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The paper presents a new methodology to model material failure, in two-dimensional reinforced concrete members, using the Continuum Strong Discontinuity Approach (CSDA). The mixture theory is used as the methodological approach to model reinforced concrete as a composite material, constituted by a plain concrete matrix reinforced with two embedded orthogonal long fiber bundles (rebars). Matrix failure is modeled on the basis of a continuum damage model, equipped with strain softening, whereas the rebars effects are modeled by means of phenomenological constitutive models devised to reproduce the axial non-linear behavior, as well as the bond–slip and dowel effects. The proposed methodology extends the fundamental ingredients of the standard Strong Discontinuity Approach, and the embedded discontinuity finite element formulations, in homogeneous materials, to matrix/fiber composite materials, as reinforced concrete. The specific aspects of the material failure modeling for those composites are also addressed. A number of available experimental tests are reproduced in order to illustrate the feasibility of the proposed methodology. Fil: Oliver, J.. Universidad Politecnica de Catalunya; España Fil: Linero, D.L.. Universidad Nacional de Colombia; Colombia Fil: Huespe, Alfredo Edmundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Manzoli, O.. Universidade de Sao Paulo; Brasil

Corrosion-induced deterioration of reinforced concrete (RC) structures results in premature failure of the RC structures. In practice concrete crack width is one of the most important criteria for the assessment of the serviceability of RC structures. It is therefore desirable to predict the growth of the crack width over time so that better informed decisions can be made concerning the repairs due to concrete cracking. Literature review shows that little research has been undertaken on numerical prediction of concrete crack width. The intention of this study was to develop a numerical method to predict concrete crack width for corrosion-affected concrete structures. A cohesive crack model for concrete is implemented in the numerical formulation to simulate crack initiation and propagation in concrete. Choices for evaluating the parameters of cohesive elements are extensively discussed which is a key for developing a plausible model employing cohesive elements. The surface crack width is obtained as a function of service time. Accurate prediction of crack width can allow timely maintenance which prolongs the service life of the reinforced concrete structures.

The way to strengthen concrete structures in civil engineering by adding external reinforcement using carbon fiber composites is widely spreading in recent years. A method for calculating the strength of reinforced concrete in hydro technical constructions with reinforcing by carbon fiber composite materials was invented with the aim to justify the solutions of strengthening concrete structures. It was taken into consideration that the characteristic features of mass reinforced concrete structure with sand operating loads which including backpressure of water in the cracks and in opened construction joints. It has evolved the relations for calculation of strength in normal cross section of bending reinforced concrete member of hydro technical constructions which strengthening with external reinforcement by carbon fiber.

The results of experimental studies of reinforced concrete constructions at complex resistance to torsion with bending are shown in the article. The main purposes of the researches are detection of regularities and determination of deformation and cracking parameters. The most important of the studding parameters are cracking load, destructive load, the coordinates of spatial cracks formation, the width of crack's opening at the axis of the longitudinal and transverse tensile reinforcement and along the entire profile of cracks; changing the distance be- tween the cracks and crack length according to increasing the deformation load; deformation of compressed concrete and reinforcement in a complex stress-strain state. The test results are presented in the form of relationships of structure's deflections, deformations of compressed concrete and reinforcement, including results which were determined by the indications of electrotensometric sockets. The obtained relationships allow us to assess the reliability of the calculating methods reinforced concrete constructions subjected the action torsion and bend- ing.

