Compression Reinforcement Research Articles

Finite Element Modeling of Dynamic Response of RPC Columns and Frames Under Coupled Fire and Explosion

Reactive powder concrete (RPC) is widely used in ultra-high-rise buildings, hydropower stations, bridges, and other important infrastructures. To study the dynamic response and damage characteristics of RPC columns and frames considering coupled fire and explosions, an analytical model of RPC columns and frames with coupled fire and explosions was established by using ABAQUS (2021) finite element software. The dynamic response and damage degree of RPC columns under coupled fire and explosions were investigated to reveal the influence laws of parameters such as cross-section size, axial compression ratio, reinforcement rate, and fire duration on the dynamic response of RPC columns at high temperatures. The dynamic response of the frame structure was analyzed when the explosion load was applied to the bottom corner columns, side columns, and top beams, respectively. The results show that the fire severely weakened the blast resistance of RPC columns; the maximum mid-span deformation and residual deformation of RPC columns decreased with the increase in cross-section size and longitudinal bar reinforcement ratio and increased with the increase in fire duration and axial compression ratio. When the explosion load was applied to the corner columns of the bottom floor of the frame, the bottom corner columns were almost completely destroyed, and there was a significant risk of the structure collapsing. Based on the results of the data analysis, a method to enhance the explosion resistance of RC frame structures using RPC materials at high temperatures is proposed.

A Parametric Study of GFRP Composite Beams with Encased I-Section using 3D Finite Element Modeling

Glass Fiber Reinforced Polymer (GFRP) materials play a crucial role in the construction industry due to their lightweight properties, corrosion resistance, and high strength. Furthermore, the GFRP reinforcement ratio is a significant factor in the strength design philosophy that governs the design of flexible members. This study presents a parametric investigation of the performance of concrete composite beams reinforced and encased with pultruded GFRP. This study investigates the effect of concrete compressive strength and GFRP reinforcement ratio on the structural behavior of composite beams with encased GFRP sections under static loads. To achieve this objective, five simply supported models were numerically simulated using the Abaqus software. The reference model comprised normal concrete with a 30 MPa compressive strength, 0.42% GFRP longitudinal reinforcing ratio, and transverse steel rebars, with the GFRP I-section encased in the center of the cross-section. The other models maintained similar properties and geometries but varied in reinforcement ratio (0.85% and 1.2%) and compressive strength (25 MPa and 20 MPa). The results showed that increasing the reinforcement ratio in composite beams with encased GFRP sections improved the ultimate capacity by approximately 29% and 41% for 0.85% and 1.2% ratios, respectively, compared to the reference beam. Conversely, reducing compressive strength below 30 MPa decreased maximum load by about 16% and 23% for 25 MPa and 20 MPa values, respectively, in relation to the reference beam.

Mechanisms of transverse compression damage and reinforcement strategies for Larch wood

ABSTRACT Transverse compression damage frequently affects active wooden components of ancient architecture, such as beams and Dou-gong, compromising structural safety. Larch (Larix gmelinii var. principis-rupprechtii (Mayr) Pilger) wood, commonly used in ancient northern Chinese architecture, has limited studies on its transverse compression damage mechanisms. Traditional reinforcement methods are often ineffective. The present study integrated plastic equilibrium theory and static loading experiments to examine the transverse compression damage mechanism of larch wood under significant deformation. It also introduced an innovative method for parcel constraints to enhance the compression strength of wooden components in ancient architecture. Results showed the transverse compressive strength of larch wood ranges from 3 to 17 MPa, with maximum load-bearing capacity doubling after enhancement. End-wrapping confinement increased the load-bearing capacity by over 16%. Load-displacement curves under different compression conditions followed a three-stage pattern: elastic, plastic, and densification. Damage in larch wood began in the plastic stage. Under localized compression, samples exhibited a sudden drop in load-bearing capacity and secondary failure at 60–70% strain. This study offers valuable insights into the damage and residual load-bearing capacity of transversely compressed wooden components. The proposed compression enhancement strategy can reinforce damaged wooden components in ancient architecture, contributing to preserving cultural heritage.

