US3152421A - Concrete building construction - Google Patents

Description

Oct. 13, 1964 K. H. MIDDENDORF CONCRETE BUILDING CONSTRUCTION 12 Sheets-Sheet 1 Filed Nov. 17. 41958 INVENTOR. KARL H. M/DE/VAF ATTORNEY Oct. 13, 1964 K. H. MIDDENDORF 3,152,421

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Oct. 13, 1964 Filed Nov. 17, 1958 K. H. MIDDEN DORF CONCRETE BUILDING CONSTRUCTION l2 Sheets-Sheet 6 KARL BY WEE@ Oct. 13, 1964 K. H. MIDDENDORF 3,152,421

CONCRETEBUILDING CONSTRUCTION Filed Nov. 17, 1958 12 Sheets-Sheet '7 aff ig. I0

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Oct. 13, 1964 K. H. MIDDENDORF 3,152,421

CONCRETE BUILDING CONSTRUCTION Filed Nov. 17. 1958 12 Sheets-Sheet*l 9 INVENTOR. 73 68 KARL ht M/DDENDQRF Fig.13 BY A from/,5y

K. H. MIDDENDORF CONCRETE BUILDING CONSTRUCTION Oct. 13, 1964 12 Sheets-Sheet 11 Filed Nov. 17, 1958 F Y .e E R0 ma Fm NN 0 EE .r W@ fr Im 9M IH. .WM FKW 8 6 9 n n M United States Patent O 3,152,421 CNCRETE BUILDING CGNSTRUCTIN Karl H. Middendorf, Costa Mesa, Calif., assigner to The Prescon Corporation, a corporation of Texas Filed Nov. 17, 1958, Ser. No. 774,293 6 Claims. (Ci. 'S0-128) My invention relates to concrete-building construction, and more particularly to a concrete building construction that includes a floor or roof slab having portions of a grid-like character, comprising spaced longitudinally and transversely extending intersecting frame members deining openings between the same, between supporting means, such as columns.

In a building construction having a roof or floor slab of the above referred to character, there are areas of solid concrete at and adjacent thev columns, that are mounted on the columns, and form cap portions for the columns, It is one of the important purposes` of my invention to provide a construction for prestressing said solid concrete areas so as to create high horizontal pressures by menas of which the shear existing in these areas can be fully met. In order to accomplish this purpose, it is desirable that the prestressing tension members can be placed anywhere desired in the depth of the slab of solid concrete around the column and to mount thel tension members in the concrete in such a manner that these normally will be as nearly straight as possible.

It is a particular purpose of my invention to provide open topped pockets or chambers in the slab at the mar.- gins of the solid area in order that the tension members can be provided at any desired depth in the concrete and can normally be placed in the concreterin as nearly a straight line as possible and can be readily tensioned economically and without difculty with well known apparatus that is at present in use and without the use of expensive anchoring means for the tension members, and Without putting sharp bends in the tension members.

In order to provide for the prestressing of the solid area of concrete adjacent the columns, I provide said open topped pockets along the margins of the solid concrete area and have these arranged opposite-each other so that the tension members can be extended from one of said pockets to the opposite pocket and provide a construction in which pockets can be made of such a size that no diiculty is encountered in providing the tension members at any depth that they may be desired and` at any location in the solid concrete that it may be desired and so that there is no lack of space for equipment necessary for stressing the tension members.

It is a further purpose of my invention to provide a method of forming the above referred to open topped pockets in the slab such that the form'rnembers for said open topped pockets can be removed as soon as the initial set of the concrete has taken place, usually two or three hours after pouring, and so that the form members that provide the voids or spaces between the intersecting members of the grid-like structure can be similarly removed. In order to accomplish this purpose, said forms are of such a character that the same can be disassembled or collapsed and removed upwardly through the tops of the openings provided in the concrete structure by means of said forms without disturbing the supporting means under the forms and under the setting concrete.

My improved concrete construction and method of manufacturing the slab can be used both in connection with a slab that is cast in-situ or in lift-slab construction.

Considerable advantage exists in the fact that the forms can be removed long before the concrete has set to its maximum strength, because this enables the re-use of the forms in other portions of the structure or in other 3,152,421 Patented Oct. 13, 1964 ICC similar structures long before it would be possible to do this if the forms were not removable in an upward direction, as, otherwise, it would be necessary to wait until the concrete had reached suicient strength that the supporting means, such as shoring under the slab, could be removed with safety.

The grid-like structure could be described as being a ribbed structure with ribs on all four sides of each of the quadrangular openings therein. In my improved construction it is possible to provide any desired spacing 0f the ribs from each other, or in other words, any size of the opening that may be desired, and the openings may be of any quadrangular character, that is, square, rectangular or trapezoidal.

When my improved slab construction is used as a lift slab construction, a further advantage exists in that the area of solid concrete that is to be around the columns can be prestressed before the slab is raised into position for mounting on the column.

It is a further purpose of my invention in lift slab construction to provide a means for supporting the slab on the columns that eliminates the use of expensive shear or lifting collars and in which all parts of the apparatus mounted in the slab for lifting purposes can be removed for further use. This is accomplished by providing columns that have reduced sections at the ultimate location of the slab providing shoulders thereon, which columns extend through openings in the slab, the slab being cast around. said columns, and after reaching its required strength and being prestressed in the manner above referred to, raised to its final position in the structure in such a location that the shoulder on the column is located closely adjacent the walls of the opening in the slab, and providing projecting means, such as horizontal ribs, in the walls of the opening and filling the space between the `reduced portion ofthe column, the shoulder and the wall of the opening with quick setting high strength concrete to key the slab to the column. The openings in the slab are made of such' a size that the slab will readily pass upwardly along the columns as it is lifted, but sufficiently small that there will not be any large gap between the top surface of the shoulder on the column and the wall of the opening in the slab adjacent thereto.

In carrying out my invention in concrete construction, it is an important purpose'to provide'a method of making pockets in a concrete structure comprising mounting removable pocket forming means in position in a form, pouring concrete in the form toy any predetermined level below the top of the pocket forming means but leaving the top exposed, and after the concrete has set sutiiciently to permit removal of the pocket forming means without damage thereto, removing said pocket forming means upwardly through the open top of the pocket, and to carry out this method without removing the supporting means for the forms from under the concrete structure.

In carrying out my invention in concrete construction, it is a further purpose to provide means on the removable pocket forms for providing grooves or recesses in the grid-like structure in which supporting means can be placed for the subsequent casting of a continuous slab over the grid-like structure without providing any sup ports on any rigid area beneath the grid-like structure.

