CONCRETE FORMING SYSTEM FOR CURVED WALLS

Abstract: A curved concrete forming structure to provide a 1000 psf system for forming curved walls having a radius in excess of 5'. The structure includes a series of arcuately curved metallic panels (11) secured in stacked side-by-side assembly. The panels (11) are each comprised of a flexible metallic skin plate (12) with spaced vertically extending ribs (13) being positioned on one side along the length of the panel. A pair of vertically spaced arcuately curved angles (22) are provided which angles have identical diameters that correspond to the diameter of the concrete wall to be poured using the concrete forming structure. The curved angles (22) are substantially stiffer and inflexible compared to the flexible skin plate. Fasteners (28) secure the curved angles in abutment with opposite ends of the ribs, and with the flexible skin plate (12) being moved from a flat form and secured by the fasteners in a curved form corresponding in diameter to the arcuately curved angles (22) to form said arcuately curved panel (11), the curved panels being assembled in stacked assembly providing a smooth continuous radius free of chords or flat spots.

Description: The present invention relates to a tension type of a modular concrete form or forming structure. According to the invention, a new and improved curved concrete forming structure is herein disclosed. The structure includes arcuately curved form panels joined together in side-by-side relation as a gang for the formation of curved walls. More specifically, the invention concerns a concrete forming system whereby the panels can be pre-formed at a factory site, if desired, and then shipped to a customer's building site for erection and for the pouring of a curved concrete wall utilizing inside and outside concrete forms which are tied together. By forming the curved steel angles for the form panels at a factory location, it has been found that considerable time can be saved and resultant cost can be reduced because of the reduced amount of labor required to assemble or erect the concrete forming panel. In the past, other types of concrete forming systems have been used and one example is shown in U.S. Patent No. 4,679,763 assigned to Economy Forms Corporation. In this patent the patentee discloses a metal form which is suited for pouring curved walls. The concrete form is actually formed to a desired curvature at the pour site. The actual curvature of the form is established at the pour site. The principal components of the form are sent in a flat form from the manufacturer to the builder and the builder then makes adjustments in the components of the form after the components have been assembled to establish a desired curvature in the form so that a concrete wall can be poured having a predetermined radius. Other techniques for forming curved walls are taught in other existing U.S. Patents including U.S. Patent No. 4,553,729 issued to Frank T. Connors. In this patent, the patentee uses a series of at least three vertically extending rows of concrete form panels which are joined together in side-by-side relation as a gang for use in the formation of straight or curved concrete walls. In this instance, each of the concrete form panels are of a so-called "straight" or "non-curved" construction. Where the radius of a wall is sufficiently large, and the length of the concrete form panels are a small increment of the curvature of the curved wall to be poured, the concrete form panels each function as a chord and co-act in the previously stated environment as a small increment in such a way as to enable a curved concrete wall to be formed. The patentee does not in this patent contemplate the use of curved concrete form panels that are pre-formed to shape in a factory location and then shipped to a job site for installation by a builder in the creation of curved concrete walls. FR-A-792495 discloses a curved concrete forming structure formed by panels in side-by-side assembly wherein each panel includes a flexible metallic skin plate attached to a pair of arcuately curved angles having identical radii of curvature of the concrete wall to be poured using the concrete forming structure. Though this known structure can be easily assembled on a job site, it does not allow concrete walls to be produced which have smooth and continuous radii of curvature. to provide a new and improved curved concrete form structures for forming curved walls to reduce labor costs of assembly whereby the components can be shipped with pre-curved components corresponding to the radii of the concrete walls to be poured. and to provide an improved curved concrete forming structure capable of producing concrete walls having smooth and continuous radii of curvature. In accordance with the invention, there is provided a curved concrete forming structure as defined in the appended claims. According to the invention the panels each include a pair of factory formed curved angles for top and bottom edges of each panel and the radii of the angles correspond to the radii of the concrete wall to be poured. These angles are preferably assembled with steel skin plates in the factory to reduce cost, but angles having different radii can be interchanged in the field if desired while still avoiding the field problems of attempting to adjust curvatures by the techniques disclosed