across the analysis methods and guidelines. However, the critical governing vulnerability for the building is found to be the same. It is observed that with the simplifying modelling assumptions, coupled with the inherent conservatism in the assessment using linear static analysis, a more conservative outcome is obtained using the linear static methods as compared to the non-linear static methods. Overall, EC8-3 provisions are found to be the most conservative of all three guidelines considered for the assessment of the example building.

Flexural Behavior of Reinforced Concrete Beams with Steel-Plate Reinforced Vertical Opening

The structural response of simply supported Reinforced Concrete (RC) beams with square vertical openings is investigated in this work. Studies were conducted using seven specimens of RC beams, with the aim of comparing beams with vertical openings to those without. Meanwhile, the other beams featured carefully positioned square openings. Note that one of these beams served as the control and had no openings. Each beam was the same length (1400 mm) with a 180×120 mm cross-section. Two-point loads were applied over a span of 1200 mm throughout the testing method, with a central load placed 300 mm from the ends. The openings were positioned in the middle of the span and came in three different widths: 20, 40, and 60 mm. Openings were made using either 1.5 mm thick square steel tubing or none at all. The major goal of this study was to determine whether the steel tube could compensate for the decrease in beam strength and the impact of decreasing beam cross-section (producing opening). Correspondingly, the beam ultimate load was found to decrease by 15.75%, 24.2%, and 32.5% for opening widths of 20 mm, 40 mm, and 60 mm, respectively, as the opening width increased. On the other hand, the performance gain for beams strengthened with steel plates when steel tubes were used was 11.78%, 12.14%, and 13.28% for the respective opening widths. Doi: 10.28991/CEJ-2024-010-09-04 Full Text: PDF

Shear repairing of reinforced concrete beams exposed to high temperature using basalt fiber reinforcing bars and CFRP ropes and strips

In this research, the shear behavior of reinforced concrete (RC) beams subjected to high temperatures and then repaired using Basalt Fiber Reinforcing (BFRP) bars and Carbon Fiber Reinforced Polymer (CFRP) ropes and strips was investigated experimentally. Eleven reinforced concrete beams with shear deficiency were cast with dimensions 200mmx300mmx1800mm in width, depth, and span length, respectively. Then, after 28 days, ten beams were heated in an electric furnace for three hours at a temperature of 650 °C. Later, nine of the heated beams were repaired using near surface mounted technique (NSM) with different configurations of BFRP bars and CFRP ropes and strips, and one beam was left unrepaired to serve as a control heated sample. The behavior of the beams was evaluated under two-point loading. The experimental results showed that using NSM CFRP or BFRP efficiently enhances the shear capacity of heat damaged beams. Using NSM rope increased the ultimate loads by 40 % to 95 % compared to control heat beams. The highest improvement in maximum load capacity was achieved by using an inclined rope positioned at 150 mm. While, using BFRP bar increased the maximum load by 37 % to 63 % compared to control heat beams depending on the configuration and spacing between bars. Also, it has been found that the overall effectiveness of CFRP rope in increasing the shear capacity is 32 % higher than that of the BFRP bars.

Rapid repair of RC columns with post-tensioned external clamps

A recent technique for repair of damaged reinforced concrete (RC) columns is reviewed. The technique involves the application of external post-tensioned clamps. The clamps are composed of steel angles and high-strength steel rods. The pairs of angles are placed on the corners of the cross-section, and they are connected with steel rods to each other. To evaluate the effectiveness of the repair technique, four large-scale RC columns with insufficient transverse reinforcement were subjected to lateral displacement reversals and constant axial load. The tests were conducted in two phases: initial testing of columns with none to light transverse reinforcement, followed by the application of clamps on the damaged columns and further testing. The study focused on the efficacy of the clamps to a) restore the lateral-carrying capacity of damaged RC columns, and b) increase drift capacity. Variations in lateral expansion of the column core and their plausible correlations with damage and ‘repairability’ are examined. Within the conditions investigated, two key requirements are proposed for safe column repair: 1) the concrete in damaged columns with cross-sectional expansion exceeding 1% should be replaced or repaired before clamps are applied as a repair measure, and 2) clamps should be proportioned to resist 100% of the maximum plausible shear demand even though perceptible contributions to shear resistance attributable to the concrete were observed in columns repaired before excessive expansion occurred. In columns with crisscrossing inclined cracks leading to lateral cross-sectional expansion of up to 1%, clamps were observed to provide effective shear resistance comparable to what conventional transverse reinforcement can provide.

