Papers by Keyword: Experiment

Abstract: UHPC (“UHPC” will be used in the paper for UHPFRC with steel fibres) offers great potential in terms of extending the service life of structures and reducing material consumption in bridge construction. One way to achieve the economical application of UHPC is to mechanically connect optimized UHPC structures with other structural elements made of conventional materials into a single functional unit. This paper describes the development of a structural system that provides effective use of the properties of UHPC and conventional concrete. An innovative coupling element made of UHPC material was developed for the connection. During development, computational and experimental analyses were performed, including static and fatigue resistance tests of the coupling and full-scale load tests of a prototype bridge girder. The article briefly summarizes the individual parts of the research and presents its results.

Abstract: Some parts made of polymeric materials are used in abrasive environments. Any damage to their integrity by abrasive environments could have a negative effect on the operation of those parts. In the paper, it is proposed to use a process and equipment for evaluating the resistance to abrasive erosion based on the application of a process of enlarging a previously made hole in the polymer material specimen using a conical abrasive tool. The feed movement of the conical abrasive tool takes place under the action of a counterweight of known size. The duration of the process of enlarging by abrasion provides information on the resistance to abrasive erosion of the specimen material. An experimental study of the resistance to abrasive erosion of a polymeric material using the enlarging process with a conical abrasive tool was designed and implemented. The experimental results were processed mathematically, and an empirical mathematical model was obtained that highlights the influence of some input factors in the abrasive process on the resistance to abrasive erosion evaluated through the duration of the enlarging process with a conical abrasive tool. The possibility of using enlarging by abrasion as a procedure for evaluating the resistance to abrasive erosion was confirmed.

Abstract: The presented article focuses on the design of composite tank which consists of wound cylindrical part (manufactured by the means of filament winding) which is bonded together with domes (manufactured by spraying or light resin transfer molding - LRTM technology). Composite structure was manufactured from glass/polyester material system by company ACO Industries Tábor. The article describes the possibility of using a bonded joint on cylinder/dome interface. This possibility was experimentally tested on specimens and also numerical simulation of full-scale model (finite element method - FEM) was performed. Developed construction is used for underground water treatment application and it is loaded with both the weight of the retained water and the pressure of the soil and groundwater during its deep burying.

Abstract: The paper focuses on the simulation process of Incremental Sheet forming (ISF) technology of the stainless steel SUS304 by the Multi-Stage Single Point Incremental Forming (MSPIF) with Abaqus software. Although being a popular stainless material with high mechanical and corrosion-resistant properties, widely used in various industries, forming of SUS304 steel by MSPIF technology still faces several challenges so in this study, with the simulation process, we have to determine the suitable values of influential factors to enhance the formability of SUS3043 sheet material. In the paper, with Abaqus software, we construct a model of simulation of SUS304 steel sheet by MSPIF technology to collect data for design of experiment (DOE). The results of the research provide valuable information on the forming process of SUS304 steel by MSPIF technology in order to improve the formability of the products.

Abstract: The paper outlines a method for comparative analysis of the load-bearing capacity and crack formation of reinforced concrete and fiber-reinforced concrete cylindrical shells based on experimental studies. To implement this task, the authors have developed a special stand. The results of tests of reinforced concrete and fiber-reinforced concrete cylindrical shells, which had the same geometric parameters, are presented. The fiber-reinforced concrete shell had additional dispersed reinforcement with steel fiber with curved ends, which was added at the stage of mixing the concrete mixture in an amount of 1% by volume of concrete. The shells were hinged at four points and loaded with a vertical distributed load applied along four strips, each 13 cm wide, and only along the body of the shell. The load-bearing capacity of the reinforced concrete shell was 101.6 kN, and the first crack appeared at a load of 64.5 kN, which is 63.48% of the load-bearing capacity. Before the loss of bearing capacity, 10 cracks with the same initial opening width of 0.05 mm had formed in the shell. The load-bearing capacity of the fiber-reinforced concrete shell was 149.9 kN, and the first crack appeared at a load of 74.9 kN, which is 49.97% of the load-bearing capacity. Before the loss of bearing capacity, 12 cracks with the same initial opening width of 0.05 mm had formed in the shell. The load-bearing capacity of the fiber-reinforced concrete shell turned out to be 1.48 times greater than that of the reinforced concrete shell.