in U.S. Patent No. 4,679,763. According to other improved features of the concrete forming structure, the construction enables a steel skin plate to be flexed to form a desired arc whereby no chording effect will be produced in the poured concrete surface. Unlike convention panel systems that require grinding or rubbing out form joints, the curved concrete forming structure of the invention produces a smooth architectural surface that requires minimal finishing labor. The all-steel concrete forming structure of the invention provides all the strength and versatility needed even though its form face or skin plate is only 4.76 mm (3/16") thick. The curved concrete forming structure has 101.60 mm (4") deep vertical stiffners to provide a 4882.43 kg/m2 (1,000 psf) system that handles any radius 152.40 cm (5') or over, which far exceeds the capabilities of any other known curved concrete forming structure. The 4882.43 kg/m2 (1,000 psf) concrete forming system enables concrete to be poured more quickly in contrast to prior art constructions. According to important features of the invention pre-rolled steel ribs are used to set the radius of each curved form panel. The curved top and bottom ribs are rolled to a curved shape and serve to securely hold the form in a predetermined radius as required. When assembling the pre-rolled steel ribs with the skins, the skin plate is placed in a position facing the ground, and top and bottom ribs are bolted to vertical stiffners on the backside of the steel skin plate. The panels conform precisely to the radius of the ribs and no torque bolts are needed. Should a given job require the pouring of walls with a different arc or tanks of a different radius, the builder can simply order extra sets of top and bottom ribs for the same forms. The panels are adapted to be stacked by bolting the top and bottom ribs adjacent forms with 19.05 mm (3/4") fit-up bolts and nuts so that the panels can be quickly assembled and disassembled after use. Typically a form panel consists of a face material, stiffeners (or cross-members), side rails (or ribs) and end rails (or end bars). To flex any of the known systems in order to achieve a radius, additional exterior structural elements are used i.e., adjustable curved walers, rolled channels or a tension strap. According to the invention, a desired radius can be attained by first rolling one of the required panel components, the side rail (or rib) to the required radius. The assembly of the panel then produces a curved panel which is independent of exterior elements. To change curvature, the panel is disassembled and the rolled component is replaced with a like piece which has been pre-rolled to the new curvature. Re-assembly of the panel then produces a new radius which is structurally inherent in the panel once again. The advantages of this invention over the prior art are as follows : 1. The concrete forming structure of the invention, and specifically its panels, curve to a smooth continuous radius as opposed to a series of 30.48 cm (1'-0") chords or flat spots shown in U.S. Patent No. 4,679,763. 2. The panel of the invention employs a rolled rib to "flex" the panel to shape and to hold it while the US-4,679,763 Patent requires that a job built templet be used to set the radius. Then a bar is flexed along the back of the panel and bolted. The bolts must be torqued to a certain level to keep the radius from changing due to the panel wanting to straighten out. Torqued bolts are at 152.40 mm (6") centers on the panels shown in US-4,679,763 and are used on the panels at 30.48 cm (1'-0") centers and not torqued. 3. Pour pressure for concrete forming structure is 4882.43 kg/m2 (1000 psf) while it is 3905.94 kg/m2 (800 psf) in US-4,679,763. This allows concrete to be poured at a faster rate. 4. The panels of the invention can be manufactured having 91.44 cm (3'-0), 121.92 cm (4'-0), 152.40 cm (5'-0) and 182.88 cm (6'-0) widths while the panels shown in US-4,679,763 are commonly manufactured having only 91.44 cm (3'), 121.92 cm (4') and 152.40 cm (5') widths. 5. The panels of the invention can be manufactured in three lengths, 121.92 cm (4'), 243.84 cm (8') and 365.76 cm (12') while the panels in US-4,679,763 are commonly in 121.92 cm (4') and 365.76 cm (12') widths. 6. The panels of the invention can be rolled to a 152.40cm (5'-0") minimum radius while the panels in US-4,679,763 are commonly manufactured having a 365.76 cm (20'-0") minimum radius. This limits the applications where the structural configuration limits in field applications to a 365.76 cm (20'-0) radius. According to the invention, the steel angle is rolled to the proper radius using a hydraulically/powered pyramid angle/channel roll. Rolling the angle does not change the metallurgical characteristics of the segment. In rolling, the yield point is exceeded to change and maintain the radius but the cross section of the shape is maintained. On all panel sizes from 91.44 cm wide x 121.92 cm long (3'x4') up to 182.88 cm wide x 365.76 cm long (6'x 12'), the same rolled angle is used. Radii range of the rolled angle is from 152.40 cm (5') radius, the smallest, to infinity. Often an angle is rolled to a certain radius, the radius can be modified, by re-rolling the angle, to a different radius should customer wish to have curved angles reshaped. There are hole layout problems that are occasionally