Search Results (1,225)

Underground granaries naturally preserve grain quality by maintaining low temperatures and reduced oxygen levels, eliminating the need for artificial cooling and pest control. However, cast-in-place reinforced concrete construction faces challenges such as waterproofing and complex on-site processes, necessitating prefabricated steel plate-concrete composite structures with robust joints for enhanced structural integrity and streamlined construction. The study utilizes a full-scale prefabricated steel plate-concrete underground silo, instrumented with strain gauges on circumferential steel bars and internal steel plates to monitor stress variations during six distinct backfilling loading cases. Concurrently, finite element models were developed using ABAQUS 6.14 software for numerical simulations, which were validated against experimental data. Stability analyses, including buckling load assessments and parameter sensitivity studies, were conducted to evaluate the effects of joint quantity and bending stiffness on the structural performance of the composite walls. The results revealed that circumferential joints play a critical role in stress distribution within the composite walls, underscoring the necessity of optimized joint design. The numerical model accurately replicated experimental results, with deviations below 9%, confirming its reliability. Furthermore, an equivalent joint design method was established, demonstrating that a joint bending stiffness ratio above 1.1 ensures that prefabricated composite walls achieve critical buckling loads comparable to cast-in-place walls. These findings provide a robust framework for enhancing the structural performance and reliability of prefabricated underground silos. Full article

The structural use of fibre-reinforced concrete (FRC) has shown to be an attractive alternative for certain structural elements, being especially suitable to withstand shear stresses in concrete beams. In the case of longitudinal steel bars to support bending stresses, the reductions are of interest. However, in the case of shear stress, it is possible to eliminate the stirrup reinforcement in certain areas. In such a case, the use of FRC may eliminate not only the material but also the tasks of preparing and placing reinforcement, achieving significant savings in labour and allowing a faster execution, avoiding human error, and providing greater security to the work. This study was developed with the aim of assessing a basic practical application of FRC for shear strength. A series of graphics have been made to be used as a calculation tool. The typical structural elements of buildings subjected to bending and shear stress have been tested and analysed. The results for steel fibre-reinforced concrete (SFRC) and polyolefin fibre-reinforced concrete (PFRC) show that fibre can substitute, to some extent, part of the longitudinal reinforcement needed to provide the required flexural strength. Additionally, the fibres can reduce or even eliminate the need for stirrups for shear strength, which leads to savings in cost and execution time. Full article

In many offshore structures, structural components are often subjected to compressive forces and seawater corrosion. Therefore, understanding their resistance to chloride ion-induced corrosion under compression is crucial. This study investigates the effects of macro polypropylene fibers and macro steel fibers on the chloride permeability and damage of concrete under uniaxial compression. Ultrasonic testing is performed before and after the uniaxial compression test to assess the damage to concrete specimens at different stress levels. Simultaneously, the Rapid Chloride Migration test is conducted on the specimens subjected to various compressive stress levels. The results reveal that the chloride permeability of concrete is influenced by the stress level after uniaxial compression. Additionally, a threshold phenomenon is observed in the chloride permeability: after reaching the threshold stress level, the chloride diffusion coefficient increases significantly. Compared with plain concrete, incorporating macro fibers raises the threshold stress level for chloride ion penetration. Furthermore, this threshold stress level increases with higher fiber content. The variation in ultrasonic velocity with stress level is also found to be an effective indicator for evaluating the chloride permeability of concrete under uniaxial compression. Moreover, a prediction model for the chloride permeability of FRC (fiber reinforced concrete) is proposed based on the results. Full article

Traditional materials such as steel and concrete often face limitations in terms of corrosion resistance and long-term performance. Over the past few decades, the search for alternative reinforcement solutions has grown, driven by the need for more sustainable, lightweight, and corrosion-resistant materials. Basalt fibers, with their superior mechanical properties and resistance to environmental degradation, have emerged as a promising candidate. This study investigated the tensile mechanical properties and constitutive behavior of basalt fiber-reinforced polymer (BFRP)–steel–BFRP composite plates. A total of 12 specimens were fabricated, varying in BFRP layer thickness, and subjected to uniaxial tensile testing. The results reveal that bonding BFRP layers significantly enhances the strengthening stiffness and strength of the steel plates, while maintaining ductility and fracture stability. The stress–strain analysis indicates a bilinear behavior, with the BFRP layers contributing to a higher slope during the strengthening stage and stable fracture strain across specimens. Additionally, a three-segment constitutive model was proposed and validated, demonstrating high accuracy in predicting tensile behavior. The findings highlight the potential of BFRP–steel–BFRP composite plates as efficient reinforcement solutions, offering a balance of strength, flexibility, and cost-effectiveness. This study provides data and modeling insights to guide the design and optimization of composite materials for structural applications. Full article

