Aleksandr Sokolov

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• Doctor of Philosophy
• Senior Researcher at Vilnius Gediminas Technical University

Accurate assessment of tension stiffening is important for predicting deflection and crack width in RC structures. Earlier studies by the authors have shown that an extended cover thickness increases tension stiffening in bending RC members. The current study experimentally and theoretically investigates curvature and tension stiffening in RC beams...

Structural strengthening solutions typically employ externally bonded reinforcement (EBR) systems with carbon fiber (CF) sheets because of these materials' lightweight, corrosion resistance, and electromagnetic immunity. However, elevated ambient temperatures can negatively impact the mechanical performance of EBR, as documented in the literature....

The paper proposes a simple deflection model for concrete bending members reinforced with steel fibers and bars (further denoted as R/SFRC members). Most of the current design approaches for such elements require the knowledge of the residual strength of steel fiber reinforced concrete (SFRC) in tension with the latter characteristic being obtained...

Developments in concrete technologies have allowed engineers to design lightweight, slender, and aesthetically attractive structures. The application of new concrete types in real projects, however, is uncommon. The lack of regulation, uncertainty in material performance, and the absence of successfully implemented projects hinders the use of moder...

Recent structural engineering trends revealed that fiber-reinforced polymers (FRP) define an efficient replacement for steel because of their lightweight and corrosion resistance. However, the unfavorable environment (elevated temperature and humidity) can affect the long-term resistance of those materials. Therefore, this study analyzes the advers...

Refractory castables, i.e., refractory aggregates and ultra-fine particle mixtures with calcium aluminate cement (CAC) and deflocculants, were created 40 years ago for the metallurgy and petrochemical industries. These materials demonstrate outstanding performance even over 1000 °C. Typically, they have no structural reinforcement, resisting compre...

Although the significance of the interaction between concrete and reinforcement for reinforced concrete mechanics is well-known, its inherent complexity necessitates in-depth microscopy research. In this study, contact zones between concrete and reinforcement were examined using a short RC tie under tension that was shorter than the mean crack spac...

The respective key-note presentation will highlight the results recently obtained by the research group on predicting the serviceability behaviour of RC members. The presentation will consist of three main parts: 1) A new bond-slip model. 2) A new deflection model for concrete bending members reinforced with steel or FRP bars and steel fibres. 3) A...

Current technology development ensures a variety of advanced materials and options for reinforcing concrete structures. However, the absence of a uniform testing methodology complicates the quantification and comparative analysis of the mechanical performance of the composite systems. The repeated mechanical loads further complicate the issue. This...

In recent years, fiber-reinforced polymeric (FRP) materials have become promising alternatives to steel because of their lightweight, electromagnetic transparency, and corrosion resistance. However, the unfavorable environment (elevated temperature and high humidity in particular) can affect the long-term mechanical performance of these materials....

Fiber reinforcement is a promising solution to cracking problems and improving the concrete's structural performance. The residual strength of the cracked concrete can characterize the reinforcement efficiency. However, quantifying the residual performance of steel fiber-reinforced concrete (SFRC) is challenging. The existing methodologies provide...

This study proposes the Strain Compliance Crack (SCC) model to capture, as reported by tests, the specifics of various cases of crack spacing and width analysis involving primary and secondary cracks in RC beams. The model dwells on calculating crack spacing based on the reinforcement strain profile. As part of the model, a new concept of the limit...

Current technology development ensures a variety of material types for reinforcing and strengthening concrete structures. However, the absence of a uniform testing methodology complicates quantification (and comparison) of the mechanical performance of the composite reinforcements. In addition, the necessity to quantify the long-term degradation of...

Refractory castables, representing a mixture of a refractory aggregate, calcium aluminate cement, ultra-fine particles, and deflocculants, have been created in the mid of past century '80s for the metallurgy and petrochemical industries. The designed castable binder shows an excellent ability to preserve the material's mechanical strength in the 60...

The present study presents an investigation of the performance of Neural Networks applied to predict the primary crack spacing of reinforced concrete members subjected to flexural loading. The investigation is carried out on the same data set as was used by the authors to develop and validate the strain compliance approach for cracking analysis of...

Steel fibre-reinforced concrete (SFRC) is an emerging class of composite for construction. However, a reliable method to assess the flexural behaviour of SFRC structural member is in lack. An analytical technique is proposed for determining the moment-curvature response of concrete beams reinforced with steel fibres and longitudinal bars (R/SFRC me...

A bond mechanism at the reinforcement-concrete interface is one of the key sources of the comprehensive functioning of reinforced concrete (RC) structures. In order to apprehend the bond mechanism, the study on bond stress and slip relation (henceforth referred as bond-slip) is necessary. On this subject, experimental and numerical investigations w...