Abstract: The paper presents the results of experimental studies and computer modeling of reinforced concrete and fiber-reinforced concrete cross-beam systems. The authors have made a special stand, the design of which allows for experimental studies of the load-bearing capacity, deformability and crack resistance of cross-beam systems under concentrated and distributed static loads. Samples of reinforced concrete and steel fiber concrete were tested, which are systems consisting of four mutually perpendicular beams of rectangular cross-section. The samples are reinforced in the lower zone with longitudinal reinforcement of class A400C with a diameter of 8 mm. Steel fiber concrete samples have additional dispersed reinforcement with steel fiber with curved ends in an amount of 1% by volume of concrete. A methodology for finite element modeling and calculation of cross-beam systems in ANSYS 17.1 has been developed, and the results obtained experimentally and based on computer modeling have been compared. Tests have shown that dispersed reinforcement leads to an increase in the load-bearing capacity of the system by 1.23 times. In finite element analysis, this increase was 1.18 times. The load-bearing capacity of the reinforced concrete cross-beam system obtained by the finite element method is 13% less than in the experiment, and that of the fiber-reinforced concrete system is 15% less. The number of cracks in a fiber-reinforced concrete system increases significantly (2 times), but the length of the cracks decreases by 2.1 times, and the width of their opening is significantly reduced - from 3 mm to 0,5 mm.

Abstract: In the field of construction, with regard to social and design requirements, it is necessary to look for innovative and advanced solutions for the materials of building and structural elements. The topic of this paper is precisely from this area, where material engineering and the field of concrete belong. The aim of the research task is to compare the properties of three different mixtures. The main goal is the analysis and comparison of samples after exposure of test samples to elevated temperatures of up to 900 °C. The mixtures are based on the same ingredients. The first mixture was a reference one, where the binder was Portland cement. In the second mix, cement was replaced, and an alkali-activated binder was used. And in the third mix, which was a modification of the first mix, part of the aggregate was replaced with light artificial aggregate. The experimental part also focused on testing and comparing the workability in the fresh state and subsequently the basic mechanical characteristics, which include strength in compression, split tension, or static modulus of elasticity. In addition, tests of resistance to frost and defrosting chemicals or determination of the tear strength of the surface layer on the test beams were also carried out.

Abstract: This paper describes an experimental investigation of the behaviour of anchors precast in Ultra High-Performance Fiber-Reinforced Concrete (UHPFRC) under static loading. Initially, the current state of the art and related experimental studies are briefly mentioned. The next part of the paper is devoted to an experimental program aimed at describing the anchorage in cement composite UHPFRC in more detail. A total of 45 pull-out tests were performed. The tests investigated the effect of the fiber quantity in volume in the UHPFRC matrix (v_f), the effective embedment depth of the anchor (h_ef) and the position of the anchor in the mould during concreting. Finally, the results are documented, the failure mode and the shape of the concrete cone, load-displacement curves and summary tables are presented. The paper concludes with a discussion of the results and further directions for solving the problem.

Abstract: The results of experimental studies and computer modeling of reinforced concrete and fiber concrete cross-beam systems are presented. The authors have made a special stand, the design of which allows to carry out researches of bearing capacity and deformability of such systems under the concentrated and distributed static loads. Samples made of reinforced concrete and steel fiber concrete and consisting of four mutually perpendicular beams of rectangular cross-section were tested. The specimens were reinforced in the lower zone with longitudinal reinforcement of 8 mm in diameter, two rods in each beam. Steel-fiber concrete specimens have an additional dispersed reinforcement of steel fiber with bent ends in an amount of 1% by volume of concrete. A procedure of finite-element modeling and calculation of cross-beam systems in the licensed program ANSYS 17.1 was developed, and a comparison of the results obtained experimentally and on the basis of computer modeling was performed. The tests showed that dispersed reinforcement of the cross-beam system with steel fiber leads to an increase in its bearing capacity by 1.23 times. During modeling and finite-element analysis in the ANSYS 17.1 program, the increase in bearing capacity was 1.18 times. At the same time, the load-carrying capacity of the reinforced concrete cross-beam system obtained by the finite-element method was 13% lower than in the experiment, and that of the fiber-reinforced concrete system was 15% lower. At the same time, the discrepancy in the approaches considering torsion and not taking it into account is about 5% for all the samples studied in the work.

Abstract: The methodology of experimental research of long cylindrical shells to determine their stress-strain state, carrying capacity and crack resistance is proposed. To implement the task, the authors have developed a special stand. Eight cylindrical shell models were made for testing - four of reinforced concrete and four of fiber concrete. Fibro-concrete specimens-shells had additional dispersed reinforcement by steel fiber with bent ends in an amount of 1% by volume of concrete. All specimens-shells had a constant length and cross-sectional radius, and varied the thickness of the shell and the size of the cross-sectional section of the board elements. The paper presents the results of tests of reinforced concrete cylindrical shell, which showed that the carrying capacity of the shell was 96.4 kN, and the first crack formed with a load of 42.9 kN, which is 44.5 % of the carrying capacity. Up to the moment of bearing capacity loss, 8 cracks with the same initial opening width of 0.05 mm and maximum final opening width of 0.8 mm had formed in the shell. Computer modeling of the shell and calculations with ANSYS 17.1 licensed software were performed. The bearing capacity determined in ANSYS was 93.0 kN, which is 3.6 % less than in the experiment. The test methodology and the developed stand are universal and will be used for further research.