Prestressed Soldier Pile Using Cap Plate

Abstract

The present invention relates to a prestressed thumb pile using a cap plate. A prestressed sheet pile using a cap plate according to the present invention for this purpose comprises: a beam member formed by connecting a front flange and a rear flange to a web; an upper cap plate installed at the upper end of the beam member so as to face the upper surface of the rear flange and the web; a lower cap plate installed at the lower end of the beam member so as to face the lower surface of the rear flange and the web; and one or more tensioning members fixed so as to penetrate both ends of the upper cap plate and the lower cap plate to introduce axial tension into the beam member. Thus, the present invention introduces prestress by means of a pair of cap plates assembled to face the upper and lower surfaces of a beam member, which are pressed against the upper and lower surfaces of the beam member by a tension member located inside the cross-section of the beam member. This prevents damage to the cap plates and the beam member caused by the load for introducing prestress being concentrated in a specific area or shear force being generated, thereby allowing prestress to be introduced into the beam member more stably.

Description

Technology Field

[0001] The present invention relates to a sheet pile used in a self-supporting temporary earth retaining wall, and more specifically, to a prestressed sheet pile using a cap plate in which a pair of cap plates disposed on the upper and lower surfaces of a beam member made of H-shaped steel are connected by a tensioning member located inside the cross-section of the beam member, and the pair of cap plates are arranged to face the upper and lower cross-sections of the beam member so that an axial force is introduced into the cross-section of the beam member during tensioning for the introduction of prestress, thereby minimizing the generation of shear force. Background Technology

[0002] For architectural or civil engineering structures, excavation work is carried out first on the ground to proceed with foundation work. In most cases, excavation is carried out using the open cut method, and in cases of deep excavation, the ground is reinforced using bracing, earth anchors, or rakers to support the earth pressure.

[0003] However, conventional ground reinforcement using bracing or rakers had limitations, such as a cramped workspace and difficulty in using heavy equipment, as reinforcement had to be performed using the excavation space. In addition, ground reinforcement using earth anchors had problems such as encroaching on private property in urban areas and damaging existing structures, as well as causing various damages such as nearby groundwater flowing into the excavation space.

[0004] For this reason, a PS beam self-supporting method has recently been proposed to support earth pressure by fixing a pair of brackets along the longitudinal direction of the pile and introducing pre-tensioning by placing steel rods or multiple steel wires between the brackets. A prior art document related to this is Korean Registered Patent No. 10-2393645 (registered on April 28, 2022, hereinafter referred to as 'Prior Art Document 1').

[0005] As illustrated in FIG. 1, the above prior art document 1 applies prestress to the king pile (1) by installing brackets (2) at the upper and lower ends of a king pile (1) made of H-shaped steel to reduce bending stress occurring in a self-supporting earth retaining wall, and by providing a tension member (3) made of a steel rod or steel wire to the bracket (2).

[0006] However, prior art document 1 fixes the bracket (2) to the outside of the flange of the king pile (1) using multiple bolts, and the bracket (2) protruding to the side of the king pile (1) acts as an obstacle that makes it difficult to pull out the king pile (1), such as by increasing the frictional force with the surrounding soil when pulling out the king pile (1).

[0007] In addition, in order to stably transmit the tension force for introducing prestress to the king pile (1), the use of a plate with a large surface area and a reinforcing plate of sufficient thickness is required for the production of the bracket (2), which increases the self-weight and volume due to the use of a large amount of steel, thereby reducing constructability. Furthermore, there is the inconvenience of having to machine a large number of fastening holes in the king pile (1) to allow for the fastening of a significant number of bolts for the stable fixation of the bracket (2), and there is a limitation in that a considerable amount of time and cost is required for the restoration work of filling in the large number of fastening holes when the extracted king pile (1) is recycled.

[0008] In particular, when a tension member (3) is installed on a bracket (2) protruding laterally from a king pile (1) and tensioned, the load is locally concentrated on the upper and lower parts of the flange of the king pile (1) where the bracket (2) is installed, and this load causes excessive shear force between the bracket (2) and the flange of the king pile (1), which causes the flange of the king pile (1) to deform or break.

[0009] Meanwhile, another prior art document regarding prestressed sheet piles is Korean Registered Patent No. 10-2312008 (registered on October 6, 2021, hereinafter referred to as 'Prior Art Document 2'). The prestressed sheet pile of Prior Art Document 2 is configured such that an upper anchorage and a lower anchorage are installed at the upper and lower ends, and the upper anchorage and the lower anchorage are connected by a plurality of steel strands to introduce prestress.

