System and method for reinforced concrete construction

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BACKGROUND OF THE INVENTION

The invention relates to the construction of the structural framework of a building or other structure of reinforced concrete, and particularly to column and beam forms which would become integral parts of the structural framework and to methods of employing such forms.

In the past, there have been many systems for fabricating structural frameworks, including the use of steel frameworks for industrial type buildings because they are comparatively inexpensive to build and can be assembled rapidly. Such buildings, however, face a serious problem in their relatively low fire ratings, since a fire can cause rapid expansion of steel columns and beams, resulting in twisting and warping which may result in the necessity of complete replacement of the building.

Reinforced concrete offers substantial advantages over steel from the standpoint of fire rating, and many specially designed concrete forms for such use have been proposed in the past. Some such forms are made of construction grade lumber and plywood which must be assembled into predetermined shapes for receiving poured concrete. Forms which are to be used multiple times may also be made from metals having the necessary rigidity and strength to support the weight of the fluid concrete during its pouring and initial stages of curing. These forms are made in many types and shapes, and are provided with a variety of means for locking them in position for the pour and unlocking to facilitate their removal after the concrete is sufficiently hardened.

Removable forms in general can be characterized as relatively expensive in terms of both capital cost and use, having in mind that they must be cleaned or otherwise reconditioned after each use, as well as transported from site to site. Indeed, their initial cost is usually such that it can be justified only on the basis of multiple uses, thereby reducing their per building cost.

SUMMARY OF THE INVENTION

The major objective of the present invention is the provision of a system and method for use in building construction which will provide a structural framework of metal-reinforced concrete columns and beams permanently encased in the sheet metal forms wherein the concrete is poured. A more specific objective is the provision of such a system and method wherein the metal forms impart a finished appearance to the surfaces of the columns and beams which are exposed in the completed building and thereby contribute to the ultimate appearance of the building at minimal cost.

In accordance with the invention, the structural framework of a building or other structure, e.g. a bridge, is composed initially of sheet metal column forms which are erected on a concrete slab or other foundation and are interconnected with and by complementary sheet metal beam forms. Prior to the pouring of any concrete, and preferably prior to erection of the forms, each form is provided with an appropriate internally located skeleton of steel reinforcing bars, and the bars within each pair of interconnected forms are spliced together by additional bar members which bridge the joints between connected forms.

In the practice of the invention, the column and beam forms, along with the appropriate internal reinforcing skeletons, are erected on a concrete slab or other foundation at least to the level of the second story of the building, or the roof level for a one-story building. All the concrete for that much of the building framework may then be poured at a single time, filling the erected column forms and then the beam forms which have been mounted thereon. If the building is to have two or more floors, the column forms may be initially of the same height as the finished building, or single story column forms can be erected for each separate story on top of the forms already in place which have been filled with concrete, together with the necessary additional beam forms for each added story. The same procedure of pouring concrete for all column and beam forms in each successive story may then be followed until the entire building framework has been poured.

One of the major advantages provided by the invention is that the individual column and beam forms can be fabricated and provided with the proper internal reinforcing skeletons by factory labor, so that they can be shipped to the building site completely ready for erection. Thus the only stage in the fabrication of the building framework which is subject to weather conditions is the actual erection of the forms and the pouring of the concrete. Due to the construction of the individual forms in accordance with the invention, their erection and interconnection at the site require a minor fraction of the time required for conventional removable forms, which must be individually assembled on site.

A particularly important characteristic of the invention lies in the technique by which the invention assures that the finished columns and beams will have properly flat sides notwithstanding that the forms in which the concrete is poured are fabricated of relatively lightweight and flexible sheet metal. This result is accomplished in accordance with the invention by initially compressing opposed sides of the forms to concave curvatures by yieldable forces calculated to permit the initially compressed sides of the form to return to essentially flat condition in response to the hydrostatic pressure of fluid concrete filling them to the proper level. More specifically, opposed sides of the forms are compressed by waler means in combination with a plurality of spaced steel bands which are stretched to predetermined tension values calculated to counterbalance the hydrostatic pressure of fluid concrete filling the form only when the initially concave sides of the form have return to substantially flat condition.

While the individual forms with which the invention is practiced will result in greater cost per building than removable forms, because the forms of the invention remain as parts of the building as compared with the use of removable forms for multiple buildings, this capital cost is easily offset by savings in labor costs, and especially in time on the job.