Earthquake Functional Recovery in Modern Reinforced Concrete Buildings

Earthquake Functional Recovery in Modern Reinforced Concrete Buildings

A performance-based ballistic design framework for RC panels and a probabilistic model for crater quantification

Ballistic design is crucial for widely utilised concrete structures in today’s unpredictable world. In the past, extensive experimental and numerical studies have investigated concrete panels, resulting in design guidelines and empirical formulations for local damage parameters. However, with the advent of performance-based design, notably in seismic design, the ballistic design of concrete structures lacks a comprehensive design philosophy. Additionally, deterministic empirical formulations for local damage parameters, particularly in the case of reinforced concrete (RC) panels’ crater formation, necessitate a probabilistic treatment. Consequently, this paper addresses the need for a well-defined ballistic design philosophy for concrete structures and introduces a probabilistic approach for crater quantification. Firstly, a novel multi-level and multi-parameter performance-based design framework for RC panels is proposed, centred on damage states, namely depth of penetration and crater area. This framework establishes an innovative design philosophy featuring four damage levels for each state. Secondly, using dimensionless explanatory functions, a Bayesian inference model is developed to estimate the crater diameter in RC panels under hard projectile impact, accounting for the associated uncertainties. LS-Dyna is used for numerical modelling of RC panels and rigid projectiles. The numerical models are validated with the experimental data and are utilised to develop the probabilistic model. This study reveals the profound influence of projectile and concrete properties in addition to the incidence angle of the projectile on crater formation. The developed probabilistic model is validated with experimental results demonstrating its reliability and accuracy. Consequently, a reliable design formula for estimating crater diameter for RC panels under hard projectile impact is proposed in addition to the novel ballistic design framework.

Meso-crack propagation of RC induced by non-uniform rebar corrosion and the predictive model of time to concrete cover cracking

Non-uniform corrosion expansion in reinforced concrete (RC) structures will lead to concrete cracking, bond degradation, and an overall reduction in load-bearing capacity, severely threatening structural safety and durability. Accordingly, meso-crack propagation of RC induced by non-uniform rebar corrosion and the predictive model of time to concrete cover cracking are investigated in this paper, and the theoretical solutions for the critical corrosion rate and the corresponding time are proposed for structural durability evaluation and design. Firstly, based on the mesh-mapping technique of multi-shape random aggregates, a finite-element generation method for three-dimensional concrete three-phase meso-scale model is proposed, with modeling corrosion-expanded cracking of RC, reproducing the crack morphology and propagation process of concrete cracking due to non-uniform rebar corrosion. Subsequently, single factor influence analysis and multi-factor orthogonal test were employed to reveal the degrees of influence of various factors on the critical corrosion rate as follows: concrete strength > cover thickness > interface layer strength > aggregate content > aggregate grading > aggregate shape. A theoretical predictive model for the corrosion expansion cracking time of the RC cover was proposed, considering the influence of key factors including concrete strength and cover thickness. Finally, the validity of theoretical prediction method and the numerical model’s damage mode are verified through accelerated corrosion tests of RC.

Incorporation of Jute Fiber in Concrete: A Literature Review

Abstract: This systematic literature review delves into the incorporation of jute fiber as a reinforcement material in concrete, examining its benefits, challenges, and potential applications. Jute fiber, a natural and biodegradable material, presents an eco-friendly and cost-effective alternative to synthetic fibers commonly used in concrete reinforcement. The utilization of jute fibers in concrete not only enhances its mechanical properties but also promotes sustainable construction practices, addressing the growing need for environmentally responsible building materials. The review synthesizes existing research on the physical, mechanical, and durability properties of jute fiber-reinforced concrete (JFRC). It explores how the unique characteristics of jute fibers, such as their high tensile strength and low density, contribute to improved concrete performance, particularly in terms of tensile and flexural strength. The addition of jute fibers helps mitigate crack propagation and enhances the ductility of concrete, making it more resilient to dynamic loads. Despite these benefits, challenges such as the hydrophilic nature of jute fibers, which can lead to increased water absorption and potential durability issues, are also addressed. Various chemical treatments and surface modifications have been explored to improve the compatibility of jute fibers with the cement matrix and enhance the overall durability of JFRC