[0010] At this time, the upper anchor and the lower anchor are positioned at the intersection of the rear horizontal member and the vertical member so as to be fitted and coupled to the rear horizontal member and the vertical member of the king pile, and are in close contact with only a part of the cross-section of the king pile, and a plurality of steel strands are arranged to connect the upper anchor and the lower anchor from the inner and outer sides centered on the rear horizontal member.

[0011] The prestressed sheet pile of prior art document 2, as described above, attempted to solve the problem of controlling the reaction force generated on the opposite side of the steel strand without a separate fixing device when the steel strand is placed on the outer side of the rear horizontal member and tensioned by fitting the upper anchor and the lower anchor at the intersection of the rear horizontal member and the vertical member.

[0012] However, prior art document 2 has a problem in that, during the process of tensioning the steel strands to introduce prestress, the load is concentrated at the intersection of the rear horizontal member and the vertical member, so the rear horizontal member and the vertical member can easily deform during the process of introducing prestress, and as the tension force of the steel strands placed on the outer side of the rear horizontal member and located outside the cross-section of the king pile acts in a way that bends and lifts the lower part of the rear horizontal member, the tension force of the steel strands is not properly reflected in the king pile, and displacement occurs due to the gap between the anchorage and the king pile, resulting in a significant reduction in the prestressing force.

[0013] In addition, some steel strands are still positioned on the outer side of the rear horizontal member, which increases the moment generated by prestressing. Furthermore, as anchoring devices protrude to the outer side of the rear horizontal member to secure the steel strands, there is a limitation in that obstacles occur during pile installation and extraction due to constraints on the drilling hole specifications.

[0014] In addition, some prior art documents have proposed providing cap-type brackets at the upper and lower ends of the sheet piles to facilitate the introduction of prestress by tension members and to promote the convenience of sheet pile recycling. However, the cap-type brackets proposed in other prior art documents still had limitations in that local shear forces were inevitably generated in parts of the bracket, causing deformation failure of the bracket, because the tension members were placed outside the cross-section or the cap-type bracket was mounted locally only on a portion of the sheet pile cross-section. Prior art literature

[0015] Korean Registered Patent No. 10-2393645 (Registered Apr. 28, 2022) Korean Registered Patent No. 10-2312008 (Registered Oct. 6, 2021) The problem to be solved

[0016] The present invention has been devised to solve the aforementioned problems. The objective of the present invention is to provide a prestressed king pile using cap plates, wherein a pair of cap plates are assembled to face each other above and below without protruding laterally from the king pile forming a self-supporting earth retaining wall, and are connected by a tensioning member located inside the cross-section of a beam member. This ensures that when the tensioning member is tensioned for the introduction of prestress, all force is transmitted only vertically, thereby reducing the loss of prestressing force and eliminating the need for a separate fixing device, as well as minimizing the generation of shear force and enabling stable prestress introduction by resisting axial force using the cross-section of the beam.

[0017] Another objective of the present invention is to provide a prestressed thumb pile using cap plates that can be easily assembled and separated so as to face the upper and lower cross-sections of a beam member.

[0018] Another objective of the present invention is to provide a prestressed sheet pile using a cap plate that can improve constructability and economic efficiency by including a beam member having a variable cross-section in which a trapezoidal side structure extending downward or front and rear flanges form an asymmetrical structure, taking into account the magnitude of different moments depending on the insertion depth.

[0019] Another objective of the present invention is to provide a prestressed king pile using a cap plate that allows a beam member having a downwardly extended trapezoidal side structure to be easily manufactured using a prefabricated H-shaped steel. means of solving the problem

[0020] The prestressed sheet pile using the cap plate of the present invention, which performs the task of achieving the above-mentioned purpose and eliminating conventional problems, relates to a sheet pile installed in a vertical position along an excavation boundary surface to form a retaining wall, and is characterized by comprising: a beam member (10) formed by connecting a front flange (11) and a rear flange (12) to a web (13); an upper cap plate (20) installed at the upper end of the beam member (10) to face the upper surface of the rear flange (12) and the web (13); a lower cap plate (30) installed at the lower end of the beam member (10) to face the lower surface of the rear flange (12) and the web (13); and one or more tensioning members (40) that are fixed so as to penetrate both ends of the upper cap plate (20) and the lower cap plate (30) to introduce axial tension force to the beam member (10).

[0021] Additionally, a plurality of reinforcing pieces (22) (32) for connecting beam members that are in close contact with the beam member (10) may be formed protrudingly on the upper cap plate (20) and the lower cap plate (30).