International audience; The durability of reinforced concrete structures is largely impacted by their transfer properties, which can be evaluated through, for example, permeability measurement. Usually, concrete permeability is studied on plain specimens and the effect of the presence of steel bars on permeability in reinforced concrete has been little studied in the literature. The steel-concrete interface presents a larger porosity than plain concrete, which can be the cause of preferential percolation paths for fluids. Such percolation paths could create a lower resistance to fluid transfer and modify transfer kinetics. For reinforced and prestressed structures with large reinforcement contents, such as found in nuclear power plants, the impact of the reinforcement on gas transfer should be identified to obtain a better assessment of the flow within the structure. The aim of this experimental study is to characterize the effect of the presence of reinforcement on such flows by measuring leakage rates, permeability, and time to reach the steady state. Measurements were performed with a Cembureau constant head permeameter on cylindrical concrete specimens with or without steel bars. Since gas transfer into concrete depends on the rate of saturation of the material, the specimens were tested at different degrees of saturation: 0%, 6%, 30%, 60%, 80%, 90% and 100%. The analysis quantifies the impact of the defects created by the steel bar for each state. The results show that material composed of concrete and reinforcement can be divided into two distinct permeability zones: the plain concrete and the steel - concrete interface with or without cracking. These two zones can be associated in series and/or in parallel according to the configuration. The consequences on permeability measurement in reinforced structures are discussed.

Corrosion of reinforcement reduces the load carrying capacity, energy dissipation and ductility of Reinforced Concrete (RC) members. In the present study, reinforcements of RC beam are subjected to 10, 25, and 30% corrosion and the respective RC beams are tested to evaluate their ultimate load behaviour. A huge drop in energy dissipation capacity of the RC beam is observed beyond the corrosion level of 10%. Further, nonlinear finite element analysis is employed to assess the load–displacement behaviour and ultimate load of RC beam. The corrosion induced damage to the reinforcement is represented in the finite element model by modifying its mechanical properties based on the results reported in the literature. The resultant load versus displacement curves of reinforced concrete beams are obtained. Good correlation is observed between the finite element analysis results and that obtained from experimental investigation on the control beam. The experimental results are also compared with the finite element analysis results for RC beams with corroded reinforcement. In order to understand the effect of corrosion on the mechanical properties of reinforcement, the corroded reinforcements are modelled in nonlinear finite element analysis by (i) reducing the area of reinforcement alone (ii) by reducing both area and mechanical properties and (iii) reducing the mechanical properties without reducing the area of steel as reported in literature. The results obtained for the beam with corroded reinforcement confirms reduction in yield stress and ultimate stress of the reinforcement steel.

Over the last few years externally bonded carbon fiber reinforced polymer (CFRP) laminates have become a popular technique for retrofitting reinforced concrete (RC) existing structures. This paper presents an experimental study on 10 RC members externally reinforced with different architectures of CFRP laminates in order to investigate the influence of the composite configurations on the structural behavior of RC members. American guidelines ACI 440.2R and Italian Code CNR-DT 200 are employed for comparison with the experimental results. Numerical models are also developed to simulate the behavior of the FRP-RC members with the aim to investigate the different failure modes observed in various strengthening configurations. One conclusion is that the Italian Code CNR-DT 200 results to be more conservative with respect to ACI 440.2R. Finite element analyses provide good predictions of the experimental evidences in terms of load-deflection, load strain diagrams, and crack distribution and lead to an accurate prediction of the debonding failure and the post-failure response.

Research is limited with respect to load-deflection behavior of slender concrete columns internally reinforced with Fiber Reinforced Polymer (FRP) spirals and longitudinal bars. An analytical buckling model based on numerical integration is presented to predict the load versus deflection performance of slender concrete columns reinforced with FRP spirals and longitudinal bars, subjected to eccentric loads. The model can be used to predict the behavior of slender concrete columns with various configurations including FRP and/or steel reinforcement, single or double spiral, and number of longitudinal bars. The longitudinal bars considered include steel, FRP, or hybrid reinforcement consisting of steel and FRP bars. The model is found to predict the experimental performance of slender concrete columns reinforced with Glass FRP longitudinal bars and spirals with satisfactory accuracy. The model is used to create interaction diagrams for FRP spiral-confined circular concrete columns with various slenderness ratios, reinforced with steel, FRP or hybrid reinforcement.

