The present invention relates to the general art of structural, bridge and geotechnical engineering, and to the particular field of overfilled arch and/or cut-and-cover structures.
The present application incorporates by reference the disclosure of co-pending patent application titled “Top Arch Overfilled System” filed by the same inventor on Mar. 22, 2002.
Frequently, overfilled arch structures formed of precast or cast-in-place reinforced concrete are used in the case of bridges to support one pathway over a second pathway, which can be a waterway, a traffic route, or in the case of other structures, a storage space of the like. The terms “overfilled arch” or “overfilled bridge” will be understood from the teaching of the present disclosure, and in general as used herein, an overfilled bridge or an overfilled arch is a bridge formed of arch elements that rest on the ground or on a foundation and has soil or the like resting thereon and thereabout to support and stabilize the structure and in the case of a bridge provide the surface of the second pathway. The arch form is generally arcuate such as cylindrical in circumferential shape, and in particular a prolate shape; however, other shapes can be used. Examples of overfilled bridges are disclosed in U.S. Pat. Nos. 3,482,406 and 4,458,457, the disclosures of which are incorporated herein by reference.
Presently, reinforced concrete overfilled arches are usually constructed by either casting the arch in place or placing precast elements. These arched structures rest on prepared foundations at the bottom of both sides of the arch. The fill material, at the sides of the arch (backfill material) serves to diminish the outward displacements of the structures when the structure is loaded from above. As used herein, the term “soil” is intended to refer to the normal soil, which can be “backfill” (soil brought to and placed in location) or “in situ” (soil in its original location). Such soil is not adequate to support the concentrated loads at the ends of a flat arch or conventional arch without load distribution through the use of arch footings and/or reinforced foundation blocks.
For the prior art structures, overfilled arches are normally formed such that the foundation level of the arch is at the approximate level of a lower pathway or floor surface of an underground structure over which the arch spans. Referring to
Furthermore, as it is necessary to limit the normal forces and bending actions in the top and sides of prior art overfilled arch systems to an acceptable level, the radius of the arch is in practice restricted. This restriction in arch radius leads to a higher “rise” R1 and R2 (vertical dimension between the top of clearance profile C1 and C2 of lower pathway surface LS1 or LS2 and crown CR1 and CR2 of the arch) in the arch profile than is often desirable for the economical and practical arrangement of the two pathways and formation of the works surrounding and covering the arch. This results in a lost height LH1 and LH2 which can be substantial in some cases.
Beams or slabs, while needing a larger thickness than arches, do not require that “rise” and, therefore, can be used for bridges accommodating a smaller height between the top of the clearance profile of the lower pathway and the top of the upper pathway. Arches, despite their economical advantage, often cannot compete with structures using beams or slabs for this reason, especially for larger spans. However, the larger thickness may result in an expensive structure whose precast elements may be difficult, unwieldy and heavy to transport to a building site. Thus, many of the advantages of this structure may be offset or vitiated.
Furthermore, as indicated in
For overfilled arches made of precast construction, the incorporation of the required height of the sides or sidewalls of the arch result either in a tall-standing precast element which is difficult and unwieldy to transport and to place and/or in the requirement of pedestals, such as pedestals F1a shown in
As discussed above, transportation and handling of precast arch elements of some arch structures are difficult. However, precast elements have certain advantages including the ability to support their own self-weight and all of the advantages associated with pre-casting of such structural elements. However, precast elements also have certain disadvantages, including the transportation issues mentioned above.
Therefore, it would be helpful to retain as many of the advantages associated with precast structural elements as possible while eliminating, or at least substantially reducing, as many of the disadvantages associated with precast structural elements as possible.
Likewise, cast-in-place structural elements have many advantages, including the ability to be customized on site and the elimination of the transportation problems associated with precast structural elements. However, cast-in-place structural elements also have certain disadvantages, including a need for a formwork support structure, as well.
Therefore, it would be expedient to retain as many of the advantages associated with cast-in-place structural elements as possible while eliminating, or at least substantially reducing, as many of the disadvantages associated with cast-in-place structural elements as possible.