For example, removable forms of conventional designs must be assembled from individual pieces on the job, and after the concrete is poured, they must remain in place for a prescribed period, especially on the under sides of the beams, to assure development of adequate strength in the concrete through its curing process. The shoring must also remain during the same period, and thereafter the forms must be dismantled and prepared for reuse. In contrast, because the forms of the invention remain as parts of the building, after the columns and beams for one floor have been poured, the forms for the next floor can be erected and poured as early as the next day.

Another important advantage of the invention is that the permanent metal forms impart such strength to the beams before the concrete has cured that much less shoring is needed than with conventional removable forms, and the shoring which is required can be removed much sooner than with conventional removable forms. This again results in considerable savings in both time and money, including reduction in the capital cost represented by the much smaller quantity of shoring required in the practice of the invention.

An additional advantage of the invention lies in its versatility in terms of the dimensions and shapes of beams with which it can be practiced, as will be more readily appreciated from the examples of special beam shapes which are described hereinafter.

In the finished structure, substantial areas of the outside surfaces of both the column and beam forms will remain exposed, and the different ways in which such exposed surfaces can be finished provide another aspect of the versatility of the invention. If, for example, the forms are made of inexpensive material such as cold rolled sheet steel, they can be painted as desired. Alternatively, they can be made of sheet metals havng naturally decorative surfaces, such as stainless steel or anodized aluminum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway perspective view of a portion of two column forms and a beam form in accordance with the present invention;

FIG. 2 is a cutaway perspective view of a portion of a column form;

FIG. 3 is a perspective view of a group of interconnected column and beam forms;

FIG. 4 is a sectional view of the connection between a vertical column and a poured concrete floor;

FIG. 5 is a cutaway perspective view of a portion of a corner connection between a column form and two horizontal beam forms;

FIG. 6 is a cutaway perspective view of a T-joint between two beam forms on a supporting column form;

FIG. 7 is a side sectional view of a packaged column form;

FIG. 8 is a fragmentary elevation of column and beam forms in accordance with the invention in a multi-story arrangement;

FIG. 9 is an elevation of the column forms in FIG. 8 looking from right to left in FIG. 8;

FIG. 10 is a fragmentary view partially in section on the line 10--10 in FIG. 11;

FIG. 11 is a fragmentary section on the line 11--11 in each of FIGS. 8 and 10;

FIG. 12 is a section on the line 12--12 in FIG. 11;

FIG. 13 is a diagrammatic sectional view illustrating the compression of one of the beam forms of the invention to concave curvatures of its opposed side walls prior to being filled with concrete;

FIG. 14 is a view similar to FIG. 13 illustrating the corresponding initial compression of the opposed side walls of a column form;

FIG. 15 is a view similar to FIG. 14 showing a modified arrangement;

FIG. 16 is a fragmentary view taken at right angles to FIG. 15;

FIG. 17 is a diagrammatic cross section illustrating a column form in accordance with the invention designed to provide a chase for piping, wiring, or the like;

FIG. 18 is a diagrammatic cross section showing another modified column form in accordance with the invention to conceal form joints;

FIG. 19 is a diagrammatic sectional view showing a beam form in accordance with the invention with built-in drip strip along a window lintel;

FIG. 20 is a diagrammatic cross sectional view showing a frustoconical beam form in accordance with the invention;

FIG. 21 is a diagrammatic cross sectional view showing another construction of column form in accordance with the invention; and

FIG. 22-23 are diagrammatic cross sectional views showing other beam forms in varied sizes in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 4 illustrate a portion of a column and beam structural framework anchored to a poured concrete foundation floor 10 by means of protruding reinforced steel bars 11 entering into the concrete within a column form 12. The form 12 telescopes over a foot anchor or shoe 13 having four sides and a plurality of slots 14 therein, allowing the form 12 to be adjusted for leveling the horizontal beam forms 15. Once levelled, the form 12 is bolted to the shoe 13 by screws 16 threaded into the slots 14 to lock the form 12 in predetermined position on the shoe 13.

The column form 12 has a plurality of opposed openings for receiving a plurality of bolts 17 threadedly locked into bracing rods 18 which are generally positioned with two pairs adjacent each other within the form 12. Each pair of rods 18 braces one pair of opposite side walls of the form, which is shown as comprising a pair of U-shaped side members 20 and a pair of sheet members 21 held together by sheet metal screws, welding, or by bolts 17 and bracing rods 18.