This article has been retracted at the request of the Editor-in-Chief due to extended similarites with a previously published paper (in Persian).The previously published paper is:F. Jafari, J. Akbari, A. Jahanpur, "Evaluation of Safety Index and Calibration of Load and Resistance Factors for Reinforced Concrete Beams under Bending, Shear and Torsion Demands", Journal of Structural and Contruction Engineering, Article 5, Vol. 3, No. 4, pp. 49-64, 2017 (in Persian)The authors of this paper failed to provide any reasoning regarding the case.

The data presented in this article are related to the research article entitled “Experimental Investigation of cracking and deformations of concrete ties reinforced with multiple bars” (Rimkus and Gribniak, 2017) [1]. The article provides data on deformation and cracking behaviour of 22 concrete ties reinforced with multiple bars. The number and diameter of the steel bars vary from 4 to 16 and from 5 mm to 14 mm, respectively. Two different covers (30 mm and 50 mm) are considered as well. The test recordings include average stains of the reinforcement and the concrete surface, the mean and maximum crack spacing, final crack patterns, and crack development schemes obtained using digital image correlation (DIC) system. The reported original data set is made publicity available for ensuring critical or extended analyses. Keywords: Reinforced concrete, Multiple bars, Tensile tests, Deformations, Cracking

The reinforced concrete beams is a structural member that is widely used in all types of building and civil constructions. These beams are subjected to different external loads that, above a critical value, may cause the collapse of the whole structure, having devastating consequences for civilians. Therefore, the a priori simulation of the internal forces developed within a reinforced concrete beam, when it is subjected to external loads, is mandatory to figure out its progressive structural response, to provide integrated risk assessment for a wide range of constructions such as buildings, bridges, etc. In this paper, we provide a simulation framework to estimate the behavior of reinforced concrete beams when they are subjected to external loads. Of particular interest to us is the simulation of the particularly damaging internal force, called Shear force. Several techniques are under study such as regression analysis, Little Genetic Algorithm (LGA) and Covariance Matrix Adaptation Evolution Strategy (CMA-ES), along with different objective functions (lineal, polynomial and rational functions) to provide a solution that satisfies both the physical and computational constraints of the targeted problem. These techniques are empirically optimized by using different parameters and genetic operators such as elitism, penalization for unfeasible individuals, crossing by one point or by linear combination of two individuals, mutation by gen or by individual. Numerical results reveal that CMA-ES algorithm together with a proper objective function, elitism and penalization allows predicting, under a relative error less than 5% (compared to experimental data taken from a tested beam), the shear response of a reinforced concrete beam in the stages near to the structural collapse.

The influence of temperature induced bond degradation on response of reinforced concrete (RC) beams exposed to fire is presented. A finite element based numerical model is developed in ABAQUS for tracing the response of reinforced concrete beams exposed to fire. Temperature induced interfacial bond degradation between concrete and reinforcing steel is specifically taken into account using bond-link element approach. The effect of temperature dependent local bond stress-slip relations on fire resistance of both normal strength and high strength reinforced concrete beams is investigated. A comparison of numerical model predictions with response parameters measured in fire tests clearly indicate that interfacial bond between reinforcing steel and concrete can influence extent of strength degradation and deflections in RC beams exposed to fire leading to relatively lower fire resistance in the beams. Hence, the current approach of assuming a perfect bond between rebar and concrete in fire resistance analysis of reinforced concrete structures may be un-conservative in certain scenarios, especially for RC beams reinforced with smooth rebars and when rebar temperature exceeds 400 °C.

The aim of the paper is a nonlinear analysis of concrete structures. For these type of tasks is an important suitable choice of model input parameters and concrete. Especially if the analysis is preceding the results of an experiment, which can determine the exact properties of concrete. The following properties of concrete are needed for nonlinear analysis: tensile strength and compressive strength of concrete. There are more procedures how to determine some unknown input parameters. The paper presents some approaches to calculating and selecting parameters, which are based primarily on the recommendations of the Model Code and professional articles. Specifically, the numerical analysis performed in our developed program which allows observing a nonlinear behaviour of concrete at loading case.

