US1171482A - Reinforced concrete structure. - Google Patents

Description

Patented Feb. 15, 191

[N VEN T 0R W] NESSES A Home) THE COLUMBIA PLANOGRAPH c0., WASHINGTON, D. c.

ROBERT B. Tours, or NORFOLK, VIRGINIA.

IBEINFORGVED conciau'rn srnuo'ruaii.

Specification of Letters Patent. i Paten'td Fl 1916.

Application filed April 28, 1314. Serial No. 834,994.

To all whom it may concern:

Be it known that I, ROBERT E. TUFTS, of Norfolk, in the county of Norfolk and State of Virginia, have invented certain new and useful Improvements in Reinforced Concrete Structures; and I- do hereby declare the following to be a full,-clear, and exact description of the invention, such as will enable others skilled in the art to which it 1 mg molds 2 for the girders, and molds 3 for appertains to make and use'the same.

This invention relates to improvements in reinforced concretestructures, such as floor or roof construction. I

. Heretofore, in the construction of concretefiooring, it has been the practice to'design'the slab from four to sixinches thick with comparatively deep beams at intervals of from five to. ten feet to'carry the slab,

/ the beams in turn being carried by deeper and heavier girders spanning from column tocolumn. In constructing such flooring, form-work for the slab, beams and girders has been erected and after placing the steel reinforcing therein, flooring concrete has been poured in the, formwork and the slab, beams and girders molded as a monolith. In some instances, the beams and girders have been poured and the slab has been poured later.

Experience has shown that the only practical material of which to 7 build the molding surfaces being wood, it

" panel, between four columns, wherein nine follows that all under eXposed surfaces of the Y floor members (which become ceiling members to the floor below), will show a reproduction of irregularities and roughness of the lumber forms and centering.

One object of my present invention is to make it practical to mold a smooth surface on the underside of the panel unitsby pre- I ,viously casting them in panels of sizes readily to be handled, on smoothcsurfaces which becomes practical under work-shop conditions where a comparatively few molds may be'prepared and used repeatedly.

With this and other objects in View, the

invention consists in certain novel features as hereinafter set forthand po nted Ollt ln the claim. 1

, In the accompanying drawings, Figure '15 "is a plan view showing a complete floor pre-castpanel units are shown; Fig. 2 is a sectional view on the lineal-e0 of Fig. 1;

Fig. 8 is an enlarged face view of one of the floorunits; Fig. 4: isan edge view of a floor by the latter.

. cast. may be cast at the shops 01-: works in-suitablequantities, and'the'y will be formedon provided under practical work-shop condiunit; Fig. 5 isan enlarged sectional view. showing the form-work, iQlIIfOIQlIlg bars,

and a precastpanel unit in place on the wooden formwork, said view corresponding to a section on the lme'y-y of Fig. 1 be.-

' fore the girders and beams are molded'and Fig. 6 is an enlarged sectional line of Fig. 1'. I r

1 represents "wooden formwork I comprisview on the located between and connecting columns 6 at the cornersof the panel, and a plurality of beams 7 extending transversely in directions at right-angles fromgirder to girder and intersecting each other so as toi forma plurality of spaces 8 which are covered in the finished floor bya plurality of precast blocks or floor units 9; The girders 5 which extend from column to column and the beams 7 which extend from girder to girder will all be preferably the same in depth, but the beams are made much narrower than the girders and are supported at their ends Before the concrete for the girders and beams is poured, panel units?) will be placed over :the spaces 8 so as to be supported upon the edges of the molds of the formwork and slightly overhang the walls thereof, as shown in Fig. 5. As previously stated, thefloor units 9 will be pre- That'is to';say,';these blocks or units smooth surfaces which may be morereadily I tions than in the wooden formwork employed in buildings for providing molding means. The precastingof the floor units results in vario-us practical and valuable advantages,.among 'whichfl'may be particularly: emphasized, the rendering of thelo-wer faces of the blocks which form the ceiling of a lower story of the'building, smooth and thereforejneatjand pleasing in appearance instead of,.;presenting a rough, unfinished appearance-aswouldbe incident to casting concrete in wooden molds such as provided by the formwork commonly employed; comparatively few mo lds for precasting the floor units need to'be. providedand these may be used repeatedly, thus reducing the cost of constructing a flooring; the panel units may be manufactured considerably in advance of the time they may be laid and while the foundations are being built for the proposed building, so that by the time they may be needed, a substantial advance in the construction of the flooring will have been made, and the panel units can be cured under favorable conditions and a harder grade of concrete can thus be obtained than by pouring the thin slab directly in place Where it is subject to drying influence of the air and sun. lVhere the slab is to have a cement wearing surface, such surface may be made a part of the panel unit at the time it is cast and can be finished better and more ornamentally under work-shop conditions than when in place in'the flooring.

