Steel-reinforced Concrete Structures Research Articles

Non-Destructive Inspection Method Using Elastic Waves for Quality Management in the Bending Process Region of BFRTP

In order to establish a sustainable infrastructure, structures must maintain their minimum required performance for an extended period. Typically, existing concrete structures are reinforced with steel, but the susceptibility of steel reinforcements to corrosion, attributed to factors such as carbonation and chlorides, can lead to performance degradation, rendering the specified requirements unmet. As a remedy, there has been a growing interest in using lightweight and corrosion-resistant fiber-reinforced polymer (FRP) bars as an alternative to traditional steel reinforcement in concrete structures. Particularly noteworthy is the use of FRP bars manufactured with thermoplastic resins (FRTP) due to their ease of processing and convenient applicability on construction sites. This study delves into the mechanical behavior evaluation by examining the propagation characteristics of elastic waves in the curved section of basalt FRTP (BFRTP). Multiple BFRTP bars underwent a 180-degree bending process, subject to various conditions, including heat and twist variations. Subsequent measurements focused on the propagation characteristics of elastic waves in the curved sections, emphasizing wave attenuation, frequency features, and propagation velocity. Additionally, bending tensile tests were conducted on the curved bars, and a comparative analysis was performed between the tensile strength and the aforementioned elastic wave propagation characteristics. The results affirm a consistent correlation between the propagation characteristics of elastic waves (amplitude ratio, centroid frequency, velocity) during the traversal of the curved BFRTP section and its tensile strength. Notably, both centroid frequency and velocity exhibited correlation coefficients exceeding 0.7, suggesting their potential efficacy as reliable indicators for estimating tensile strength.

Experimental Investigation of GFRP-Reinforced Hollow Square Concrete Column

Due to their great structural efficiency and efficient utilization of materials, steel-reinforced hollow-core concrete columns are often employed in utility poles, ground piles, and piers for bridges. Based on research, these columns' performance is impacted by many design parameters. However, corrosion can be a problem in steel-reinforced concrete structures. This paper examines the differences between using steel and GFRP longitudinal bars in hollow-section square concrete columns and explores the potential benefits of using GFRP bars as an option that is economically viable and non-corrosive. According to the study results, the computational results clearly show how an increased longitudinal GFRP reinforcement ratio improves the columns' bearing capability, but when compared to steel reinforcement, it provides less bearing capability. For the same reinforcement ratio (1.46 %, 3.29 %, and 4.9 %), The findings demonstrated that GFRP columns had a decrease in the axial bearing load by 13.1%, 9.2 %, and 9.4%, respectively.

Crack detection and damage evaluation of asymmetrical steel-reinforced concrete frame nodes using acoustic emission technology

ABSTRACT Detecting cracks in steel-reinforced concrete (SRC) frame nodes is crucial for ensuring structural safety. This study employs acoustic emission (AE) technology to monitor the growth of concrete structural defects in real time. The aim is to establish a sensitive assessment method based on AE parameters to accurately assess the damage stages of SRC frame nodes by considering the complex crack extension mechanism in SRC structures. An experimental study of the AE characteristics of SRC frame nodes under low-cycle loading was performed. The crack evolution process of SRC frame nodes was monitored and analysed using the AE parameters. The results showed that ringing count is the AE parameter more sensitive to the damage of the SRC frame node. The damage evaluation method was established based on the variation coefficient analysis of the AE parameters. Considering the sudden change in the growth rate of the damage index, the damage evolution process of the SRC frame nodes can be accurately divided into three stages: initial crack compaction, rapid crack expansion, and crack penetration. These stages are consistent with the mechanical properties of SRC frame nodes.