In carrying out my method, I have provided a new and improved concrete form for forming pockets and similar spaces or voids in a concrete structure, and it is a purpose of my invention to provide such a form with upstanding corner members and wall forming members extending between them to form a quadrangular enclosure, and provide means for preventing both outward and inward movement relative to each of the opposing walls of said quadrangular enclosure, comprising detachable holding means engaging the wall forming members to hold the same against inward movement, that are so constructed and arranged that the connecting wall forming members are detachable from the corner members upon disengagement of the holding means from the wall forming members, so that the form can be removed upwardly.

It is an important purpose of my invention to provide a form member that is removable in an upward direction, which may be collapsed or disassembled in order to be removed in such an upward direction and which is provided with means to prevent either outward or inward collapse of the form and to provide a support for a working platform over the opening in the form. It is a further important purpose of my invention to provide means for supporting the bottom of such a form in such a manner that it can be removed in an upward direction and to provide means on the form that provides impressions in the frame members of the grid structure for supporting suitable means on which a slab may be cast without providing any supporting shores or similar bracing means under the same.

It is a further purpose of my invention to provide such a form member that is made up of flat wall forming members that can be readily stacked and which do not have any projecting hardware of any kind thereon and which are used in connection with corner posts that are provided with means for clamping bar-like holding members thereto that extend from one of said corner posts to the next corner post along the inner face of each of said wall panel members adjacent the top and bottom thereof so as to prevent inward movement of said wall forming members relative to each other and to thoroughly brace the form. Preferably the bars are made of ordinary pipe and only the corner posts have to be of any special design.

It is a further purpose of my invention to provide simple means for mounting a top wall panel or working deck and a bottom wall panel when desired on such form so that these can be readily removed to enable the form to be removed from the concrete structure, all parts of the form being removable upwardly through the openings created in the concrete structure by the forms.

In my improved slab construction deck slabs that can be made of either regular concrete or insulating concrete are adapted to be laid on top of the joists or set in pockets, and in floor construction, light weight covers of light weight concrete, corrugated steel, asbestos, transite or aluminum can be laid over the joists and a slab thick enough to carry the load and ducts and piping poured monolithically over the entire area. Furthermore such slabs may be poured on temporary forms carried by supporting members temporarily fixed in pre-formed impressions in the grid-like structure. It is to be understood that, depending on the design considerations, such superimposed slabs may be free of the supporting ribs or developed into combined sections of the ribs by bonding the slab with the grid-like structure in a well known manner. In roof construction, plastic domes can be set in the open spaces between the members of the grid construction forming the quadrangular openings as sky-lights, should this be desired. As the tops of the pockets are open, and when covered by a removable slab member, adjustment in the stress created by the tension members can be made at any time after completion of the struc- ,ture should this be found to be desirable.

My improved form member can be made either with wooden side wall panels held together in a suitable manner in quadrangular form or of metallic side wall forming sections, an object being to provide a metallic form that has the advantages of being withdrawable upwardly through an opening created by the form, in a similar Inanner to my form members utilizing Wooden wall panels. In order to accomplish this purpose a plurality of upstanding wall forming sections are provided that have a ipair of wall portions extending perpendicularly to each other and each of which extend around a corner of the form and members mounted between adjacent ends of these wall forming sections, said angular wall forming sections and the members between them being connected together to form a quadrangular enclosure and having bracing means detachably connected with the members mounted between said sections and said sections to hold the opposed wall forming portions of said sections against relative movement inwardly toward each other or outwardly away from each other.

More specifically it is a purpose of my invention to provide a metallic concrete form having a plurality of such upstanding wall forming sections that have stiftening formations along the top, bottom and end margins thereof and members mounted between adjacent ends of these wall forming sections that have a vertical stitfening formation thereon that is mounted between the end margin stiffening formations of the wall forming sections, and to provide bracing members extending across the end margin stifening members of adjacent sections and detachably connected therewith and with the members mounted between the adjacent ends of said wall forming sections, and further to provide transverse bracing means detachably connected with these members that are mounted between the adjacent wall forming sections to hold the opposed wall forming portions of the wall forming sections against relative inward and outward movement. Furthermore, in the metallic walled form it is a further purpose to provide top and bottom stiftening formations that provide means for mounting a top and a bottom wall member in position on the form in a similar manner to that used in the form having the wooden side panels, and to provide detachable projecting means on the outer faces of said wall forming members that provide grooves or recesses in the grid-like structure for the supporting means for forms for the subsequent casting of a continuous slab over the grid-like structure.

Other objects and advantages of my invention will appear as the description of the drawings proceeds. I desire to have it understood, however, that I do not intend to limit myself to the particular details shown or described except as dened by the claims.

In the drawings:

FIG. 1 is a plan View of a portion of a oor or roof slab made in accordance with my invention.

FIG. 2 is a fragmentary enlarged vertical sectional view taken on the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary section taken on the line 3 3 of FIG. 2.

FIG. 4 is a fragmentary plan view on an enlarged scale of the marginal portion of the slab shown in FIG. 1.

FIG. 5 is a fragmentary plan view on an enlarged scale of a portion of the structure shown in FIG. 1, with the forms in position but the top panels thereof removed.

FIG. 6 is a vertical sectional view taken substantially on the line 6-6 of FIG. 5, but showing the top walls of the form members in position.

FIG. 7 is a view partly in section and partly in plan of the portion of the structure shown in FIG. 4, but prior to removal of the forms and tensioning of the tension members.

FIG. 8 is a section on an enlarged scale taken on the line 8 8 of FIG. 1 after removal of the forms.

FIG. 9 is a fragmentary vertical sectional View through a portion of the grid structure in a lift slab construction, showing the forms in position and the slab in its position prior to being lifted.

FIG. 10 is a view similar to FIG, 9 of a grid construction in which the slab is cast in-situ.

FIG. 11 is a fragmentary plan view on an enlarged scale of the corner portion of the form, showing the corner post and portions of the wall panels and holding means therefor.

FIG. 12 is a fragmentary vertical sectional View taken on the line 12-12 of FIG. 11, but showing the top wall panel in position.

FIG. 13 is a similar view taken on the line 13-13 of FIG. 11.

FIG. 14 is a fragmentary vertical sectional View of a portion of a grid structure made in accordance with my invention, showing one form of removable slab structure mounted thereon.

FIG. 15 is a similar view showing a different mounting for the removable slab structure.

