Studies in engineering Volume 1-4

by University of Minnesota

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 edition. ...effect of the swelling in the concrete itself. In this connection reference should be made to some of the tests described further on, for those specimens were kept under the same conditions as the 12-foot beam and show identical changes with the change in seasons. For example the beams of figures 10 and 11 described on page 24, in which should be noted especially the large and rapid increase in the total shrinkage during the last two months. Likewise the shrinkage curve of the two-way slab of page 31 shown in figure 15, and the flattening of the curves for the beams of figure 13 during this same period, are suggestive of this same influence. The sharp rise in all these curves together with the sudden break in the deflection curve of figure 6 all occurring at the same time, bring out sharply the effect of the dry heat. Very noticeable illustrations of this same effect have been frequently noted in slabs over boilers or other warm, dry places. In some cases very alarming sags have been observed. The effect of shrinkage acts in two ways to increase the deflection in beams and slabs. First, the compression fibres must shrink a greater amount than those on the tension side due to the effect of the steel, this inequality resulting in increased deflection. Second, the shrinkage on the tension side operates to increase the number of cracks and thus, by increasing the average deformation, further increase the deflection. These effects decrease with an increase in the depth of the beam, for the angular change would be less as the depth increased. The effect of the shrinkage however is much less than that of the time effect in increasing deflection, because the latter acts on both top and bottom to produce increased deformation. In buildings of...

36 pages, Paperback

Published September 13, 2013