A plurality of concrete reinforcing steel bars 22 are attached to the bracing rods 18, by means of wire ties 23, to maintain the bars 22 in predetermined positions spaced inwardly of the inner surfaces of the form 12. Bars 22 ae similarly attached to similar reinforcing bars 24 projecting from adjacent beam forms 15, and also to the base anchoring bars 11, as shown in FIGS. 1, 5 and 6.

The horizontal beam form 15 is similar to the column forms 12 except that it comprises a U-shaped member 25 forming three side walls and inturned flanges 26 leaving an open side or slot 27. A plurality of spaced metal straps 28 are secured by welding or screws to the flanges 26 to hold the upper ends of the beam form side walls in fixed relation defining the open slot 27 through which concrete 30 can be poured from a chute 32 or other supply source. FIG. 1 shows the beam form 15 as of square section, but it will usually be rectangular and of substantially greater depth than width, e.g. 24 inches deep and 12 inches wide.

The rods 18 within both the column and beam forms may have internal threads in each tip thereof for a bolt 17, or may have a protruding end portion with external threads for threadedly attaching each end through the openings in the opposed form walls for further strengthening the column and beam forms 12 and 15 and for precisely locating and holding the reinforcing steel bars 22 and 24. Thus the bracing rods 18 form additional reinforcing within each poured concrete column and beam while the concrete is setting. Thereafter, the nuts or bolts by which the rods 18 are attached to the walls can be quickly removed, and the same threaded portions of the rods 18 used to attach steel or other wall panels to the inside and outside of the building structure. The completed poured concrete columns and beams are left with the inexpensive metal forms 12 and 15 surrounding them.

The resulting framework, which provides structural members of reinforced concrete with leave-in-place thin metal walls, substantially increases the fire rating of the completed building. Inasmuch as the walls have concrete columns and beams, they can stand long periods of high temperature, for instance, a four-hour rating, without being damaged or warped as with steel columns and beams used in steel buildings, and thereby promote the rapid repair of a fire damaged building and a reduced insurance ratee for the owner of the building.

FIG. 2 more clearly illustrates the use of the bracing rods 18 to support the reinforcing bars 22, which may be placed in each corner defined by intersecting bracing rods 18 and wrapped with wire 23 to hold them in place. This advantageously spaces the reinforcing bars 24 a predetermined distance within the forms 12 to promote the desired fire rating, which may be determined by the distance the bars are spaced interiorly of the outer surfaces of the reinforced concrete.

FIG. 4 more clearly illustrates the mounting of a column form 12 on a foundation 10 with the aid of the steel dowels 11 which are connected to the vertically extending reinforcing bars 22 utilizing a plurality of wire stirrups 40 for holding the unit in position until the concrete 30 has set to form the column. The rods 18 can be seen in this view as well as the shoe 13, which is secured by screws or other attaching members 41 to the foundation 10 and held by screws 16 passing through openings in the wall 21 to hold the form 12 in place. Alternatively, the screws 16 and slots 14 can be dispensed with, and each form 12 can be properly levelled by shims until the concrete 30 has been poured and set.

FIG. 5 illustrates the connection of a column form 12 to a pair of beam forms 15 in a miter joint 43 held with a small angle member 44 which may be screwed or welded in place at the miter joint 43. The vertical reinforcing bars 22 are connected to the horizontal reinforcing bars 24 by means of wire ties 23. The end of the beam form 15 may have cutawy portions 45 to provide a connection with the column form 12 so that when fluid concrete is poured into the open slot 27 of the beam form 15, it can flow into the vertical column forms 12, encapsulating the reinforcing bars 22 and 24 as well as the bracing rods 18 to the level of the flanges 26 of the beam forms 15.

FIG. 6 is a perspective view illustrating a T-joint in which a pair of beam forms 15 are connected. with joint connecting members 50, each having a cutaway portion 51 providing an opening into the vertical column form 12. Horizontal reinforcing bars 24 and vertical reinforcing rods 22 are again connected with wire 23 to each other, and are also held in place by the bracing rods 18 which are not illustrated in this view.