The referenced co-pending patent application discloses and teaches a means and method of forming an arch structure system that overcomes problems associated with the mechanical inadequacy of normal soil to support bridge and other structures of interest to that, and to this, invention. The advantages associated with the means and method disclosed in the referenced co-pending patent application are substantial. Therefore, it would be valuable to utilize the teaching of the referenced co-pending patent application in a manner which also realizes the advantages associated with the retention of the advantages associated with both precast and cast-in-place overfilled arch structures while reducing, or possibly eliminating, many of the disadvantages associated with such precast and cast-in-place structures.
While the advantages associated with the means and method disclosed in the referenced co-pending patent application are substantial, it would be extremely beneficial if further advantages in support could be realized.
Bending moments applied to an overfilled bridge structure are induced by the overfill and loads, such as traffic, carried by the bridge structure. These bending moments must be accommodated by the bridge structure. Prior overfilled structures counter these bending moments by increasing structural thickness, providing larger amounts of steel reinforcement and/or by increasing the size and stiffness of the arch supports. These measures may be costly and may not be as efficient as possible.
Therefore, there is a need for a means for efficiently minimizing bending moments induced in an overfilled arch structure.
The technology disclosed and taught in the referenced co-pending patent application significantly improves the efficiency of an overfilled bridge structure in accommodating such loading over prior art structures. However, it would be helpful if these load accommodating efficiency advantages could be further improved.
Overfilled arch structures, in particular overfilled flat arches, are sensitive to outward displacement of the arch ends. This outward displacement leads to increased bending moments in the arch. Prior overfilled structures counter these bending moments by increasing structural thickness, providing larger amounts of steel reinforcement and/or by increasing the size and stiffness of the arch supports. These measures may be costly and may not be as efficient as possible.
Therefore, there is a need for a means for efficiently reducing the outward displacements, and particularly the sensitivity of an overfilled arch to outward displacements, of arch footings.
The technology disclosed and taught in the referenced co-pending patent application significantly improves the efficiency of an overfilled bridge structure in preventing such footing outward displacement as compared to prior art structures. However, it would be helpful if these resistances to arch footing outward displacement are further improved.
It is a main object of the present invention to provide an overfilled arch structure which is easier to handle and transport than presently-available arch structures.
It is another object of the invention to provide overfilled arch structure elements which are easier to handle and transport than presently-available arch structure elements yet which yield as strong and stable structures as presently-available arch structures.
It is a specific object of the present invention to provide an overfilled arch structure which includes a composite section of precast and cast-in-place concrete.
It is another object of the present invention to provide an overfilled arch structure which includes a means for efficiently counteracting bending moments induced in the overfilled arch structure.
It is another object of the present invention to provide an overfilled arch structure which includes a means for efficiently reducing the sensitivity of an overfilled arch to outward displacements of arch footings.
It is another object of the present invention to provide an overfilled arch which is prestressed to induce moments herein which counteract moments induced therein by overfill and loads on the arch structure.
It is another object of the present invention to provide an overfilled arch which has an arch end that is customized to induce eccentricities between an arch thrust reaction and a centerline of the arch.
It is another object of the present invention to provide an overfilled arch has a sensitivity to outward displacement of arch footings that is reduced as compared to presently-available arches.
It is another object of the present invention to provide an overfilled arch which utilizes treated soil to create a foundation for the arch.
It is another object of the present invention to provide an overfilled arch which includes a composite section of precast concrete and cast-in-place concrete and which utilizes soil to create a foundation for the arch, a foundation that not only reduces (vertical) settlements, but also (horizontal) displacements.
It is a another object of the present invention to provide an overfilled arch which consists of a composite of precast concrete and cast-in-place concrete layers and which utilizes the technology disclosed and taught in the referenced co-pending patent application.
It is another object of the present invention to provide an overfilled arch which uses support geometry to automatically counteract the moments induced therein by overfill and loads on the arch and which utilizes the technology disclosed and taught in the referenced co-pending patent application.
It is another object of the present invention to provide an overfilled arch which uses prestressing to automatically counteract the moments induced therein by overfill and loads on the arch and which utilizes the technology disclosed and taught in the referenced co-pending patent application.
