WO2007145477A1

WO2007145477A1 - Precast concrete segment having connecting structure using steel duct, and connecting structure thereof

Info

Publication number: WO2007145477A1
Application number: PCT/KR2007/002892
Authority: WO
Inventors: Seong Woon Kim; Young Jin Kim; Byeong Moo Jin; Tae Hoon Kim; Se Jin Park; Je Chun Kim
Original assignee: Daewoo Engineering & Construction Co., Ltd
Priority date: 2006-06-15
Filing date: 2007-06-14
Publication date: 2007-12-21
Also published as: CN101356318B; KR100738999B1; CN101356318A

Abstract

The present invention relates to precast concrete segments and their assembled structures. While supporting facile assembly, the inventive concrete segments provide sufficient resistance against shear force since they contain steel ducts, which also double as shear keys, for installing tendons. Herein is provided a precast concrete segment comprising a cylindrical steel duct placed therein such that said steel duct runs through said segment along the direction of assembly with a neighboring precast concrete segment, wherein said steel duct is installed with tendons therein to apply tension, and wherein the upper part of said steel duct protrudes from the top surface of said precast concrete segment so as to function as a shear key, and wherein the lower part of said steel duct comprises a socket having a widened diameter so as to allow the protruding upper part of a steel duct from the neighboring concrete segment to be inserted therein.

Description

PRECAST CONCRETE SEGMENT HAVING CONNECTING STRUCTURE USING STEEL DUCT AND CONNECTING

STRUCTURE THEREOF

Technical Field

[1] The present invention relates to precast concrete segments capable of forming assemblies through steel ducts contained therein as well as said assemblies of these segments. More specifically, the present invention relates to a precast concrete segment having a novel structure as well as their assemblies in which a steel duct, also doubling as a shear key, is integrated therein for the installation of tendons to provide sufficient resistance against shearing force as well as facile segment assemblies for the final structure.

[2]

Background Art

[3] When assembling precast concrete segments, shear keys must be installed to provide shear resistance derived from the mechanical locking-in of the surfaces so that a shear connection can be established across the discontinuity present between the segments. In precast concrete segments, these shear keys are generally made into a protrusion from one of the sides of the segment during their production. Such method of producing concrete segments with protruding shear keys is prone to inadvertent breakage of shear keys upon removal from a mold. This becomes particularly problematic as the shear keys become smaller and have longer protrusions. Furthermore, the filling of concrete is often incomplete for the part of the mold responsible for forming shear keys, leading to segments with improperly formed shear keys upon removal from a mold.

[4] Meanwhile water leakage may occur through the segment discontinuity when tendons are placed continuously between two segments to be joined. Water leaking from installation holes for tendons at the segment discontinuity, namely the intersegment junction, induces corrosion of tendons, which in turn, leads to damaged tendons; thus, severe problems such as structural collapse may arise at the level of the entire structure. Therefore, special measures should be taken to prevent the corrosion of those tendons that are continuously placed between two joining segments during their assembly.

[5]

Disclosure of Invention Technical Problem

[6] The present invention aims to provide precast concrete segments in which shear keys, an important element that generates shear resistance between the segments, can be formed readily without damaging the precast concrete segments during construction in which these segments are assembled. In addition, the present invention aims to provide precast concrete segments in which corrosion of tendons by water leaking into the space where these tendons are continuously placed can be prevented in the assembly of these segments.

[7]

Technical Solution

[8] The objects of the present invention mentioned above can be accomplished by the inventive precast concrete segments. Herein is provided a precast concrete segment comprising a cylindrical steel duct placed therein such that said steel duct runs through said segment along the direction of assembly with a neighboring precast concrete segment, wherein said steel duct is installed with tendons therein to apply tension, and wherein the upper part of said steel duct protrudes from the top surface of said precast concrete segment so as to function as a shear key, and wherein the lower part of said steel duct comprises a socket having a widened diameter so as to allow the protruding upper part of a steel duct from the neighboring concrete segment to be inserted therein.

[9] In one embodiment of the present invention, said protruding upper part of said steel duct may comprise a tapered spigot so as to allow facile insertion into the socket of a neighboring concrete segment. In another embodiment of the present invention, said socket of the steel duct can be formed by attaching a steel pipe to the lower part of said steel duct, wherein said steel pipe has an inner diameter that matches outer diameter of said steel duct.

