Tendon-receiving duct with longitudinal channels

Abstract: A tendon-receiving duct (20) having a tubular body (22) with an interior passageway (26) and a plurality of corrugations (24) extending radially outwardly of the tubular body (22). Each of the plurality of corrugations (24) has an interior opening to the interior passageway (26). The tubular body has longitudinal channels (28,30,32) formed on the tubular body (22) so as to establish fluid communication between adjacent pairs of the corrugations (24). The tubular body (22) is formed of a polymeric material. The channels (28,30,32) are formed on the outer wall of the tubular body (22) and open to the interior passageway (26) of the tubular body (22) and extend for the length of the tubular body (22).

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to ducts as used in post-tension construction. More particularly, the present invention relates to the formation of a polymeric duct used for retaining multi-strand tensioning systems within an encapsulated environment. DESCRIPTION OF RELATED ART For many years, the design of concrete structures imitated the typical steel design of column, girder and beam. With technological advances in structural concrete, however, its own form began to evolve. Concrete has the advantages of lower cost than steel, of not requiring fireproofing, and of its plasticity, a quality that lends itself to free flowing or boldly massive architectural concepts. On the other hand, structural concrete, though quite capable of carrying almost any-compressive load, is weak in carrying significant tensile loads. It becomes necessary, therefore, to add steel bars, called reinforcements, to concrete, thus allowing the concrete to carry the compressive forces and the steel to carry the tensile forces. Structures ofreinforced concrete maybe constructed with load-bearing walls, but this method does not use the full potentialities of the concrete. The skeleton frame, in which the floors and roofs rest directly on exterior and interior reinforced-concrete columns, has proven to be most economic and popular. Reinforced-concrete framing is seemingly a quite simple form of construction. First, wood or steel forms are constructed in the sizes, positions, and shapes called for by engineering and design requirements. The steel reinforcing is then placed and held in position by wires at its intersections. Devices known as chairs and spacers are used to keep the reinforcing bars apart and raised off the form work. The size and number of the steel bars depends completely upon the imposed loads and the need to transfer these loads evenly throughout the building and down to the foundation. After the reinforcing is set in place, the concrete, a mixture of water, cement, sand, and stone or aggregate, of proportions calculated to produce the required strength, is placed, care being taken to prevent voids or honeycombs. One of the simplest designs in concrete frames is the beam-and-slab. This system follows ordinary steel design that uses concrete beams that are cast integrally with the floor slabs. The beam-and-slab system is often used in apartment buildings and other structures where the beams are not visually objectionable and can be hidden. The reinforcement is simple and the fprms for casting can be utilized over and over for the same shape. The system, therefore, produces an economically viable structure. With the development of flat-slab construction, exposed beams can be eliminated. In this system, reinforcing bars are projected at right angles and in two directions from every column supporting flat slabs spanning four or five meters in both directions. Reinforced concrete reaches its highest potentialities when it is used in pre-stressed or post-tensioned members. Spans as great as one hundred feet can be attained in members as deep as three feet for roof loads. The basic principle is simple. In pre-stressing, reinforcing rods of high tensile strength wires are stretched to a certain determined limit and then high-strength concrete is placed around them. When the concrete has set, it holds the steel in a tight grip, preventing slippage or sagging. Post-tensioning follows the same principle, but the reinforcing tendon, usually a steel cable, is held loosely in place while the concrete is placed around it. The reinforcing tendon is then stretched by hydraulic jacks and securely anchored into place. Pre-stressing is done with individual members in the shop and post-tensioning as part of the structure on the site. In a typical tendon tensioning anchor assembly used in such post-tensioning operations, there are provided anchors for anchoring the ends of the cables suspended therebetween. In the course of tensioning the cable in a concrete structure, a hydraulic jack or the like is releasably attached to one of the exposed ends of each cable for applying a predetermined amount of tension to the tendon, which extends through the anchor. When the desired amount of tension is