[0022] Additionally, a pair of web reinforcing members (14) are protruded on both sides of the upper and lower ends of the web (13) and are provided in a vertical position on the bottom surface of the upper cap plate (20) and the upper surface of the lower cap plate (30), and can be bolted together with either of the reinforcing members (22)(32) for connecting beam members.

[0023] Additionally, an anchor head (50) is provided in the upper part of the upper cap plate (20) and the lower part of the lower cap plate (30) with a wedge hole (51) formed therein for the wedge (41) of the end of the tension member (40) to pass through, and a plurality of anchor head supporting reinforcing pieces (23) (33) that are in close contact with and fixed to the anchor head (50) may be formed on the upper cap plate (20) and the lower cap plate (30).

[0024] Additionally, the beam member (10) may be formed such that the web (13) forms a trapezoidal side structure extending downward, and the front flange (11) may have an inclined portion (11a) at its upper end that is inclined backward.

[0025] Additionally, the beam member (10) of the above-mentioned trapezoidal side structure may be manufactured by: i) a step of manufacturing a pair of split segments (S1, S2) by diagonally connecting and cutting one side point (P1) located on one end of the web (13) in the longitudinal direction and the other side point (P2) located on the other end, based on the height (h) of the existing H-shaped steel; and ii) a step of manufacturing a new beam member (10) by rotating one of the segments in the longitudinal direction and welding the webs (13) of each segment together.

[0026] Additionally, iii) a step of trimming the ends by cutting the angled webs (13) formed at both ends of the newly manufactured beam member (10); may be further included.

[0027] In addition, the beam member (10) may be formed in an asymmetrical structure such that the rear flange (12) is positioned further outward than the front flange (11) with respect to the centroidal axis (G). Effects of the invention

[0028] According to the prestressed sheet pile using the cap plate of the present invention, a pair of cap plates assembled to face the upper and lower surfaces of a beam member introduce prestress by pressing against the upper and lower surfaces of the beam member with a tensioning member located inside the cross-section of the beam member. Since all force is transmitted only vertically, the loss of prestressing force can be minimized, and the use of a separate fixing device to suppress movement of the beam member during the prestress introduction process is not required. Furthermore, it is possible to prevent damage to the cap plates and the beam member caused by the load for introducing prestress being concentrated in a specific area or shear force being generated, thereby allowing prestress to be introduced to the beam member more stably.

[0029] In particular, since the cap plate assembled on the upper and lower surfaces of the beam member is assembled in a manner that covers the upper surface of the beam member, the cap plate assembly work performed as a preparatory step for inserting the beam member into the ground can be carried out quickly and smoothly, and when the beam member is pulled out, the cap plate can be easily separated from the beam member by cutting the tension member, thereby ensuring constructability and convenience and increasing the recyclability of the beam member.

[0030] Furthermore, during the process of assembling the cap plates to the beam member, instead of machining or welding fastening holes in the flange of the beam member to secure the cap plates, a pair of cap plates can be simply secured to the beam member by forming fastening holes in a separately attached web reinforcement and connecting them with tension members while the cap plates are pre-assembled and fixed. This minimizes damage to the beam member caused by the formation of fastening holes or welding, thereby minimizing restoration work for the recycling of the beam member.

[0031] Furthermore, by forming a trapezoidal structure in which the beam member expands downward in response to the moment acting on the beam member increasing proportionally with depth due to the pressure of surrounding soil, or by forming the front and rear flanges in an asymmetrical structure such that the rear flange is positioned further outward than the front flange relative to the centroidal axis of the beam member to account for the compressive stress generated in the rear flange upon the introduction of tension force, it is possible to design an optimal stress distribution while maintaining a constant amount of steel used for manufacturing the sheet pile, thereby not only promoting efficiency but also further improving constructability through the lightweighting of the sheet pile.

[0032] Furthermore, since the trapezoidal beam member can be easily manufactured by cutting and reassembling prefabricated H-shaped steel, manufacturing convenience can be ensured. Brief explanation of the drawing