[10] In another aspect of the present invention, a segment assembly of two precast concrete segments is provided. In this segment assembly, the precast concrete segment comprises a cylindrical steel duct integrated therein that runs through said segment along the direction of assembly, wherein said steel duct has an upper part that protrudes from the top surface of said precast concrete segment, and wherein the lower part of said steel duct comprises a socket with a widened diameter so as to allow the protruding upper part of a steel duct from the other concrete segment to be inserted therein, and wherein the protruding upper part of said steel duct is inserted into the socket located at the lower part of the other concrete segment to form an integral assembly of segments that joins said two concrete segments through mutual penetration of said steel duct.

[11] In one embodiment of the present invention, said steel duct that penetrates both concrete segments is installed with a tendon capable of applying tension to bring about the assembly of said two segments. In another embodiment of the present invention, said segment assembly may comprise a sealing member installed on the exterior top surface of said segment, wherein the other precast concrete segment is deposited over said sealing member, and wherein grout material is injected to fill the space created between the upper and lower segments by said sealing member to form a grout section between said upper and lower segments.

Advantageous Effects

[12] In the present invention, sufficient shear resistance can be provided at the junction of neighboring precast concrete segments by the steel duct functioning as a shear key. In particular, the forming of shear keys is greatly facilitated since a normal, undamaged shear key integral with the segment becomes available. In addition, because the steel duct is placed continuously between two segments to be joined, water leakage through the segment junction into the steel duct is prevented. Also, the concrete making up the segment is strengthened. Overall, a tidy-looking concrete segment can be achieved.

[13]

Brief Description of the Drawings

[14] The objects and characteristics of the present invention mentioned above will be made clearer by the following detailed description of the preferred embodiments of the invention with reference to the attached drawings. In the attached drawings,

[15] Figure 1 is a perspective view of the inventive precast concrete segment wherein only the part installed with a steel duct is illustrated in the form of a rectangular block.

[16] Figure 2 is a cross section perspective view of the precast concrete segment shown in Figure 1 from which a part of concrete was removed.

[17] Figures 3 is a perspective view of the steel duct embodiment shown in Figure 1.

[18] Figure 4 is a cross section perspective view of the steel duct embodiment shown in

Figure 2.

[19] Figures 5 and 6, respectively, are a perspective view and cross section perspective of another embodiment of the steel duct according to the present invention wherein additional steel duct was used form a socket.

[20] Figure 7 is a schematic perspective view of the block equipped with the steel duct illustrated in Figure 5. Figure 8 is a cross section perspective view of the precast concrete segment shown in Figure 6 from which a part of concrete was removed.

[21] Figure 9 is a schematic cross section perspective view showing the vertical assembly of the segments illustrated in Figure 2.

[22] Figure 10 is a schematic cross section perspective view showing the assembled segments illustrated in Figure 2.

[23] Figure 11 is a schematic cross section perspective view showing the vertical assembly of the segments illustrated in Figure 8.

[24] Figure 12 is a schematic cross section perspective view showing the assembled segments illustrated in Figure 8.

[25] Figure 13 is an exploded perspective view showing an embodiment of the inventive segment in which a precast concrete pier segment is piled on top of another.

[26]

Best Mode for Carrying Out the Invention

[27] Preferred embodiments of the present invention will be described in more detail with reference to the attached drawings.

[28] Figure 1 is a perspective view of the inventive precast concrete segment 10 wherein only the part installed with a steel duct 1 is illustrated in the form of a rectangular block. Figure 2 is a cross section perspective view of the block shown Figure 1 from which some concrete was removed. Figures 3 is a perspective view of the steel duct 1 embodiment shown in Figure 1 and Figure 4 is a cross section perspective view of the steel duct 1 embodiment shown in Figure 2.

[29] In the following, the present invention is described in detail with reference to the attached drawings.

[30] As illustrated in Figures 1 and 2, a steel duct 1 placed inside runs through the precast concrete segment 10 (hereafter abbreviated as "segment") for establishing a shear connection along the direction of the assembled segments 10. Said steel duct 1 is a cylindrical steel pipe through which a tendon is placed so as to provide tension.