Understanding the development and multiaxial distribution of expansions is of critical importance in the appraisal of structures affected by alkali–silica reaction. Such expansions were monitored for 33 480-mm reinforced concrete cubes in an effort to develop an improved understanding of the expansion mechanisms in reinforced concrete and broaden the database of experimental results available from which to build tools to aid in the performance assessment of affected structures. The cubes were fabricated using three different concrete mixtures of varying reactivity and contained uniaxial, biaxial, and triaxial reinforcement layouts with different reinforcement ratio combinations. In all cases, the cubes expanded at greater rates in unreinforced directions than in reinforced directions. Furthermore, the reinforcement ratios did not significantly influence expansion behavior, especially in the cases of uniaxially, equal biaxially, and equal triaxially reinforced specimens. Increasing the number of reinforced directions resulted in reduced volumetric expansion development over time and greater differences between expansions in reinforced and unreinforced directions. Cubes with end-anchored, deformed steel reinforcing bars placed in three layers developed expansions exceeding steel yield strains in all directions. Cubes with bars placed in two layers exhibited differential expansions between locally reinforced concrete regions at the edges of elements and unreinforced core regions. Mixture reactivity and environmental conditioning influenced expansion rates but not trends of the multiaxial distribution of volumetric expansions.

The paper deals with the calculation and assessment of the crack width and crack resistance of reinforced concrete tanks for liquids and containers according to Eurocode. Detailed analysis of the provisions of EN 1992-3 related to the calculation of cracks is made. The interpretation of code provisions used in IDEA StatiCa software is explained. Comparative calculations are executed for standard reinforced concrete and fiber concrete cross-sections.

Strengthening of concrete structures with a new concrete layer has been commonly used for columns, beams and slabs. This technique is economic and efficient for structural strengthening since it uses the same base materials, steel and concrete. It is usually applied on the compressed face of the concrete element due to concrete’s recognized behaviour under compression, posing several challenges to control cracking and resistance when applied on the tensile face. For assessing the performance of the strengthening method, twelve slab specimens were designed and tested monotonically. The main parameters to assess in this work were the debonding behaviour and load, and the relationship between the latter and the relative displacements at the interface of the two concrete layers. The performance of the strengthened structures strongly relies on the interaction of the two concrete layers, with this being the main subject of the research about overlaid concrete. The load transfer capacity of the interface depends on the interface shear strength, which in turn is highly dependable on substrate roughness, cleanliness and curing conditions of the newly added layer. Interface performance may be improved by using steel connectors crossing the interface, properly anchored on both layers. The importance for these elements grows as the existing concrete is more deteriorated, since adhesion strength will decrease with lower quality concrete. This paper presents the experimental research for the application of bonded concrete overlays on the tensile face of reinforced concrete slabs, mainly aimed at office buildings and parking facilities, where spatial clearances or inaccessibility to the lower side of the slabs are recurrent. A ductile behaviour upon debonding was achieved for the specimens with reinforcement crossing the interface, and a debonding load up to three times that of the reference specimens without reinforcement crossing the interface.

The paper presents comparison of creep measurments in normal concrete and concrete modified with dispersed reinforcement - polypropylene and steel fibres (FRC). The tests were performed for two levels of applied load: 40% and 80% of the destructive load at the load time, respectively, at 1, 4, 7 and 28 days. The resulting creep strain was compared with the calculating method from Eurocode 2, and Pre-norm Fib 2010. Significant differences in the results of the creep calculated based on the Code and measured in the research were noticed. It was also shown that the creep of FRC has different development compared to the normal concrete especially under early-age load. The value of proposed creep factor for young concrete calculated based on study results was few times higher than calculated based on the Code. The creep strain of fibre reinforced concrete loaded at the age of 24 hours was, moreover much higher than of concrete without fibres. The paper illustrated differences in the dynamics and final values of creep deformation of normal concrete and fibre reinforcement concrete.