[0033] FIG. 1 is a structural diagram of a king pile according to prior art literature, FIG. 2a is a perspective view of a prestressed sheet pile using a cap plate according to an embodiment of the present invention, FIG. 2b is an exploded perspective view of a prestressed sheet pile using a cap plate according to one embodiment of the present invention, FIG. 2c is a perspective view illustrating the detailed structure of an upper cap plate according to one embodiment of the present invention. FIG. 2d is a perspective view illustrating the detailed structure of a lower cap plate according to one embodiment of the present invention. FIG. 2e is a perspective view showing a state in which a fixing magnet for preventing detachment of the anchor head is attached to a reinforcing piece for supporting the anchor head of the upper cap plate. FIG. 2f is a perspective view showing a state in which a fixing magnet for preventing detachment of the anchor head is attached to a reinforcing piece for supporting the anchor head of the lower cap plate. FIG. 2g is a bottom perspective view showing a state in which a fixing magnet for preventing detachment of the anchor head is attached to the bottom surface of the upper cap plate, FIG. 2h is a perspective view showing a state in which a fixing magnet for preventing detachment of the anchor head is attached to the upper surface of the lower cap plate. FIG. 2i is a perspective view illustrating the structure of an upper cap plate, a lower cap plate, and an anchor head according to another embodiment of the present invention. FIG. 3 is a side view of a beam member according to an embodiment of the present invention, FIG. 4a is a moment diagram showing the change in magnitude of the moment acting on a king pile in shallow, good quality ground, FIG. 4b is a moment diagram showing the change in magnitude of the moment acting on a king pile in deep soft ground, FIG. 5a is an exemplary diagram showing the process of manufacturing a beam member of the present invention using a prefabricated H-shaped steel. FIG. 5b is an exemplary diagram showing another process of manufacturing the beam member of the present invention from prefabricated H-shaped steel. FIG. 6 is an example diagram showing a beam member with an asymmetric structure. FIG. 7a is a stress diagram showing the change in stress during the process of introducing prestress into a king pile having a symmetric flange structure, FIG. 7b is a stress diagram showing the change in stress during the process of introducing prestress to a king pile having an asymmetric flange structure, FIG. 8a is a perspective view showing a beam member with an asymmetric structure having a front flange and a rear flange of different widths. FIG. 8b is a perspective view showing a beam member with an asymmetric structure having a front flange and a rear flange of different thicknesses, FIG. 9 is a structural diagram of a self-supporting earth retaining wall constructed using prestressed sheet piles according to the present invention. Specific details for implementing the invention

[0034] In the following, preferred embodiments of the present invention will be described in detail based on the details illustrated in the drawings; however, specific descriptions of related known functions or configurations are omitted if it is determined that such descriptions may unnecessarily obscure the essence of the present invention.

[0035] As illustrated in FIG. 2a, a prestressed pile using a cap plate according to one embodiment of the present invention comprises a beam member (10), an upper cap plate (20), a lower cap plate (30), and a tension member (40), wherein the upper cap plate (20) and the lower cap plate (30), which are respectively arranged to face the upper and lower surfaces of the beam member (10), are connected by a tension member (40) located inside the beam member (10) to introduce prestress into the beam member (10).

[0036] The beam member (10) is formed by connecting a front flange (11) and a rear flange (12), which are spaced apart while facing each other, via a web (13). The front flange (11) is positioned on the inside of the excavation boundary and is exposed due to excavation, while the rear flange (12) is positioned on the outside of the excavation boundary and is always buried in soil regardless of whether excavation occurs.

[0037] Additionally, a pair of web reinforcing members (14) are formed protruding from both sides of the upper and lower ends of the web (13) of the beam member (10). The pair of web reinforcing members (14) are assembled to be in contact with the upper cap plate (20) and the lower cap plate (30) to be in contact with the upper and lower surfaces of the beam member (10), thereby additionally transmitting and distributing the load generated by the tension of the tension member (40) to the web (13), thereby promoting the introduction of axial force and preventing damage to the beam member (10) caused by localized concentration of load.

[0038] In order to transfer and distribute the load transmitted from the upper cap plate (20) and the lower cap plate (30) to the web (13), it is preferable that the web reinforcing member (14), which additionally connects the upper cap plate (20) and the web (13) and the lower cap plate (30) and the web (13), be provided so as to be vertical to the surface of the web (13), the bottom surface of the upper cap plate (20), and the top surface of the lower cap plate (30), respectively.

[0039] As illustrated in FIGS. 2b and 2c, the upper cap plate (20) includes a plate body (21) that is in close contact with the upper surface of the beam member (10), and the plate body (21) is formed in a flat structure such that its bottom surface is in contact with the upper surface of the rear flange (12), the web (13), and the web reinforcement (14), and is provided with a plurality of through holes (211) that allow a plurality of tension members (40) to pass through the upper cap plate (20) in close proximity to the rear flange (12), and an anchor head (50) can be assembled at the top of the through holes (211) having a wedge hole (51) for tensioning and fixing the end of the tension member (40).