[31] As illustrated in the drawings, the lower part of said steel duct 1, being flush with the bottom face of said segment 10, does not protrude outside, whereas the upper part of said steel duct 1 juts out from the top face of said segment 10. As will be described later, the protruding upper part of said steel duct 1 is inserted into the lower part of another steel duct 1, which is integrated into a neighboring segment 10 through its bottom face, during the assembly of neighboring segments 10. To ensure a facile insertion of said steel duct 1 between these neighboring segments 10, the lower part of said steel duct 1 preferably comprises a socket 11 with widened diameter as illustrated in Figures 3 and 4. In addition to this socket 11, the upper part of said steel duct 1 may comprise a spigot 12 with a tapering diameter. Although a socket 11 is formed by mechanical processing in the steel duct 1 shown in Figures 3 and 4, a separate steel duct with a wider diameter may be attached to the steel duct 1 to form the socket 11.

[32] As another embodiment of the inventive steel duct 1, Figures 5 and 6 show the perspective view and a cross section perspective view, respectively, of a steel duct 1 with a socket 11 formed by attaching a separate steel duct as explained above. A schematic perspective view of the block equipped with the steel duct 1 illustrated in Figure 5 is given in Figure 7. Figure 8 is a schematic perspective view of the cross section formed by removing a part of concrete from the precast concrete segment shown in Figure 6. As illustrated in Figures 5 and 6, the lower part of said steel duct 1 can be fastened with another steel duct with a larger diameter, for example through welding or screw tightening (screw holes are formed on the outer surface of the lower part of said steel duct and inside the steel duct with a larger diameter for screw tightening) to form a socket 11 thereon. Such steel ducts 1 with sockets 11 formed by separate steel ducts attached may as well comprise a tapered spigot 12 in their upper parts.

[33] Also it should be noted, while not shown in the drawings, that said steel duct 1 may receive treatments to roughen its surfaces or be provided with such elements as bolts that can be introduced within said concrete segments 10 so as to strengthen the attachment of said steel duct 1 with said segments 10.

[34] The following explains the assembly procedure and the assembled structure of those segments 10 equipped with steel ducts 1 as described above.

[35] Figure 9 is a schematic cross section perspective view showing the vertical assembly of the segments 10 illustrated in Figure 2. Figure 10 is a schematic cross section perspective view showing the assembled segments. Figure 11 is a schematic cross section perspective view showing the vertical assembly of the segments 10 illustrated in Figure 8. Figure 12 is a schematic cross section perspective view showing the assembled segments illustrated in Figure 8.

[36] As depicted in the drawings, the protrusion of steel duct 1, namely spigot 12, that protrudes from one side of a segment 10, which is equipped with said steel duct 1 installed within, is inserted inside the socket 11 of another steel duct 1 placed within a neighboring segment 10, during the assembly of these neighboring segments. A plurality of segments 10 are assembled sequentially in such fashion to build the final structure.

[37] In the assembled structure mentioned above, said steel duct 1 can function as a shear key to provide resistance against the shearing force at the junction of the two segments 10 since it straddles both segments 10 across this junction. In particular, as previously explained, the assembly of segments 10 and the connection between said steel ducts 1 can be quite facile since said steel ducts 1 are equipped with sockets 11. To recapitulate, problems such as breakage of the shear key during the manufacture of segments or production of mal-formed shear keys arise when shear keys are formed as a protrusion out of the same concrete material as the segment as is the case with prior art precast concrete segments. In the present invention such problems no longer become an issue since steel ducts 1 are employed to form shear keys. Furthermore, one needs only to place the steel duct 1 during the manufacture of a segment 10, which greatly simplifies the production of shear keys and leads to enhanced productivity in the manufacture of the segments 10.

[38] Meanwhile, it should be noted that besides functioning as shear key, said steel duct

1 can also perform as an installation hole in the placement of tendons (not shown). As described above, a plurality of segments 10 can be assembled and then steel ducts 1 therein can be installed with tendons to confer tension to the entire structure. No additional ducts, therefore, are required.

[39] Accordingly, water leakage inside the steel ducts 1 through the junction between the segments 10 can be prevented in the present invention since the inserted steel duct 1 forms a continuous connection across both segments 10 in the assembly to form a water-tight seal.

