The Determination of the Parameters of a Vibration Machinef the Internal Compaction of Concrete Mixtures

The determination of the rational parameters of a vibration machine for the internal compaction of concrete mixtures. We researched the “vibration machine – concrete medium” system wherein the concrete medium is represented by a system with distributed parameters that takes into account the resilient, viscous, inertial and energy properties of the compacted concrete medium. We researched the propagation of the viscous-resilient-plastic deformation waves in the contracted concrete mixture represented in the form of a half-space. We determined the amplitudes of the oscillations and stresses occurring in the compacted mixture depending on its physical and mechanical characteristics. We determined the oscillation amplitude of the vibration machine, identified its rational parameters. We determined the regularity of the motion of the compacted mixture and the vibration machine depending on the physical and mathematical characteristics of the compacted mixture, the thickness and width of the compacted layer, the angular oscillation frequency and the amplitude of the exciting force. The presented dependences enable the substantiation of the rational parameters of the vibration machine and the modes of vibratory action.

The Theory of Concrete Mixture Vibratory Compacting

Purpose. The creation of the compacting vibratory process theoretical basis enabling the assessment of the efficiency and the choice of rational modes of the vibration influence on the concrete mixture, based on the minimal energy input in the process of its compacting.Methodology. The paper contains the description of the mechanism of compacting under the action of external vibration forces whereat a variable tensely deformed condition occurs in the concrete mixture. In this case the primary structural links break, the links between its separate elements weaken, the final movements of mineral particles result in the creation of a more compact packing. As the basic factor determining the character of the compacting process, the authors propose to use the product of voltage and the velocity of the vibratory action, which presents the power of the vibratory action on the compacted medium.Results. The authors have obtained analytical expressions enabling the determination of the growth of the concrete mixture density in time function depending on the type of the vibratory load and the power of the applied vibratory action on the compacted medium. The paper contains the theoretical and experimental values of the specific work that provides compacting up to the values required by the technological norms depending on the consistence of the concrete mixture at vertical and horizontally directed vibrations.Conclusions. The authors have specified the existing hypothesis and proposed a more general power hypothesis of the process of vibratory compacting of concrete mixtures, applicable to the description of the vibration process and concrete media treatment by various vibratory mechanisms, tools and machines. One can use the obtained results to set the rational modes and duration of the vibratory action on the compacted medium depending on the amount and type of the specific work of compacting and also to determine the basic parameters of vibration machines of various technological purpose.

Vibratory Therapy of Postimmobilizational Contractures of the Knee Joint

For the treatment of postimmobilizational contractures of the knee joint and the development of the optimal method of vibratory therapy, the comparative analysis of results of the treatment of 49 patients aged 15 to 67 was carried out. In the basic group (29 patients) the vibration therapy action was performed instead of classical mechanotherapy (the frequency 12 hertz within the first 710 days of the treatment, 15 hertz within the following days, the vibration amplitude 2 mm; the vibratory action duration 57 min). Good results were obtained in | 62,1% of the patients, satisfactory results were in 34,5% of the patients, unsatisfactory results were in 3,4% of the patients, in the control group (20 patients) 45%, 30% and 25%, respectively.

Experiments to determine the effects of impact, vibratory action, and a long-continued change of load on wrought-iron girders

The author observes that the experiments which were undertaken, nearly twenty years ago, to determine the strength and form of the Tubular Bridges which now span the Conway and Menai Straits, led to the adoption of certain forms of girder, such as the tubular, the plate, and the lattice girder, and other forms founded on the principle developed in the construction of these bridges. It was at first designed that the ultimate strength of these structures should be six times the heaviest load that could ever be laid upon them, after deducting half the weight of the tubes. This was considered a fair margin of strength ; but subsequent considerations, such as generally attend a new principle of construction with an untried material, showed the expediency of increasing i t ; and instead of the ultimate strength being six times, it was in some instances increased to eight times the weight of the greatest load.

VIII. Experiments to determine the effect of impact, vibratory action, and long-continued changes of load on wrought-iron girders

A question of great importance to science and the security of life and property has been left in abeyance for a number of years,—namely, to determine by direct experiment to what extent vibratory action, accompanied by alternate severe strains, affects the cohesive force of bodies. It is immaterial whether the body be crystalline, homogeneous, or elongated into fibre, such as cast or wrought iron; the question to be solved is, how long will a body of this description sustain a series of strains produced by impact (or the repeated application of a given force) before it breaks? In the case of bridges and girders, this is a subject on which no reliable information has yet been given which may be considered as a safe measure of strength for the guidance of the architect and engineer. It is true that regulations have been established by the Lords Commissioners for Trade; but they appear to have had their origin on limited data, and in cases where the material and workmanship are good they may be relied upon as sufficient for the public safety. What, however, is wanted is experimental data to enable the engineer to comply satisfactorily with the conditions of the Board of Trade, and cordially to unite with the Government in affording ample security to constructions in cases where the lives of the public are at stake. To remove all doubts on this question, I have been enabled, through the liberality and at the request of the Board of Trade, to undertake a series of experiments to determine, or to endeavour to ascertain, whether a continuous change of load, and the strains produced by those changes, have any effect (and to what extent) upon the ultimate strength of the structure,—or, in other words, to ascertain the rate of endurance the material is able to sustain under these trials.