Some Mooted Questions in Reinforced Concrete Design eBook

This eBook from the Gutenberg Project consists of approximately 181 pages of information about Some Mooted Questions in Reinforced Concrete Design.

Some Mooted Questions in Reinforced Concrete Design eBook

This eBook from the Gutenberg Project consists of approximately 181 pages of information about Some Mooted Questions in Reinforced Concrete Design.
“In shallow beams there is little need of provision for taking shear by any other means than the concrete itself.  The writer has seen a reinforced slab support a very heavy load by simple friction, for the slab was cracked close to the supports.  In slabs, shear is seldom provided for in the steel reinforcement.  It is only when beams begin to have a depth approximating one-tenth of the span that the shear in the concrete becomes excessive and provision is necessary in the steel reinforcement.  Years ago, the writer recommended that, in such beams, some of the rods be curved up toward the ends of the span and anchored over the support.”

It is solely in providing for shear that the steel reinforcement should be anchored for its full value over the support.  The shear must ultimately reach the support, and that part which the concrete is not capable of carrying should be taken to it solely by the steel, as far as tensile and shear stresses are concerned.  It should not be thrown back on the concrete again, as a system of stirrups must necessarily do.

The following is another loose assertion by Mr. Turner: 

“Mr. Godfrey appears to consider that the hooping and vertical reinforcement of columns is of little value.  He, however, presents for consideration nothing but his opinion of the matter, which appears to be based on an almost total lack of familiarity with such construction.”

There is no excuse for statements like this.  If Mr. Turner did not read the paper, he should not have attempted to criticize it.  What the writer presented for consideration was more than his opinion of the matter.  In fact, no opinion at all was presented.  What was presented was tests which prove absolutely that longitudinal rods without hoops may actually reduce the strength of a column, and that a column containing longitudinal rods and “hoops which are not close enough to stiffen the rods” may be of less strength than a plain concrete column.  A properly hooped column was not mentioned, except by inference, in the quotation given in the foregoing sentence.  The column tests which Mr. Turner presents have no bearing whatever on the paper, for they relate to columns with bands and close spirals.  Columns are sometimes built like these, but there is a vast amount of work in which hooping and bands are omitted or are reduced to a practical nullity by being spaced a foot or so apart.

A steel column made up of several pieces latticed together derives a large part of its stiffness and ability to carry compressive stresses from the latticing, which should be of a strength commensurate with the size of the column.  If it were weak, the column would suffer in strength.  The latticing might be very much stronger than necessary, but it would not add anything to the strength of the column to resist compression.  A formula for the compressive strength of a column could not include an element varying with

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Some Mooted Questions in Reinforced Concrete Design from Project Gutenberg. Public domain.