US1887875A - Floor construction - Google Patents

Description

Nov. 15, 193 2. E. A. NELSON FLOOR CONSTRUCTION Filed July 26, 1928 moment.

Patented Nov. 15, 1932 UNITED STATES,

ELMER A. mason; or nomvron'r, PENNSYLVANIA, nssrenou, BY nnsivn Assion MENTS, TO NATIONAL FIREPROOFING CORPORATION, OF PITTSBURGH, PENNSYL- V'ANIApA CORPORATION OF PENNSYLVANIA i z noon CONSTRUCTION i Application fiieanu 26, 1923. Serial no; 295,516. r i

This invention relates broadly to floor con struction and more particularly to a floor construction comprising hollow structural units. It relates still more particularly to a floor construction of the type disclosed in the patent to Toupet No. 1,404,710, issued J anuary 24, 1922, and in the reissue thereof, No. 15,369 ofMay 30,1922, and is in the nature of an improvement over such construction.

In a floor construction made up of struc tural units of the type above mentioned the units are placed end to end and extend as a beam between spaced supports. Such a beam tends to sag between the supports and due to such tendency a compressive stress is exerted at the upper portions of the structural units comprising it intermediate I the supports, such compressive stress being greatest at substantially the center of the span. Due

to the tendency to sag between the supports a compressive stress is also exerted at the lower portions of the structural units above and adjacent each support. I

The condition of a beam when its upper portion is under compression and its lower portion is under tension isknown as positive The condition of a beam when its upper portion is under tension and its lower portion is under compression is known as negative moment. Thus, the portion of the beam intermediate the supports is under positive moment; and the portion ofthe beam above and immediately adjacent a support is under negative moment. There is a transition point between the portion of the beam under positive moment and a portion under negative moment at which the moment of the beam is zero.

Floor known which have been made up entirely of a single size and shape of structural unit,suc h,

for instance, as that of the Toupet patents above referred to. In designing the strucural units several factors must be taken into consideration. One of the primary factors structures have heretofore been is weight. The modern tendency is to reduce 1 5 the weight ofa floor to'the minimum while still maintaining the requisite strength. This factor is of particular importance in high buildings in which the columns have'to support a tremendous Weight, and it is ab solutely essential to reduce the weight of the floor to the with safety- I Another primary consideration in the depositive moment intermediatethe supports and in the nature of a negative moment above therefore be of sufficient compressive strength at their upper portions to sustain the greatest compressive stress which may be exerted thereupon, which stress occurs substantially at the central point between supports, and must be of sufficient compressive strength at their lower portions to sustain the greatest compressive. stress which may be exerted 7 thereupon, which stress occurs substantially above a support. ample factor of safety must, of course, be provided. j V s The Toupet structural unit was designed to provide for a construction made up entirely of a single unit, such unit being designed primarily with regard to taking care of the positive moment existing throughout the major area of the floor without special regard to the requirements of the negative momentv a relatively minor area of the floor.

In the case of the Toupet unit the upper portion thereof was designed to ,havesufficient strength to sustain the greatest compressive stress which might be exerted theregreatest possible" extentcon'sistent and immediately adjacent a support. The structural units comprising the floor must 55 signing of floorsisthat the structural units I termediate supports there is practically no need for great strength at the lower portion of a structural unit as the stresses at that point are tensile stresses and are taken by iron or steel bars, in cooperation with the structural units. However, above and immediately adjacent supports there is need for a very strong construction in the lower portion of the structural unit. Therefore, if a single unit is used throughout a floor, either an un due weight of material must be used at certain portions thereof, or the floor at certain portions will fall below the required factor of safety as to strength. The latter difliculty has been encountered with floors constructed in accordance with the Toupet patents. It hasbeen suggested to remedy this defect by increasing the strength of the structural unit so that it provides the required factor of 7 safety at all points in thefioor. T 0 do this,

however, would unduly increase the weight of the floor and would thus introduce a defect equally bad.

. I provide a floor construction comprising normal structural units but having at portions thereof structural units of greater strength than normal units and adapted to cooperate therewith to form the floor. By normal units I mean' units such, for eX- ample, as that of the Toupet patents which are adapted for use at most points in a floor, but which are not specially designed to meet the reversed stresses imparted at certain points thereof, such, for instance, as at and adjacent the supports. I propose, in other words, to form a floor using normal units where such units are of sufficient strength to give the required factor of safety and use a unit of modified construction at portions where the normal unit would be inadequate.