[0040] Meanwhile, in order for the plate body (21) to be assembled in place and not detached, and to transmit the load transmitted from the tension member (40) to the beam member (10), a plurality of reinforcing pieces (22) for connecting beam members that are in close contact with the beam member (10) may be formed protruding downward from the plate body (21) of the upper cap plate (20). Preferably, one reinforcing piece (22) for connecting beam members may be formed on the front of the plate body (21) to be in contact with the front of the web reinforcing member (14), and a pair of opposing reinforcing pieces (22) for connecting beam members may be formed on both sides of the plate body (21) to be in contact with and support the rear flange (12) or both sides of the web reinforcing member (14), and one reinforcing piece (22) for connecting beam members may be formed on the rear of the plate body (21) to be in contact with the rear of the rear flange (12). It is preferable that a pair of reinforcing pieces (22) for connecting beam members, formed on both sides of the plate body (21) in this manner, be formed to be in contact with and support both sides of the rear flange (12) so as to more effectively suppress the plate body (21) from twisting during the tensioning process of the tension member (40).

[0041] Additionally, the reinforcing piece (22) for connecting the beam member formed on the front surface of the plate body (21) can be bolted together in contact with the web reinforcing member (14). That is, to ensure convenience during the transportation and construction of the king pile, the reinforcing piece (22) for connecting the beam member and the web reinforcing member (14) are fixed by bolting, and the bolt can be removed before the final prestressing operation.

[0042] As described above, the plate body (21) and the reinforcing piece (22) for connecting a plurality of beam members are integrated, and a pair of web reinforcing members (14) are integrated and reinforced in the beam member (10), so the upper cap plate (20) can be easily and stably assembled by being placed over the upper part of the beam member (10) without separate welding.

[0043] As illustrated in FIGS. 2b and 2d, the lower cap plate (30) includes a plate body (31) formed in a flat shape so as to be in contact with the lower surface of the beam member (10). The plate body (31) is formed in a flat shape so as to have its upper surface in contact with the rear flange (12), the web (13), and the lower surface of the web reinforcement (14). It is provided with a plurality of through holes (311) that allow a plurality of tension members (40) to pass through the upper cap plate (20) and the lower cap plate (30) in a vertical position. An anchor head (50) can be assembled at the bottom of the through holes (211), with a wedge hole (51) formed therein for tensioning and fixing the end of the tension member (40). At this time, the wedge hole (51) is formed in a conical shape so that a wedge (41) installed at the end of the tension member (40) can be inserted and coupled.

[0044] Meanwhile, in order for the plate body (31) to be assembled in place and not detached, and to transmit the load transmitted from the tension member (40) to the beam member (10), a plurality of reinforcing pieces (32) for connecting beam members that are in close contact with the beam member (10) may be formed protruding upward from the plate body (31). That is, one reinforcing piece (32) for connecting beam members may be formed on the front of the plate body (31) to be in contact with the front of the web reinforcing member (14), a pair of reinforcing pieces (32) for connecting beam members may be formed on both sides of the plate body (31) to be in contact with the rear flange (12) or both sides of the web reinforcing member (14), and one reinforcing piece (32) for connecting beam members may be formed on the rear of the plate body (31) to be in contact with the rear of the rear flange (12).

[0045] Since the anchor head (50) assembled on the upper part of the upper cap plate (20) and the lower part of the lower cap plate (30) may be moved in a horizontal position during the prestressing process of the tension member (40), it is preferable that a plurality of anchor head supporting reinforcing pieces (23) (33) are formed on the upper cap plate (20) and the lower cap plate (30) to be in close contact with and fixed to the anchor head (50).

[0046] As illustrated in FIGS. 2c and 2d, the anchor head supporting reinforcing pieces (23)(33) may be formed to be in close contact with the front and rear surfaces and one side of the anchor head (50). A pair of anchor head supporting reinforcing pieces (23)(33) that are in close contact with the front and rear surfaces may have an L-shaped cross section to prevent the anchor head (50) from moving upward or downward, and it is preferable to additionally form bolt holes (23a)(33a) into which bolts are fastened to fix the anchor head (50) in the assembled position. Thus, the anchor head (50) is slidably inserted from the side of the upper cap plate (20) and the lower cap plate (30) and assembled to the upper cap plate (20) and the lower cap plate (30), and can be fixed by bolts fastened to the bolt holes (23a)(33a).

[0047] Although not shown in the image, the reinforcing piece (23, 33) for supporting the anchor head may be formed to be in close contact with both the front and rear sides and both sides of the anchor head (50) to support it.

[0048] In addition, a fixing magnet (60) that prevents detachment by fixing the anchor head (50) assembled on the upper cap plate (20) and lower cap plate (30) by magnetic force rather than a bolt may be provided on the upper cap plate (20) and lower cap plate (30).