applied to the cable, wedges, threaded nuts, or the like, are used to capture the cable at the anchor plate and, as the jack is removed from the tendon, to prevent its relaxation and hold it in its stressed condition. Multi-strand tensioning is used when forming especially long post-tensioned concrete structures, or those which must carry especially heavy loads, such as elongated concrete beams for buildings, bridges, highway overpasses, etc. Multiple axially aligned strands of cable are used in order to achieve the required compressive forces for offsetting the anticipated loads. Special multi-strand anchors are utilized, with ports for the desired number of tensioning cables. Individual cables are then strung between the anchors, tensioned and locked as described above for the conventional monofilament post-tensioning system. As with monofilament installations, it is highly desirable to protect the tensioned steel cables from corrosive elements, such as de-icing chemicals, sea water, brackish water, and even rain water which could enter through cracks or pores in the concrete and eventually cause corrosion and loss of tension of the cables. In multi-strand applications, the cables typically are protected against exposure to corrosive elements by surrounding them with a metal duct or, more recently, with a flexible duct made of an impermeable material, such as plastic. The protective duct extends between the anchors and in surrounding relationship to the bundle of tensioning cables. Flexible duct, which typically is provided in 6 to 42 meters sections is sealed at each end to an anchor and between adjacent sections of duct to provide a water-tight channel. Grout then may be pumped into the interior of the duct in surrounding relationship to the cables to provide further protection. Various patents have issued, in the past, for devices relating to such multi-strand duct assemblies. For example, U.S. Design Patent No. 400,670, issued on November 3, 1998, to the present inventor, shows a design of a duct. This duct design includes a tubular body with a plurality of corrugations extending outwardly therefrom. This tubular duct is presently manufactured and sold by General Technologies, Inc. of Stafford, Texas, the licensee of the present inventor. In particular, FIGURES 1 and 2 are illustrations of the prior art duct that is being manufactured by General Technologies, Inc. As can be seen in FIGURE 1, the tubular duct 10 has a tubular body 12 and a plurality of corrugations 14 which extend radially outwardly from the outer wall 16 of the tubular body 12. The tubular body 12 includes an interior passageway 14 suitable for receiving multiple post-tension cables and strands therein. The interior passageway 18 of the tubular body 12 is suitable for receiving a grout material so as to maintain the multiple strands in a liquid-tight environment therein. FIGURE 2 shows the tubular body 12 as having the corrugations 14 extending outwardly in generally spaced parallel relationship to each other and in transverse relationship to the longitudinal axis of the tubular body 12. A wall 16 will extend between the corrugations 14. The tubular body 12, along with the corrugations 16, are formed of a polymeric material. The duct 12 can be any length, as desired. Couplers-can be used so as to secure lengths of duct 10 together in end-to-end relationship. One of the problems associated with the prior art duct 10 is that it is not stiff enough in the longitudinal direction. The duct 10 will flex too easily. It becomes difficult to profile such an easily flexible duct. When the cables are being installed in the interior passageway 18, the cablepusher used to install the cable within the interior passageway 18 is likely to strike the walls of the interior passageway 18 when the duct is flexed. Because of the force used to install the cable through the duct 10, the walls of the duct can break or become damaged if the cable strikes the walls of the duct. It is desirable to manufacture a duct 10 with greater stiffness and rigidity in the longitudinal direction so as to avoid the flexing and deflection of the duct. An additional problem with the duct 10, as shown in FIGURES 1 and 2, is that air has a possibility of being trapped in the corrugations. When air bubbles form within the interior of the corrugations, the grout used to seal the interior 18 does not effectively encapsulate the cable on the interior 18. As such, it is desirable to manufacture the duct 10 such that the potential for trapped air bubbles within the corrugations 14 is reduced. The present inventor is also the inventor of U.S. Patent No. 5,474,335, issued on December 12, 1995. This patent describes a duct coupler for joining and sealing between adjacent sections of duct. The coupler includes a body and a flexible cantilevered section on the end of the body. This flexible cantilevered section is adapted to pass over annular protrusions on the duct. Locking rings are used to lock the flexible cantilevered