Chloride binding by layered double hydroxides (LDH/AFm phases) and alkali-activated slag pastes: an experimental study by RILEM TC 283-CAM

Chloride binding by the hydrate phases of cementitious materials influences the rate of chloride ingress into these materials and, thus, the time at which chloride reaches the steel reinforcement in concrete structures. Chloride binding isotherms of individual hydrate phases would be required to model chloride ingress but are only scarcely available and partly conflicting. The present study by RILEM TC 283-CAM ‘Chloride transport in alkali-activated materials’ significantly extends the available database and resolves some of the apparent contradictions by determining the chloride binding isotherms of layered double hydroxides (LDH), including AFm phases (monosulfate, strätlingite, hydrotalcite, and meixnerite), and of alkali-activated slags (AAS) produced with four different activators (Na2SiO3, Na2O·1.87SiO2, Na2CO3, and Na2SO4), in NaOH/NaCl solutions at various liquid/solid ratios. Selected solids after chloride binding were analysed by X-ray diffraction, and thermodynamic modelling was applied to simulate the phase changes occurring during chloride binding by the AFm phases. The results of the present study show that the chloride binding isotherms of LDH/AFm phases depend strongly on the liquid/solid ratio during the experiments. This is attributed to kinetic restrictions, which are, however, currently poorly understood. Chloride binding by AAS pastes is only moderately influenced by the employed activator. A steep increase of the chloride binding by AAS occurs at free chloride concentrations above approx. 1.0 M, which is possibly related to chloride binding by the C–(N–)A–S–H gel in the AAS.

Evaluation of the Corrosion Activity of Reinforcement in Drainage Gallery of Concrete Dam using Half-cell Potential (HCP)

Dams are essential structures for water management, providing various benefits crucial for human survival and economic growth. However, steel corrosion in concrete dams poses a significant threat, leading to structural deterioration and potential collapse. Detecting corrosion in the early stage is critical to prevent catastrophic failures. This study investigates corrosion risk in a concrete dam's drainage gallery using half-cell potential (HCP) measurements, a common method for assessing corrosion activity in reinforced concrete. The electrochemical process of steel corrosion in concrete, influenced by factors like chloride or carbonation exposure and temperature, is discussed. The HCP method is a nondestructive technique for determining the corrosion rate of steel reinforcement in concrete structures. It involves measuring the potential difference between reinforcing steel and reference electrodes; typically, a copper/copper sulphate electrode is used. The potential difference between the two electrodes is then used to calculate the corrosion rate of the reinforcing steel. The HCP method is a reliable and cost-effective way to identify potential corrosion problems before they become severe. The present study used CorMap II® to measure HCP on the upstream face of the dam's drainage galleries. Results indicate predominantly low corrosion risk across tested locations, with minimal uncertainty. However, interpretations must consider environmental factors' influence on measurements. The study's findings offer valuable insights for future corrosion assessments and underline the importance of preventive measures for concrete dam integrity.

Damage Detection in FRP-Reinforced Concrete Elements.

Fiber-Reinforced Polymer (FRP) composites have emerged as a promising alternative to conventional steel reinforcements in concrete structures owing to their benefits of corrosion resistance, higher strength-to-weight ratio, reduced maintenance cost, extended service life, and superior durability. However, there has been limited research on non-destructive testing (NDT) methods applicable for identifying damage in FRP-reinforced concrete (FRP-RC) elements. This knowledge gap has often limited its application in the construction industry. Engineers and owners often lack confidence in utilizing this relatively new construction material due to the challenge of assessing its condition. Thus, the main objective of this study is to determine the applicability of two of the most common NDT methods: the Ground-Penetrating Radar (GPR) and Phased Array Ultrasonic (PAU) methods for the detection of damage in FRP-RC elements. Three slab specimens with variations in FRP type (glass-, carbon- and basalt-FRP, i.e., GFRP, CFRP, and BFRP, respectively), bar diameter, bar depths, and defect types were investigated to determine the limitations and detection capabilities of these two NDT methods. The results show that GPR could detect damage in GFRP bars and CFRP strands, but PAU was limited to damage detection in CFRP strands. The findings of this study show the applicability of conventional NDT methods to FRP-RC and at the same time identify the areas with a need for further research.

ОПТИМИЗАЦИЯ ПОЛУПЛОСКООВАЛЬНЫХ ГНУТОСВАРНЫХ ПРОФИЛЕЙ ДЛЯ БАЛОЧНЫХ КОНСТРУКЦИЙ.