Analysis and Design of Box Culvert for Durability against Varying Thickness of Cushion

Abstract: This study presents the structural analysis of a reinforced concrete (RCC) box culvert with dimensions 1m x 2m x 1.5m, subjected to varying cushion loadings of 0.770m, 1.010m, and 1.200m, using STAAD.Pro software. The analysis focuses on both Ultimate Limit State (ULS) and Serviceability Limit State (SLS) criteria to ensure the structural integrity and durability of the culvert. For ULS, load combinations include dead load, live load, earth pressure, and cushion load, assessing the culvert's capacity to withstand maximum expected loads without failure. The study evaluates bending moments, shear forces, and ensures that the flexural and shear strengths of the culvert are within permissible limits. Results indicate that even under the highest cushion loading, the culvert design remains robust with appropriate reinforcement. For SLS, the analysis incorporates quasipermanent load combinations to evaluate deflections and crack widths, ensuring the structure's functionality and aesthetic durability under normal service conditions. Deflections and crack widths for all cushion depths were found to be within acceptable limits, demonstrating the culvert's ability to maintain serviceability and resist long-term degradation. Overall, the analysis confirms that the RCC box culvert, when designed according to the principles of ULS and SLS, achieves a balance between safety, functionality, and durability, ensuring reliable performance over its service life.

Flexural performance of narrow RC beams hybrid strengthened by TRECC plate

This paper proposes a novel hybrid strengthening method for narrow reinforced concrete (RC) beams that combines fiber-reinforced polymer (FRP) textile-reinforced engineered-cementitious composites (TRECC) plates along with a self-locking anchorage system. To evaluate the effectiveness of the proposed system, a series of four-point bending tests were conducted. These tests were designed to understand the effects of different strengthening methods, number of FRP grid layers, and TRECC bond lengths. The results showed that the hybrid strengthening system could effectively prevent the end debonding failure and impede the development of the intermediate debonding in the TRECC plate. Consequently, the TRECC plate can continue to carry the force, leading to a significant increase in strengthening efficiency, quantified as the increased ratio of the peak load of the strengthened beams to that of the reference beam. Furthermore, increasing the number of FRP grid layers can also improve the strengthening efficiency. However, longer TRECC bond length in hybrid strengthened beams will reduce the strengthening efficiency since the intermediate debonding will be more susceptible to occur; the design for appropriate bond length is necessary. Finally, an analytical model to predict the flexural capacity was derived and verified against the experimental results.

Numerical Modeling of Uniaxial Corroded Reinforced Concrete Columns Exposed to Fire

Corroded concrete structures remain at risk of fire damage throughout their lifespan. This study explores the fire resistance of reinforced concrete columns, considering the simultaneous impact of corrosion and high temperatures. Thermal–structural models of the corroded concrete columns are developed using SAFIR software (2022). The numerical results are compared with published test data on temperature distributions and axial displacement–time curves. Then, parametric analyses are conducted to investigate the influence of various factors, such as corrosion degree, concrete compressive strength, cover thickness, and fire exposure models, on the fire performance of the concrete columns. The findings reveal that corrosion significantly undermines fire resistance: notably, columns with severe corrosion exhibited a 47% reduction in fire resistance. Conversely, increased concrete strength can bolster the fire resistance of intact columns, particularly when the concrete cover is minimal. Enhancing the cover thickness proves to be an effective strategy to mitigate the thermal degradation of steel reinforcements, thereby extending the columns’ fire resistance by as much as 23%. The study introduces coefficients to quantify the effects of corrosion, fire exposure, material strength, and cover thickness, culminating in a practical formula to calculate the fire endurance of corroded reinforced concrete columns. This formula could complement existing fire safety regulations.

