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This paper presents the evaluation of the fracture test of high-strength structural (HSS) steel grades S460 using a finite element (FEM) numerical model. Steels with better strength characteristics may exhibit different stress-strain diagram behavior and therefore material models need to be adequately prepared. The numerical model, which accurately simulates the experiments, was prepared using known information from tensile testing of high-strength steel. The aim is to determine the material parameters with high accuracy using inverse analysis so that complex numerical models of building structures such as steel halls and bridges can be prepared. The paper contains results from an experimental investigation compared with results from a numerical model of a tensile fracture test. Due to the good agreement, the derived material parameters can be applied in future research on high-strength structural steel in the construction industry. [ABSTRACT FROM AUTHOR]

The present study uses the results of experimental investigations of the electrical resistivity of four types of concrete mixtures for numerical analysis of the durability of concrete exposed to an aggressive environment. Two concretes are reference concretes (one without and one with chemical additives for air entrainment), and the other two concretes contain metallurgical sludge waste (MSW) as a partial replacement of fine aggregate. With the derived diffusion coefficient and maturation factor, numerical models were used to estimate the durability of an exemplary reinforced concrete structure exposed to chloride ions. The elementary model was used to estimate the corrosion initiation time of reinforcement. The model allows a general specification of the structure and material properties. The results show the effect of chemical admixtures and MSW on the structure's durability in an aggressive environment and the differences with respect to other concretes. The study extends the portfolio of numerical calculations of the durability of unconventional concretes. [ABSTRACT FROM AUTHOR]

The degradation of reinforced concrete (RC) in aggressive environments is caused by a combination of factors ranging from force loading to weathering, to various chemical agents. Reinforcement corrosion in RC structures caused by excessive chloride ion diffusion is then one of the highly critical factors related to the potential destruction of this construction. Considering these facts, it is highly desirable to investigate the behaviour of concretes under a combination of force and chemical loading. The present study thus provides the basic results of an experiment in which laboratory concrete specimens were first subjected to partial loading in a press machine, then immersed in a fully saturated salt solution, and in the last step the compressive strength was determined. The loaded specimens were compared with specimens without the first loading and also with specimens immersed in normal water. This makes it possible to evaluate the combined effect. The results were evaluated also with respect to the strength increase under maturation of concrete in time. The results showed that concrete immersed in water after initial partial loading has a lower ultimate strength. Then, concrete without preloading force but immersed in chloride solution showed lower values and concrete preloaded and immersed in chloride for 90 days had the worst residual strength result. [ABSTRACT FROM AUTHOR]

Current transport infrastructure in Europe depends on numerous steel and concrete-steel bridges, often from high-strength steel. One of the main engineering challenges related to such bridges is to ensure their reliability during their whole lifespan. It is not easy as load by automotive or rail transport typically induces fatigue effects, especially on steel parts. It is usually necessary to execute periodic inspections which should make possible timely detection of issues (cracks) which would make effective repairs possible. Thus, it is important to be able to plan these inspections in right times and to inspect the critical details with focusing on their fatigue damage. The paper discusses some challenges related to this approach. The Direct Optimized Probabilistic Computation method (DOProC) is combined with linear fracture mechanics analytical solution to find the time of the first inspection. Then it is assumed that modified solution can be used to find times of further inspections. In the paper there are discussed issues related to the speed of the DOProC in such application and the approaches to limit the computational time without a loss of precision. [ABSTRACT FROM AUTHOR]

Lightweight fibre-reinforced concrete with waste red ceramic fine aggregate and artificial expanded clay coarse aggregate was in the interest of this research. Copper-coated steel fibre was added to the mix by volume in amounts of 0.0%, 0.5%, 1.0%, and 1.5%. Compressive strength, splitting tensile strength, static and dynamic modulus of elasticity, the flexural limit of proportionality, and shear strength were analysed after curing. To test the durability characteristic a non-destructive test method (NDT) using a 4-point Wenner probe was used to examine the surface resistivity. The simple relationships between the individual results were analysed to specify whether and how fibres affect these values. Mathematical correlations based on linear trend lines were prepared for this purpose. The results show which experimental results are interrelated and which are completely linearly independent. The conclusions can expand knowledge in the field of the concept of NDT methods and their use instead of destructive methods. [ABSTRACT FROM AUTHOR]

Concrete is a typical material used in structures exposed to the combined effect of aggressive substances and mechanical stress. This combination leads to problems with durability, loss of load capacity and safety. The research was carried out in order to evaluate three performance parameters, namely compressive strength, dynamic modulus of elasticity and durability due to corrosion caused by chlorides. Two different non-destructive testing devices (NDTs), namely a 4-point Wenner Probe and an rCON meter, were used to examine surface resistivity (SR) and volume resistivity (BR) in a very short test time. These are important properties of hardened concrete related to the corrosion resistance of reinforced concrete structures. An ultrasonic method was used to determine the dynamic modulus of elasticity. The article shows the correlations between the measurement of surface and volume electrical resistivity against the elementary characteristics of plain concrete C40 / 50. These correlations are analyzed at different times since concreting, thus providing a description of maturing of concrete. [ABSTRACT FROM AUTHOR]

In the construction of steel structures and especially bridges, the use of high-strength steel (HSS) has been increasing in recent decades. The use of steel with a higher yield strength allows the design of slimmer as well as more aesthetic constructions. Design often leads to cost and material savings. In cases where the ultimate limit state of the structure is not a decisive factor of the design (but on the contrary the serviceability limit state, dynamic behavior of the structure, stability or fatigue of the material), the advantage of HSS becomes questionable. In such cases, the resulting resistance of the HSS structure is affected mainly by fatigue resistance. The article is focused on the initial study of fatigue damage prediction of HSS structures using linear fracture mechanics and probabilistic approach. [ABSTRACT FROM AUTHOR]

The importance and increasing application of concrete with fibres in civil engineering are undeniable. The application of fibres in the cement matrix improves the properties of the cement matrix, but there are also a number of disadvantages related to the preparation of the concrete mix. Therefore, it is necessary to increase knowledge in the preparation of these materials, their testing, and the statistical evaluation of test results. Despite many of results available worldwide from the measurement of a wide range of fibre concretes, there is still a need to consider statistical parameters for local materials. The present paper demonstrates the possibilities of statistical evaluation of crack mouth opening displacement (CMOD) tests, which were carried out on 12 specimens. Beams of 150 × 150 × 550 mm in size with notch were prepared from grade C25/30 concrete reinforced with MEZ D10/52 fibre. The geometric properties of all specimens were determined and correlated with the results of the CMOD test. Statistical parameters showing the variance of the geometric values and the test results are partial. [ABSTRACT FROM AUTHOR]