I further provide a floor construction comprising in general normal hollow structural units but having at spaced points hollow structural units of substantially the same external dimensions as normal units but of modified construction. Thus, a floor ofthe same thickness throughout may be formed using two distinct structural units which has not heretofore, so far as I am advised, been contemplated. In order to provide the requisite strength at and adjacent the supports in constructions made up of structural units of the Toupet type, for example, it has been customary to use throughout the floor units of greater depth than required to sustain normal stresses, thus unduly increasing the weight of the floor. I

It has also been proposed to provide the requisite strength by increasing the weight of steel in the structure, but such provision has the disadvantage of greatly increasing the cost of the building. All of these disadvantages are done away with by my invention wherein the floor thickness remains constant throughout, the required strength is provided at all points in a floor and the weight of the floor is reduced to a minimum.

In the accompanying drawing I have shown a present preferred embodiment of the invention wherein Figure 1 is a perspective view with portions cut away of a floor constructed in accordance with my invention; and' Figure 2 is a cross-sectional view of a structural unit formed in accordance with my invention. V 7

Referring more particularly to the drawing, reference numeral 3, designates a support or I-bea-m surrounded by fire proofing 2. In constructing a building the respective I- beams 3 are set in place and a temporary scaffold or support 4 constructed. The upper surface of the scaffold 4 is coincident with the lower surface of the floor which is to be formed thereon.

Structural units 5 are laid on the scaffold and other similar structural units are brought into abutting relationship therewith and end to end so that the respective units are in proper relative position. The units 5 are similar to the structural units disclosed in the Toupet patents, and are used intermediate the supports 3.

As above pointed out, however, such units are unsatisfactory for use adjacent the supports, and in accordancewith my invention a structural unit 7 is provided which is used adjacent each support. This structural unit 7 has substantially the same external dimensions as the units 5, butisstrengthened at its lower portion to withstand the increased compressive stresses exerted at and adjacent the supports. It is provided with four downwardly converging strengthening ribs 8, two of which merge, one at each side, into the lower portion of the shell of the structural unit so as to greatly increase the compressive strength of the unit at its lower portion. While the additional weight due to the two outside strengthening ribs 8 is not great compared with the total weight of the unit, it is great enough to render inadvisable the "construction of a floor composed entirely of units 7. The strength of the units 5 is sufiicient for the general floor construction to sustain the stresses normally exerted therein so that I propose to use the units 7 only adjacent the supports. The number of such units used adjacent a support is governed by the specific construction in question and may vary according to the needs of the designer. Usually not more than two or three such units will be required at each side of the center of the support. In Figure 1 only a single unit 7 is shown at each side of the. support 2.

' Both the units'5 and 7 are generally proiii) , v the structural units and thus greatly increase the shearing strength The key pockets 10 would not be practicable in 'the structural units 5, but by reason of the additional strengthening ribs 8 at the lower portions of the units 7, ample provision is made for the use of such lower key pockets.

The structural units 5 and 7 are laid in place on the scaffoldet and steel strengthening bars 11 are set in place between respective rows of structural units. The strengthening bars 11 may be disposed in accordance with the needs of the designer and the stresses to be sustained, but inasmuch as such bars are tension strengthening members, they areusually predominantly located at portions of the construction wherein the structural units are under tension They do not assist materially in relieving the compressive stresses exerted on the structural units. After the structural units and the strengthening bars are set in place, concrete or grout 12 is poured between the units and around the bars and enters the key pockets 9 and 10, thus effectively providing for the support of the floor construction after the concrete or grout has set and the scaffold 4 has been removed. Suitable wood sleepers 13 may be set on top of the structural members and a cinder concrete fill 14 poured between the sleepers. A wood floor16 may then be laid and nailed to the sleepers. may be used.

While the external dimensions of my improved structural unit 7 are substantially the same as the external dimensions ofthe unit 5, my improved unit is so constructed internally as to provide a substantially oval cavity having a substantially V-shaped strengthening member extending thereacross. The oval cavity provides for greatly increased strength at the lower portion of the structural unit 7 relatively to the strength at the lower portion of the unit 5. The strength at the upper portion of the structural unit 7 is substantially the same as that at the upper portion of the unit 5. Therefore, a floor may be formed using the two units appropriately combined to provide for maximum strength and minimum weight at the same time.