encountered when changing the radius over too large a range so the range of the radius change is preferably limited to +/- 152.40 cm (5') except at the minimum radius of 152.40 cm (5'). Other objects and features of the present invention will become more fully apparent in view of the following detailed description taken in conjunction with the accompanying drawings illustrating a preferred embodiment, as follows : Fig. 1 is a perspective view of a curved concrete forming structure embodying important features of the invention; Fig. 2 is an enlarged fragmentary exploded view showing the curved wall in assembled side-by-side relation; Fig. 3 is an enlarged cross sectional view taken on line 3-3 looking in the direction indicated by the arrows as seen in Fig. 2; Fig. 4 is an enlarged fragmentary view illustrating the manner in which a panel can be arcuately curved and further illustrating the method of doing so; Fig. 5 is an enlarged fragmentary view of an angle shown in full and dotted lines illustrating the manner in which the angle is curved in accordance with the invention; Fig. 6 is an enlarged fragmentary cross sectional view taken on the line 6-6 looking in the direction indicated by the arrows as seen in Fig. 1; and Fig. 7 is an enlarged fragmentary perspective view showing the manner in which the formed arcuately curved panels are stacked and carried upon a flat bed truck to a customer for final assembly and use in a curved concrete forming structure. According to the invention it is contemplated that the concrete forming structure 8 shall be of an all steel construction and shall include a curved inner form 9 and a curved outer form 10 which are identical. The forms 9 and 10 are each comprised of a series of arcuately curved panels 11 that are securable in stacked side-by-side assembly horizontally and vertically relative to one another. Each of the panels 11 includes a flexible skin plate 12. U-shaped spaced vertical ribs 13 are positioned along the length of the panel 12 at predetermined intervals and are welded in fixed assembly therewith. In this respect, the U-shaped ribs include connected rib legs 14, 15 and 16 with the end rib legs 14 and 16 being welded to the skin plate 12 at their junctures generally noted at 17 (Figure 4). The flexible steel skin plate preferably has a 4.76 mm (3/16") thickness and is backed by the vertical stiffeners or ribs 13 which are preferably 101.60 mm (4") deep. The U-shaped ribs 13 and the skin plate 12 have essentially the same vertical dimension. The ribs 13 have closure cap plates 18 and 19 at upper and lower ends thereof (Figure 2). These cap plates 18 and 19 are secured in welded assembly with the ribs 13 as indicated at 20 and 21 as seen in Figure 2. Curved angles 22 are formed in a rolling operation from flat stock 23 as shown in Figure 5. Each of the curved panels 11 has a pair of vertically spaced arcuately curved angles 22-22. The angles 22-22 have identical radii corresponding to the radii of the concrete wall to be poured. In the formation of the angle 22 from flat stock to the proper radius, consideration must be given to its physical and its metallurgical characteristics. It is a standard hot rolled angle 22, ASTM A-36, 101.60 x 76.20 x 9.525 mm (4" x 3" x 3/8"), which is rolled by many steel mills. The angle 22 is purchased in standard 1219.2 cm (40'-0") lengths from available suppliers. In buying the standard angle from mills, there are "mill tolerances" which must be accepted constituting variations in leg lengths and thickness. These variations are listed in standard steel handbooks and are accepted by everyone in the steel industry. The present concrete forming system has been constructed to accommodate the mill tolerances. As a standard steel shape, the angle can be used for anything the assignee produces, therefore it is inventoried as raw material. It is then drawn from inventory as required. When an order is received, the angle 22 is drawn from inventory. If the radius is to be 1219.2 cm (40'-0") or larger, the angle is sheared on an angle shear to exact length. Two sets of holes or slots 24 are then punched on a rack punch (which spaces the holes) into horizontal or lapped angle leg 22a and into upright angle leg 22b (Figure 4) and then the angle is rolled on an angle roll. (The lapped angle leg 22a laps the ends of the rib 13 when assembled.) If the radius is less than 1219.2 cm (40'-0") the entire 1219.2 cm (40') length is rolled, burned to exact length, and the holes 24 are punched on the rack punch in accordance with a predetermined hole layout on a templet. It has been found that in the rolling and cutting of the angles 22 above and below 1219.2 cm (40') radius, that there is a greater tendency for the angles to stretch and to distort on the tighter radii. This is the hole layout problem mentioned before. It has been further found that each phase of the manufacture of the angle from inventory to punching and rolling, the angle 22 distorts more at the holes 24 than between the holes. Several years ago preliminary work was conducted involving heavy-duty forms for tunnels and shafts. It was determined customers would buy panels which could go from job to job and the customer could buy ribs to fit the job. This was experimental with changes and refinements being made on each job. These early forms differed from the modern rentable forms herein