FIG. 16 is a plan View of a. modified form of form with the top thereof removed.

FIG. 17 is a fragmentary vertical sectional view taken on the line 17-17 of FIG. 16.

FIG. 18 is a fragmentary section on an enlarged scale taken on the line 18-18 of FIG. 17.

FIG. 19 is a similar view taken on the line 19-19 of FIG. 17.

FIG. 20 is a similar view taken on the line Ztl-2t) of FIG. 17.

FIG. 21 is a fragmentary View partly in section and partly in elevation taken on the line 21-21 of FIG. 16.

FIG. 22 is a fragmentary section similar to FIG. 20 of a modification.

FIG. 23 is a fragmentary section of a concrete `structure resulting from the modified form shown in FIG. 22, and

FIG. 24 is a fragmentary section taken on the line 24-24 of FIG. 17.

Referring in detail to the drawings, in FIG. 1 is shown a portion of a lift slab that embodies my invention. Said lift slab is mounted on a post 20, which is shown as being of concrete, the lift slab having a solid area 21, which constitutes a cap portion mounted on the post 20. Extending between each of the posts 20 from the solid area 21 adjacent said post and supported thereby and the next post thereto, similarly provided with a solid portion 21, is a grid structure, the posts being arranged in rows both transversely and longitudinally of the slab. Said grid structure comprises a plurality of parallel frame members or joists 22, which extend in one direction in said structure, and similar frame members or joists 23 that extend transversely to said first mentioned frame members or joists, said joists or frame members 22 and 23 intersecting at right angles to each other as shown in the drawings, the same being integrally united with each other at said intersections 24. Thus the members 22 extend along one pair of opposite sides and the members 23 extend along the other pair of opposite sides of the openings 25 in said grid-like structure, which extend entirely through the same. The frame members or joists along the marginal edge of the slab preferably widen so as to provide sufcient cross section thereof at the ends of said frame members for accommodating the tension members that are preferably provided in each thereof. The widened portions of the frame members 22 are indicated at 22' and instead of the openings between the joists 22 being rectangular, as is true of the openings 25, said openings 25 are trapezoidal. Itis, of course, to be understood that all the marginal ends of both the frame members 22 and 23 are similarly made.

The frame members 22 and 23 are provided with tensionmembers 26, which extend longitudinally thereof in any desired arrangement to obtain the desired prestressed condition of said tension members for their span and the load that they are to carry. While a plurality of tension members both vertically and horizontally of each of said frame members 22 and 23 extending from one marginal edge to the other marginal edge of the slab would ordinarily be provided, in FIG. l, due to the small scale of the drawing, the tension members in each of the joists or frame members are merely indicated by a single dotted line in each of said frame members or joists. Said tension members, as will be obvious from FIG. 1, traverse the solid area 21 around each of the posts 20.

In a structure of the character forming the subject matter of my invention, whether a lift slab construction is provided or a cast in-situ construction is provided, the area of solid concrete 21 around each of the posts is subjected to a great amount of shear, and in order to provide said solid area 21 with means for resisting this shear, means is provided for prestressing this area in both directions. Tension members 27, 28, 29 and 30 are provided for this purpose. Said tension members extend between pockets 31 and 32 at the marginal edges of the solid area 21. It will be noted in the form of slab shown in FIG. 1 that there are a plurality of pockets along each marginal edge of the solid area 21, the pockets 31 having the tension members 27 and 23 extending between the same, the tension members 27 and 28 extending at right angles to each other, while the pockets 32 only have the tension members 29 and 30 extending between the same, the tension members 29 extending between one pair of pockets 32 and the tension members 30 extending between another pair of pockets 32.

The ends of said tension members terminate in said pockets 31 and 32 and in recesses 33 in the marginal portions of the slab. Suitable anchoring means for the tension members are provided. The anchoring means may be of any preferred or desired character, but are shown for the tension members 26 in FIG. 4 as comprising an anchor plate 34, a collar 35 and spacing members 36, which are inserted between the collar 35 and the anchor plate 34 after the collar 35 has been moved to the position shown in FIG. 4 by a suitable hydraulic jack engaging with the collar 35 in a suitable manner. Preferably the tension members 26 have heads 37 thereon that engage the adjacent face of the collar 35 to hold said tension members in assembled position with respect to said collar and in stressed condition after insertion of said spacing members 36. The tension members 27, 28, 29 and 30 are similarly anchored in the pockets 31 and 32. While FIG. 1 of the drawings shows some characteristics of a lift slab construction that would not be present in a slab cast in-situ, the above referred to structural features would be present in a slab cast irl-situ or a lift slab. While the formations 31 and 32 are referred to as pockets, the use of this terminology is not intended to have any bearing on the size of the voids provided in these locations, as said pockets provide rather large chambers in which suicient space exists for the placing of the anchoring members for the tension members and the tensioning of said tension members.

The pockets 31 and 32 and the openings 25 are provided by means of forms that are substantially the same in construction, the forms being of such a character that the parts thereof are removable upwardly through the open tops of t'ne openings 25 and the open tops of the pockets 31 and 32. The forms are of such a character that any quadrangular opening or pocket can be provided by means of the same, by slight variations in the positioning of the walls thereof, and said pockets or openings may be square, rectangular or of any other suitable quadrangular shape. While a certain arrangement of pockets around the column is shown in FIG. 1, the arrangement of pockets and of tension members extending between the pockets will vary in accordance with the load that will be sustained by the solid concrete area 21, which is dependent upon the number of joists or frame members 22 and 23 that are positioned between each of said solid areas 21 and the next adjacent solid area 21 in either direction in the slab. In FIGS. 5, 6, and 9 to 13 inclusive, the forms for the pockets and the openings are shown as being applied to both a lift slab and in-situ construction.