A new technical solution for semi-flat bent-welded profiles is presented, optimized for bending strength characteristics, the originality of which has been confirmed by patent examination. Rectangular profiles with a ratio of width and height 1/3 along the middle section line served as the basis for their shaping, which ensures maximum strength. As a prototype, semi-flat profiles are assembled on the basis of flat-oval profiles with maximum strength due to the ratio of width and height 1/3.064 along the middle section line. The calculation of the optimal parameters of thin-walled sections using an approximate technique using their average lines, repeatedly tested in solving optimization problems for bent-welded profiles of various shapes and outlines, is presented. A comparative analysis of the design parameters revealed a positive effect of optimized profiles in truss and girder structures, including a reduction in the consumption of structural material, a decrease in stress concentration, and a reduction in building height. The prospects of expanding the scope of their rational use with the addition of pipe-concrete and steel-reinforced concrete structures are indicated.

Quantitative Characterization of Passivation Process of Steel Reinforcement in Concrete towards Durability against Anticorrosion Based on Electrochemical Methods

The passivation behavior of steel reinforcements in concrete is significantly influenced by the environment, concrete pore solution, and the passive film formed on the steel surface. The present study used electrochemical methods to successfully characterize the passivation process of steel reinforcements in concrete. The passivation behavior of commonly used HRB400 steel reinforcement material in concrete was studied using various electrochemical parameters quantitatively. As the soaking test time increased, the OCP gradually increased and stabilized after 5 days, indicating that the steel electrode transitioned from an active state to a passive state in the simulated liquid environment of concrete. The steel reinforcement developed a protective passive film that reduced its tendency to corrode. According to EIS, after soaking for one day, the steel electrode showed significant early passivation, indicated by an increase in its arc diameter. The WE arc gradually increased in the first 5 days of immersion, suggesting dynamic passive film formation and development. Beyond 5 days, the passive film stabilized with minimal further changes in its impedance spectrum, indicating carbon steel electrode passivation. The working electrode’s impedance increased significantly on the fifth day, and gradually increased slightly after 10 days, indicating comprehensive coverage by the oxide film. Attributed to the growth and development of the oxide film, the electrode resistance reached a relatively stable state after the fifth day. The shift in corrosion potential offers an indication of the level of passivation of the steel reinforcements. The decrease in the anode Tafel slope and increase in the corrosion potential indicate the formation and stabilization of an oxide film on the steel surface, which is beneficial for its long-term durability in concrete structures. By analyzing the OCP, EIS, and dynamic potential polarization curve method data, it is possible to gain insights into the passivation behavior of steel reinforcements in concrete structures. This study aims to provide a basis for optimizing the corrosion protection of steel reinforcements in concrete structures. The significance of this study lies in a deep understanding of the passivation behavior of steel bars in concrete, providing a theoretical basis for improving the durability and lifespan of steel bars in concrete structures.

Effects of GFRP Stirrup Spacing on the Behavior of Doubly GFRP-Reinforced Concrete Beams

This study investigates the impact of varying glass fiber-reinforced polymer (GFRP) stirrup spacing on the performance of doubly GFRP-reinforced concrete beams. The research focuses on assessing the behavior of GFRP-reinforced concrete beams, including load-carrying capacity, cracking, and deformability. It explores the feasibility and effectiveness of GFRP bars as an alternative to traditional steel reinforcement in concrete structures. Six concrete beams with a cross-section of 300 mm (wide) × 250 mm (deep), simply supported on a 2100 mm span, were tested. The beams underwent four-point bending with two concentrated loads applied symmetrically at one-third of the span length, resulting in a shear span (a)-to-depth (h) ratio of 2.8. The experimental findings reveal that altering the GFRP stirrup spacing along the longitudinal axis of the beams, from 200 mm (equivalent to the effective depth (d)) to 50 mm (equal to (d⁄4)), altered the mode of failure from flexure-shear to flexure-compression. However, when the spacing was equal to or less than (d⁄3), there was no significant improvement in load-carrying capacity, as the contribution of GFRP bars in resisting shear loads was limited. Under service loads, the GFRP-reinforced beams exhibited wider cracks, but reducing the stirrup spacing helped restrain crack widening. Incorporating GFRP bars in the compression zone had a positive effect on reducing crack width in the tension zone. Additionally, using GFRP stirrups with spacing varying between (d) and (d⁄2) in the pure bending region increased the deflection ductility indexes. To enhance the ductility of GFRP-reinforced concrete beams, it is recommended to use GFRP stirrups in the pure bending region with spacing greater than the spacing between GFRP stirrups in the shear spans. The study highlights that the current ACI code overestimates the shear capacity provided by GFRP stirrups, particularly when the spacing is less than or equal to (d⁄3). Doi: 10.28991/CEJ-2024-010-02-011 Full Text: PDF