disclosed in almost every detail with the only common thing being the skin plates were re-used on different radii. The early experimental forms had 6.35 mm (1/4") thick skin plate, large mill-rolled channel stiffeners, and deep burned ribs with welded flanges. The attachment of the ribs to the panels differed from job to job, which is now constant. The early forms were used in shafts and tunnels where the outside surface of the concrete would be formed by the earth. There was no outside forms and no ties between the inside and outside. They were always a compression ring and were not designed to be used in tension. We built the forms to match the job. This made the panels different on every job. According to the invention, the panels are now built, then the panels are fit to the job and they can be used on inside and outside surfaces with internal and over-the-top ties. The new forms here disclosed each use a 4.76 mm (3/16") thick skin plate with bent plate channel stiffeners. Bent plate is used because of the accuracy of its dimensions compared to mill-rolled sections which have tolerances either plus or minus. There is the rolled rib (angle 101.60 x 76.20 x 9.525 mm (4"x3"x3/8")), that attaches to the panel thru the bent plate stiffener and the leg of the angle which pulls the skin plate into the proper radius. The panel is complete with an angle, rolled to the proper radius, and bolted top and bottom. In order to assemble components of the panel together and to each other, rib slots 25 and rib holes 26 are provided (Figure 4). Also, the cover plate 18 is provided with cover plate slots 27 (Figure 4), for securing these components as illustrated in the drawings, bolt and nut fasteners of fastener assemblies 28 have been employed. When the panels are assembled together, the skin plate 12 on each panel co-acts with all other skin plates on adjacent panels to provide a smooth continuous radius free of chords or flat spots in contrast to the teachings of the prior art on other all metal panels such as are shown in U.S. Patent No. 4,679,763. The pre-rolled steel ribs 13 are bolted to the flexible skin plate or panels 12 to lock in the radius when this subassembly is subsequently secured with the curved angles 22-22. The panel can then be shipped pre-assembled from the factory to the job site to simplify job site work (Figure 7). This design eliminates costly templates as required by the prior art. The forms 9 and 10 are provided with top tie/lift brackets 30 and 31. These brackets are suitably bolted to the curved angles 22 as indicated at 32. Tie bolt and nut assemblies 33' secure the forms 9 and 10 in a proper spaced relation relative to one another after they have been secured with opposed lift brackets 30 and 31 (Figure 1). Tie bearing brackets 33 are bolted at 34 to the ribs 13 and the curved angle 22. These brackets 33 are installed at pre-drilled tie locations to accommodate 50 Kip She-bolts or Taper Ties 35. The ties serve to assist in the securement of the inner and outer curved forms 9 and 10 in predetermined spaced relationship to provide the curved concrete forming structure 10 that is adapted to receive concrete to provide a 4882.43 kg/m² (1,000) psf system as previously described. Alternative tie holes 36 are provided to permit versatility in the tie placement when the inner and outer forms 9 and 10 are secured together. Aligner plates 37 are bolted at 38 to the adjacent curved angles 22-22 when the panels 11-11 are stacked on top of one another as shown in Figure 1. These aligner plates 37 serve to insure vertical alignment of the stacked curved panels 11,11 and serve to eliminate the need for walers in most applications. Walkway brackets 39-39 are bolted at 40 to the vertical stiffeners or ribs 13 for safe, positive connection wherever needed. A contractor can simply add lumber to these brackets to meet OSHA (Occupational Safety and Health Administration) scaffolding requirements. One additional difference between the earlier experimental forms for tunnels and shafts and the new form herein disclosed involves the way in which the stacked panels are bolted together. The earlier experimental forms had large burned ribs, had a complicated series of alternate holes in the rib that allowed the rib to be bolted onto the panels, and then when the panels were bolted together, the heads of the bolts would nest into a hole on the adjacent rib. With the new herein disclosed form, the bolts go thru the two ribs plus the plate welded to each end of the stiffeners. The new form has been greatly simplified as compared to the experimental ones that were first developed. After a customer has placed an order for a concrete form structure 8 capable of forming a curved concrete wall having a given radius, the panels can be formed as previously described if not already in stock and a group of the panels 11 are strapped together as indicated at 40 in Figure 7 and shipped on a flat bed truck 41 to the customer for installation to a job site where the curved concrete wall is to be built. As various possible embodiments may be made in the above invention for use for different purposes and as various changes might be made in the embodiments and method above set forth, it is understood that all of the above matters here set forth or shown in the accompanying drawings are to be interpreted as illustrative and not in a limiting sense.