Referring to FIGS. 5 and 6, a form for one of the pockets 31 is shown therein with a portion of the form for 7 one of the openings 25 shown adjacent thereto. Said forms comprise wall panel members 38 and corner members 39, which are substantially corner posts extending from the top to the bottom of the form on all of the four corners thereof. Referring to FIG. l1. it will be noted that the wall panels 38 have beveled end edges 4) that seat against oppositely beveled vertical walls 41 on the corners posts 39. Said corner posts have an arcuate body portion 42 terminating in the thickened end portions 43 that are provided with the beveled vertical edges 41. Said corner posts 39 have inwardly extending bracket portions 44 at the top and bottom thereof, the bracket 44 at the bottom of each post 39 being reversed in position from the bracket portion 44 at the top thereof. Said bracket portions are spaced from the opposite extremities 45 of said post-like members 39. Said post-like members are reversible, that is, the same can be reversed top for bottom and all the post-like members are interchangeable. Adjacent each bracket portion 44 is a horizontal shoulder 46, which provides a flat face on the post 39 and a straight wall portion 47 is provided on the inner face of the curved wall portion 42 at the shoulder 46. The bracket is provided with a socket portion 43 and has a portion 49 projecting inwardly beyond the shoulder 46 that has a fiat wall 56 thereon. Said bracket 44 also has a pair of laterally extending portions or arms 51 thereon, each of which has a substantially vertically extending portion 52 terminating in a at terminal edge 53 and a cylindrically curved portion 54 forming a socket in each of said portions 51. The portions 51 of said bracket are connected by means of a connecting portion 55, which has a at edge that is a continuation of the edge 53.

Cooperating with the bracket 44 is a clamping plate 56, which has a flat body portion, the under face of which is adapted to engage the shoulder 46, and wing portions 57 that are of a semi-cylindrical character having a curved wall portion 53 and a at wall portion 59 connecting the opposite ends of the curved portion S. The clamping plate 56 is preferably provided with an obliquely extending edge portion 6i) that is located adjacent the straight or flat portion 47 of the curved wall 42. The clamping plate 56 is provided with an opening 61 therein, through which the shank of a headed member 62 extends, said headed member having a head 63 located adjacent the ilat outer face of the clamping plate 56. A nut 64 is engaged with the opposite end of the member 62, being fixed thereto by welding or otherwise so that the nut 64 will serve substantially as a tixed head on the headed member 62 at the opposite end thereof from the head 63. The member 62 also extends through an opening 65 in the bracket 44 axially aligning with the socket 48, and a compression 'coil spring 66 is mounted in the socket between the clamping plate 56 and the bottom wall of said socket 48. The screw-threaded shank of the member 62 engages with the screv -thrcads provided in the opening 65 so that the rotation of the headed member 62 by engagement of a tool with a head 63 thereof will move the headed member bodily up and down relative to the bracket 44 and thus the clamping plate 56 up and down with respect to the bracket 44.

Extending between each of the corner posts 39 along the inner faces of the wall panels 38 are holding means comprising bars 67, which are shown as being in the form of hollow tubular members, such as ordinary pipes. The ends of the pipes 67 may be either smooth or threaded and, preferably, are threaded to aid in the gripping action of the clamping means, as will be described below. The threads 68 on the ends of the pipes 67 preferably engage corresponding serrations 69 in the curved wall portions 54 of the socket forming portions 51 of the brackets 44. It will be obvious that upon rotation of the head 63 of each of the headed members 62 the clamping members 56 on each of the post-like members will clamp the threaded ends 66 of a pair of pipes 67 in the sockets provided by the curved portions S4 of the portions 51 of said brackets 44, the two pipes thus clamped extending at right angles to each other. It will also be obvious that upon rotation of the head 63 of one of said headed members 62 in the opposite direction, the action of the coil spring 66 will cause the clamping plate 56 to be moved away from the bracket 44 to space the clamping portions 57 from the socket portions 54 and thus release the pipes 67 from the brackets. It will also be noted that the passages within the brackets for accommodation of the pipes extend backwardly from the portions at which the clamping of the pipes takes place, so that the pipes 67 can be removed from the corner posts by first moving one end inwardly toward the outer rim portion of the corner post with which it is assembled sufficiently to withdraw the oposite end thereof from the socket of the corner post opposite that into which it has been moved further inwardly, whereupon the corner post so released can bc removed and the pipe then removed from the other corner port with which it has remained assembled by withdrawing the same therefrom, as the opposite corner post will no longer be interfering with the disengagement of the pipe therefrom. With the assembly of the corner posts and pipes the opposite action will, of course, take place.

If the heads 63 of the headed members 62 are not readily accessible in the lower ends of the posts because of being on the under side of the form, the adjustment of the clamping means can be made by engaging the head formed by the nut 64 with a suitable tool, the head portion 64 being in an accessible position at the upper side of the bracket portion 44 on the lower end of the post 39. It will be noted that the enlargements 43 have sockets 70 therein, which are provided for the purpose of inserting the ends of U-shaped tie members 71 into the same whereby the forms are spaced from each other the proper distance to get the desired thickness of the wall between them, such as the frame members 22, for example. The proportion of the parts is such that the edges 53 of the portions 51 and the edge of the connecting portion 55 are in transverse alignment with the top edge of the pipes 67, as will be obvious from FIG. 12. The top wall panel 72 of the form rests on the pipes 67 at the top of the form and on the edges of the portions 51 and 55 aligning therewith. The bottom wall panel 73 is mounted in position below the pipes 67 at the bottom of the form and is suspended therefrom by suitable brackets 74, which are detachably mounted on the wall panel 73, any desired or necessary number thereof being provided for supporting the bottom wall panel 73.

In FIG. 6 a completely assembled form is shown for forming oneof .the pockets or chambers 31 at the margin of the solid concrete portion 21, and has a bottom wall 73 spaced a predetermined distance from a supporting surface 75 .by suitable means, such as chairs 76. A box-like enclosure is thus provided spaced from the supporting surface 75, which may be a floor slab of concrete or similar material, in the case of a lift slab, a bottom wall of a suitably supported form being substituted for the slab 75 in `the case of in-situ pouring of the concrete. It will be noted that the top edges of the side walls 38 are located above the top surface 77 of the concrete 21 poured around said form and, if desired, beveled strips 78 may be provided along the walls 38 below the top edges thereof, as shown in FIG. 6, or adjacent said top edges as shown in FIGS. 9 and l() to provide recesses in the poured slab around the pockets and openings created by the forms to permit the setting of a removable slab on the shoulders resulting around the top of said pockets or openings. The portions of the forms for the openings 25 shown in FIGS. 5 and 6 are of the same construction as the form for the pocket, except that there is no necessity of providing a .bottom wall 73 in said forms. The corner posts 39 and the wall panels 3S, as well as the top wall panel 72, are constructed and mounted in the same way for the openings 25 as for the pockets 31. The forms for the openings 25 would, as shown in FIG. l, have longer wall panels 38 than the pockets 31, while the Wall panels 38 for the pockets 32 would include wall panels of the same length as for the openings 25 and shorter wall panels for the shorter walls of the pockets, since these are shown as being considerably longer than they are wide.