It is another object of the present invention to provide an overfilled arch which retains many of the advantages associated with precast overfilled bridge structures while eliminating, or at least substantially reducing, many of the disadvantages associated with a precast overfilled bridge structure.
It is another object of the present invention to provide an overfilled arch which retains many of the advantages associated with cast-in-place overfilled bridge structures while eliminating, or at least substantially reducing, many of the disadvantages associated with a cast-in-place overfilled bridge structure.
It is another object of the present invention to further improve the advantages realized by the technology disclosed and taught in the referenced co-pending patent application.
These, and other, objects are achieved by an overfilled bridge arch that includes both precast and cast-in-place layers. The overfilled bridge arch can also be prestressed in an efficient and effective manner, or the ends of the arch arranged in such a way, such that bending moments induced by loading are efficiently and effectively accommodated and sensitivity of the arch to arch footing outward displacement is also reduced.
The overfilled arch bridge structure embodying the present invention can be used in conjunction with the technology disclosed and taught in the referenced co-pending patent application to thereby realize additional advantages for each technology.
The composite overfilled bridge structure embodying the present invention thus realizes advantages for both precast and cast-in-place structures as well as reducing, or even eliminating, many disadvantages associated with such precast and cast-in-place arches. Additional advantages are also realized due to the composite nature of the structure of the present invention, including the ability to efficiently waterproof the structure as well as to include efficient joint seals.
The overfilled bridge and elements thereof embodying the present invention make an overfilled bridge efficient to transport, handle and erect, yet will produce a stable and efficiently waterproofed structure.
Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description and the accompanying drawings.
Broadly, the overfilled arch bridge structure and the elements thereof embodying the present invention can be independently used or used in conjunction with the overfilled bridge disclosed in the referenced co-pending patent application. While the present invention will be disclosed in combination with that structure, it should be understood that the present invention can be used independently of such structure and no limitation is intended by the disclosure of this invention in combination with the invention disclosed in the referenced co-pending patent application. The basic structure disclosed in the referenced patent application is shown in
As discussed above, the overfilled bridge structure embodying the present invention combines precast and cast-in-place advantages and also stabilizes the arch structure.
Referring first to
As can be understood from
The precast layer of the arch forms the complete arc of the arch span, but is thinner, and therefore lighter to transport and handle than prior art precast arches. The precast arch elements are sized to be able to support their own self-weight during transportation and placement, as well as to be sufficiently strong to enable casting layer 34 of cast-in-place concrete over the precast layer 32. Those skilled in the art will understand how to size and form precast layer 32 based on the teaching of this disclosure. The composite section of precast and cast-in-place concrete thus formed has the thickness and strength of previous structures which are exclusively precast or exclusively cast-in-place arches.
The main advantages of the composite arch system embodying the present invention include: the weight of the transported elements is lower, and can be lower by half, than prior precast elements (or alternatively the elements can be made wider such that fewer elements need to be transported); and the cast-in-place layer 34 facilitates load sharing longitudinally along the arch to distribute concentrated loads. Furthermore, placement of waterproofing between precast elements is better facilitated than in prior structures. Thus, the composite system embodying the present invention has advantages over either a fully precast arch. No formwork or formwork support structure is required to form the arch embodying the present invention. The elimination of formwork or formwork support structures will result in considerable saving in costs associated with the formwork, and the clearance below the arch will not be reduced during construction since a temporary support structure is not required. Thus, the structure embodying the present invention also has advantages over cast-in-place arches.
As also mentioned above, the overfilled bridge structure of the present invention includes means for reducing the bending moments within the overfilled arches, as well as reduces the arch's sensitivity to any outward displacement of the arch footings. Reducing the bending moments also reduces the structural depth and steel reinforcement required with the advantages concomitant to such reduction.
Broadly, the means include either customized arch end geometry or prestressed arches, with the prestressing occurring either prior to or during loading.
Referring to
The structure embodying the present invention improves over the basic arch footing shown in
Referring to
The means embodying the present invention is illustrated in
Referring next to
Prestressing can also be used to reduce the bending moments within an earth overfilled arch. Prestressing is illustrated in
As shown in
It is understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangements of parts described and shown.
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