Seismic Performance of Multistory Reinforced Concrete Buildings by Pushover Analysis

Abstract: In this investigation the analysis of G+4, G+11 and G+21 building is situated in New Delhi (Zone IV. The seismic analysis of of G+4, G+11 and G+21 building as per IS 1893-2002. In this research pushover analysis was performed in SAP 2000 and after that is designed as per IS 456-2000 for different loads. This analysis gives better understanding seismic performance of building & also shows damage or failure of buildings. The building performance level is determined by pushover curve & demand curve. The result shows that the failure is noticed in the column of ground storey of the building. After that enlarged amount of reinforcement in the ground story the buildings have reached life safety performance level.

Machine Learning Applications for Predicting Faulting in Jointed Reinforced Concrete Pavement

Machine Learning Applications for Predicting Faulting in Jointed Reinforced Concrete Pavement

Experimental investigation of face mask fiber-reinforced fully recycled coarse aggregate concrete

To address the challenges associated with the disposal of construction and demolition waste (C&DW) and discarded personal protective equipment, this study investigates the feasibility of using face mask (FM) fibers to enhance fully recycled coarse aggregate (FRCA) concrete. The current study uses six FM fiber volume fractions (0, 0.1 %, 0.2 %, 0.3 %, 0.4 %, 0.5 %) for FRCA concrete reinforcement. According to the mechanical performance test results, adding FM fibers can enhance the splitting tensile strength (up to 8.22 % contents 0.1 % FM fiber) and flexural strength (up to 26.92 % contents 0.2 % FM fiber) of FRCA concrete. While excessive FM fibers (over 0.3 %) affect compressive strength negatively, the damaged concrete retains integrity due to the bridging action of FM fibers combined with scanning electron microscopy (SEM) analysis. Comparatively, the hydrophilic inner layer of disposable medical masks features a better microstructural fiber arrangement, increasing tensile strength by 14.51 % and 111.68 % compared to the filter and outer layers, respectively, making it ideal for enhancing FRCA concrete. All samples achieved a "Good" rating in the UPV tests, confirming the feasibility of FM fiber-reinforced FRCA concrete. The calculation method for FRCA concrete mechanical properties prediction considers the contribution of fibers in addressing the disparate effects of FM fiber incorporation, with correlation coefficients of 0.904 and 0.827 for splitting tensile strength and flexural strength, respectively. Environmental and economic impact analysis indicates that FM fiber-reinforced FRCA concrete can reduce carbon emissions by 71.25 % and save 29.05 % of economic costs.

Long-term deterioration behavior of round-end hollow piers during cyclic solar radiation

Reinforced concrete (RC) hollow piers are inevitably impacted by solar radiation during their service life. However, normal investigation approaches are inadequate for characterizing the long-term degeneration of RC structures under cyclic solar radiation. In this article, a novel elastoplastic-thermodynamic numerical approach has been suggested for evaluating the long-term deterioration behavior of hollow piers during cyclic solar radiation and ambient temperature fluctuations. The findings suggest thermal effect caused by solar radiation and ambient temperature fluctuations might cause the pier surface concrete to crack. The maximum first principal strain of pier surface concrete in July is approximately 1.21 times greater than the concrete peak tensile strain. Tensile damage of pier concrete rises with cyclic times of solar radiation. Tensile damage of surface concrete rose from 0.495 to 0.566 and 0.610, as exposure time increased from 1 to 10 and 100 years. Reducing the surface short wave absorption rate, increasing concrete specific heat, and decreasing pier wall thickness is beneficial to minimizing long-term tensile damage of pier concrete.

A numerical algorithm for damage progression of reinforced concrete bridge piers during air temperature and solar radiation cycles

Reinforced concrete (RC) solid piers are unavoidably affected by air temperature changes and solar radiation during service life. Nevertheless, the deterioration of pier concrete with increased exposure age remains unclear. A novel thermal-mechanical numerical algorithm (finite element model) for characterizing the deterioration characteristics of RC structures under cyclic environmental loads has been suggested. The deterioration of RC pier concrete after 100 years of air temperature and solar radiation cycles is simulated. The numerical results demonstrate that tensile damage of pier concrete during air temperature and solar radiation cycles increases continuously with exposure age. After one year of exposure, the tensile damage value of pier surface concrete increased to 0.201 and further increased to 0.286 and 0.357 as the exposure age grew to 10 and 100 years. Pier concrete tensile damage can be mitigated by using surface short-wave absorption-reducing methods, controlling the thermal properties of concrete, and raising the concrete peak tensile strain. The proposed finite element framework and numerical solutions enable a viable simulation-based method for the analysis of bridge structural long-term deterioration behavior and design of the bridge engineering.