Optimization of Mechanical Performance of Full-Scale Precast Concrete Pipes with Varying Concrete Strengths and Reinforcement Using Factorial Design

The use of precast concrete pipes for water and sewage transportation systems is a very important element of a country’s infrastructure. The main aim of this study was to investigate the effects of concrete’s compressive strength and reinforcement levels on the mechanical performance of spun-cast full-scale precast concrete pipes in the local construction industries of developing countries. A test matrix was adopted using a full 32 factorial design. The studied concrete’s compressive strength was 20, 30, and 40 MPa, and reinforcement levels were 60%, 80%, and 100%, representing low, medium, and high levels, respectively. The medium level of reinforcement represented the reinforcement requirement of ASTM C76 in concrete pipes. A total of eighteen full-scale pipes of 450 mm diameter were cast in an industrial precast pipe unit using a spin-casting technique and were tested under a three-edge bearing load. The experimental results showed that the crack load and ultimate load of the tested pipes increased with higher levels of concrete strength and reinforcement levels. For example, an approximately 35% increase in the 0.30 mm crack load was observed when the concrete strength increased from 20 MPa to 30 MPa for all tested levels of reinforcement. Similarly, around a 19% increase in ultimate load was observed for pipes with 80% reinforcement compared to identical pipes with 60% reinforcement. It was found that the pipe class, as per ASTM C76, is highly dependent on the concrete strength and reinforcement levels. All of the pipes exhibited the development of flexural cracks at critical locations (crown, invert, and springlines). Moreover, concrete pipes cast with low-level strength and reinforcement also showed signs of crushing at the crown location near to the pipe failure. The analysis of variance (ANOVA) results showed that the main factors (compressive strength and reinforcement levels) were significantly affected by the cracking loads of precast pipes. No significant effect of the interaction of factors was observed on the crack load response. However, interaction factors, along with main factors, have significant effects on the ultimate load capacity of the concrete pipes, as indicated by the F-value, p-value, and Pareto charts. This study made an effort to illustrate and optimize the mechanical performance of pipes cast with various concrete strengths and reinforcement levels to facilitate the efficient use of materials for more resilient pipe infrastructure. Moreover, the exact optimization of concrete strength and reinforcement level for the desired pipe class will make the pipe design economical, leading to an increased profit margin for local spin-cast pipe fabricators without compromising the pipe’s quality.

Nonlinear Analysis and Optimization of Recycled Aggregate Concrete Cross-Sections Based on Restoring Force Models

This research presents a simplified approach using a uniaxial restoring force model to analyze the seismic response of recycled aggregate concrete (RAC) frames. Nonlinear simulations were conducted to explore how factors like axial compression ratio, reinforcement ratio, and cross-sectional geometry affect the ductility and seismic performance of RAC sections. The findings reveal that a reduction in the axial compression ratio from 0.60 to 0.57 results in a 15% increase in ductility, while a higher reinforcement ratio leads to a 20% enhancement. In addition, rectangular sections were found to be more sensitive to variations in material strength than square sections, offering key insights for structural optimization. The method proposed here also enhances computational efficiency by minimizing resource consumption and improving the convergence of nonlinear iterative procedures. These findings provide a theoretical foundation for optimizing the design and seismic evaluation of RAC structures, promoting their broader application in engineering practice.

Numerical study on the flexural performance of HVFA-SCC beam with compression reinforcement

Abstract The increasing demand for concrete as the primary construction material has led to greater cement production and associated CO2 emissions. High Volume Fly Ash-Self Compacting Concrete (HVFA-SCC) was developed to address this issue. The present study aims to investigate the flexural performance of HVFA-SCC beams reinforced with compression reinforcement. This study involved laboratory testing of an HVFA-SCC beam under flexural static loading. The beam had dimensions of 300 mm width, 125 mm height, and 3200 mm length. The beam was designed to experience a flexural failure mode. Longitudinal reinforcement was placed at the bottom and top portions of the beam to resist the tensile and compressive stresses induced by the applied load. During the loading test, displacement, load, and strain in the reinforcing steel were recorded. The detailed behavior of the beam was explored through numerical modeling and analysis using the finite element software ATENA. Parametric studies were conducted to evaluate the influence of concrete compressive strength and tensile reinforcement ratio.