sections into position so as to lock the coupler onto the duct. U.S. Patent No. 5,762,300, issued on June 9, 1998, to the present inventor, forms the state of the art and describes a tendon-receiving duct according to the preamble of claim 1 and a duct, support apparatus. This duct support apparatus is used for supporting a tendon-receiving duct. This support apparatus includes a cradle for receiving an exterior surface of a duct therein and a clamp connected to the cradle and extending therebelow for attachment to an underlying object. The cradle is a generally U-shaped member having a length greater than a width of the underlying object received by the clamp. The cradle and the clamp are integrally formed together of a polymeric material. The underlying object to which the clamp is connected is a chair or a rebar. U.S. Patent No. 5,954,373, issued on September 21, 1999, to the present inventor, shows another duct coupler apparatus for use with ducts on a multi-strand post-tensioning system. The coupler includes a tubular body with an interior passageway between a first open end and a second open end. A shoulder is formed within the tubular body between the open ends. A seal is connected to the shoulder so as to form a liquid-tight seal with a duct received within one of the open ends. A compression device is hingedly connected to the tubular body for urging the duct into compressive contact with the seal. The compression device has a portion extending exterior of the tubular body. Thus, the present invention seeks to provide a tendon-receiving duct which improves the rigidity of the duct in the longitudinal direction, and which facilitates the removal of air bubbles from within the interior of the duct. These and other advantages of the present invention will become apparent from a reading of the attached Specification and appended Claims. According to this invention there is provided A tendon-receiving duct comprising a tubular body having an interior passageway, there being a plurality of tendons extending through the passageway, and a grout material filling the interior of the passageway wherein the body has a plurality of corrugations extending radially outwardly therefrom, each of said plurality of corrugations being in spaced relationship to an adjacent corrugation, each of said plurality of corrugations opening to said interior passageway, said tubular body having a wall extending between each adjacent pair of said corrugations, wherein said tubular body has at least one longitudinal channel extending between each adjacent pair of corrugations of said plurality of corrugations, said longitudinal channel extending outwardly of said wall for a distance equal to a distance that each of said plurality of corrugations extends outwardly from said wall, said longitudinal channel having an interior opening to said interior passageway of said tubular body and having a first end opening into one of said adjacent pair of corrugations and a second end opening into the other of the said pair of corrugations, the grout material filling said plurality of corrugations and the said longitudinal channel, the or each longitudinal channel being of substantially uniform cross-section along its length. Preferably said tubular body has a plurality of said longitudinal channels extending between said adjacent pair of corrugations. In one embodiment said tubular body has a circular cross-section at said wall in a plane transverse to a longitudinal axis of said tubular body. In an alternative embodiment said tubular body has an oval cross-section at said wall in a plane transverse to the axis of said tubular body. Preferably said tubular body has a first end and a second end, said longitudinal channel having a one end opening at said first end and an opposite end opening at said second end, said longitudinal channel communicating with each of said plurality of corrugations between the first and second ends of the tubular body. Conveniently the body is formed of a polymeric material. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIGURE 1 is a upper perspective view showing a prior art tendon-receiving duct. FIGURE 2 is a side elevational view of the prior art tendon-receiving duct, as shown in FIGURE 1. FIGURE 3 is an upper perspective view of the tendon-receiving duct in accordance with the teachings of the present invention. FIGURE 4 is a side elevational view of the tendon-receiving duct in accordance with the teachings of the present invention. FIGURE 5 is a cross-sectional view as taken across lines 5-5 of FIGURE 4. FIGURE 6 is a partial cross-sectional view taken across lines 6-6 of FIGURE 3. FIGURE 7 is a side elevational view showing the tendon-receiving duct of the present invention with tendons installed therein. FIGURE 8 is an upper perspective view showing an alternative embodiment of the tendon-receiving duct of the present invention. FIGURE 9 is an end view showing the tendon-receiving duct of FIGURE 8. DETAILED DESCRIPTION OF THE