The behavior of reinforced and prestressed concrete plates has been studied under drop weight impact loading. The reinforced and prestressed concrete plates having the size 0.8 m x 0.8 m and thickness 100 mm. The impact was applied by dropping a mass of 242.8 kg from a fixed height. The characteristic strength of concrete cubes was 51.38 MPa. The generated impact force and deflection time response were measured and the failure modes of the plate specimens were studied. The results thus obtained for reinforced and prestressed concrete plates were compared and discussed. Prestressed concrete plates were found to have higher impact resistance and performed better in comparison to the conventional reinforced concrete plates. The deflection at bottom surface of prestressed concrete plate has also reduced.

The paper presents the results of an experimental research of four three–span models of reinforced concrete strips with the dimensions of 7140×500×190 mm. The aim of the research was to demonstrate the influence of the ratio of longitudinal reinforcement on the load-bearing capacity and the mechanism of destruction. The paper contains the description of the experimental stand and models along with the results of experimental tests which were compared with the results of the calculations based on traditional methods.

The limitation or the neglecting of concrete role in resisting the shear stress causes the need of high amount of steel bars reinforcement in beam-column joints. This will cause problem if the steel bars reinforcement congestion occurs where the steel bars reinforcement may not be easy to be installed. This paper discuss the analysis and design of king cross steel profile to be implemented as alternative reinforcement in reinforced concrete beam-column joints. With the simplifying assembling the use of king-cross steel profile implants at beam-column-joints as a shear reinforcement could be expected to replace the transversal reinforcement and enhance the joint shear strength. Therefore various arrangements of beam-column reinforcement are studied analytically.

Experimental results on steel-reinforced concrete penstocks with different ratios between the cross-sectional areas of the inner steel lining and the hoop reinforcement are presented. The formulas for the strength analysis of steel-reinforced concrete penstocks are improved to, in particular, take into account failure of the bond of the steel lining and reinforcement to concrete.

The aim of this paper is to set up a method to determine the strain capacity of tension bars of reinforced concrete (RC) subjected to pure tension. Due to the interaction between reinforcement and concrete and due to the presence of cracks, the stresses in both reinforcement and concrete are varying along the length of the tension bar. The strain capacity of the tension bar is seen as the average strain in the reinforcement at the load level corresponding to the ultimate stress capacity of the reinforcement at the cracks. The result of the approach is in overall good agreement when comparing with 24 tests.

This paper presents a critical comparison of the existing code provisions for the shear strength of concrete beams. The comparison is based on the computerized filtering-out of the in-evitable statistical bias from the available multivariate database on shear strength, on an examination of the predicted size effects on shear strength and their underlying hypotheses and on the results of recent high-fidelity numerical simulations of shear failure. In addition to examining the existing models, the present comparison also provides several key considerations for testing the scientific soundness of any model of shear failure in concrete beams, which is necessary for future revisions to the design code provisions.

The paper presents the results of experimental and theoretical investigations of the mechanisms of crack formation in reinforced concrete beams subjected to quasi-static bending. The boundary-value problem has been formulated in the framework of brittle fracture mechanics and solved using the finite-element method. Numerical simulation of the vibrations of an uncracked beam and a beam with cracks of different size serves to determine the pattern of changes in the spectrum of eigenfrequencies observed during crack evolution. A series of sequential quasi-static 4-point bend tests leading to the formation of cracks in a reinforced concrete beam were performed. At each loading step, the beam was subjected to an impulse load to induce vibrations. Two stages of cracking were detected. During the first stage the nonconservative process of deformation begins to develope, but has not visible signs. The second stage is an active cracking, which is marked by a sharp change in eingenfrequencies. The boundary of a transition from one stage to another is well registered. The vibration behavior was examined for the ordinary concrete beams and the beams strengthened with a carbon-fiber polymer. The obtained results show that the vibrodiagnostic approach is an effective tool for monitoring crack formation and assessing the quality of measures aimed at strengthening concrete structures.