A novel method for temperature self-sensing of reinforced concrete

In this work, a temperature-sensing reinforced concrete has been developed using capacitance and resistance-based measurements. No additives are required for self-temperature sensing. Steel bars in the reinforced concrete are used as electrodes. To determine the self-sensing properties of the reinforced concrete specimen, it is cooled from room temperature to −9 °C and heated from room temperature until it reaches 50.9 °C. The varying capacitance and resistance values of the sample concerning temperature changes are evaluated. Fractional changes in capacitance and resistance upon cooling are 80.6% and 276%, respectively. Fractional changes in capacitance and resistance upon warming are 60% and 35%, respectively. Temperature coefficients of capacitance and resistance (fractional change in capacitance and resistance per unit change in temperature) upon cooling are 2.5 × 10−2/°C and 8.6 × 10−2/°C, while upon warming they are 2.2 × 10−2/°C and 1.3 × 10−2/°C. This study aims to use capacitance and resistance-based sensing techniques to detect temperature variations in steel-reinforced concrete structures. Further studies are planned to investigate various factors such as moisture, porosity, aggregate proportion, and water content that affect the self-temperature-sensing performance of reinforced concrete.

Investigations on geopolymer-based seawater sea-sand high performance concrete slabs reinforced with basalt FRP bars under direct contact explosions

Adopting locally available raw materials like seawater and sea-sand in coastal areas and oceanic islands has facilitated meeting the demands of marine engineering. However, these raw materials contain corrosive elements that could threaten the steel reinforcement in concrete structures, thus non-corrosive fibre-reinforced polymer (FRP) bars are proposed. In the present study, the geopolymer-based seawater sea-sand high performance concrete (G-SHPC) slab reinforced with basalt FRP bars was designed to preliminarily evaluate its dynamic behaviour under contact explosions. Tests were conducted on three large-sized slabs with different TNT charge weights, including 0.8 kg, 1.6 kg and 2.2 kg. To complement the experimental investigation, a numerical simulation was then performed in ANSYS-DYNA. A Continuous Surface Cap (CSC) model was developed to accommodate the unique characteristics of G-SHPC. Two different blast modelling methods, including the Arbitrary Lagrangian-Eulerian (ALE) algorithm and a hybrid Finite-Element (FE) and Smooth Particle Hydrodynamics (SPH) algorithm, were examined to faithfully reproduce the contact explosion phenomena. The structural models considered the bond-slip behaviour, and three bond-slip models were compared. The numerical results obtained through the ALE algorithm and the beam-in-solid bond-slip model exhibited fair agreement with the test results, with a maximum error of less than 6.3%. A parametric study was further conducted to establish the damage identification diagram. Formulas based on empirical data were formulated to anticipate the damage degrees of G-SHPC slabs exposed to contact explosions.