Data Driven Framework with Graphical User Interface for Predicting Flexural Behavior of FRCM Strengthened RC Beams

In this study, the flexural capacity of reinforced concrete (RC) beams strengthened with fiber-reinforced cementitious matrices (FRCM) was computed using machine learning (ML) algorithms including: (i) adaptive neuro-fuzzy inference system (ANFIS), (ii) artificial neural network (ANN), and (iii) extreme gradient boosting (XGBoost). A total of 198 pertinent experimental datasets were compiled and included six types of FRCM composites (PBO, carbon, glass, basalt, coated carbon, and combined glass and carbon). The considered input parameters comprise the beam cross-sectional details, area of tensile and compressive steel reinforcement, mechanical properties of FRCM composite, and concrete compressive strength. To assess the reliability of ML models, four existing analytical models and one established standard guideline were used for comparison. Moreover, six statistical metrics were employed, along with an overfitting analysis, to determine the best-fitting model. Graphical fitting of the optimal model was depicted using the Taylor diagram, violin plot, as well as multi-panel histogram plot. Based on both graphical and statistical metrics, the XGBoost model attained the highest precision compared to all analytical and ML-based models. The correlation coefficient and MAPE of the XGBoost model were 0.9977 and 2.98%, respectively. To interpret the influence of individual parameters on the flexural strength of the FRCM-strengthened RC beams, a feature importance plot based on SHAP explanatory theory was deployed. Ultimately, a user-friendly graphical interface was developed and made accessible to aid practicing engineers in estimating the flexural strength of FRCM-strengthened RC beams, offering an effective alternative to complex design procedures.

Inelastic buckling of reinforcing bars - constitutive model for monotonic compression

Abstract Reinforced concrete structures can be subjected to plastic deformation as a result of seismic actions or exceptional loads. In this case, inelastic buckling of the compressed reinforcement bars may occur. According to the provisions of the EC2 standard, bar buckling is not taken into account in the ultimate limit state check; the same physical models are used for both tension and compression bars. The models of compression bars known in the literature, which take into account inelastic buckling, reproduce their behaviour in a limited range of mechanical properties of steel or require a large amount of data. This paper proposes a new, simple, four-linear model of the behaviour of compression reinforcing bars taking into account inelastic buckling. The proposed model shows satisfactory agreement with experimental results. It can be applied to model the behaviour of steel bars with different mechanical properties in the analysis of the plastic hinge behaviour of reinforced concrete elements.

Comparative study of fibers extracted from the stems and roots of the Cameroonian pennissetum purpureum for their applications in compressed earth brick reinforcement and textile engineering

This work focuses on the extraction and experimental characterization of pennisetum purpureum fibers extracted from stems and roots, harvested in the Batié Kingdom, in the West Region of Cameroon. After extracting fibers using the boiling water technique, they are chemically treated to improve their properties and performance and to facilitate their incorporation into various composite materials. For the physical characterizations, it is measured: the absolute and apparent densities, the linear mass, the water absorption rate, and the diameter via the microscope. The mean values of the diameters and the measure of their frequency distributions are calculated, followed by the statistical analysis using the maximum entropy principle, in order to find the most probable diameter necessary for technological applications. For the mechanical properties, only the tensile tests are performed, with the determination of the young modulus of both the stems and roots. The results thus obtained showed that the fibers of the stems have an absolute density of (1.35 g/cm3), a linear mass of (54.6 tex), an apparent density of (0.45 g/cm3), a water content of (12.73%), an absorption rate of (142.46%), a porosity of (65.91%), a mean diameter of (7 mm), an elastic modulus of (3.98 GPa), a tensile strength of value of (1186.59 MPa) and an elongation of 16.17%, while the root fibers have an absolute density of (1.34 g/cm3), a linear mass (16.76 tex), an apparent density of (0.37845 g/cm3), a water content of (12.25%), an absorption rate of (193.16%), a porosity of (71.92%), a diameter of (4 mm), an elastic modulus of (1.55 GPa), a tensile strength of a value of (1960.35 MPa) and an elongation of 60.6%. Thus, the fibers of the stems have good mechanical properties, which make them an appropriate material in several applications, such as the reinforcement of composite materials.