Each panel unit may have reinforcing rods 10 molded therein as indicated by dotted lines in Figs. 3 and 4. The formwork and reinforcing having been prepared and the precast panel units 9 placed in position on the molds'as shown in Fig. 5, the concrete for :the girders and beams will be poured, so that in the finished flooring, ledges 11 will be provided at the edges of the girders and beams, on which the thin precast panel units will be supported, and the upper faces will be flush with the upper faces of the girders and beams.

I am aware that precast structural elements are notnew in the broadest conception of the words, and I am further aware that various inventions have been made, some looking toward using precast slabs supported by beams at two edges only and using the slabs in similar manner as were they ordinary wooden plank bridging from beam to beam and with no substantial supports provided except on the two ends of the precast slabs. It has been proposed to precast one large slab for each bay, and support the slab at the corners by allowing the same to seat directly on the columns. This last men tioned method is objectionable for several reasons, among which may be mentioned the fact that for practical dimensions of floor bays, the slabs would become extremely heavy both on account of the large area and r on account of the necessarily great thickness in orderto obtain required strength for the large spans. A further objection is the comparatively small bearing area offered by supporting the precast slabs only at their corners.

Some inventors have proposed to form mechanical bonds or keys between the precast slabs and later molded beams, which practice is objectionable owing to the fact that efiicient methods of bonding, keying or dovetailing concrete members are impractical. Other inventors have employed hollow tile blocks arranged on 'flat false work with. spaces between the blocks to be filled with reinforced concrete beams but these are intended and are used with comparatively small blocks of burn-ed clay with the object of having the hollow blocks fill the spaces Attention is called to the fact that 1 propose to attain to a ceiling of pleasing appearance by forming nests of symmetrically arranged panels in each bay and by further producing under workshop conditions finished surfaces to these panels.

Further attention is called to the fact that in my invention each bay has a plurality of panels (therefore each is as small and light as the number of panels selected will determine) and that each panel is rigidly sup ported on all four sides by beams or beams and girders bordering the panels and since my slab units have substantially equal reinforcement in both directions, they are in the conditions of plates of homogeneous bending resisting materials supported at every point of their peripheries. It will require no argument to show that this condition of reinforcing and supporting the precast slab units will result in twice the strength of the slab units as would be the case were they supported on two sides only. l Vhile various attempts have been made to bond or anchor the slab units to the in closing and supporting beams; on account of the comparatively thin slabs which I may employ, and on the account of obstructions ofiered by protruding reinforcing fabric or bars, I prefer to make no attempt to mechanically bond my slab units at their edges with the surrounding and supporting beams. Another reason for not desiring any mechanical bond is that under stress and de flection of the slab units, there is a tendency to form a crack in the floor surface in the locality of juncture of slab unit and beam. I have already mentioned reasons for not being able to obtain an efficient bond between slab units and beams and I con sider a partial and ineffective bond worse than none, for the reason that it will be misleading. With my units resting on ledges on the beams and with no mechanical bond with the beams, a tendency to crack in the upper surface near beam support will result in a tendency to open the joint between slab unit and beam and will avoid the possibility of setting up a crack in the slab proper, while a slight opening of this joint will have noefi'ect on the strength of the floor system what I claim as new and desire to secure by Letters-Patent, is Y I A reinforced concrete floor structure comprising a plurality of intersecting concrete girders forming rectangular panels, 001- umns supporting said panels at the intersections of said girders, concrete beams dividmg each panel into a plurality of smaller spaces, said beams intersecting each other 1 and made integral at their ends with the girders forming the panel, said girders and beams formed with ledges surrounding said smaller spaces, and precast panel units closing said spaces, said panel units havingless thickness than the thickness of the girders and beams and resting on said ledges with 7 their upper faces flush with the upper faces ofthe girders and beams.

In testimony whereof, I have signed this specification in the presence of two subscribing witnesses.

Witnesses: J NO. H. LOWE J. H. WEAVER.

Copies of this patent may be obtained for five cents each, by addressing the Gomniissioner of Patents,

Washington, I). (5.

ROBERT BQTUFTs. V

Images