Prediction model for heating rate of section steel during the induction heating demolition process of steel reinforced Concrete：Experimental and numerical analysis

Traditional demolition techniques face challenges in effectively separating steel and concrete components of steel-reinforced concrete (SRC) structures. To address this issue, our research group has developed induction heating demolition (IHD) technology, a method allowing for environmentally sustainable and recyclable separation of section steel and concrete. To clarify the underlying mechanisms of the induction heating (IH) process applied to section steel, we undertook experiments on 32 samples of section steel. Our investigations focused on delineating the roles of two key parameters: the heating power (P) and the size of the sections involved. We found the heating rate (V) of the section steel to be significantly influenced by P, in conjunction with the flange and web plate thicknesses. To further unravel the transformations occurring in the steel's internal physical properties throughout the IH process, we devised a numerical simulation approach capable of faithfully replicating the IH process as it applies to section steel. This analysis revealed a diminishing IH efficiency for the section steel, with values declining from 0.7 to roughly 0.4 as the temperature escalated. Utilizing both experimental and numerical data, we formulated a predictive model for the section steel's V, aiming to facilitate the planning stage of IHD implementations. The model exhibits a predictive deviation maintaining a margin within 10 %, demonstrating its substantial reliability. This investigation provides novel strategies to curtail construction waste emissions in building demolition endeavors, thereby presenting a promising avenue toward more sustainable practices in the industry.

Probabilistic models for characteristic bond stresses of steel-concrete in steel reinforced concrete structures

Steel-reinforced concrete (SRC) composite structures are widely employed in modern buildings because of their elevated load-carrying capacity, robust stability and remarkable resilience to corrosion and fire. To safely utilize SRC composite structures, reliable bonding between steel and concrete is crucial in designing and constructing SRC members and connections. With this objective in mind, the current study aims to establish accurate models for estimating the characteristic bond stresses (i.e., initial, peak and residual bond stresses) and determining the necessary anchorage length between the profiled steel and the adjacent concrete. To realize these goals, a total of 660 push-out tests and their results were compiled from existing literature for model development. Probabilistic bond stress models were created by integrating existing models with key variables related to the mechanical properties and geometrical characteristics of concrete, steel section and stirrup. Bayesian theory and the Markov Chain Monte Carlo (MCMC) method were utilized to refine and select the most precise model. The evaluation results demonstrate that the probabilistic models provide more accurate predictions for initial, peak and residual bond stresses compared to existing models. With the assistance of this reliable analytical technique, the established model for peak bond strength was finally applied to determine the minimum required anchorage length for steel within concrete.

Dynamic self-balanced electrochemical model for non-uniform corrosion of steel reinforcement in concrete under combined effects of heat-moisture-chlorine-oxygen

In this study, we developed a dynamic self-balanced electrochemical model to explore the intricate interplay between coupled heat-moisture transmission and the corrosion process of steel reinforcement in concrete structures. The model accounts for the diffusion, convection, and adsorption mechanisms of chloride ions in both the cement paste and interfacial transition zone (ITZ) phases. Additionally, it incorporates the balance between gaseous and dissolved oxygen, along with oxygen consumption during cathodic reactions. This framework allows for the dynamic self-balancing of macrocell and microcell, thus offering a comprehensive understanding of the non-uniform corrosion process under various environmental factors including temperature, humidity, chloride ions, and oxygen. To validate the model, we employed comprehensive monitoring approaches, coupled with artificial climate-accelerated corrosion experiments. These were designed to record variables such as temperature, humidity, oxygen concentration, and corrosion current density under time-varying environmental conditions. Our results indicate that while temperature within the concrete remains relatively uniform, humidity exhibits a non-uniform distribution. This non-uniformity in humidity is particularly noticeable at concrete cover surface, leading to convection and accumulation effects of chloride ions. Moreover, we observe a strong correlation between oxygen concentration and relative humidity. Corrosion current density for steel rebar is found to be higher at edge regions compared to central regions, owing to varying distances from the external soaking solution. The insights gained from this research offer valuable theoretical guidance for the design, construction, and maintenance of reinforced concrete structures, particularly those exposed to marine environments.