A failure mechanism seen after the 6th February 2023 Kahramanmara earthquake sequence, buckling of compression reinforcement in RC beams

A failure mechanism seen after the 6^th February 2023 Kahramanmara earthquake sequence, buckling of compression reinforcement in RC beams

Comparison of Flexural Performance of Reinforced Concrete Beams Reinforced with Steel Plates and Corrugated Steel Plates

To explore the mechanical properties of reinforced concrete beams strengthened by steel plates of various shapes, reinforced concrete beams strengthened with steel plates and corrugated steel plates were tested via a two-point loading test. Based on tests, further investigations investigated the deflection of the sample under different loads and the influence of corrugated steel plate properties (thickness, wave height, strength) on the flexural capacity of the reinforced beam, culminating in the development of corresponding numerical models. The findings indicate that the corrugated steel plate has the best reinforcing effect. In contrast to reinforcement utilizing steel plates containing an equivalent quantity of steel material, the corrugated steel plate augments the space within the reinforced beam and the lower shaft region, enhancing the efficiency of the upper compressive steel reinforcement and concrete in bearing loads, bolstering overall load-bearing potential, and exhibiting superior resistance to deformation. To maintain the ductility of the specimen, interface failure must be prevented. Too high wave height will affect the coordination of wave thickness and strength and inhibit the improvement of flexural performance. Therefore, reinforcement design should prioritize wave height determination.

Failure mode analysis and dynamic response prediction of fully confined reinforced concrete slabs under blast loading

Abstract With the development of human society, various accidental explosions and terrorist attacks have occurred frequently, posing a great threat to the safety of building structures. In order to improve the safety of building structure, the finite element model of reinforced concrete slab was established by ANSYS/LS-DYNA finite element analysis software. By comparing with the experimental results, the accuracy of the established finite element model was verified, and the failure modes of reinforced concrete slab under different scaled distances were analyzed. The effects of three damage factors: concrete compressive strength, protective layer thickness and reinforcement ratio on the dynamic response of the slab were analyzed. Based on the Π theory of dimensional analysis, the dimensionless relationship between the peak displacement of the mid-span of the plate and the scaled distance of the explosion is obtained. On the basis of a large number of numerical simulation results, the dimensionless relationship for quickly predicting the dynamic response of the plate is summarized. The results show that with the increase of scaled distance, the failure mode of the plate will gradually change from brittle shear failure to plastic bending failure. Increasing the compressive strength and reinforcement ratio of concrete and reducing the thickness of the protective layer can reduce the peak displacement of the mid-span of the slab and improve the anti-explosion performance of the slab. It is verified that the proposed dimensionless prediction relationship can better predict the dynamic response of reinforced concrete slabs at different scaled distances, so as to provide some reference for the field of structural anti-explosion.

+Analytical Approach for Predicting the Moment-Curvature Response of Structural Lightweight Reinforced Concrete Beams

With the switch towards performance-based design procedures, the prediction of the flexural behavior of lightweight reinforced concrete, LWRC, members using advanced and reliable analytical tools has been of great interest to researchers. This paper proposes nonlinear analytical and numerical procedures based on sectional analysis and finite element methods for predicting the moment-curvature and load-deflection responses of structural LWRC beams subjected to pure bending. The proposed analytical and numerical models were validated experimentally by casting and testing a series of eight full-scale LWRC beams under four-points bending configuration. The effects of different compressive strengths of concrete and tensile reinforcement ratios on the flexural behavior of LWRC were examined. The analytical and numerical predictions of the load-deflection behavior and the moment-curvature and load-deflection responses of the LWRC beams investigated, compared very well with the corresponding responses measured from experiments, and test results of previous studies existing in the literature. Among the parameters evaluated using sensitivity analysis, the compressive strength had a significant influence on the flexural strength and stiffness of LWRC beams, whereas the compressive reinforcement ratio was the most important factors affecting the energy absorption and curvature ductility. Moreover, the theoretical models developed could serve as viable tools for simplifying the design process of structural lightweight reinforced concrete members and enhance their applications.