This study aims to investigate the bending load-bearing capacity of precast hollow composite slabs composed of ultra-high-performance concrete (UHPC) and Normal Concrete (NC). Through finite element numerical analysis and verification, this study analyzes various key factors influencing the performance of the composite slab, including the wall thickness of the square steel tube, the diameter of transverse reinforcing bars, the thickness of the precast bottom slab, and the strength grade of the concrete. The results indicate that the use of UHPC significantly enhances the bending performance of the composite slab. As the wall thickness of the square steel tube and the strength of UHPC increase, both the yield load and ultimate load capacity of the composite slab show considerable improvement. By conducting an in-depth analysis, this study identifies different stages of the composite slab during the loading process, including the cracking stage, yielding stage, and ultimate stage, thereby providing important foundations for optimizing structural design. Furthermore, a set of bending load-bearing capacity calculation formulas applicable to UHPC-NC precast hollow composite slabs is proposed, offering practical tools and theoretical support for engineering design and analysis. The innovation of this study lies not only in providing a profound understanding of the application of composite materials in architectural design but also in offering feasible solutions to the energy efficiency and safety challenges faced by the construction industry in the future. This research demonstrates the tremendous potential of ultra-high-performance concrete and its combinations in modern architecture, contributing to the sustainable development of construction technology. Full article

Bridge fires present unique challenges due to their potential for catastrophic structural failures, leading to extensive traffic disruptions, economic losses, and, in some cases, loss of life. In the aftermath of a fire incident, assessing the structural integrity and future viability of concrete bridges has become a paramount concern for civil engineers and safety inspectors. The critical decision to rehabilitate or demolish a fire-damaged structure hinges on accurately assessing the extent of damage incurred. Enhancing the fire resilience of concrete structures is a critical endeavor within civil engineering, necessitating accurate evaluation methods to analyze conditions after fire exposure. Focusing on concrete bridges, this study aimed to establish a comprehensive review of research on the effects of fire, providing engineers with the necessary means to develop guidelines for post-fire assessment to enhance safety and operational readiness. It proposes an in-depth examination of various methods as strategic decision-making tools. The assessment involves estimating the temperature, the extent of damage to concrete, and the reduction in the strength of both concrete and reinforcement. To achieve this, a detailed review of the existing literature on the impact of fire on concrete and its steel reinforcements is conducted. Current post-fire assessment tools have also been evaluated to improve the efficiency of the evaluation process. This study establishes a systematic post-fire assessment review framework that incorporates assessment information domains (including non-destructive testing, destructive testing, advanced computational modeling, and digital-twin technology) to provide a practical solution for accurately determining the safety and operational readiness of fire-damaged concrete bridges. Full article

Fiber-reinforced polymers (FRPs) are often incorporated as internal (primary) reinforcement in new concrete constructions or as external (secondary) reinforcement in retrofitting and strengthening of existing concrete structures. Under fire conditions, the response of FRP-incorporated concrete structures are altered due to the presence of FRPs; thus, their fire performance is different from that of concrete structures with conventional metallic reinforcement. However, the fire resistance of these FRP-incorporated structural members continues to be evaluated through standard fire resistance tests, which are similar to conventional steel and concrete structural members. Despite the complexity of this testing approach and its drawbacks, standard fire testing remains a cornerstone in evaluating FRP-incorporated concrete structural members. Thus, this paper sheds more light on the fire testing procedure and discusses the distinctive factors that differentiate the fire performance of FRP-incorporated concrete structures from that of conventional concrete structures and the need for additional provisions to test such structures. To address the current shortcomings, a set of additional testing protocols and procedures for undertaking fire resistance tests on FRP-incorporated concrete structural members are presented. The performance criteria to be applied to evaluate the failure of FRP–RC structural members under fire conditions are discussed. Full article

The corrosion of steel reinforcements substantially degrades the longevity of reinforced concrete structures, particularly in marine settings. This investigation introduces a comprehensive model that simulates the processes involved in moisture and chloride ion transport, rebar corrosion, and the consequent cracking of concrete. The model reveals that the transport dynamics of chloride ions are primarily dictated by their penetration rates through the solution. The sensitivity of the steel to corrosion is a function of the concentrations of water and chloride ions, whereas the rate of corrosion predominantly depends on the availability of oxygen at the corrosive site. Oxygen diffusion is the rate-limiting step in the entire process of the electrochemical reactions of the rebar. And the peak corrosion rates are observed at the interface between the solution and the gas phase. The model calculates the stress and strain in the concrete resulting from volumetric expansion due to oxidization of the steel bars. By accurately reproducing the progression of corrosion-related damage, this model provides crucial insights for predicting the service life of offshore concrete structures and enhancing durability against aggressive environmental conditions. Full article