While I have shown and described a present preferred embodiment of the invention, it is to be understood that the same is not limited thereto but may be otherwise embodied within the scope of the following claims.

Alternatively, a cement floor 15 Iclaim:" v15..

1. A 'floor'construction supported at'spaced points comprising hollow structuralsunits adapted to withstand normal compressive stressesbetween the supported points and hollowstructural units of the samedepth made out'of more material than the first mentioned structural units adapted to withstand com pressive'stresses greater than normal at their lower portions at the supported points.

spaced points wherein'the compressive stresses exerted on thestructural units comprising it are greatest at the supported points, normal hollow'structural units between the supported points and hollow structural units of the same depth relatively thickened so as to bexof v greaterthan normal compressive strength in the region of thesupported points.

3. In 'afloor construction supported at spaced points wherein the compressive stresses exerted on the structural units com: prising it are greatest-at the-supported points, normal hollow. structural units between the supported points and hollow structuralunits of the same depth of relatively strengthened construction so'as to be adapted to withstand themaximum compressive stresses at the sup ported points disposed at such points.

I 4. In a floor construction supported at spaced points wherein" the compressive stresses exerted at the lower portions of the structural units comprising, it are greatest at the supported points, normal hollow structural units between the supported points.

"and hollow structural units relatively strengthened at their lower portions in the region of the supported points, the comprestural units at their respective upper portions- 'being no less than the compressive strength of such first mention-ed structural units at their respective upper portions. 7

5. In a floor construction supported at spaced points wherei n the compressive stresses exerted at the lower portions of the structural units comprising it are greatest at the supported points, normal hollow structural units between the supported points and hollow structural units of relatively heavier. construction at theirlower portions and of no lighter construction at their upper portions in-the region ofithe supported points. i

'6. A floor construction comprising in general normal hollow structural units but having at spaced points special hollow structural units of substantially the same'external dimensions as normal units but composed of a substantially greater cross-sectional weight of material, such special structural units being disposed relatively to such normal structural units to withstand stresses greater than those normallyv exerted at the positions of such normal structural units.

sive strength of such second mentioned struc- I 75 2. In floor construction. supported at r 7. A hollow structural unit of generally rectangular cross-section having'strengthening ribs radiating from its lower portion and having a plurality of key pocketsat each side.

8. A hollow structural unit comprising an upper portion adapted vto withstand'high compressive stresses and having key pockets in its side faces, and a lower portion thickened to withstand compressive stresses substantially as high as those adapted to be withstood by the upper portion and having key.

less than the compressive strength of each unit of the second mentioned form at. the upper portion thereof. 7

13. A hollow structural unit of generally rectangular transverse cross-section having side Walls thickened adjacent the bottom of the unit to provide material of suificient depth to accommodate key pockets, and a key pocket in at leastone of such side Walls adjacent thebottom of the unit.

In testimony whereof I have hereunto set In hand.

y r ELMER A. NELSON.

adapted to withstand normal compressive stresses,each unit of the other form being of substantially the same depth as each unit of the first mentioned form, being fashioned out of a quantity of material greater than that out of which each unit of the first mentioned form is fashioned, and being adapted to withstand greater compressive stresses than the compressive stresses adapted to be withstood by each unit of the first mentioned form, the respective units of the second mentioned form being disposed in the floor construction in such positions, respectively, as

to receive greater compressive stresses than the compresslve stresses exerted in such floor construction on the respective unlts of the firstmentioned form.v I

11. A floor construction, comprising in combination two forms of structural unit, the units of both forms being generally similar and having generally'the same outside vdimensions so as to be adapted to be used together, the units of one of the forms, however, being respectively fashioned out of more material than the units of the other form whereby to render the respective units of the first mentioned form capable of withstanding greater compressive stresses than the compressive stresses adapted to be with- I stood by the respective units of the second mentioned form. p

12. A floor construction, comprising in combination two forms of structural unit, the compressive strength of each unit of one of such forms at the lower portion thereof being greater than the compressive strength of each unit of the other of such forms at the lower portion thereof, the compressive strength of each unit of the first mentioned form at the upper portion thereof being no

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