In constructing the grid structure for lift slab construction, the bottom edges of the Wall panels 38 are seated directly on the oor slab 75 on which the lift slab is to be poured. The adjoining forms are positioned in the proper spaced relation by means of the tie members 71 and triangular cant strips 79 may be provided at the lower edge portions of the walls 38 on the outer sides thereof, as shown in FIG. 9. If the slab is cast in-situ, the bottom edges of the walls 38 of the forms are mounted on suitable bottom form members 80 for the joists 22 that are mounted on suitable shores 81, and which are provided with side walls 82 to form a channel member receiving a pair of walls 3S therebetween.

Should it be desired to vary the rectangular shape of the pockets from a square or oblong rectangle to another quadrangular form, such as a trapezoidal pocket, such as the pockets 25', then the same corner posts 39 are used as in .the other pockets, but a pair of the wall panels 38 that provide the obliquely extending walls of the pockets are sawed somewhat differently at the ends thereof that engage with the corner posts 39 so that these wall panels 38 willrinterit with the obliquely extending edges 41 of the corner posts 39 in a similar manner to that shown in FIG. 11 for the wall panels 38, and instead of providing straight pipes 67, the pipes 67 are provided on two sides of the form, which are bent at their ends to provide socket receiving portions that extend parallel to each other at opposite ends thereof, with the main body portions thereof extending obliquely to said end portions so that said pipes 67 will engage firmly against the corresponding wall panels 38. In FIG. 7 the pocket 33 is shown as being formed by means of side wall portions 83 and an end wall 84 spaced from the outer wall 85 of the form. The top wall 72 of the form for the pocket 25 has to be shaped to correspond to the angular relationship of the side walls 38 `to the side walls 38, as is obvious. In the case of both the top walls 72 and 72', the corners are beveled, as at 86, to provide for a proper iit between the top wall and the corner posts. The bottom wall of the form, when such is used as shown in FIG. 6, is similarly beveled at the corners. v

Referring to FIGS. 2 and 3, the lift slab that has been poured on a suitable support, such as Va concrete slab 75, is shown as having been raised into position. In pouring the slab, openings are left in the solid portion 21 thereof for the posts, the openings being sufficiently large that the main body portions 87 of said posts will lit loosely in the openings provided in the slab. A suitable form is used for forming the opening in the slab so that a plurality of obliquely extending faces 8S and 89 alternate'alongrthe sides of said opening, forming ribs 90 of a saw-tooth character projecting into the opening. The opening is of such -a size ythat even with the form left in place, which may be a sheet metal formY for the sake of thinness, the main body portion 87 of the post will slide through the opening as the slabis lifted to the position it is to have in use. The upper end portion 91 of the post is reduced in diameter to provide a shoulder 92 surrounding the same between the main body portion S7 and the reduced portion 91. In forming the reduced portion, apcorrugated tubular member is preferably utilized as a form for said upper end portion of the post so that a series of corrugations 93 run around said post in the reduced upper end portions thereof projecting toward the ribs 90 in the opening in the slab. If desired, a spiral reinforcement 94 may be provided in the post, extending into the reduced upper end portion 91 as shown.

After the slab has been poured and has set to its proper structural strength the tension members 27, 28, 29 and 30 are tensioned and after such tensioning has been done the slab is raised to the position shown in FIG. 2. While the means for raising the slab is retained in position to hold the slab in its final position, a quick setting early high strength concrete filling 95 is poured into the space between the walls of the opening in the solid concrete slabportion 21 and the reduced portion 91 of the post to completely ll the space between the shoulder 92 and the top edge of the opening and between the ribs 90 and the corrugations 93. After this filling has set to substantially full strength, the holding means are removed. The slab is thus mounted on the posts without the use of any shear collars or any other metal structure that has been previously found necessary. The posts and the slab will be firmly keyed together so that the slab will be firmly mounted on the shoulder 92 on the post 20. Portions of the means previously used for lifting the slab that are in engagement with the concrete are shown in position in FIG. 2 and comprise headed rod-like rnembers 96 that are provided with suitable threaded ends 97 for engagement with a pulling member and a bearing plate 9S that is adapted to receive the thrust of the pulling apparatus against the top end of the column 20. While FIG. 2 illustrates the top or yupper end of a column, it is obvious that such a shouldered arrangement can be provided at any point along a column where a lift slab is desired to be mounted on a shoulder such as the shoulder 92 provided on the column 20. The headed members 96 are removable from the concrete, being wrapped with paper or other suitable material to prevent bonding of these in the concrete 21 and thus all of the lifting apparat-us is disengageable from the slab for use in another location as soon as the lifting operation has .been completed.

After the forms have been removed any desired type of decking may be provided on the grid structure and any desired cover slab may be provided over the pockets provided in the margins of the solid concrete structure 21 around a column. In FIG. 8 a removable slab 99, which is shown as being of concrete but which may be of any other desired material, is shown as being mounted on the dividing wall 100 between an opening 25 and the pocket 31, the pocket having a bottom wall 101, while the opening 25 is open at the bottom. The covering slab 99A is shown as extending across the dividing wall 100 which aligns wit-h one of the frame members 22 and thus for-ms a portion thereof, and as Ibeing seated in a groove or recess 102 in the concrete body 21, which has been formed by means of the wedge-like strip 78 that was mounted on the one wall member 38 of the form for the opening 31 shown in FIG. 6.

In FIG. 14 is shown a pair of frame members 22 intersect-ed by a frame member 23 to provide a grid structure having the openings 25 therein and cover slabs 99, 103

and 104 are shown as being mounted over said openings 25 with the end of the cover slab 99, which may be assumed to be a continuation of the slab 99 shown in FIG. 8, in abutting engagement with the slab 103 over the frame member 22 and with the slabs 103 and 104 in butting engagement with each other over the frame member 22.

Instead of providing such an arrangement as shown in FIG. 14 for the cover slabs, the cover slabs 105, 106 and 107 are shown in FIG. 15 as being mounted on frame members 22, which are the same as the frame members 22 except for the fact that grooves 108 have been provided therein in a similar manner to that disclosed for the pocket 31 in FIG. 6. The beveled ends of the cover slabs 105, 106 and 107 are seated in said grooves or recesses 108 with the top surface thereof flush with the top surfaces of the frame members 22". Obviously all the marginal edges of the various cover slabs for the openings in the grid structure in this mounting of the cover slabs will be similarly beveled and all the frame members on which the same would be seated would have similar grooves or recesses 103 therein for receiving the 1 1 beveled edges of the cover slabs. Also, referring to FIG. 8, the top surface of the solid body of concrete 21 would, in such case, be made flush with the top surfaces of the frame members 22".