[40] Figure 13 illustrates an example of said segment 10, wherein a precast concrete pier segment is placed on top of another in an exploded perspective view. In the piling up of the inventive segments 10 to form a single structure, grout can be injected to adjust the spacing between the segments 10. As shown in Figure 13, a sealing member 21 having a length corresponding to the required spacing of the segments 10 can be attached on the top exterior surface of the lower segment 10, followed by a deposition of the upper segment 10. The space between the upper and lower segments 10, formed by said sealing member 21, can be injected with grout material such as non-shrinking mortar to form a grout section so that the spacing between the segments 10 or the horizontal level can be adjusted. It is thus preferred that the injection of grout material to adjust the spacing precedes the installation of tendons inside said steel ducts 1 to apply tension.

[41] It is also possible, as illustrated in Figure 13, to install said sealing members 21 around the steel duct 1. In this case, it is preferred that the injection and filling of grout material in the space between said sealing member 21 and steel duct 1 take place after tendons are installed inside said steel duct 1 to apply tension.

[42] Although precast concrete piers were given as an example of the inventive segment

10, by no means the scope of the present invention is limited as such; the segment 10 of the present invention may find various uses including segments used for upper structures of bridges.

[43]

Industrial Applicability

[44] In the present invention, as described previously, steel ducts can function as shear keys to provide resistance against the shearing force at the junction of the two precast concrete segments since these steel ducts straddle both segments at the junction. In particular, said steel ducts are installed at pre-determined positions followed by pouring of concrete to form precast concrete segments of the present invention. Since such segments enable the formation of unbroken, functional shear keys, obtainable as an integral part of said segments, production of shear keys become greatly facilitated. In addition, because the steel duct is placed continuously across the junction between two segments, water leakage through the segment junction into said steel duct can be prevented. The steel duct used also strengthens the concrete in the segment. Overall, a tidy-looking concrete segment can be produced.

Claims

[1] A precast concrete segment 10 comprising a cylindrical steel duct 1 placed therein such that said steel duct 1 runs through said segment 10 along the direction of assembly with a neighboring precast concrete segment 10, wherein said steel duct 1 is installed with tendons therein to apply tension, and wherein the upper part of said steel duct 1 protrudes from the top surface of said precast concrete segment 10 so as to function as a shear key, and wherein the lower part of said steel duct 1 comprises a socket 11 having a widened diameter so as to allow the protruding upper part of a steel duct 1 from the neighboring concrete segment 10 to be inserted therein.

[2] The precast concrete segment according to Claim 1, wherein the protruding upper part of said steel duct 1 comprises a tapered spigot 12 so as to allow facile insertion into the socket 11 of a neighboring concrete segment 10.

[3] The precast concrete segment according to Claims 1 or 2, wherein said socket 11 of the steel duct 1 is formed by attaching a steel pipe to the lower part of said steel duct 1, and wherein said steel pipe has an inner diameter that matches outer diameter of said steel duct 1.

[4] The precast concrete segment according to Claims 1 or 2, wherein a sealing member 21 is installed on the exterior top surface of said segment 10 so as to create space upon deposition of another precast concrete segment 10 for injection of grout material thereto, said space being created between the upper and lower precast concrete segments 10.

[5] A segment assembly of two precast concrete segments 10, the precast concrete segment comprising a cylindrical steel duct 1 integrated therein that runs through said segment 10 along the direction of assembly, wherein said steel duct 1 has an upper part that protrudes from the top surface of said precast concrete segment 10, and wherein the lower part of said steel duct 1 comprises a socket 11 with a widened diameter so as to allow the protruding upper part of a steel duct 1 from the other concrete segment 10 to be inserted therein, and wherein the protruding upper part of said steel duct 1 is inserted into the socket

11 located at the lower part of the other concrete segment 10 to form an integral assembly of segments that joins said two concrete segments 10 through mutual penetration of said steel duct 10.

[6] The segment assembly according to Claim 5, wherein said steel duct 1 that penetrates both concrete segments 10 is installed with a tendon capable of applying tension to bring about the assembly of said two segments 10. [7] The segment assembly according to Claims 5 or 6 comprising a sealing member

21 installed on the exterior top surface of said segment 10, wherein the other precast concrete segment is deposited over said sealing member 21, and wherein grout material is injected to fill the space created between the upper and lower segments 10 by said sealing member 21 to form a grout section between said upper and lower segments 10.