[0049] That is, as shown in FIGS. 2e and 2f, a fixing magnet (60) that is magnetically coupled to the anchor head (50) to prevent the anchor head (50) from detaching may be additionally attached to the outer side of the anchor head support reinforcing piece (23)(33), or as shown in FIGS. 2g and 2h, a tension member (40) may be attached so as to penetrate the bottom surface of the upper cap plate (20) or the upper surface of the lower cap plate (30). In this case, an opening (60a) may be formed in the fixing magnet (60) so that it is easy to remove when tensioned.

[0050] As shown in FIGS. 2a and 2b, the tension member (40) is made of a steel rod or a steel wire, and the upper end is fixed to the anchor head (50) by passing through the through hole (211) of the upper cap plate (20) and the lower end is fixed to the anchor head (50) by passing through the through hole (311) of the lower cap plate (30). As a result, the upper cap plate (20) and the lower cap plate (30), which are respectively assembled at the upper and lower ends of the beam member (10), are connected to each other by the tension member (40) and fixed to the beam member (10), and are additionally fixed to the beam member (10) by a bolt that passes through the reinforcing piece (22)(32) for connecting the beam member and is fastened to the web reinforcing member (14).

[0051] Meanwhile, since a plurality of tension members (40) are installed to connect the upper cap plate (20) and the lower cap plate (30) in close proximity to the rear flange (12) on both the left and right sides of the web (13) through through holes (211) (311) formed in the upper cap plate (20) and the lower cap plate (30), when the plurality of tension members (40) are fixed to the upper cap plate (20) and the lower cap plate (30) in a tensioned state to introduce prestress, the upper cap plate (20) and the lower cap plate (30) that are in contact with the upper and lower surfaces of the beam member (10) press the beam member (10) from above and below, so the shear force between the cap plate (20) and the beam member (10) is minimized, and compressive stress is introduced by resisting with axial force.

[0052] As such, the prestressed pile using the cap plate of the present invention is connected by a tension member (40) installed so that the upper cap plate (20) and the lower cap plate (30), which are arranged to be in contact with the upper and lower surfaces of the beam member (10), are positioned inside the beam member (10). In contact with the rear flange (12), the web (13), and the web reinforcement (14), all force is transmitted only vertically during the process of introducing prestress to the beam member (10), thereby minimizing shear force and allowing prestress to be introduced stably without causing structural damage to the cap plate (20). Additionally, the assembly and separation of the upper cap plate (20) and the lower cap plate (30) are easy, ensuring convenience in underground insertion and extraction operations.

[0053] As shown in FIG. 2i, the anchor head (50) may be formed with a square structure of four wedge holes (51) distributed therein, and correspondingly, the upper cap plate (20) and the lower cap plate (30) may be formed such that four tension members are arranged in a square structure and positioned inside the cross-section of the beam member. This has the disadvantage that when steel wires are arranged in a line along the conventional flange, eccentricity is generated around the weak axis of the beam, which can cause lateral torsional buckling in the direction of the pile length, making it impossible to apply prestressing force beyond a certain size. On the other hand, the method in FIG. 2i has the advantage that the eccentricity length is small (half the diameter of the steel wire) because the steel wire is installed in close contact with the web, and thus prevents lateral torsional buckling.

[0054] As illustrated in FIGS. 3 to 4b, the beam member (10) includes a web (13) having a trapezoidal side structure that extends downward to minimize the use of steel and enable effective response to moments of different sizes depending on the depth, and the front flange (11) may have an inclined portion (11a) formed with an upper portion inclined backward.

[0055] Since the king pile has a cantilever beam structure with a free end at the top, the magnitude of the moment is relatively small at the top of the excavation surface, and due to the pressure of the soil increasing in proportion to the excavation depth, it has a moment diagram in the shape of a second-order parabola with a relatively large magnitude of moment at the bottom. Reflecting this, conventionally, prefabricated H-shaped steel (300×300 or 350×350) with the same beam height and the same symmetrical flange was used according to site conditions, but in this case, unnecessary cross-sections are used at the top, making it uneconomical.

[0056] Accordingly, the present invention has another technical difference in that the cross-section of the beam member (10) is designed based on the maximum moment value, but the upper part is made smaller so that the use of steel used for the construction of the beam member (10) is minimized to reduce the weight of the king pile, and additionally, the beam member (10) including a web (13) having a side structure in the shape of a trapezoid that extends downward can be easily manufactured using a ready-made H-shaped steel.