Reshaping concrete

Less Economically Developed Countries (LEDCs) struggle to meet the demand for affordable housing in their growing cities. There are several reasons for this, but a major constraint is the high cost of construction materials. In LEDCs, material costs can constitute 60 to 80 percent of the total cost of residential construction. Nonetheless, their construction mimics the materially inefficient practices of the More Economically Developed Countries (MEDCs), which were developed to reduce labor over material costs. As a result, prismatic beams and flat slabs are often used despite their structural inefficiency. The mounting use of steel-reinforced concrete structures in LEDC cities also raises concern for the environmental costs of construction; construction accounts for 20-30 percent of LEDC carbon emissions. This research addresses these challenges with a flexible and accessible methodology for the design and analysis of materially efficient concrete elements that may reduce the economic and environmental costs of urban construction. Designed for the constraints of LEDCs, structural elements are optimized to reduce the embodied carbon associated with the concrete and reinforcing steel while resisting the required loads of a standard building structure. The optimization method includes a novel approach to 3D-shape parameterization, as well as a decoupled analytical engineering analysis method that accounts for the key failure modes and constraints of reinforced concrete design. This method is then built into an open-source toolkit, combined with machine learning for real-time analysis and visualization, and tested using lab- and full-scale prototypes. The goal of this research is to present several generalizable methods that are applicable and accessible to LEDC building designers. These methods can enable the design of concrete elements for multiple performance criteria such as structural behavior, acoustic transmission, and thermal mass. They can also enable an accessible design practice through machine learning, real-time iterative workflows, and visualization tools that include the end-user in the architectural design process. This paper provides a high-level overview of ongoing research that explores how materially efficient design methods might enable sustainable development through low-cost, low-carbon concrete structural systems for affordable housing in LEDCs.

Experimental study on deflection of concrete member reinforced with GFRP bars under static loading

GFRP bar has superior properties such as high corrosion resistance, high tensile strength, many times lighter than steel. Corrosion properties of traditional reinforcement due to the impact of the surrounding environment seriously affect the quality as well as the life of the structure. Therefore, GFRP bars are very suitable for replacing steel reinforcement in concrete structures that require the above special requirements, contributing to increasing the life of the work. This paper presents experimental results on instantaneous deflection of flexural members including: two GFRP reinforced concrete beams and a reference reinforced concrete beam; two reinforced concrete slabs GFRP and reinforced concrete slabs control. The results show that the deflection of GFRP reinforced concrete members is larger than that of reinforced concrete members. In addition, the content of longitudinal reinforcement and concrete strength also affect the deflection of the structure.

Guided wave-based cross-scene interfacial debonding detection in reinforced concrete structures

The cross-scene problem within the field of guided wave-based interfacial debonding detection in steel-reinforced concrete structures is a significant challenge. This issue arises when the methods initially designed for laboratory-configured structures or numerical models are adapted to real-world scenarios. In response to this challenge, driven by the concept of domain adaptation, a novel method—the discriminative wavelet adversarial adaptation network (DWAAN)—is proposed to assess the health of analogous structures using diagnostic insights from a reference structure. The proposed method utilizes continuous wavelet transform to segregate signal components. A feature extraction network, designed with the convolutional neural network architecture, extracts domain confusion and damage-sensitive features through guided adversarial adaptive training in the wavelet domain. Both the adversarial and statistical alignment are employed during training for comprehensive optimization of data distribution discrepancies. The effectiveness of the proposed method is assessed in both the homogeneous and heterogeneous cross-scene interfacial debonding detection scenarios, revealing an average performance enhancement of 32.5% in distinct homogeneous applications and 26.6% in heterogeneous scenarios, when compared to the traditional supervised learning approach. In addition, the present method demonstrates robust convergence stability, evidenced by the minimized training fluctuations. The proposed method holds promising potential for practical applications in interfacial debonding detection in reinforced concrete structures while addressing the cross-scene challenge.

