Open bottom fiber reinforced precast concrete arch unit

Abstract

A one-piece open bottom fiber reinforced precast concrete arch unit is buried in compacted soil and has an arcuate top wall portion integrally connecting arcuate side wall portions. The fiber reinforced wall portions have a configuration which provides ductility and flexure strength for effectively utilizing the surrounding compacted soil to resist deflection of the unit in response to a load and to redistribute stresses in the unit. Each of the side wall portions of the unit has a reducing wall thickness towards its bottom and has a radius of curvature greater than the rise of the unit and at least twice the radius of curvature of the top wall portion. Bands of continuous fibers may be attached by adhesive resin to the outer surface of the arcuate side and top wall portions of the unit near opposite ends of the unit to increase the load carrying capacity of the unit.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to open bottom precast concrete arch units of the type constructed to be buried in the ground or soil and as generally disclosed, for example in U.S. Pat. No. 3,482,406, No. 4,558,969, No. 5,281,053, No. 6,161,342, No. 6,205,717, No. 6,406,220, No. 6,408,581 and No. 6,640,505. Such precast concrete arch units are produced in various sizes and spans, for example, by Bebotech Corporation in Middletown, Ohio who offers part elliptical and part circular shapes and as a single or one-piece casting or as a twin or two-piece casting with spans from 12 feet to 84 feet. In such precast concrete arch units, it is common to have a wall thickness of 8 to 14 inches and to have embedded in the concrete walls steel reinforcing bars or rods which may be in the form of a mesh. The steel reinforcing bars or rods provide the concrete arch unit with sufficient strength to support the soil above the arch unit and any load which may be applied to ...

AI Technical Summary

Benefits of technology

[0003] The present invention is directed to an improved one-piece open bottom precast concrete arch unit which is designed for underground use and to be buried in compacted soil. The arch unit of the invention provides all of the desirable features mentioned above and is effective to utilize the surrounding soil mass as a resistance support for the arch unit and thereby minimize the production cost of the arch unit by substantially reducing the volume and weight of concrete and the weight of reinforcement within the arch unit. The arch unit of the invention eliminates the use of steel reinforcing bars or rods and thus eliminates the labor required to position steel reinforcement bars or rods between the forms which are used to precast the arch unit.

[0004] In accordance with one embodiment of the invention, a one-piece arch unit is precast with opposite arcuate side wall portions integrally connected by an arcuate top wall portion. The side wall portions have a radius of curvature substantially greater than the radius of curvature of the top wall section, and the radius of curvature of the top wall portion is substantially less than the vertical height or rise of the arch unit and also substantially less than the span of the arch unit between the bottoms of the side wall portions. The precast concrete arch unit of the invention is reinforced with a predetermined volume of reinforcing fibers such as steel fibers which provide the arch unit with substantial ductility and flexure strength in order to utilize the resistance forces produced by the compacted soil mass surrounding the arch unit. Utilizing the compacted soil to resist bulging of the side wall portions of the arch unit enables a substantial load to be supported by the top wall portion.

[0005] The interaction between the arch unit of the invention with the surrounding soil in combination with the fiber reinforcement not only provides for eliminating steel reinforcement bars and rods, but also provides for substantially reducing the wall thickness of the precast concrete arch unit. The reduction in the wall thickness of the arch unit further increases the ductility of the unit and facilitates the transfer of loads and stresses within the arch unit. Additional economies are achieved by varying the wall thickness of the side wall portions to proportion the strength provided by the arch unit to the applied loads and stresses for the varying conditions around the perimeter of the arch unit. Tapering of the side wall portions also reduces the volume of concrete required to cast the arch unit, thereby further reducing the weight and production cost of the arch unit. In a modification of the invention, one or more elongated bands of longitudinally extending reinforcing fibers are connected or bonded to peripheral or arcuate sections of the top and side wall portions.

Problems solved by technology

While an arch unit may be precasted in two or more sections to facilitate transportation, substantial additional time and labor is required to assemble and connect the sections at the site where the arch units are installed.

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