This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
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DETAIL OF LOWER PORTION OF GUARANTY BUILDING (NOW CALLED PRUDENTIAL BUILDING). BUFFALO, N. Y.
Reproduced by Courtesy of the Northwestern Terra-Cotta Company the types shown below are generally considered more economical. In calculating the weight of the construction, the arch should be figured separately from the filling above, as the weights of these are different. The same remark applies to all systems of concrete construction.
For Systems Nos. 3 and 5. A.B.C.E H. same as tor No 9. D = slab of cinder concrete K = angles for support of ceiling. L = expanded metal ceiling. M= hangers securing ceiling angles to beams N = slab of cinder concrete on expanded metal, protecting webs of bearns O = solid concrete haunch protecting web of beams.
For System No 7. A.BC.D E. same as for No. 9. O = solid concrete slab.
For System No. 9. A = top floor. 1$ = under floor. C = wood screeds or sleepers. D = arch, cinder concrete. E = expanded metal sheet. F = cinder concrete filing around and under screeds. G = expand d metal wrapping of flanges to receive screened plaster as shown at P H= main floor beam. J = tie rods.
For system No 8. A.B.C DEF G.H. same as for No. 9.
For System No. 4. A.B.C D E.H. same as for No. 9.
Fig. 55 shows System No. 3, with a furred-down ceiling to give a level effect. This ceiling is not a necessary part of the construction, and is often omitted. The space between ceiling and floor slab is available for running of pipes, wires, etc.; and, to avoid punching of beams when such use is made of this space, the ceiling is dropped below the flanges of beams far enough to allow the passage of pipes, wires, etc.
This system is the one generally employed for long spans and heavy loads, as it gives the most substantial protection to the steel, and has certain elements of strength not possessed by the other systems, as follows: The haunches, besides protecting the webs and flanges of beams, shorten in effect the span of floor slab, and stiffen the floor beams against side deflection. The sheets of expanded metal can be made in effect continuous over all floor beams, and, because of this, the whole construction from wall to wall acts together, and has the advantage of a continuous beam over a number of supports. While it is impossible to state exactly what this advantage amounts to, on account of the uncertainty of actual conditions conforming to the theoretical assumption, it is probably safe to assume that the strains in the floor slab of a construction having this continuous feature would not be more than three-quarters as much as if the slabs were discontinuous. It should be noted in the above system, that if the furred ceiling is omitted the lower flanges of the beams are protected in a manner similar to that shown for System No. 7.
System No. 5, illustrated by Fig. 56, differs from System No. 3 only in the method of protecting the beam. As will be seen, all the strength afforded by the haunch is lost by this construction, and, as will also be seen later from results of tests, the protection is much less fireproof.
Fig. 57 shows System No. 4, which differs from System No. 3 only in the entire omission of protection to floor beams. This system is therefore only semi-fireproof, and in event of fire in the story below would not be to any degree fireproof. It is sometimes used with a fireproof suspended ceiling, but, as will be noted further on, tests of such ceilings have shown them to be of questionable value as efficient fire barriers.
Fig. 58 shows System No. 8. This system is chiefly adapted to light loads on moderately long spans where the beams are in general not over 8 inches or 9 inches deep. In such cases, where a flush ceiling is desired, it is sometimes more economical than some of the other systems with suspended ceiling.
It has the disadvantage from the standpoint of strength, that the load all comes on the lower flanges of beams, and further, that all continuous effect of slabs is lost.
Fig. 59 shows System No 7, really a modification of System No. 3, in which, in order to save depth, the floor slab is flush with the top of the floor beams.
This system also has the disadvantage of loss of continuous effect. In all the above systems, the more common spans are from 5 feet to 8 feet. The company controlling the patents, however, claim to be able with safety to adapt the construction to longer spans, even under heavy loads.
In these systems, as well as in all others where a cinder filling is used on top of the floor slab, the filling should contain some cement, as otherwise the unneutralized cinders are likely to cause corrosion of the steel.
The depth of floor slab varies with the load and the span, but is ordinarily 3 inches or 4 inches for loads under 200 lbs. and spans of about 5 feet.
Plate IV illustrates types of the Roebling system of fireproof floors. Fig. 60 shows System A, Type 1, which consists in general of a wire center sprung between the bottom flanges of floor beams, and upon which is deposited cinder concrete in the form of a segmental arch whose top is flush with the top of floor beams.