Experimental and numerical studies on corrugated steel retrofitted damaged reinforced concrete arches

The corrugated steel (CS) reinforcement method has been adopted for strengthening dilapidated bridges and culverts owing to its advantages of convenient construction, good corrosion resistance, and high deformability. However, the current design method for corrugated steel retrofitted damaged reinforced concrete (CSRDRC) arches is excessively conservative as it only considers the bearing capacity of the CS, neglecting the contributions of the original reinforced concrete (RC) structure and the infill layer. This paper studied the behaviour of CSRDRC arches under three-point loading experimentally and numerically. The experimental results demonstrate that the bearing capacity and initial stiffness of the arches are significantly enhanced after CS reinforcement. The increase in damage degree of the original structure has a slight effect on the bearing capacity and initial stiffness, but an obvious adverse effect on the ductility of the CSRDRC arches. A finite element model (FEM) was developed and verified against test results and then utilized to conduct parametric analysis. Finally, a simplified formula was proposed for predicting the axial compressive bearing capacity of CSRDRC arches.

Strengthening and repair of RC beams using natural sisal Fabric-Reinforced Cementitious Matrix composite

The present work reports the results of an experimental program on the mechanical characterization of Reinforced Concrete (RC) beams externally strengthened/repaired by natural sisal Fabric-Reinforced Cementitious Matrix (FRCM) composite. For such, undamaged and pre-cracked RC beams were U-wrapped with a sisal FRCM composite and then tested under bending load. The results showed significant increases in shear strength, up to 25 % for beams with stirrups and 75 % for beams without them. The strengthened/repaired beams also presented stirrups yielding delay during the tests. When compared with other synthetic FRCM strengthening systems from the literature, the enhanced mechanical results of the present work were mechanically equivalent. The cracking pattern and debonding of the sisal FRCM wrap system were measured by the Digital Image Correlation (DIC) technique. The wrap application reduced the crack propagation and debonding behavior was not detected. Finally, the experimental results were confronted with an analytical approach guided by ACI 549.4R-20 and considered sufficiently accurate.

Efficacy of PZT Sensors Network Different Configurations in Damage Detection of Fiber-Reinforced Concrete Prisms under Repeated Loading.

Real-time structural health monitoring (SHM) and accurate diagnosis of imminent damage are critical to ensure the structural safety of conventional reinforced concrete (RC) and fiber-reinforced concrete (FRC) structures. Implementations of a piezoelectric lead zirconate titanate (PZT) sensor network in the critical areas of structural members can identify the damage level. This study uses a recently developed PZT-enabled Electro-Mechanical Impedance (EMI)-based, real-time, wireless, and portable SHM and damage detection system in prismatic specimens subjected to flexural repeated loading plain concrete (PC) and FRC. Furthermore, this research examined the efficacy of the proposed SHM methodology for FRC cracking identification of the specimens at various loading levels with different sensor layouts. Additionally, damage quantification using values of statistical damage indices is included. For this reason, the well-known conventional static metric of the Root Mean Square Deviation (RMSD) and the Mean Absolute Percentage Deviation (MAPD) were used and compared. This paper addresses a reliable monitoring experimental methodology in FRC to diagnose damage and predict the forthcoming flexural failure at early damage stages, such as at the onset of cracking. Test results indicated that damage assessment is successfully achieved using RMSD and MAPD indices of a strategically placed network of PZT sensors. Furthermore, the Upper Control Limit (UCL) index was adopted as a threshold for further sifting the scalar damage indices. Additionally, the proposed PZT-enable SHM method for prompt damage level is first established, providing the relationship between the voltage frequency response of the 32 PZT sensors and the crack propagation of the FRC prisms due to the step-by-step increased imposed load. In conclusion, damage diagnosis through continuous monitoring of PZTs responses of FRC due to flexural loading is a quantitative, reliable, and promising application.