[0057] As illustrated in FIG. 5a, the beam member (10) of the trapezoidal side structure of the present invention can be manufactured through the steps of: i) manufacturing a pair of split segments (S1, S2) by diagonally connecting and cutting one side point (P1) located on one end of the web (13) and the other side point (P2) located on the other end, based on the height (h) of a prefabricated H-shaped steel having a front flange (11) and a rear flange (12) that are symmetrical with respect to the centroidal axis (G); and ii) manufacturing a new beam member (10) by rotating one of the segments (S2) in the longitudinal direction and welding the webs (13) of each segment (S1, S2) together.

[0058] As illustrated in FIG. 5b, step i) may produce a pair of split segments (S1, S2) by connecting a point (P1) that divides one end of the web (13) in a ratio of m:n and a point (P2) located at the corner of the other end of the web (13) in a straight line, and step ii) may produce a beam member (10) with a trapezoidal side structure by rotating one of the produced pair of split segments (S1, S2) in the longitudinal direction and welding them together so that the webs (13) of each segment are butted together. The method of FIG. 5b is suitable when the height (h) of the initial H-shaped steel is sufficiently high and selected to correspond to the calculated maximum moment value, or when there are limitations on significantly increasing the height due to constraints on the size of the hole for inserting the beam.

[0059] However, since the beam member (10') produced in the manner shown in FIG. 5b has the problem that it is difficult to effectively respond to a moment whose size gradually changes with depth due to the extreme difference in height (h) between the two ends, and that it is difficult to stably introduce prestress because a sufficient contact area is not secured between the upper cap plate (20) and the upper surface of the beam member (10), as shown in FIG. 5a, in step i), it is preferable to produce a pair of symmetrical split segments (S1, S2) by cutting a straight line between a point (P1) of the web (13) that divides one end into m:n and a point (P2) of the web (13) that divides the other end into n:m, based on the height (h) of the existing H-shaped steel. The method of FIG. 5a is suitable when the initial height (h) of the H-shaped steel is insufficient or when there are no special restrictions on the size of the hole for inserting the beam.

[0060] Meanwhile, a new beam member (10) formed by welding a pair of split segments (S1, S2) together has an angled web (13) formed at both ends, so it has a structure that makes it difficult to meet the upper cap plate (20) and the lower cap plate (30). Therefore, as step iii), the beam member (10) can be completed by trimming the angled web (13) formed at both ends of the newly manufactured beam member (10) to finish the ends.

[0061] As illustrated in FIG. 4b, the cross-section of the beam member (10) is designed based on the maximum moment value. Since the moment value tends to decrease in both the upper and lower parts of the beam member (10) based on the location where the maximum moment value is exerted, the lower part of the location where the maximum moment value is exerted can be manufactured to maintain a constant cross-section in order to reduce the consumption of unnecessary steel. To this end, as step iv), the beam member (10) can be manufactured by additionally welding an H-shaped steel cut to a certain length to the lower part of the newly manufactured beam member (10).

[0062] Meanwhile, in another embodiment, as shown in FIG. 6, the beam member (10) may be formed in an asymmetrical structure such that the rear flange (12) is positioned further outward than the front flange (11) with respect to the centroidal axis (G).

[0063] When prestress is introduced to a king pile made of a prefabricated H-shaped steel, as shown in Fig. 7a, the magnitude of the compressive stress increases by the amount of the prestressing effect, so it may exceed the allowable resistance of the H-shaped steel, which is why there is a problem requiring the use of a larger H-shaped steel.

[0064] Accordingly, the present invention proposes that the neutral axis of the cross section (hereinafter referred to as the "central axis") be moved toward the compression side by a certain ratio in response to the stress generated by prestressing, thereby reducing the excess allowable resistance force. That is, when the centroid axis (G) of the beam member (10) is moved toward the compression side, as shown in FIG. 7b, the beam member (10) is manufactured in a state where the stress on the compression side is reduced and the stress on the tension side is increased, and by introducing prestress into the beam member (10), the tensile resistance force that was exceeded in conventional steel sections can be maintained within the allowable value.

[0065] The beam member (10) of such an asymmetric structure can be manufactured through the steps of: i) determining in advance the ratio of stress caused by load and stress caused by prestressing; and ii) determining the area and shape of the rear flange (12) and the front flange (11) according to the determined ratio. At this time, the steel may be replaced with high-strength steel depending on the stress excess.

[0066] Meanwhile, the asymmetrical beam member (10) can be manufactured such that, as shown in FIG. 8a, the front flange (11) has a greater width than the rear flange (12) so that the centroidal axis (G) is closer to the front flange (11) than to the rear flange (12), or as shown in FIG. 8b, the front flange (11) has a thicker thickness than the rear flange (12) so that the centroidal axis (G) is closer to the front flange (11) than to the rear flange (12).