To assign the length of overlapping joints of compressed reinforcement in one design section of reinforced concrete elements

Introduction. Overlapping reinforcement joints in monolithic reinforced concrete structures are the most common, because they have sufficient simplicity and low labor intensity when installed on a construction site. When designing such joints in structures subject to compressive load, questions often arise related to the need to arrange an increased overlap length of compressed reinforcement in accordance with the requirements of domestic regulatory documents. Aim. The aim of the work is an analysis of modern design practice, as well as available experimental studies of the bearing capacity of compressed reinforced concrete elements with overlapping reinforcement joints located in the same design section. Materials and methods. The analysis was carried out by studying the provisions of domestic and foreign regulatory and technical documentation, as well as the results of experimental studies available in the public domain. Results. The data on the methods available in the design practice for determining the overlap length of compressed reinforcement are systematized, including the case, when the joints are located in the same design section. Conclusions. Based on the results of the work, the existing approaches for assigning the length of the overlap of compressed reinforcement located in the same design section of reinforced concrete structures were analyzed. The methods adopted in Russian and foreign regulatory and technical documents, as well as experimental research on this topic, are considered. Based on the results of the analysis of the available data, it can be said that additional studies to assess the effect of the overlap length of the compressed reinforcement on the strength of reinforced concrete elements can optimize their design solutions – without reducing the required level of reliability.

Comparative study of fibers extracted from the stems and roots of the Cameroonian pennissetum purpureum for their applications in compressed earth brick reinforcement and textile engineering

This work focuses on the extraction and experimental characterization of pennisetum purpureum fibers extracted from stems and roots, harvested in the Batié Kingdom, in the West Region of Cameroon. After extracting fibers using the boiling water technique, they are chemically treated to improve their properties and performance and to facilitate their incorporation into various composite materials. For the physical characterizations, it is measured: the absolute and apparent densities, the linear mass, the water absorption rate, and the diameter via the microscope. The mean values of the diameters and the measure of their frequency distributions are calculated, followed by the statistical analysis using the maximum entropy principle, in order to find the most probable diameter necessary for technological applications. For the mechanical properties, only the tensile tests are performed, with the determination of the young modulus of both the stems and roots. The results thus obtained showed that the fibers of the stems have an absolute density of (1.35 g/cm3), a linear mass of (54.6 tex), an apparent density of (0.45 g/cm3), a water content of (12.73%), an absorption rate of (142.46%), a porosity of (65.91%), a mean diameter of (7 mm), an elastic modulus of (3.98 GPa), a tensile strength of value of (1186.59 MPa) and an elongation of 16.17%, while the root fibers have an absolute density of (1.34 g/cm3), a linear mass (16.76 tex), an apparent density of (0.37845 g/cm3), a water content of (12.25%), an absorption rate of (193.16%), a porosity of (71.92%), a diameter of (4 mm), an elastic modulus of (1.55 GPa), a tensile strength of a value of (1960.35 MPa) and an elongation of 60.6%. Thus, the fibers of the stems have good mechanical properties, which make them an appropriate material in several applications, such as the reinforcement of composite materials.

Thermal and mechanical analysis of thermal break structure in balcony with basalt fiber reinforced polymer

Thermal break structure is an effective design to reduce building energy consumption in balcony. The traditional stainless-steel bars or other FRP components reinforced thermal break structures can't enable both mechanical performance and thermal insulation concurrently because these materials are difficult to have low thermal conductivity and high mechanical properties at the same time. This paper proposes to use basalt fiber reinforced polymer (BFRP) to construct the thermal break structure due to the high load-bearing capacity and thermal insultation of BFRP. The thermal performance of the structure is systematically verified through three-dimensional simulation. Influence of thermal break widths, loading point positions, shear reinforcement forms and reinforcement types on the mechanical properties of the structure is investigated. The results show that BFRP can significantly reduce the linear heat transfer transmittance while ensuring structural mechanical properties. A larger thermal break width leads to the low load-bearing capacity of the structure. Lower BFRP compressive reinforcements need enough diameter to provide compressive strength and shear reinforcement forms can significantly increase the mechanical properties of the thermal break. Upper tensile reinforcements can be selected depending on the stiffness and insulation requirements in practical engineering. Based on experimental results, force transfer mechanism is analyzed and the rationality of the structural design is identified. The maximum length of the cantilever slab without shear reinforcement forms is approximately 2.94 m when meets the serviceability limit state. The results suggest that newly designed BFRP thermal break structure can effectively solve thermal bridge problems in balcony.