Instead of providing a form for the pockets or openings that is provided with at wooden wall panels, a metallic form that can be removed upwardly through the opening left in the concrete by the form is shown in FIGS. 16 to 21, inclusive, and FIG. 24. Said form comprises the metal wall sections 109 that have the vertically extending wall portions 110 connected by means of curved wall portions 111, said vertically extending wall portions 110 extending at right angles to each other. Mounted between the adjacent ends of each of the wall sections 109 are wall portions 112 that complete the quadrangular enclosure of the form. Each said angular wall sections 109 is provided with a box-like reinforcement 113 extending up and down along each of the vertical end edges thereof and the members 112 overlap the box-like reinforcements 113 as shown in FIG. 16, said box-like reinforcements projecting slightly beyond the vertical end edges of the wall sections 109. Each of said members 112 is provided with a stitfening means extending vertically of the same, comprising the obliquely extending walls 114 connected by means of a transverse wall portion 115.

Each of the wall portions 116 of the wall sections 109 is provided with a box-like reinforcement 116 along the upper margin thereof, and a similar box-like reinforcement 117 along the lower margin thereof. The top and bottom reinforcements are connected at the curved corner portions 111 of the wall sections by means of plate-like members 118 that are welded to the box- like reinforcements 116 and 117, said box-like reinforcements being welded to the vertical wall members 11) in any suitable manner. The portions 115 of the stiifening members for the intermediate wall forming members 112 are provided with a plurality of keyhole slots in each end thereof, the endmost keyhole slot being indicated by the numeral 119, the intermediate slot of each row by the numeral 120 and the innermost slot by the numeral 121. The inner walls 122 of the stiifening formations 113 are each provided with a similar keyhole slot 123.

Each of the forms is provided with a pair of transversely extending braces 124 and 125. The braces 124 and 125 are the same in construction, but are located somewhat differently in the form, as will be explained below. Each of said transverse braces is provided with a main body portion 126 and an adjustable portion 127 telescopically received within the main body portion 126. The connection between the portions 126 and 127 is shown more in detail in FIG. 21, the member 127 being longitudinally slidably mounted in the member 126 and each of the members being provided with slots for reception of a locking wedge 128. The inner member 127 is provided with a plurality of opposite pairs of slots 139, which are arranged at regular distances along said member 127 so that a wedge 128 may be passed through the single pair of diametrically opposed slots 130 in the lof said members 124 and 125 is provided with a plug 131 xed in each end thereof, as by means of welding, one of said plugs being mounted in the end of the main body portion 126 of each of said braces on the opposite end thereof from that having the slots 130 therein and the other plug 131 being mounted in the unslotted end of the member 127 of said transverse brace. The adjustment of the members 126 and 127 is made such that Athe plugs 131 will properly cooperate with the keyhole slots in the stitfening formations on the members 112. In order for the plugs to cooperate with said keyhole slots, each of said plugs is provided with a head portion 132 and a reduced neck portion 133 that spaces the head portion 132 from the main body portion of the plug 131. The neck portion 133 is of a diameter such that it will t snugly in the smaller portion 134 of the keyhole slot with which it is associated, while the head portion 132 of each of said plugs is of such a size as to readily pass through the enlarged portion 135 of each of said slots. The keyhole slots, it will be noted upon reference to FIG. 17, are reversed so that the lower transverse braces 124 and 125 will be interlocked with the stiffening formations on the members 112 by an upward movement thereof, while the upper bracing members 124 and 125 will be interlocked therewith by a downward movement thereof.

The bracing members 124 have the headed plugs 131 thereof mounted in the uppermost and lowermost keyhole slots 119, while the heads on the plug members 131 of the transverse braces 125 engage in the keyhole slots 120, thus locating the main body portion of the transverse bracing member 125 at the top and bottom of the form closely adjacent the transverse bracing member 124 at said top and bottom. The transverse bracing members 124 provided at the top and bottom of the form, respectively, have the outermost portions thereof in transverse alignment with the top surfaces 136 and the bottom surfaces 137 of the top bracing formations 116 and bottom bracing formations 117 of said wall sections, respectively. The upper brace 124 and the stilfening formations 116 thus serve as supporting means for a top wall panel 138, while the stiffening formations 117 and the bottom transverse brace 124 serve as supporting means for the bottom wall panel 139, Z-shaped brackets being provided on the bottom wall panel members 139 for mounting the bottom wall panels on the form, said brackets 140 being detachably secured by suitable securing elements 141 to the bottom wall panel 139.

Transverse bracing means 142 is provided adjacent the top and bottom of each of the vertical walls of the form at the connection between the angular wall forming sections 109 and the intermediate wall forming members 112, said bracing members 142 being of a U-shaped cross section and having a plurality of headed members 143 extending through the web portion 144 thereof. Each of said headed members 143 has a head 145 on the inner side of the web portion 144 and a head 146 spaced from the head 145 by a narrow neck portion 147. The heads 146 are of such a size that they will readily pass through the enlarged portions 135 of the keyhole slots 121 and through similar enlarged portions of the keyhole slots 123 provided in the vertical stiffening formations 113 in the wall forming sections 109, while the narrow neck portions 147 will fit snugly in the smaller portions of said keyhole slots 123 and 121. It will accordingly be obvious that by inserting the reinforcing member 142 with the heads 146 on the headed members 143 thereof in the enlarged portions of the keyhole slots 121 and 123 and then moving the reinforcing bar 142 downwardly, in the case of the upper reinforcing bar, or upwardly, in the case of the lower reinforcing bar, the reinforcing bars 142 will be interlocked with the wall forming members 112 and 109 in such a manner as to transversely brace the same.

It will be noted upon reference to FIG. 17 that with the transverse bracing members 124 and 125 in position and with the wedges 128 inserted therein to hold the members 124 and 125 in proper adjusted position, the overlapping edge portions 148 of the member 112 will be in engagement with the outer faces of the stiifening formations 113, while the transverse bracing members 142 will be in engagement with the inner faces of said stiifening formations 113, and that the transverse braces 124 and 125 will hold the members 112 from movement toward and away from each other and thus relative to each other.

v The form will thus be held in its proper quadrangular will also be noted upon reference to FIGS. 18 to 21 inclusive, that the vertical walls 11@ of the wall sections 109 have portions 149 that extend vupwardly above the top walls 136 of the longitudinal stiffening members 116 to thus Vprovide means for coniining the top wall panel 13S within the side walls'Y of the form. Similarly, the side walls 110 have portions 150 that extend beyond the bottom walls 137 of the longitudinal stiifening formations 117 to similarly confine the bottom wall panels 139 within the side walls of the form.