FIG. 7 shows a column form packaged for shipment with corrugated board members 60 covering each end of the form and a plurality of corrugated board straps 61 wrapped around the form. The straps 61 have steel straps 62 fastened therearound to hold the corrugated board in place. This packaging serves to prevent the forms 12 from getting scratched, and also provides additional reinforcing against the static pressure of the concrete when the form is filled. Thus straps 62 would not be removed until the columns were poured and set.

The invention is utilized by erection of each of the vertical column forms 12 and attachment of the beam forms 15 to each other and to their respective reinforcing bars 22 and 24. Once a complete system is set up, concrete is poured to fill the column forms 12 and the beam forms 15, encapsulating the reinforcing bars 22 and 24 and the bracing rods 18. After the concrete has set, the bolts 17 can be removed from the threaded openings in the rods 18, which are encapsulated in concrete, and the bolts 17 may be used to attached wall panels to the completed columns and beams. It is also contemplated that the columns may form pilasters on the interior of the building and can have their surfaces enhanced by the attachment of elongated angle iron members to the threaded ends of the rods 18, or by welding to the sides of the forms, for attaching wall paneling to cover the columns.

FIG. 3 illustrates the use of a plurality of column forms 12 connected to a plurality of horizontal beam forms 15 to define the structural framework of a building. After the interconnected forms have been filled with concrete which has had time to set, the resulting framework is ready for the attachment of wall panels and a roof. It should, however, be clear that multi-storied buildings can be formed by pouring the first level, mounting additional forms thereon for the pouring of the next level in the same manner, and so forth.

FIG. 8 illustrates the application of the invention to a multi-story building on a foundation slab 100, utilizing column forms 101 and 102, and beam forms 105 and 106. In FIG. 8, the column forms 101 for the second and third floors are shown as of larger section than the column forms 102 for the third floor, e.g. 2 ft. square for the lower floors and 1 ft. square for the roof. The beam forms 105 and 106 are shown as of the same dimensions for all floors, e.g. 1 ft. thick and 2 ft. high.

Except for the differences in dimensions, the forms 101 and 102 are of the same configuration, each being composed of a pair of U-shaped members 110 of steel sheet of suitable quality, e.g. 12-gauge, with inturned flanges 111 along both edges. The form is completed by assembling the members 110 with their flange portions 111 in abutting relation, and then welding the assembled members together at appropriately spaced intervals.

The beam forms 105 are formed of two sheet metal members 115 of generally L-shaped section, each of which is also provided with flanges 116 and 117 as shown extending at right angles inwardly from the edges of the L-shaped portion. The form 105 is assembled by welding the two L-shaped members 115 together along the abutting flanges 116, and by welding or bolting connecting straps 118 to the opposed flanges 117 at spaced intervals leaving slot openings between the flanges 117.

The beam forms 106 are of somewhat different construction from the beam forms 105 in order to adapt them to use with a precast floor slab 120 (FIG. 10) of conventional construction forming a support for a topping layer 121 of reinforced concrete which is poured thereon in place and anchored to the adjacent concrete beam by right angled reinforcing bars 123. For this purpose, each beam form 106 includes one L-shaped component member 115 and a second L-shaped component member 125 which is of greater height than the member 115 by an amount substantially equal to the vertical thickness of the completed slab 120 with its concrete topping 121. The member 125 includes flanges 126 and 127 which correspond to the flanges 116 and 117, and which are connected by inclined straps 128 corresponding in spacing and function with the straps 118.

The beam forms 106 are utilized to form the spandrel beams along the exterior of the building framework as shown in FIG. 10, and the beam forms 105 are utilized interiorly of the framework, as shown in FIG. 11. The flange 117 along the inner side of each form 106 defines a shelf for receiving and supporting the edge of the slab 120. Then when the concrete topping 121 is subsequently poured, the portion of the L-shaped component 125 above the level of flange 117 forms a dam enclosing the space between itself and the edge of the slab 120 which will also be filled with concrete.

The column forms 101 are shown as of a height reaching to the level of the slab for the third floor of the building. Each of these forms which is located on the exterior of the structural framework has rectangular cut-outs 130 at the appropriate levels and locations in its faces to receive the beam forms 105 and 106 for the second floor of the buildings, and similarly located rectangular slots 131 at its upper end which will match the beam forms 105 and 106 for the third floor. The column forms 102 are provided with similar slots at their upper end