The layer approach is a simple tool to predict the moment–curvature behaviour of steel fibre reinforced concrete (SFRC) beams. The material stress–strain response of compressive concrete and tensile reinforcement is simple, as for ordinary RC structures, whereas the residual stress–strain relation for SFRC in tension determines the accuracy of the...

Various types of materials and technologies have been developed either for reinforcing or strengthening concrete structures. However, there is no uniform methodology to quantify and compare the mechanical characteristics of different reinforcement systems. Residual stiffness of flexural elements is the suggested measure of the reinforcement’s struc...

The authors have recently proposed a new concept of crack analysis based on the assumed reinforcement strain profile between the adjacent cracks. Mean crack spacing is obtained from the equality of mean strains of the tensile reinforcement assessed from the strain profile and the mean value calculated by EC2. The current study considers mean crack...

The study carried out at Vilnius Gediminas Technical University (Vilnius Tech) reports test results on cracking of seven RC beams of the rectangular section. The beams were subjected to a short-term loading under a four-point bending configuration. The experimental program was aiming at evaluating the effect of section height, reinforcement ratio,...

The paper critically evaluates design code techniques (ACI 318-14, ACI 318-19, and Eurocode 2) for the instantaneous curvature analysis of reinforced concrete (RC) beams. The study examines the soundness of the assumption that a fully cracked section represents the lower bound of the effective moment of inertia (or bending stiffness) used along wit...

Various materials and reinforcement technologies have been created for concrete structures. However, there is no uniform methodology to compare the mechanical characteristics of different reinforcement systems. In structural systems, residual stiffness can estimate the efficiency of the reinforcement. This study introduces a simplified approach for...

The contribution of concrete to the tensile stiffness (tension stiffening) of a reinforced concrete (RC) member is a key governing factor for structural serviceability analyses. However, among the current tension stiffening models, few consider the effect brought forth by concrete shrinkage, and none studies take account of the effect for very long...

Cracking effects are the intrinsic attribute of serviceability analysis of reinforced concrete elements. These effects are the research object of numerous studies, which have been carried out for more than half a century. Despite extensive research, there is no commonly accepted methodology for cracking analysis. The existing approaches employ empi...

p>This study introduces a simplified tension-stiffening approach for the flexural stiffness analysis. It employs a new testing layout designed with the purpose to form multiple cracks in a small laboratory specimen. The proposed analytical model is based on the following assumptions: smeared crack approach; linear strain distribution within the sec...

The paper presents a comparison of the novel strain compliance concept, proposed for predicting the crack spacing of reinforced concrete structures with neural network predictions. The concept represents an alternative way to accurately analyze the cracking behavior of reinforced concrete elements while maintaining compatibility of deformation beha...

In the present trend of constructing taller and longer structures, the application of lightweight aggregate concrete is becoming an increasingly important advanced solution in the modern construction industry. In engineering practice, the analysis of lightweight concrete elements is performed using the same algorithms that are applied for normal co...

Featured Application The proposed numerical analysis principles are applicable for a design for serviceability of fibre-reinforced polymer (FRP)–concrete elements. Abstract Advanced materials have been created for structural application during the past decades. Engineers, however, faced severe problems due to the absence of a reliable technique fo...

In the present trend of constructing taller and longer structures, the application of lightweight aggregate concrete is becoming an increasing important advanced solution in the modern construction industry. In engineering practice, the analysis of lightweight concrete elements is performed using the same algorithms used for normal concrete element...

Application of high-strength steel can serve improving structural efficiency as well as solve structural problems when traditional materials are inapplicable due to strength limitations. Innovative structural solutions, however, are facing problems related to the absence of corresponding design procedures and reliable constitutive models. Cold-form...

Experimental and numerical studies have been carried out on reinforced concrete (RC) short tensile specimens. Double pull-out tests employed rectangular RC elements of a length determined not to yield any additional primary cracks. Tests were carried out with tensor strain gauges installed within a specially modified reinforcement bar and, alternat...

p>The present study develops a mean crack spacing model for fibre-reinforced polymer (FRP) reinforced concrete (FRP-RC) beams. The proposed model is based on stress-transfer approach and compatibility of mean strain in the FRP reinforcing bars, in order to predict the mean spacing of primary cracks in the stabilised cracking stage upon flexure. Typ...

p>This paper reports the experimental and numerical studies of concrete beams reinforced with glass fibre-reinforced polymer (GFRP) reinforcing bars with and without the addition of steel fibres. GFRP- reinforced concrete beam specimens of equivalent geometry were produced and tested under symmetrical two-point loading configuration. Deformation an...

This paper reports the experimental study on creep behaviour of reinforced concrete (RC) tension members subjected to long-term constant loading. An innovative testing rig was designed and four replicates were fabricated for concurrent testing of multiple specimens under the same temperature and humidity conditions. Four direct tension specimens we...

Experimental investigation of structural behavior of glass fiber reinforced polymer (GFRP) space truss bridge model subjected to static loading is discussed in this paper. Bridge prototype was assembled using GFRP profiles produced by Fiberline Composites Ltd, steel bolts and GFRP brackets. In order to load the structure, wooden bridge deck was ins...