[0067] Thus, by manufacturing the H-shaped steel into a variable cross-section structure by considering the compressive stress caused by prestressing in advance, the load can be effectively controlled within the tensile and compressive stresses of the H-shaped steel, thereby providing a structurally superior and economical cross-section compared to conventional H-shaped steel with the same amount of steel used, and a sufficient gap can be secured between the tension member (40) located inside the cross-section of the beam member (10) and the centroidal axis (G) for the smooth introduction of prestress.

[0068] As shown in FIG. 9, the prestressed sheet piles of the present invention are installed so as to be spaced apart from each other in a vertical position along the excavation boundary, and a plurality of earth retaining plates (70) are installed between adjacent prestressed sheet piles to form a self-supporting earth retaining wall.

[0069] It will be understood by those skilled in the art that the prestressed sheet pile using the cap plate according to the present invention described above can be implemented in other specific forms without altering the technical concept or essential features of the present invention.

[0070] Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting, and the scope of the invention is defined by the claims set forth below rather than by the foregoing detailed description, and all modifications or variations derived from the meaning and scope of the claims and equivalents should be interpreted as being included within the scope of the invention. Explanation of the symbols

[0071] 10: Beam member 11: Front flange 12: Rear flange 13: Web 14: Web reinforcement 20: Upper cap plate 21: Plate body 22: Reinforcing piece for connecting beam members 23: Reinforcement piece for anchor head support 30: Lower cap plate 31: Plate body 32: Reinforcing piece for connecting beam members 33: Reinforcement piece for anchor head support 40: Tension member 41: Wedge 50: Anchor Head 51: Wedge hole

Claims

Claim 1 The invention relates to a king pile installed in a vertical position along an excavation boundary surface to form an earth retaining wall, wherein a front flange (11) and a rear flange (12) are connected by a web (13) to form a beam member (10), and a pair of web reinforcing members (14) protrude from both upper and lower sides of the web (13) in a vertical position relative to the bottom surface of an upper plate (20) and the top surface of a lower cap plate (30); and an upper portion installed at the upper end of the beam member (10) in contact with the rear flange (12) and the top surface of the web (13), wherein a plurality of beam member connecting reinforcing members (22) are formed protruding downward to be in close contact with the beam member (10), at least one beam member connecting reinforcing member (22) is bolted to the web reinforcing member (14), and a plurality of anchor head supporting reinforcing members (23) are formed protruding upward with an L-shaped cross-section to prevent the anchor head (50) from detaching upward. A cap plate (20); a lower cap plate (30) installed at the lower end of the beam member (10) and in contact with the lower surface of the rear flange (12) and the web (13), and having a plurality of beam member connecting reinforcing pieces (32) formed protruding upward so as to be in close contact with the beam member (10), wherein at least one beam member connecting reinforcing piece (32) is bolted to the web reinforcing member (14), and a plurality of anchor head supporting reinforcing pieces (33) formed protruding downward with an L-shaped cross-section to prevent the anchor head (50) from detaching downward; and one or more tension members (40) having both ends fixed to penetrate the upper cap plate (20), the lower cap plate (30), and the anchor head (50) to introduce axial tension force to the beam member (10). A prestressed anchor pile using a cap plate, characterized by including: an anchor head (50) provided on the upper part of the upper cap plate (20) and the lower part of the lower cap plate (30), having a wedge hole (51) formed therein for the tension member (40) to pass through, and fixed by a bolt passing through the anchor head support reinforcing piece (23) or fixed by a fixing magnet (60) attached to the upper and lower cap plates (20) (30). Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A prestressed thumb pile using a cap plate, characterized in that, in claim 1, the beam member (10) has a trapezoidal side structure in which the web (13) is extended downward, and the front flange (11) has an inclined portion (11a) at the upper end that is inclined backward. Claim 6 In claim 5, the beam member (10) of the above-mentioned trapezoidal side structure further comprises: i) a step of producing a pair of split segments (S1, S2) by diagonally connecting and cutting one side point (P1) located on one end of the web (13) in the longitudinal direction and the other side point (P2) located on the other end, based on the height (h) of the existing H-shaped steel; ii) a step of producing a new beam member (10) by rotating one of the segments in the longitudinal direction and welding the webs (13) of each segment together; and iii) a step of trimming the ends by cutting the angled webs (13) formed at both ends of the newly produced beam member (10). Claim 7 A prestressed thumb pile using a cap plate, characterized in that, in claim 1, the beam member (10) is formed in an asymmetrical structure such that the rear flange (12) is positioned further outward than the front flange (11) with respect to the centroidal axis (G).

Images