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Equations to predict crack widths in partially prestressed members with different types v.f prestressing steel and the nonprestressed remforcement are given. Evaluating the available test data by statistical analysis, it is shown that both the bonded preslressed sleet and rhe nonprestressed steel influence rhe crack widrh. II is also shownthar as highly modified Gergely-Llll:;: equalion can be used lo predict rhe crack widrh of parrially presrressed members. [ABSTRACT FROM AUTHOR]

Results of test on plain and confined concrete prisms subjected to different strain rates are presented. The tests show that the predominant effect of transverse reinforcement is an increase in strain under maximum stress and slope of the descending branch of the stressstrain curve. High loading rates increased strength but did not have a pronounced effect on shape of the stress-strain curve. [ABSTRACT FROM AUTHOR]

The difficulty in estimating accurately the losses due to creep, shrinkage, and relaxation of steel lies in: (a) prediction of coefficients related to the quality of concrete, steel, and the environment in which the structure will be kept during the period of loss, (b) the interdependence of the amount of prestress loss produced by the three contributory causes. In practice the designer may recourse to results of tests or to recommended practice for values of creep, shrinkage, and relaxation. Once these values are established, the errors resulting from Item (b) above should be eliminated. This paper is written for this purpose. Using a step-by-step procedure which accounts for elastic and creep recoveries of concrete and the effect of variation in stress level on the relaxation of steel, graphs are prepared for use in practice. The use of these allows economical design by accurate esti-mate of the loss in prestress without the necessity of performing the computations of the step-by-step procedure. [ABSTRACT FROM AUTHOR]

Fertilized Leghorn eggs were incubated at temperatures between 37.6 and 38.2 degrees C at a relative humidity of 60%. Electrical, mechanical and optical techniques were tested to find a non-invasive method for recording the embryonic cardiac activity. By means of electrical recording techniques no appropriate signals could be picked up with the shell being intact. Difficulties arose from potential changes generated by the system shell-shell membranes in contract with the electrolyte solutions. When the shell was locally removed, ECG-analogical potential changes could be recorded in these circumscribed areas from the 14th day of incubation, provided that conditions favoured the projection of the integral vector on the direction of the leads. Recording conditions were considerably improved when the holes in the shell were located above large vessels. Under such conditions, the signals of cardiac activity were mainly produced by pulsation of the vessels at the area of contact of the electrodes. However no improvement of the results could be obtained by chronical implantation of the electrodes; this method frequently impaired the course of incubation. Attempts to record cardiac activity by means of the mechanical systolic impulse failed because of the practical impossibility of reducing external vibrations below the level of the signal. The best reproducible results, being also the least susceptible to disturbances, were attained by measuring the variations of the current of the light flowing through the egg. By this method, the heart rate could reliably be recorded already from the 3rd day of incubation without any impairment of the embryo. The reliability of the optical method was checked by different modes of application.