INVENTION Referring to FIGURE 3, there is shown the tendon-receiving duct 20 in accordance with the teachings of the preferred embodiment of the present invention. The tendon-receiving duct 20 includes a tubular body 22 having a plurality of corrugations 24 extending radially outwardly of the tubular body 22. Each of the corrugations 24 is in spaced relationship to an adjacent corrugation 24. The tubular body 22 has an interior passageway 26 suitable for receiving tendons (or post-tension cables) therein. Each of the plurality of corrugations 24 open within the tubular body 22 to the interior passageway 26. Longitudinal channels 28,30 and 32 are formed on the tubular body 22 and communicate between the corrugations 24. The tubular body 22 has a wall section 34 formed between the corrugations 36 and 38, for example. The wall portion 34 will define the inner wall of the interior passageway 26. The longitudinal channel 28 will extend between the corrugation 36 and the corrugation 38 in parallel relationship to the longitudinal axis of the tubular body 22. Similarly, the longitudinal channel 30 will extend between the corrugation 36 and the corrugation 38. Longitudinal channel 32 extends also between the corrugation 36 and the corrugation 38. Each of the longitudinal channels 28, 30 and 32 have a first end opening into the corrugation 36 and a second end opening into the corrugation 38. Each of the longitudinal channels 28, 30 and 32 have an interior which opens to the interior passageway 26. In normal use, when grout is introduced into the interior passageway 26, it will begin to fill the voids within the interior passageway 26. The grout will initially fill the interior of the corrugation 36 and push air bubbles outwardly therefrom. These air bubbles can migrate along the channels 28, 30 and 32 toward the corrugation 38. Eventually, the grout will fill the channels 28, 30 and 32 and slowly move into the interior of corrugation 38. As such, air bubbles within the corrugation 38 are pushed further outwardly along the length of the respective longitudinal channels 28, 30 and 32. The longitudinal channels 28, 30 and 32 will communicate between the multiple corrugations formed on the exterior of the tubular body 22. Importantly, the longitudinal channels 28, 30 and 32 provide rigidity and stiffness in the longitudinal direction of the tubular body 22. As such, the tubular body 22 is less likely to curl up, whip or wobble during the installation of the tendons by a cablepusher. Because of the added stiffness provided by the longitudinal channels associated with the tubular body 22, installation of cables can occur in a quicker and more convenient manner. There is less likely of duct breakage when the tendons can be installed in a quick and easy manner without wobble or whip by the duct 20. FIGURE 4 shows a side view of the duct 20 of the present invention. In FIGURE 4, it can be seen that the longitudinal channels 28,30 and 32 can extend generally for the length of the tubular body 22. Each of the longitudinal channels 28, 30 and 32 will communicate with the various corrugations 24 therebetween. The longitudinal channels 28, 30 and 32 are equally radially spaced from adjacent channels around the diameter of the tubular body 22. In the embodiment shown in FIGURES 3 and 4, a total of five longitudinal channels will be formed. The longitudinal channels extend outwardly of the wall portion 34 between the respective pairs of corrugations 24. Each of the longitudinal channels 28, 30 and 32 will extend outwardly from the wall 34 a distance equal to the amount that the corrugations 24 extend outwardly from the wall 34. FIGURE 5 is a cross-sectional view showing the configuration of the various longitudinal channels 28, 30, 32, 40 and 42. In FIGURE 5, the arrangement of the longitudinal channels 28, 30, 32,40 and 42 is particularly illustrated. Each of the channels is spaced an equal radial distance from an adjacent channel. Each of the channels 28, 30, 32, 40 and 42 extends outwardly from the wall 34 a distance equal to the amount that the corrugation 24 extends outwardly from the wall 30. Wall 30 has an inner surface 44 which defines the interior passageway 26 of the duct 20. Each of the longitudinal channels 28, 30, 32, 40 and 42 has an interior which communicates with the interior passageway 26 of duct 20. In this arrangement, the grout can flow freely through the various channels 28,30,32,40 and 42 so as to enter the corrugations 24. The outwardly extending channels 28, 30, 32, 40 and 42 will add rigidity and stiffness along the longitudinal direction of the duct 20. In FIGURE 5, it can be seen that the duct 20 is circular in cross-section transverse to the longitudinal axis of the duct 20. FIGURE 6 shows a close up illustration of the relationship of corrugations 50 and 52 relative to the longitudinal channels 54 and 56. The corrugation 58, illustrated in FIGURE 6, has an interior passageway 64. Each of the longitudinal channels 54 and 56 will