Carbonation and chloride ingress are the most important damaging mechanisms for steel-reinforced concrete. The combination of these two corrosion processes accelerates the destruction of concrete, leads to extensive structural repairs, negatively impacts durability, and significantly reduces the service life of the structure. One possible and effective way to reduce chloride diffusion through the concrete pore system is through the use of crystalline materials. An experimental study focused on the ability of an applied crystalline coating to increase the chloride resistance of carbonated concrete is presented in this paper. Carbonated concrete specimens treated with a crystalline coating were exposed to a sodium chloride solution for various periods of time, and a water-soluble chloride ion content analysis was performed on powder samples taken from the tested specimens. Chloride profiles presenting the chloride ion concentrations at selected depths are presented for multiple types of concrete at various ages to show the effect of crystalline technology on the chloride resistance of concrete. The results of this study confirm the impact of carbonation on chloride ion ingress through concrete and show that crystalline coatings can improve the chloride resistance of concrete. Using crystalline coatings on carbonated concrete can, from a long-term perspective, significantly reduce the chloride ion content in concrete placed in an aggressive environment. The crystalline coatings were functional even after 28 days, when the concentration of chloride ions was below the critical concentration. The crystalline coating was able to reduce the concentration of chloride ions by 68% under the surface of the concrete and by 65% at depths of 20–25 mm after 180 days of immersion, compared to the untreated concrete. Crystalline coatings reduce the depth of critical chloride ion concentration, effectively protect the concrete reinforcement against corrosion and extend the service life of the structure. Full article

Rigid road pavements and industrial floors are not only subjected to moving traffic loads, but can also be exposed to environmental influences such as acid attack. The strength and corrosion resistance of fiber-reinforced concrete with steel fibers (15–25 kg/m³) and polypropylene fibers (2–3 kg/m³) in an acidic environment were compared. The influence of the amount and type of dispersed reinforcement on water absorption and the volume of permeable voids, which in turn characterizes the durability of fiber-reinforced concrete under the action of acids, was determined. The change in the compressive strength of the studied fiber-reinforced concrete after 12 months of exposure in an acidic environment was studied. At low dosages of fibers (15 kg/m³ for steel and 2 kg/m³ for polypropylene fibers), dispersed reinforcement has little effect on the corrosion resistance of concrete. In turn, the decrease in the compressive strength of concrete without fibers after 12 months of aging in acid medium led to a reduction in the design class of the concrete from C25/30 to C20/25. At a higher consumption of dispersed reinforcement (25–30 kg/m³ of steel fiber and 2.5–3.0 kg/m³ of polypropylene fiber), fiber-reinforced concrete had a higher corrosion resistance while maintaining the design compressive strength class C25/30. Structural changes in fiber-reinforced concrete after aging in an acidic environment were determined by X-ray diffraction analysis and compared with samples aged in water. It has been experimentally confirmed that the efficiency of polypropylene fibers in an acidic environment is not lower than that of steel fibers. However, the use of polypropylene fibers is economically advantageous. Full article

The growing demand for reinforced concrete (RC) structures, driven by population growth, significantly contributes to carbon emissions, particularly during the construction phase. Steel rebar production, a major contributor to these emissions, faces challenges due to high material consumption and waste, often stemming from market-length rebar and conventional lap splices, impeding decarbonization efforts. This study introduces a comprehensive strategy to minimize rebar consumption and waste, advancing decarbonization in the civil and construction industry. The strategy integrates a special-length-priority minimization algorithm with lap splice position adjustments or couplers to reduce rebar consumption, waste, and carbon emissions. A case study evaluates distinct scenarios regarding rebar consumption. The study demonstrates that conventional rebar practices, such as market-length rebar and lap splices, lead to excessive consumption and waste, impeding decarbonization. Couplers significantly reduce rebar requirements, though cutting waste remains when combined with market-length rebar. Special-length-priority optimization with lap splice adjustments demonstrates greater efficiency in reducing consumption while minimizing cutting waste, proving effectiveness. The combination of special-length-priority optimization and couplers achieves the greatest reductions in rebar consumption, waste, and carbon emissions, making it the most efficient strategy for future construction projects. These findings emphasize the importance of optimizing rebar consumption in advancing decarbonization and promoting sustainable practices in the civil and construction industry. Full article