Ductility assessment of GFRP reinforced concrete beams with a wedge-based mechanical model accounting for discrete fibers and confinement

Glass fiber-reinforced polymer (GFRP) bars for internal reinforcement for concrete have gained attention due to their non-corrosive properties, high resistance, and electromagnetic transparency. On the other hand, the brittle behavior and low modulus of elasticity of FRP bars limit their application and diffusion in the civil construction market. From this perspective, this work investigates the influence of three components on the increase of ductility of GFRP beams: i) discrete alkali-resistant glass fibers added to the concrete; ii) confinement of the concrete with GFRP stirrups; and iii) use of longitudinal reinforcement on the compression zone. An experimental program including four over-reinforced beams with different reinforcement configurations was conducted. The beams were tested in four-point bending configuration and the use of fibers, stirrups and compression reinforcement contributed to substantially increasing the beam ductility index. Finally, a concrete wedge model was developed to obtain equivalent stress-strain relationships for the concrete in compression. The model was successfully validated against experiments and proved to be a useful tool for rationally evaluating GFRP RC beams’ ductility.

A refined method for designing the strength of normal cross-sections of eccentrically compressed concrete elements with composite polymer reinforcement

Introduction. The operating standards for the design of concrete structures with composite reinforcement SP 295.1325800.2017 do not consider the work of compressed reinforcement when calculating eccentrically compressed elements. The previous studies proposed a method for calculating the strength of normal cross-sections of eccentrically compressed elements. Though this method has shown a reasonably high agreement with the experimental data, it has also indicated some underestimation of the load-bearing capacity of such elements. In this paper, a further analysis of the developed method is performed and suggestions for its refinement are formulated in order to identify additional reserves of strength of concrete elements reinforced with composite reinforcement.Aim. To refine the method for designing the strength of normal cross-sections of eccentrically compressed concrete elements with composite reinforcement, to compare the refined method with experimental and theoretical data, as well as to assess its reliability.Materials and methods. Theoretical studies are based on the results of the tests that included the experimental examination of concrete samples reinforced with composite reinforcement under the action of eccentrically applied static compressive load consisting of four series of specimens with a total of 12 specimens.Results. The suggestions were formulated for specifying the value of the height of the compressed zone, as well as the value of tensile stresses in composite reinforcement for designing the strength of normal cross-sections of eccentrically compressed concrete elements with composite reinforcement.Conclusions. Based on the analysis of experimental data, a refined methodology for designing the strength of normal cross-sections of eccentrically compressed concrete elements reinforced with composite reinforcement is proposed. In addition, the assessment of the proposed refined method is carried out, which proved to have the required level of reliability, while providing the best convergence with the experimental data.

The effect of compression reinforcement on the shear behavior of concrete beams with hybrid reinforcement

The effect of compression reinforcement on the shear behavior of concrete beams with hybrid reinforcement

Predicting and optimizing maximum flexural strength of planar composite plate shear walls – concrete filled with the application of LR and RSM

Traditional theoretical models, while conservative, overlook the complex, nonlinear interactions between material and geometric parameters that influence wall flexural strength. Additionally, the extent to which these models maintain their conservative assumptions across varying parameters remains uncertain. This study aims to develop advanced predictive models for the flexural strength of planar composite plate shear walls—concrete filled (C-PSW/CF) by employing Linear Regression (LR) and Response Surface Methodology (RSM). Central Composite Design (CCD) was utilized to design numerical experiments to analyze the effects of varying parameters, including steel plate yield strength, concrete compressive strength, wall depth, depth-to-thickness ratio, and reinforcement ratio. A validated complex finite element modeling (FEM) procedure was used to analyze numerical experiments involving varying parameters of the selected variables. Both LR and RSM were applied to the generated dataset to formulate predictive equations for the maximum moment capacity of walls. Interaction plots were developed to reveal the nonlinear relationships between the variables and identify the most effective parameters influencing the wall strength. Comparisons between theoretical predictions, RSM, and LR models revealed that RSM provided the most accurate predictions, closely aligning with FEM results and effectively capturing the nonlinear interactions between wall parameters. The findings of this paper contribute to the development of more practical, accurate and optimized design methods for C-PSW/CF, ultimately improving both structural safety and efficiency.