communicate with the interior 64 of the corrugation 50 at one end of the channels 54 and 56. Similarly, each of the channels 54 and 56 will communicate with the interior 64 of corrugation 64 at the other end of the longitudinal channels. As grout fills the interior 62 of the corrugation 50 it will eventually push the air bubbles outwardly therefrom and migrate along the longitudinal channels 54 and 56 so as to enter the corrugation 52. FIGURE 7 shows the installation of tendons or cables 60 through the interior passageway 26 of the duct 20. After the tendon 60 are installed into the interior 26 of the duct 20, the grout can be introduced therein so as to flow through the interior passageway 26 so as to fill any voids or spaces within the interior passageway 26 between the tendon 60 and the inner walls of the duct 20. This grout will also fill the corrugations 24 and the longitudinal channels 28, 30 and 32. FIGURE 8 shows an alternative embodiment of the present invention used in association with a duct 80 which has an oval cross-section in a plane transverse to the longitudinal axis of the duct 80. The duct 80 also shows that the longitudinal channels 82, 84, 86 and 88 will open at the end 90 of the duct 80. The longitudinal channels 82, 84, 86 and 88 will communicate with each of the corrugations 92 extending outwardly of the wall 94 of the duct 80. Each of the longitudinal channels 82, 84, 86 and 88 will extend along the length of the duct 80 so as to open at the opposite end 96 of the duct 80. The longitudinal channels 82, 84, 86 and 88 will add rigidity to the duct 80 along its longitudinal axis. The channels 82, 84, 86 and 88 will also facilitate the ability to cause grout to migrate properly through the interior passageway 98 of the duct 80. FIGURE 9 shows a an end view of the duct 80. In particular, it can be seen the arrangement of the longitudinal channels 82, 84, 86 and 88 around the wall 94 of the duct 80. The longitudinal channels 82, 84, 86 and 88 open so as to communicate with the interior passageway 98 of the duct 80. The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction may be made within the scope of the appended claims. The present invention should only be limited by the following claims and their legal equivalents.

Claims: A tendon-receiving duct (20) comprising: a tubular body (22) having an interior passageway (26), there being a plurality of tendons (6) extending through the passageway, and a grout material filling the interior of the passageway wherein the body has a plurality of corrugations (24) extending radially outwardly therefrom, each of said plurality of corrugations (24) being in spaced relationship to an adjacent corrugation, each of said plurality of corrugations (24) opening to said interior passageway, (26) said tubular body (22) having a wall (34) extending between each adjacent pair of said corrugations (36, 38), characterised in that said tubular body has at least one longitudinal channel (28) extending between each adjacent pair of corrugations (36, 38) of said plurality of corrugations, said longitudinal channel (28) extending outwardly of said wall (34) for a distance equal to a distance that each of said plurality of corrugations (24) extends outwardly from said wall (34), said longitudinal channel (28) having an interior opening to said interior passageway (26) of said tubular body (22) and having a first end opening into one (36) of said adjacent pair of corrugations and a second end opening into the other (38) of the said pair of corrugations, the grout material filling said plurality of corrugations (24) and the said longitudinal channel (28), the or each longitudinal channel being of substantially uniform cross-section along its length. A duct according to Claim 1, wherein said tubular body (22) has a plurality of said longitudinal channels (28, 30, 32, 40, 42) extending between said adjacent pair of corrugations (36, 38). A duct according to any one of the preceding Claims wherein said tubular body (22) has a circular cross-section at said wall (34) in a plane transverse to a longitudinal axis of said tubular body (22). A duct (80) according to any one of Claims 1 or 2 wherein said tubular body has an oval cross-section at said wall (94) in a plane transverse to the axis of said tubular body. A duct (20) according to any one of the preceding Claims wherein said tubular body (22) has a first end and a second end, the or each longitudinal channel (28, 30, 32, 40, 42) having one end opening at said first end and an opposite end opening at said second end, the or each longitudinal channel (28, 30, 32, 40, 42) communicating with said plurality of corrugations between the first and second ends of the tubular body (22). A duct (20) according to any one of the preceding Claims wherein the body (22) is formed of a polymeric material.

Inventors: SORKIN FELIX L, SORKIN, FELIX L.
Applicants: SORKIN FELIX L, SORKIN, FELIX L.
Application year: 2001
Main classification: E04C5
IPC codes: E04C5