Claims: A curved concrete forming structure (8) to provide a system for forming curved walls having a radius in excess of 152.4 cm (5 feet) and including a series of arcuately curved metallic panels (11) secured in stacked side-by-side assembly, each panel (11) including a flexible metallic skin plate (12), spaced vertically extending ribs (13) positioned along the length of the panel (11), the ribs and the skin plate having essentially the same vertical dimensions, a pair of vertically spaced arcuately curved angles (22) having identical radii of curvature corresponding to the radii of curvature of the concrete wall to be poured using the concrete forming structure, the curved angles (22) being substantially stiffer and inflexible compared to the flexible skin plate, characterized by the curved angles having corners positioned in abutment with opposite ends of the ribs, the corners of said angles being remotely spaced from said skin plate, the ribs (13) having oversized fastener rib holes (25), the curved angles (22) each having a pair of legs, the legs having fastener leg holes (24) aligned with the oversized fastener rib holes (25), and fasteners (28) cooperable in secured relation therewith such that as the fasteners are secured, the flexible skin plate (12) is moved by said fasteners from a flat form to a curved form corresponding in curvature to the arcuately curved angles (22) to form the arcuately curved panel (11), said angles each having a horizontal leg with an outermost end remote from said corner associated therewith and with said outermost end being positioned for smooth edgewise engagement against said skin plate when secured by said fasteners (28), the curved panels (11) when assembled in stacked assembly providing a smooth, continuous radius free of chords of flat spots. The curved concrete forming structure of claim 1, further characterized by comprising a first set of bolt and nut fasteners (28) cooperable with the aligned holes (24, 25) securing the panels together when stocked in superimposed assembly together. The curved concrete forming structure of claim 1 or 2, further characterized by including confronting inner and outer curved forms (9, 10), each comprised of a series of stacked and side-by-side located groups of the arcuately curved metallic panels (11), tie bearing brackets (33) bolted to the panels on the confronting inner and outer curved forms, and ties (35) extending through the panels on the confronting inner and outer curved forms (9, 10) and retainingly engaged with the tie bearing brackets (35) securing the confronting forms in predetermined spaced gap relation. The curved concrete forming structure of claim 1, 2 or 3, further characterized by each of the ribs (13) being of a U-shaped metallic construction and having one rib leg welded to the flexible skin plate, cap plates (18, 19) welded to opposite ends of the ribs, the curved angles having angle legs (22a, 22b) secured on one side of each of the cap plates by the fasteners. The curved concrete forming structure according to any of claims 1 to 4, further characterized by the flexible skin plate (12) being comprised of steel and having a thickness of about 4.762 mm (3/16") and by the curved angles each being comprised of hot rolled steel having a thickness of about 9.525 mm (3/8"). The curved concrete forming structure according to any of claims 1 to 5, further characterized by aligner plates (37) being bolted (38) to the curved angles on the adjoining stacked panels securing the stacked panels in vertical alignment. The curved concrete forming structure according to any of claims 1 to 6, characterized by the ribs and the skin plate being essentially of the same vertical dimensions, the curved angles being substantially stiffer and inflexible compared to the flexible skin plate. The curved concrete forming structure according to any of claims 1 to 7, further characterized by tie bearing brackets (33) being bolted to the panels on the confronting inner and outer curved forms, and ties (35) extending through the panels on the confronting inner and outer curved forms and retainingly engaged with the tie bearing brackets securing the confronting forms in predetermined spaced gap relation.

Inventors: LEHMANN, LARRY W.
Applicants: SYMONS CORPORATION
Application year: 1988
Main classification: E04G11
IPC codes: E04G11