Concrete is the most widely used material for bridge structures in Lithuania. A case study performed by the authors revealed that application of fibres might improve serviceability of such structures. However, adequacy of prediction of the post-cracking behaviour of steel fibre reinforced concrete might be insufficient. The latter issue is closely...

The capacity of steel fibers to ensure the structural integrity of reinforced concrete specimens coated with CFRP sheets was investigated. Test data for four ties and eight beams reinforced with steel or glass-FRP bars are presented. Experiments showed that the fibers significantly increased the cracking resistance and altered the failure character...

Исследовали способность стальных волокон (фибр) обеспечить конструкционную целостность армированных бетонных образцов, покрытых углепластиковыми листами (СFRP). Приведены результаты испытаний четырех растягиваемых призм и восьми бетонных балок, армированных стальными либо стеклопластиковыми стержнями. Экспериментально установлено, что использование...

Due to the highly complex cracking behaviour of reinforced concrete structures, their design for serviceability is one of the most challenging tasks of engineering practice. Existing test data support a general inference that the deformation behaviour of concrete elements is affected by the arrangement of reinforcement in the tensile zone. Most of...

The increasing application of high-performance materials in civil engineering led to the development of reinforced concrete (RC) structures with reduced cross sections and increased spans. In such structures serviceability limit state often becomes the governing condition of the design. Present study investigates the deformation behaviour of high-s...

Although the efficiency of steel fibres for improving mechanical properties (cracking resistance and failure toughness) of the concrete has been broadly discussed in the literature, the number of studies dedicated to the fibre effect on structural behaviour of the externally bonded elements is limited. This experimental study investigates the influ...

Basalt polymers are rather new materials for civil engineering; therefore, identification of peculiarities and limitations of application of such polymers in concrete structures (particularly bridges) is of vital importance. This paper experimentally investigates deformation behaviour and cracking of flexural elements, which are predominant paramet...

The paper reports test results for steel-fiber-reinforced concrete beams. Four-point bending tests on 12 full-scale beams (with longitudinal reinforcement ratios of 0.3 and 0.6%) were carried out to investigate the postcracking behavior of the members. The content of fibers, spaced at equal intervals, ranged from 0 to 120 kg/m3, resulting in the am...

The paper deals with analysis of structural lightweight concrete. New lightweight concrete mixture made with expanded clay aggregate has been proposed and applied for experimental rein-forced concrete beams. Totally 8 beams with different rein-forcement ratios (0.309%, 0.557%, 0.895% and 1.255%) were tested under short-term four point bending loadi...

The paper reports test results for steel-fiber-reinforced concrete beams. Four-point bending tests on 12 full-scale beams (with longitudinal reinforcement ratios of 0.3 and 0.6%) were carried out to investigate the postcracking behavior of the members. The content of fibers, spaced at equal intervals, ranged from 0 to 120 kg/m 3 , resulting in the...

Adequate modeling of reinforced concrete (RC) cracking and, particularly, post-cracking behavior (tension-stiffening), as one of the major sources of a nonlinearity, is the most important and difficult task of the deformation analysis. Present investigation aims at deriving a steel-related tension-stiffening relationship based on the smeared crack...

The present paper reports results of the investigation on shrinking of the concrete mixture which is often used for casting the new bridges. The study is based on the experimental results obtained in three research projects which were performed under financial support provided by the Lithuanian State Fund of Research and Studies at the Vilnius Gedi...

Modelling of behaviour of cracked tensile concrete is a complicated issue. Due to bond with reinforcement, the concrete between cracks carries a certain amount of tensile force normal to the cracked plane. The concrete adheres to reinforcement bars and contributes to overall stiffness of the structure. The phenomenon, called tension-stiffening, has...

Analysis of the literature has shown that two main factors, which should be taking into consideration in designing of continuous bridges, are the influence of cracking on serviceability of the structures and inelastic behaviour of structural elements. Crack control is often the governing design criterion for the choice of the amount of longitudinal...

Based on a method proposed by the authors, a new tension-stiffening law has been proposed for short-term deformational analysis of flexural reinforced concrete members. It was derived from experimental moment-curvature diagrams of RC beams reported by the authors. A quantitative dependence has been established between the length of the descending b...

Present research was aiming at deriving tension stiffening relationship based on EC2 provisions for deformation analysis of bending RC structures. According to the algorithm proposed by the first author, a tension stiffening relationships were derived from moment-curvature diagrams of reinforced concrete beams calculated according to EC2 technique....

Present research was dedicated to investigation of finite element size effect on deformational behaviour of reinforced concrete members. Post-cracking behaviour of reinforced concrete beams assuming different finite element sizes has been investigated by commercial finite element software ATENA. Softening behaviour of tensile concrete has been mode...