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This application claims priority to U.S. Provisional Application No. 60/896,055, entitled “Precast Arch-Shaped Overfilled Structure”, filed Mar. 21, 2007, the details of which are incorporated by reference as if fully set forth herein.
The present application relates generally to open bottom precast concrete arch structures of the type to be buried in the ground to form an overfilled structure, and more specifically to such a precast arch structure having a unique configuration that facilitates high overfill depths.
Various configurations for precast concrete arch structure have been used. It would be desirous to provide a configuration that is both adapted to high overfill applications and is also cost effective.
In one aspect, an overfilled structure includes a footing and first and second precast concrete bridge elements that have upper ends connected by a crown joint. The precast concrete bridge elements form an open bottom arch structure that is supported on the footing. The footing extends the full span of the lower end of the arch structure and includes spaced apart upwardly facing recesses to receive the lower ends of the precast concrete bridge elements. The precast bridge elements are sized and shaped such that the resulting arch structure has an upper portion that is formed by a first half-ellipse shape and a lower portion formed by part of a second half-ellipse shape. The two half-ellipse shapes meet at an elevation along the rise of the arch structure, and such elevation defines the largest span of the arch structure. The resulting arch structure includes lower ends that come back inward toward each other, such that the span at the bottom of the arch structure is less than the largest span.
In another aspect, an arch system for use in forming an overfilled structure includes at least one footing and at least one precast concrete bridge element forming an open bottom arch structure that is supported on the at least one footing. The arch structure has an upper portion and a lower portion that meet at an elevation along the rise of the arch structure, and such elevation defines the largest span of the arch structure. The arch structure includes lower ends that come back inward toward each other, such that the span at the bottom of the arch structure is less than the largest span.
The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
FIG. 1 is a front view of an embodiment of an arch structure;
FIG. 2 is a section view of the arch structure of FIG. 1;
FIG. 3 is a detail, section view of an embodiment of a crown joint of the arch structure of FIG. 1;
FIG. 4 is a detail view of the crown joint of FIG. 3 with a seal;
FIG. 5 is a front view of an embodiment of a footing for use with the arch structure of FIG. 1;
FIG. 6 is a top, section view of an embodiment of a wingwall and headwall connection for use with the arch structure of FIG. 1;
FIG. 7 illustrates an embodiment of an overfilled structure built using the arch structure of FIG. 1; and
FIG. 8 is a schematic elevation of an arch structure.
Referring to FIGS. 1 and 2, an overfilled arch structure 10 includes a footing 12 that supports two precast concrete bridge elements 14 and 16. The precast concrete bridge elements 14 and 16 have respective upper ends 18 and 20 that are connected by a joint 22 at the crown of the arch structure 10. Together, the two precast concrete bridge elements 14 and 16 form an open bottom arch structure that is supported on the footing 12 in that lower ends 24 and 26 of the precast concrete bridge elements 14 and 16 opposite the upper ends 18 and 20 are spaced-apart from each other rather than being joined like the upper ends.
The lower ends 24 and 26 are located in spaced-apart, upwardly facing recessed portions 28 and 30 of the footing 12. The footing 12 spans the lower end of the arch structure 10 between the lower ends 24 and 26 of the precast concrete bridge elements 14 and 16 and includes two end portions 34 and 36 on either side of middle portion 38. The end portions 34 and 36 extend upwardly to the recessed portions 28 and 30 at an angle θ relative to the horizontal. The lower ends 24 and 26 are supported at an elevation above an upper surface 40 of the middle portion 38. The footing 12 may be precast or cast-in-place. Earthen material around the footing may be suitably compacted and configured to support the footing. The footing has a generally inverted polygonal approximation to an arch shape (but could be a true arch shape) and serves to carry water, or it can be filled up (with gravel etc.) and form the support of a carriageway.
Referring to FIG. 2, the precast concrete bridge elements 14 and 16 are shaped such that the resulting arch structure 10 has an upper portion 42 that is formed by a half ellipse and a lower portion 44 that is formed by part of a second half ellipse. The two half ellipse shapes meet at an elevation represented by dashed line 46 along the rise of the arch structure 10, and such elevation defines the largest span S1 of the arch structure. The resulting arch shape includes lower portions 48 and 50 that curve back inward toward each other such that the span S2 at the bottom of the arch structure 10 is less than the largest span S1.