The integration of cutting-edge technologies into reinforced concrete (RC) design is reshaping the construction industry, enabling smarter and more sustainable solutions. Among these, machine learning (ML), a subset of artificial intelligence (AI), has emerged as a transformative tool, offering unprecedented accuracy in prediction and optimization. This study investigated the flexural behavior of steel rebar RC beams, focusing on varying concrete compressive strengths via theoretical, experimental and ML analysis. Nine steel rebar RC beams with low (SC20), moderate (SC30) and high (SC40) concrete compressive strength, measuring 150 × 200 × 1100 mm, were produced and subjected to three-point bending tests. An average error of less than 5% was obtained between the theoretical calculations and the experiments of the ultimate load-carrying capacity of reinforced concrete beams. By combining three-point bending experiments with ML-powered prediction models, this research bridges the gap between experimental insights and advanced analytical techniques. A groundbreaking aspect of this work is the deployment of 18 ML regression models using Python’s PyCaret library to predict deflection values with an impressive average accuracy of 95%. Notably, the K Neighbors Regressor and Gradient Boosting Regressor models demonstrated exceptional performance, providing fast, consistent and highly accurate predictions, making them an invaluable tool for structural engineers. The results revealed distinct failure mechanisms: SC30 and SC40 RC beams exhibited ductile flexural cracking, while SC20 RC beams showed brittle shear cracking and failure with sudden collapse. Full article

In the case of engineering structures, the performance of a structure will gradually deteriorate with an increase in the usage time, leading to a decrease in the safety of the structure. In addition, even if the safety of a structure is reliable, its current structure type may no longer meet the latest usage requirements. Therefore, four reinforced concrete specimens were produced in this study: one was a cast-in-place specimen, and three were specimens connected by a T-shaped steel plate with steel cladding reinforcement. This article first introduces the structural form and construction method of the new types of joints, and then it describes the quasi-static testing that was conducted to analyze seismic performance indicators such as the failure characteristics, bearing capacity, ductility, stiffness degradation, and energy dissipation. Finally, combined with a strain analysis of the steel bars and steel plates, the force transmission mechanism of the new types of joints was investigated. The research content of this paper helps to promote the progress of structural retrofitting and strengthening work and the sustainable development of the construction industry. Full article

This study researches the bending and shear performance of the fragile cross-section of square hollow steel-reinforced concrete columns using experiments, numerical analysis, and theoretical investigation. First, three tests of square hollow steel-reinforced concrete column (HSrCC) specimens considering different sectional sizes and grouting conditions were conducted. The bearing capacity and load transfer mechanisms under bending and shear loading were experimentally compared. Second, a numerical model was established based on the experimental results, and then parametric studies were performed on the bearing capacity and deformation of the structure. Last, a peak load calculation formula was derived in this study considering thickness and strength for a 400 × 400 square HSrCC. Based on the experimental results, the failure process of the specimen can be divided into four steps. Grouting increases stiffness at the front part of the specimen but induces significant damage at the rear compared to the no-grouting case, with the maximum strain increasing by 25%. Increasing the cross-sectional area of the concrete short column effectively improves the overall performance, with the maximum tensile strain of the concrete short column being reduced by approximately 1.2 times. Under the given sectional dimensions, parametric analysis suggests that the optimal square hollow steel thickness and steel strength range from 14 mm to 16 mm and from Q355 to Q420, respectively. The proposed peak load calculation formula demonstrates a discrepancy of less than 5.06% when compared with the numerical model results. These findings provide valuable references for the design of square hollow steel-reinforced concrete columns. Full article

Split reinforced concrete column (SRCC), recognized for their exceptional ductility as seismic members, have faced developmental challenges due to the complexities of on-site casting. This study presents an innovative steel sleeve dry connection assembled SRCC, which is highly modular and simplifies construction, aiming to promote the engineering application of this innovative ductile seismic structural system. This study used a validated 3D finite element (FE) method to analyze internal joint forces. Key parameters influencing joint performance, such as the axial compression ratio (u) and cross-sectional equal division ratio (n), were analyzed in detail. Subsequently, a comparative of dynamic analysis of SRCC and normal reinforced concrete column (NRCC) frames was conducted, leading to recommendations for structural strengthening. The analysis revealed that the sleeve can provide effective protection for the core area of the joint. The ductility of SRCC is 2–3 times higher than that of NRCC. A detailed formula for calculating the shear-bearing capacity of SRCC joints was derived, showing strong agreement with numerical simulations. At a high seismic intensity of 9°, the acceleration response of the SRCC frame is significantly reduced compared to the NRCC frame, with the maximum base shear (MBS) decreasing by approximately 4 times, which significantly enhances its seismic performance. However, due to the larger inter-story displacements, it is necessary to incorporate energy-dissipating braces to comply with code requirements. Collectively, these findings underscored that the proposed SRCC system significantly enhances seismic performance by improving ductility and energy dissipation, providing a robust foundation for future studies and practical applications in seismic design. Full article