Применение сталежелезобетонных конструкций в мостовых сооружениях

Purpose: To analyze the possible use of combined structures for bridge superstructures, to expand the range of steel-reinforced concrete structures, to explore innovative structural solutions for beams with low material consumption and increased reliability and durability. Methods: Analysis of the advantages of known combined structures, of materials used for their design, calculation of design options of bridge superstructures with the use of existing engineering techniques and involving calculation programs. Results: Traditional design solutions of bridge superstructures do not always have sufficient reliability and durability. A number of effective beam structures have been developed at the Department of “Building Structures, Buildings and Constructions” of the PGUPS, which can be used in bridge structures. New developments of beams with the use of steel-reinforced concrete and steel-fiber concrete are presented. A combined design of the bridge superstructure with the use of steel-reinforced concrete and steel-fiber concrete, protected by patents for inventions, is proposed. Static and constructive calculation of superstructure variants has been performed with the use of the SCAD computing complex, the stress-strain state of the structure has been analyzed, the reduction of material consumption, labor intensity and other advantages of the combined superstructure design in comparison with traditional solutions of superstructure costructions made of steel and reinforced concrete have been considered. Practical significance: The advantages of combined constructions for bridge structures have been identified, a decrease in the material intensity and labor intensity of the proposed design solutions has been established with an increase in the bending stiffness of the superstructure, its reliability and durability. The proposed structural solutions of beams can be used for bridges of large spans in conditions of heavy dynamic loads.

Atmospheric chloride-induced corrosion of steel-reinforced concrete beam exposed to real marine-environment for 7 years

Steel-reinforced concrete structure easily suffers from chloride corrosion when exposed to a marine atmosphere environment. In this work, OPC/slag concrete beams combined with loading were naturally exposed to My Island (Qingdao, China) for 7-years and their chloride distributions were investigated as well as carbonation and corrosion-products. The results show that a concentration (Cs,%)-time (t,month) relationship was obtained as Cs=0.022t for concrete surface-chloride. With the increasing corrosion-depth, twice chloride accumulations occurred and were located near the carbonation depth and frontier, respectively. Slag increased the depth and height of the first accumulation peak-value while exacerbating its faster decrease of chloride concentration compared to the control. The chloride increment in the tensile zone was greater than its reduction in the compressive zone. The chloride corrosion mainly occurred in the stirrup bends, where the inner corrosion products mainly contained α-FeOOH and γ-FeOOH while further transforming into Fe3O4 in its outer layer.

ПОРІВНЯННЯ ЕФЕКТИВНОСТІ МЕТОДІВ РЕКОНСТРУКЦІЇ СТАЛЕЗАЛІЗОБЕТОННИХ ОДНОПРОЛІТНИХ МОСТІВ

The paper contains developed the method of strengthening steel-reinforced concrete single-span bridge structures that have undergone wear and tear due to long-term operation and require expansion. Have been described the structural solution and the principle of operation under load of the existing typical steel-reinforced concrete single-span bridges. As an example have been considered real emergency bridge structure in the village of Dashiv of the Haysyn district of the Vinnytsia region, in need of urgent reconstruction. Have been described in detail its main structural elements and technical condition. Have been shown possible rational ways of expanding and strengthening the structure in two variants. Variant 1 – reinforcement of existing steel and reinforced concrete structures with partial blocking of road traffic. Variant 2 – replacement of the span structure with a complete shutdown of the bridge for the duration of the construction and installation works. Have been developed basic constructive schemes for the reconstruction of the structure for the first and second variants. Have been described the technological sequence of strengthening the bridge structure according to both mentioned methods, have been analyzed the advantages and disadvantages and have been estimated the cost indicators of the reconstruction of each of the proposed variants. Have been proven that the strengthening method (variant 1) is more appropriate if it is necessary to partially operate the structure during construction and installation works. This method makes it possible to restore the design load-bearing capacity of the bridge structure with the provision of modern dimensional requirements and traffic safety requirements for less cost. The method of complete replacement of the span structure (variant 2), despite the higher cost, should be preferred in all other cases according to dynamics of constant growth of traffic flow in our country. With variant 2, it is possible to achieve not only the required dimensions, but also higher load-bearing characteristics of the bridge structure in a shorter period of time. The reliability and efficiency of each of the methods is confirmed by the corresponding strength calculations.