Papers by Keyword: Testing

Abstract: Existing masonry columns are often susceptible to cracking due to overloading. Moreover, their fragility under earthquakes’ forces is of particular concern in seismic-prone regions. In order to mitigate these structural deficiencies, Fiber Reinforced Polymers (FRPs) are commonly used for external confinement. Full-jacketing, by means of FRP-wrapping is recognized to be very effective in improving the load bearing capacity and the ductility of masonry columns. Unfortunately, long-term effects seem to be detrimental for the masonry core, since its breathability is obstructed by the polymeric resin. Thus, a discontinuous application of the FRP-confinement appears to be more indicated in stone-masonry columns, allowing the humidity cycles to recur. On the other hand, the discontinuous wrapping negatively affects the confinement effectiveness, since both confined and unconfined masonry regions participate in the bearing capacity. In this sense, the present research is aimed to study the discontinuous confinement of half-scale masonry columns by means of Carbon-FRP strips. Unconfined and confined specimens were tested under uniaxial compression. The CFRP-confinement was studied by investigating the lateral strain in the confined and unconfined portions of the specimens. The results are reported and discussed in the paper in terms of failure modes, axial stress-strain and axial stress versus lateral strain relationships. The outcomes are reasonably convenient for a proper analytical interpretation of the phenomenon.

Abstract: Concrete is typical composite material and its properties can be very variable. Material properties are also influenced with the technology of processing, manufacturing and treatment after concreting. Reinforcement in form of fibers is often added for improving tensile strength. This paper deals with specific testing of fibre concrete. Test results of series of specimens are presented for selected transport concrete composition, which is reinforced with amount of fibers 25, 50, 75 kg / m³. Fibers were added directly into the into the concrete mixer in the factory. Each series includes more than 25 test samples. The tests include the compressive strength of a cube and cylindrical, testing of modulus of elasticity, and the split tensile strength in the direction perpendicular to and parallel to the filling. Within the research project also a few types of bending tests were performed. Four variants of bending test that vary in span of 500 or 600 mm, samples with and without a notch, and in a three- / four-point configuration. As a summary, broader evaluation and functional dependencies are derived.

Abstract: Advances in technology and sustainability requirements create substantial demand for material research. In construction industry, possibilities of innovation of concrete are opened by using recipes based on new activation methods, where alkaline activated composites can be included. This article focuses on this area where the results of the recipe verified under industrial conditions are presented, and the way of processing is significantly different from the laboratory conditions. The aim of the article is to present the material properties and differences of alkali activated specimens that are compared with series of common concrete material properties based on composition from the same aggregate material base. It was found that the most significant differences are the modulus of elasticity. In both of the recipes, the same design cube compressive strength is used. The article presented also experiment and nonlinear analysis of the alkali-activated beam without shear reinforcement, which was used to study the mechanism of damage and collapse of AAM beam. Nonlinear analysis was used thanks to complex knowledge of material properties. Numerical modelling uses the ATENA software. Test of small structural element is complemented by an advanced crack detection diagnosis with the use of acoustic emission.

Abstract: The paper reviews the theory of technical evaluation of the containment and the experience of using the mobile geodetic diagnostic system at the nuclear power plant unit No. 4 of Rostov NPS. The paper considers the results of a regular built-in system designed to determine and evaluate the strain-stress state of containments during the acceptance in service, commissioning stage and operating period. A comparison with the results of the geodetic system obtained at the same stages of containment existence.

Abstract: The main aim of this paper was to describe the viscosity and injection mold filling behavior of PA6 with 15% of glass fibers. Injection molding is one of the most widely used processes for polymer products. The quality of these products is directly linked to correct choice of process parameters. It is necessary to understand the filling behavior of the polymer material during the injection molding process. The spiral flow test was carried out in this study to explore the effects of several injection process parameters. The resulting lengths of spiral flow were compared. The polymer material under test was Polyamide 6 with 15% of short glass fibers (trade name: Durethan BKV 15). Virtual testing as well as real testing was performed. A predominantly linear relationship between the flow length and the mold temperature, melt temperature and injection pressure is described here. A special mold was designed for this test.

Abstract: This paper presents experimental and numerical results on the deformations and failureof integral composite T-joints subjected to a realistic combined tensile and bending (mixed mode)load case. For this reason, standard pull-off and mixed mode load cases are experimentally studiedby means of a novel test fixture which keeps the force angle constant to the T-joint’s base and allowsfor repositioning of the specimen in order to minimize constraining forces. Two types of specimenswith varying deltoid radius are investigated. Additionally, kinematically nonlinear numerical simulationsare performed to locate damage onset and deformations of the specimens. It is found that thesimulations are in good agreement with the experimental results.

Abstract: The work is dedicated to determination of stress-strain behavior of Ti6Al4V alloy deformed in conditions of biaxial tension provided by free bulging testing. The dome height during each test was continuously measured and recorded using a magnetostrictive position transducer. All the tests were performed using stepped pressure regime with jump pressure changing between two values at evenly spaced time moments. This experimental technique provides the possibility to study strain rate sensitivity index variation during the test and subsequently construct strain and strain rate dependent material model. The output data of each test include the evolution of dome height, subsequent pressure regime and final thickness of the specimen at the dome pole. In the framework of this study the processing of such data in order to evaluate the material behavior is discussed. Inverse analysis with different material models was implemented as well as special direct technique allowing one to construct stress-strain curves based on the results of free bulging tests with pressure jumps. The obtained material model was verified by finite element simulation.

Abstract: This manuscript presents the experimental testing and assessment of the combustible material behavior with a focus on modification by fire retardant during the process of combustion. We experimentally tested the material of representative natural thermal insulation made of hempen fiber and we compared these specimens with the application of representative fire retardant. The testing was proceed in accordance with the experimental method created with the purpose of evaluating the material behavior when exposed to a direct mid-height flame for a longer time period under laboratory conditions. The main aim of the experimental testing was possible improvement of fire-technical characteristic of building material for improve the fire protection.

Abstract: The paper deals with the testing of perimeter protection elements for burglar resistance. Burglar resistance describe the time which a burglar needs for overcoming of barriers and reaching for the protected object. For describing of the movement of a burglar in the protected buildings and areas, is important to determine a burglar resistance of individual barriers and building objects, which a burglar has to overcome. The most effective method for determining of burglar resistance is a practical testing.

Abstract: For describing the movement of a burglar in protected buildings and areas, is important to determine the resistance of individual barriers and building object, which a burglar has to overcome. The most used method to determine burglar resistance of a secure storage unit is a practical test. This paper deals with the test of selected secure storage units by describing the procedure of testing itself as well as the result of burglar resistance test.