Referring to FIG. 22 the form shown therein is shown as having aside wall portion 110' that has a stiifening formation 116 running along the same and has a recess forming projection 151 detachably mounted thereon by means ofa suitable fastening element, such as the bolt 152, the recess forming formation 151 being shown as of a circular character and as hollow, although the particular structure thereof may be varied as may be found desirable. Said member 151 for forming the projection on the form should, however, be of a tapering character such as shown in FIG. 22, to make the withdrawal of the form from the concrete easier. The wall 110 of the form shown in FIG. 22 is the same as the wall 110 of the form previously described, the only diiference in the forms being that the recess forming member 151 is provided thereon. Said recess forming member is mounted in such `a position that the recess 153 provided in the vertical wall 154 of the concrete structure, in which the opening or pocket is formed by means of the form, is located the thickness of a top wall panel 138 below the top surface of the wall portion 154 that has been poured around the form. Accordingly, when it is desired to provide a deck slab 155 on top of a gridslike structure having the wall portions 154 by pouring the same, a supporting panel 156 for the slab that is to be poured can be mounted on the transverse bracing member 124, the plug portion 131 of which may be seated in a recess 153 and a corresponding recess similarly cast in a wall corresponding to the wall 154 transversely across from the recess 153. Obviously a desired number of such recess forming members 151 may be provided on the forms in the desired locations for providing the opposite pairs of recesses 153 for mounting any desired number or arrangement of, transverse bracing members 124 in position on a grid-like structure for supporting panels similar to the panels 156 to be utilized under a poured slab such as the slab 155. After the slab has been poured and the concrete has set, the bracing members 124 can be removed by removing the wedges 128 and telescoping the portions 127 thereof within the portions 126 to remove the headed plugs 131 from the recesses 153, whereupon the Ypanels 156 can be removed downwardly through` the openings 25 in the grid structure.

What I claim is:

1. Inconcreteconstruction a lift slab having rectangular openings therein, Ya solid area of uniform thickness surrounding each of said openings, supporting columns for said slab, means in each of said solid areas of said slab for prestressing, said, area to compress said area toward the center of said opening, comprising a plurality of prestressing members extending across said area on each side of said opening and comprising prestressing members extending perpendicularly to one pair of opposed sides of said.opening and prestressing members extending perpendicularly tothe other pair of opposed sides of said opening, and means for supporting said slab on said column comprising a wide, ilat upwardly facing shoulder on eachrof said columns spaced from the upper end thereof and lreduced portions circular in cross section on said columns extending upwardly from said shoulders andmounted in said opening, horizontal ribs on the walls of said openings projecting toward said reduced portions and high strength concrete filling said openings and extending into engagement with said shoulders and between said ribs.

2. In a building construction, columns having reduced end portions providing shoulders thereon, and a reinforced monolithic concrete structure mounted on said columns comprising an area of solid prestressed concrete of uniform thickness adjacent each column extending horizontally beyond said column in all directions, and each centrally supported on a column, said area having an opening receiving said reduced end portion of said column and a grid-like structure integrally united with and extending between said solid concrete areas, said grid-like structure comprising spaced longitudinally extending and spaced transversely extending prestressed frame members, said longitudinally and transversely extending frame members intersecting and being integrally united to dcne openings extending through said structure between the same, certain of said longitudinally extending and certain of said transversely extending frame members intersecting said solid areas, means for compressing each of said solid areas toward the center of said column receiving opening, comprising prestressing members extending longitudinally within both the longitudinally and transversely extending frame members that intersect said solid area, said prestressing members being embedded in and extending across said solid area on opposite sides of said column receiving opening in alignment with the frame members in which the same extend, and a plurality of other prestressing members embedded in and traversing said solid area on each side of said column receiving opening out of alignment with the frame members, said other prestressing members including prestressing members extending in parallelism to each of the prestressing members aligning with said frame members, and a concrete filling in said column receiving openings between the walls 'thereof and the reduced end portions of said columns.

3. In a building construction, columns having reduced end portions providing shoulders thereon, and a reinf forced monolithic concrete structure mounted on said columns comprising an area of solid prestressed concrete of uniform thickness adjacent each column extending horizontally beyond said column in all directions, and each centrally supported on a column,` and a grid-like structure integrally united with and extending between said solid concrete areas, .said grid-like structure comprising spaced longitudinally extending and spaced transversely extending prestressed frame members, said longitudinally and transversely extending frame members intersecting and being integrally united to deiine openings extending through said structure between the same, certain of said longitudinally extending and certain of said transversely 4extending frame members intersecting said solid areas, each of said solid areas having a central opening therein receiving the reduced end portion of one of said columns, means for compressing each of said solid areas toward the center thereof comprising prestressing members extending longitudinally within both the longitudinally and transversely extending frame members that intersect said solid area, said prestressing members being embedded in and extending across said solid area in alignment with the frame members in which the same extend and on opposite sides of said central opening and including prestressing members extending across said solid area adjacent said central 4opening and prestressing members transversely spaced therefrom and extending across said solid area remote from said central opening, and a plurality of other prestressing members out of alignment with said frame members embedded in said solid area, said other prestressing members including prestressing members extending parallel to and positioned between said prestressing members that are adjacent said central opening and prestressing members that are parallel to and positioned between the prestressing members that are remote from said central opening and the prestressing members that are adjacent said central opening, and a concrete filling in said column receiving openings between the walls thereof and the reduced end portions of said columns.