In some embodiments, the resulting arch structure 10 has a largest span S1 of between about 18 feet and 24 feet, a rise R of between about 25 feet and 30 feet, a clearance C of between about 27 feet and 31 feet and a bottom span S2 of between about 15 feet and 18 feet (e.g., a largest span S1 of around 21 to 22 feet, a rise R of around 26.5 to 27.5 feet and a bottom span S2 of around 16 to 17 feet). The wall thickness T of the precast concrete bridge elements 14 and 16 is between about 1.1 and 1.5 feet. The largest span S1 may be at an elevation of between about nine and 13 feet from the lower end of the arch structure 10.
In some embodiments, a ratio of the largest span S1 to the rise R is about 75 to 85 percent, a ratio of the rise R to the bottom span S2 is about 165 to 175 percent and a ratio of the largest span S1 to the bottom span S2 is about 130 to 140 percent. A ratio of the height H of the largest span S1 to the rise R is about 35 to 45 percent.
In a typical application the arch system may be overfilled with any suitable material, the depth of which may vary. The overfill material may be compacted as necessary. In one example the overfill depth from the top of the arch to ground level may be between about 90 and 130 feet (e.g., between 105 and 115 feet).
Referring to FIG. 3, the joint 22 between the precast concrete bridge elements 14 and 16 is formed by a threaded rod or bolt or bolt pair 52 that extends through both of the concrete bridge elements tying them together at the crown of the arch structure 10. The bolt 52 extends through openings 54 and 56 that are aligned to allow the bolt to pass therethrough. A sleeve 58 (e.g., formed of PVC) may be located in the openings and about the bolt 52. Notches 60 and 62 are formed in the precast concrete bridge elements 14 and 16 to facilitate placement of the bolt 52 in the openings 54 and 56. Once the bolt 52 is positioned in the openings 54 and 56 and secured therein, grout or other filler substance may be used to fill the notches 60 and 62.
As can be seen by FIG. 3, upper ends 18 and 20 of the precast concrete bridge elements 14 and 16 include a feature facilitating the joining and alignment of the precast concrete bridge elements. In this embodiment, the upper end 18 includes a rib 64 that is sized to fit in a groove 66 of upper end 20. The bolt 52 passes through the rib 64 and the groove 66. Referring to FIG. 4, the joint 22 may be sealed using a wrap 68 or other suitable sealing material.
Referring to FIG. 5, the footing 12 includes the spaced-apart, upwardly facing recessed portions 28 and 30 that receive the lower ends 24 and 26 of the precast concrete bridge elements 14 and 16. Wedges 70 and 72 (e.g., formed of hardwood) may be used to locate the lower ends 24 and 26 and fill gaps within the recessed portions 28 and 30 once the lower ends are located therein. Grout may also be placed in the recessed portions 28 and 30. Shims 74 may be used to level the precast concrete bridge elements 14 and 16.
Referring back to FIG. 1, a headwall 76 and wingwalls 78 and 80 are connected to one or both ends of the arch structure 10. A precast curb 82 (represented by dashed lines) may also provided in the precast concrete bridge elements 14 and 16 that are located at the ends of the structure to provide support for walls 76, 78 and 80. Referring to FIG. 6, the headwall 76 and wingwalls 78 and 80 are connected by a dowel bar splicer system 84.
As shown by FIG. 7, the arch structures 10 can be aligned to form various structures, such as bridges. In some embodiments, the arch structures 10 may be configured such that, once aligned, they form a curve portion 86 or a straight portion 88 as required at the particular installation.
FIG. 8 shows a schematic side elevation of an arch structure 100 in isolation with rise R, largest span S1, height H to largest span and bottom span S2 shown.
In an alternative embodiment, the upper part of the structure may be a half-ellipse shape and the lower legs of the structure may be in the shape of a series of arc segments with ends tangentially connected. In still another embodiment, the upper part of the structure may be formed by a shape in the form of a series of arc segments with ends tangentially connected, and the lower legs of the structure may be in the shape of a series of arc segments with ends tangentially connected. In either case, the largest span will be defined where the tangent line of the overall structure is vertical.
A number of detailed embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, multiple units may be connected together end-to-end to form an elongated bridge/tunnel to be overfilled. Adjacent sections may include joint seals as appropriate. End walls may also be provided for the elongated bridge/tunnel. Size and location of rebar within the precast elements may be varied according to expected overfill height and/or other requirements for a given installation. Accordingly, other embodiments are within the scope of the claims.