Several advanced constitutive models of concrete have been developed in recent decades, some of which are able to reproduce the behaviour of concrete structures with a high level of accuracy. Yet given their complex formulation, their application by most practitioners can entail some difficulties. This paper describes the adoption of an alternative, simplified comprehensible constitutive model for the ultimate limit state analysis of 3D reinforced concrete structural elements. The proposed model is described and the undertaken assumptions are justified. Different uniaxial stress strain models can be adopted, particularly neglecting the tensile strength of concrete permits to study the goodness of the stress field method and the strut-and-tie method for 3D elements. This model was implemented into a non-linear finite element-based tool developed by the authors. The results of twelve four-pile caps and three socket base column-to-foundation connections are shown. The proposed approach facilitated the identification of the flow of forces and allowed a better understanding of the structural response., The authors wish to thank the Spanish Ministry of Education for the FPU fellowship FPU12-01459 received by the first author, and the Spanish Ministry of Economy and Competitiveness for funding Project BIA 2012-32300.

This paper deals with the experimental testing and theoretical analysis of the flexural load-bearing capacity of I-shaped pillars in noise barriers made of reinforced concrete, prestressed concrete and prestressed steel fiber reinforced concrete. The pillars were loaded as a cantilever under a flexural load, which corresponds to their actual loading when the effect of wind on the panels of the noise barrier is taken into account. For the purpose of the present research, three specimens of I-pillars were tested. The results of the experimental loading tests, as well as the calculated results and the comparison between them, are herein presented.

The objective of this study is to analyze the effect of variability of concrete stress-strain characteristics on the bearing capacity of eccentrically compressed reinforced concrete elements. Relevance of this issue is caused by wide application of the nonlinear stress-strain model for calculations of reinforced concrete structures. A distinctive feature of calculations with the use of the nonlinear stress-strain model is the need of joint use of concrete strength and stress-strain characteristics. In addition to that, valid regulations of Russian Federation deal with the average values of stress-strain characteristics, and there are no information on their variability.

A model for predicting the behaviour of steel fibre reinforced concrete elements is presented.In spite of its simplicity, it is characterised by both generality and objectivity.It realistically describes the brittle tensile behaviour of plain concrete.It effectively describes the effect of fibres on post-cracking concrete behaviour.Its predictions are validated for a wide range of structural configurations. The present numerical investigation offers evidence concerning the validity and objectivity of the predictions of a simple, yet practical, finite element model concerning the responses of steel fibre reinforced concrete structural elements under static monotonic and cyclic loading. Emphasis is focused on realistically describing the fully brittle tensile behaviour of plain concrete and the contribution of steel fibres on the post-cracking behaviour it exhibits. The good correlation exhibited between the numerical predictions and their experimental counterparts reveals that, despite its simplicity, the subject model is capable of providing realistic predictions concerning the response of steel fibre reinforced concrete structural configurations exhibiting both ductile and brittle modes of failure without requiring recalibration.

The article reflects the results of experimental studies of carbon-fiber reinforced concrete under compression and tension. Qualitative change of concrete strength and stress-strain properties at its dispersed reinforcement with carbon fibers is fixed. As a result of the statistic processing of experimental data, analytical dependencies for determination of carbon-fiber reinforced concrete main strength and stress-strain characteristics under compression and tension are suggested. Calculation diagram of non-linear straining of carbon-fiber reinforced concrete at static effect is presented.

Reinforced concrete column confined using two layers of stirrups is a new kind of column form recently proposed by the authors. The concrete of the column is under three different levels of confinement, namely unconfined concrete cover, singly confined, and doubly confined concrete core. This column form provides a simple but effective solution for reinforced concrete columns located in seismic hazard zones and/or reinforced concrete columns with large axial load ratio, where large amount of transverse reinforcement is necessary to achieve a ductile response. This study aims to investigate the axial compressive behavior of square reinforced concrete columns confined using two layers of stirrups. In total, 15 columns were prepared and tested under axial compression. Two different stirrup configurations were investigated. The axial responses and the failure modes of the columns were examined in detail, and the average stress–strain curve of the singly confined and doubly confined concrete core was derived. A stress–strain model with satisfactory accuracy was proposed based on the interpretation of test results.