4. In a building construction, columns having reduced end portions providing shoulders thereon, and a reinforced monolithic concrete structure mounted on said columns comprising an area of solid concrete of uniform thickness adjacent each column extending horizontally beyond said column in all directions and supported on said column, and a grid-like concrete structure integrally united with said solid area comprising a pair of transversely spaced frame members extending away from said said column on each side of said solid area, the frame members extending from opposite sides of said solid area being longitudinally aligned, said structure having open topped pockets between the margins of said solid area and right angularly intersecting members of said grid-like structure, said pockets including pairs of opposed pockets out of alignment with said columns and pairs of opposed pockets in alignment with said columns, all said pockets having bottom walls and having a depth greater than half the thickness of said solid area, each of said solid areas having a central opening therein receiving said reduced end portion of one of said columns, means for compressing each of said solid areas toward the center thereof, comprising prestressing members extending longitudinally within said frame members and embedded in and extending across said solid area adjacent said central opening, prestressing members embedded in and traversing said solid area in parallelism to and between the prestressing members, that are adjacent said central opening and terminating in the pockets that are aligned with said column, and prestressing members embedded in and extending across said solid area in parallelism to the prestressing members that are adjacent said central opening, said last mentioned prestressing members extending between said pockets that are out of alignment with said column and terminating therein, and a concrete filling in said column receiving openings between the walls thereof and the reduced end portions of said columns.

5. In a building construction, columns having reduced end portions providing shoulders thereon, and a reinforced monolithic concrete structure mounted on said columns comprising an area of solid prestressed concrete of uniform thickness adjacent each column extending horizontally beyond said column in all directions, and each centrally supported on a column, and a grid-like structure integrally united with and extending between said solid concrete areas, said grid-like structure comprising spaced longitudinally extending and spaced transversely extending prestressed frame members, said longitudinally and transversely extending frame members intersecting and being integrally united to define openings extending through said structure between the same, certain of said longitudinally extending and certain of said transversely extending frame members intersecting said solid areas, each of said solid areas having a central opening therein receiving said reduced end portion of one of said columns, means for compressing each of Said solid areas toward the center thereof comprising prestressing members extending longitudinally within both the longitudinally and transversely extending frame members that intersect said area, said prestressing members being embedded in and extending across said solid area in alignment with said frame members in which the same extend and on opposite sides of said central opening and other prestressing members embedded in and traversing said solid area in parallelism with each of said prestressing members that align with said frame members, said other prestressing members extending on opposite sides of said central opening and being out of alignment with said frame members, each of said columns having a wide, flat upwardly facing shoulder thereon spaced from the upper end thereof, and a high strength concrete tilling between the walls of said 15 central opening and said reduced upper end portion seated on said shoulder and providing means for connecting said columns and said solid concrete areas to support said structure on said columns.

6. In a building construction, columns, and a reinforced monolithic concrete structure mounted on said columns comprising an area of solid concrete adjacent each column extending horizontally beyond said column in all directions and supported on said column, and a gridlike concrete structure integrally united with said solid area comprising a pair of transversely spaced frame members extending away from said column on each side of said solid area, the frame members extending from opposite sides of said solid area being longitudinally aligned, said structure having open topped pockets at the margins of said solid area, said pockets having a depth greater than half the thickness of said solid area and including pairs of opposed pockets out of alignment with said column and pairs of pockets in alignment with said column, said pockets in alignment with said column each extending between a pair of said frame members, means for compressing each of said solid areas toward the Center thereof, comprising prestressing members extending longitudinally within said frame members and embedded in and extending across said solid area adjacent the center thereof in alignment with the frame members within which the same extend, prestressing members embedded in and traversing said solid area in parallelism to and between said prestressing members that align with said frame members, said last mentioned prestressing members terminating in the pockets that are aligned with said column, and prestressing members embedded in and extending across said solid area between and terminating in said pockets that are out of alignment with said column and extending in parallelism to the prestressing members that align with said frame members, said solid areas having central openings therethrough in alignment with said columns, each of said columns having a reduced upper end portion providing a wide, flat upwardly facing shoulder thereon spaced from the upper end thereof, said reduced upper end portion of said column being mounted in said central opening and a high strength concrete filling between the walls of said central opening and said reduced upper end portion seated on said shoulder and providing means for connecting said columns and said solid concrete areas to support said structure on said columns.

References Cited in the file of this patent UNITED STATES PATENTS 999,286 Wilson Aug. 1, 1911 1,678,504 Glover July 24, 1928 2,075,591 Schuster Mar. 30, 1937 2,230,153 Allbright Jan. 28, 1941 2,315,634 McCall Apr. 6, 1943 2,414,738 Henderson Jan. 21, 1947 2,477,256 Kneas July 26, 1949 2,531,576 McClellan et al. Nov. 28, 1950 2,715,013 Slick Aug. 9, 1955 2,720,017 Youtz Oct. 11, 1955 2,721,369 Burke Oct. 25, 1955 2,775,019 Bemis Dec. 25, 1956 2,783,638 Henderson Mar. 5, 1957 2,852,931 Bonet Sept. 23, 1958 2,929,235 Cheskin Mar. 22, 1960 FOREIGN PATENTS 145,214 Sweden 1954 301,716 Sweden 1954 556,570 Great Britain 1943 589,804 Great Britain 1947

Claims (1)

1. IN CONCRETE CONSTRUCTION A LIFT SLAB HAVING RECTANGULAR OPENINGS THEREIN, A SOLID AREA OF UNIFORM THICKNESS SURROUNDING EACH OF SAID OPENINGS, SUPPORTING COLUMNS FOR SAID SLAB, MEANS IN EACH OF SAID SOLID AREAS OF SAID SLAB FOR PRESTRESSING SAID AREA TO COMPRESS SAID AREA TOWARD THE CENTER OF SAID OPENING, COMPRISING A PLURALITY OF PRESTRESSING MEMBERS EXTENDING ACROSS SAID AREA ON EACH SIDE OF SAID OPENING AND COMPRISING PRESTRESSING MEMBERS EXTENDING PERPENDICULARLY TO ONE PAIR OF OPPOSED SIDES OF SAID OPENING AND PRESTRESSING MEMBERS EXTENDING PERPENDICULARLY TO THE OTHER PAIR OF OPPOSED SIDES OF SAID OPENING, AND MEANS FOR SUPPORTING SAID SLAB ON SAID COLUMN COMPRISING A WIDE, FLAT UPWARDLY FACING SHOULDER ON EACH OF SAID COLUMNS SPACED FROM THE UPPER END THEREOF AND REDUCED PORTIONS CIRCULAR IN CROSS SECTION ON SAID COLUMNS EXTENDING UPWARDLY FROM SAID SHOULDERS AND MOUNTED IN SAID OPENING, HORIZONTAL RIBS ON THE WALLS OF SAID OPENINGS PROJECTING TOWARD SAID REDUCED PORTIONS AND HIGH STRENGTH CONCRETE FILLING SAID OPENINGS AND EXTENDING INTO ENGAGEMENT WITH SAID SHOULDERS AND BETWEEN SAID RIBS.

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