It is well known that shear stress at peak of reinforced concrete beams decreases with increasing effective depth. Thus, several existing design codes and models have included various forms of formulas considering the size effect on shear strength of reinforced concrete beams; however, past experimental researches show that tension reinforcement ratio is also associated with the shear strength of reinforced concrete beams. To examine the effect of tension reinforcement ratio and effective depth on shear strength of reinforced concrete beams, this study has conducted experiments in which the effective depth (150, 300, 500, and 780 mm) and tension reinforcement ratio (1%, 2%, and 3%) are employed as variables. Besides, a formula for the shear strength considering both variables is proposed based on data samples collected from the present experiment and previous research. The proposed formula gives predictions comparable to the results of existing shear tests. Furthermore, rational predictions are made for effective depth of beams, compressive strength of concrete, shear span-to-depth ratio, and even tension reinforcement ratio exceeding 3%.

This paper presents an analytical study on the fatigue response of reinforced concrete beams strengthened with fiber reinforced polymers (FRP). The study gathers the experimental results from the international literature and from authors' experiments and investigates the critical parameters that affect fatigue performance of reinforced concrete (RC) beams. A new analytical model is proposed for predicting the fatigue life of FRP strengthened RC beams. The parameters used are the maximum stress of tensile steel (σ max ) to the yielding strength (f y ) ratio, as well as the axial rigidity of longitudinal steel (k s ) and FRP (k f ) reinforcement. The predictions of the proposed model are compared against the experimental results as well as against the predictions of fatigue models in the literature.

Durability deterioration of structure is a highly random process. The maintenance of degenerated structure involves the calculation of the reliability of time-dependent structure. This study introduced reinforced concrete structure resistance decrease model and related statistical parameters of uncertainty, analyzed resistance decrease rules of corroded bending element of reinforced concrete structure, and finally calculated timedependent reliability of the corroded bending element of reinforced concrete structure, aiming to provide a specific theoretical basis for the application of time-dependent reliability theory.

Aggressive environmental conditions, such as exposure to the sea climate or use of de-icing salts, have a strong influence on durability of reinforced concrete (RC) structures due to reinforcement corrosion-induced damage. In the present paper, a recently developed three- dimensional (3D) chemo-hygro-thermo-mechanical model for concrete is briefly discussed. The model was implemented into a 3D finite element code and its application is illustrated through numerical analysis of a RC beam-end specimen with stirrups, exposed to aggressive environmental conditions. Damage of concrete cover due to expansion of corrosion products and transport of rust through concrete pores and cracks are computed. Subsequently, the influence of corrosion-induced damage of concrete cover on pull-out resistance of deformed reinforcement is investigated. The comparison between numerical results and experimental evidence shows that the complex coupled mathematical model is able to realistically predict the phenomena related to corrosion of steel reinforcement in concrete

The use of steel fibres in plain concrete helps in improving the mechanical properties of concrete structure. Thus the aim of present study is to investigate the effect of steel fibres on torsional strength improvement of concrete. The research evaluates the torsional strength and combined torsional-shear-bending strength. In this study, 20% of fly ash (class-C) is added as a replacement of binder to its weight and 1.5% steel fibres by weight of concrete. Experimental results show an improvement in torsional strength, combined torsional-shear-bending strength and crack resistance of concrete by addition of steel fibres in the concrete and a decrease in the deflection. Based on the experimental results the modified coefficient of the empirical formulae has been suggested to predict the torsional strength and torsional stress of steel fibre reinforced concrete.

The paper deals with the issues of uniaxial tension tests of concrete and fibre reinforced concrete. Possible shapes of specimens and arrangements of the experiment are discussed, including the consequences arising from the adjustments. Behaviour of sample during loading, before and after initiation of the first crack is studied, stresses in the critical cross-section as well as loading methods are analysed.