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[0001] (1) Field of the Invention
[0002] The present invention relates generally to a method of manufacturing preflex beams, and particularly to a method for simultaneously manufacturing a plurality of preflex beams used as simple beams or continuous beams, using cambered plate girders or non-cambered rolled shape steels.
[0003] (2) Description of the Prior Art
[0004] A conventional art is described with reference to preflex beams used as simple beams.
[0005]
[0006] In the conventional method for manufacturing preflex beams, in order to prevent the plate girders from being horizontally buckled, there should be installed a plurality of horizontal buckling preventing devices that are spaced at regular intervals along the lengths of the plate girders and forcibly hold the plate girders. For the application of the conventional method, two supporting stands and a plurality of horizontal buckling preventing devices are necessary for a set of plate girders, and a concrete base having a thickness of more than 250 mm is necessary to resist a horizontal buckling force that may be generated when preflexion loads are applied to the plate girders. Accordingly, excessive working area is needed. Only two preflex beams can be manufactured by the one time application of preflexion loads, so that excessive manufacturing time is required. In particular, the conventional method can only be applied to the manufacture of straight preflex beams.
[0007] Accordingly, the present invention has been made to overcome the above problems occurring in the prior art, and an object of the present invention is to provide a method for manufacturing preflex beams, which is capable of manufacturing two or more straight or curved preflex beams by means of one time load applying work.
[0008] Another object of the present invention is to provide a method for manufacturing preflex beams, in which non-cambered rolled shape steels are cambered by plastic deformation.
[0009] A further object of the present invention is to provide a method for manufacturing preflex beams used as piles or pillars, in which compressive stress is given concrete with which both flanges of the rolled shape steels are covered.
[0010] In order to accomplish the above object, the present invention provides a method for manufacturing preflex beams using cambered plate girders, comprising the steps of preparing a first set of cambered upper and lower plate girders, and connecting the upper and lower plate girders of the first set to each other by a plurality of PS steel bars at fulcrum positions; preparing a second set of cambered upper and lower plate girders, and connecting the upper and lower plate girders of the second set to each other by a plurality of PS steel bars at predetermined positions; arranging the first set of the upper and lower plate girders and the second set of the upper and lower plate girders in parallel while being spaced apart from each other by a predetermined interval; connecting the upper plate girders of the first and second sets by a plurality of upper crossbeams spaced apart from one another by predetermined regular intervals, and connecting the lower plate girders of the first and second sets by a plurality of lower crossbeams spaced apart from one another by predetermined regular intervals; placing a plurality of lower supporting stands under the lower crossbeams, respectively; placing a plurality of hydraulic jacks between the upper and lower plate girders of each set at load applying positions, and applying preflexion loads to the upper and lower plate girders using the hydraulic jacks; and covering the upper flanges of the upper plate girders and the lower flanges of the lower plate girders with concrete.
[0011] In order to manufacture the preflex beams used as simple beams, the fulcrum positions are respectively situated on both side ends of the plate girders, and the load applying positions are spaced respectively apart from the both side ends of the plate girders by about L/5.
[0012] In order to manufacture the preflex beams used as the internal beams of continuous beams, the fulcrum positions are respectively spaced inwardly apart from both side ends of the plate girders by about L/5, and the load applying positions are spaced respectively apart from the both side ends of the plate girders by about L/3.
[0013] In order to manufacture the preflex beams used as the external beams of continuous beams, the fulcrum positions are respectively spaced inwardly apart from both side ends of the plate girders by about L/5, and the load applying positions are spaced respectively apart from the both side ends of the plate girders by about L/4 and 0.5 L, so as to use the preflex beams as the external beams of continuous beams.
[0014] In the manufacture of preflex beams used as simple beams and the internal and external beams of continuous beams, in a case where the length of the plate girders is 20 m or less, the lower supporting stands are placed at the applying positions of preflexion loads, and the method further comprises the step of respectively placing a plurality of upper supporting stands under the upper plate girders at the same positions as those for the lower supporting stands after the step of placing the lower supporting stands.
[0015] In a case where the length of the plate girders is 20 to 30 m, the lower supporting stands are placed at three positions respectively spaced inwardly apart from both side ends of the lower plate girders by about 0.1 L and 0.5 L, and the method further comprises the step of respectively placing a plurality of upper supporting stands under the upper plate girders at the same positions as those for the lower supporting stands after the step of placing the lower supporting stands.
[0016] In a case where the length of the plate girders is 30 m or more, the lower supporting stands are placed at four positions respectively spaced inwardly apart from both side ends of the lower plate girders by about 0.1 L and 0.3 L, and the method further comprises the step of respectively placing a plurality of upper supporting stands under the upper plate girders at the same positions as those for the lower supporting stands after the step of placing the lower supporting stands.
[0017] Another method for manufacturing preflex beams, comprises the steps of preparing a first set of cambered upper and lower plate girders; preparing a second set of cambered upper and lower plate girders; connecting the upper plate girders of the first and second sets by a plurality of upper crossbeams spaced apart from one another by predetermined regular intervals, and connecting the lower plate girders of the first and second sets by a plurality of lower crossbeams spaced apart from one another by predetermined regular intervals; placing a plurality of lower supporting stands under the lower plate girders, respectively; placing a plurality of props on the lower crossbeams at predetermined positions, respectively; placing a plurality of hydraulic jacks between the upper and lower plate girders of each set at load applying positions; enclosing the upper and lower plate girders of all sets and the hydraulic jacks with a square frame; applying preflexion loads to the upper and lower plate girders using the hydraulic jacks; and covering the upper flanges of the upper plate girders and the lower flanges of the lower plate girders with concrete.
[0018] In the same manner as that of the previous method in which a square frame is not employed, this method for manufacturing preflex beams employs the positions of PS steel bars and the applying positions of preflexion loads determined depending upon the use of beams and the length of plate girders, and further comprises the step of placing a plurality of upper supporting stands.
[0019] When the second set of upper and lower plate girders arranged in parallel with the first set of upper and lower plate girders is plural, a plurality of preflex beams can be manufactured by one time application of preflexion loads.
[0020] In accordance with a second embodiment of the present invention, a method for manufacturing preflex beams using non-cambered rolled shape steels comprises the steps of preparing a first set of non-cambered straight upper and lower rolled shape steels, and connecting the upper and lower rolled shape steels of the first set to each other by a plurality of PS steel bars at fulcrum positions; preparing a second set of non-cambered straight upper and lower rolled shape steels, and connecting the upper and lower rolled shape steels of the second set to each other by a plurality of PS steel bars at fulcrum positions; arranging the first set of the upper and lower rolled shape steels and the second set of the upper and lower rolled shape steels in parallel while being spaced apart from each other by a predetermined interval; connecting the upper rolled shape steels of the first and second sets by a plurality of upper crossbeams spaced apart from one another by predetermined regular intervals, and connecting the lower rolled shape steels of the first and second sets by a plurality of lower crossbeams spaced apart from one another by predetermined regular intervals; placing a plurality of lower supporting stands under the lower crossbeams, respectively; placing a plurality of hydraulic jacks between the upper and lower rolled shape steels of each set at load applying positions, and applying preflexion loads to the upper and lower rolled shape steels using the hydraulic jacks so as to camber the upper and lower rolled shape steels by plastic deformation; placing a plurality of props on the lower crossbeams at predetermined positions, respectively; removing the PS steel bars placed at fulcrum positions and the hydraulic jacks placed at load applying positions; placing a plurality of hydraulic jacks on the upper rolled shape steels of each set or under the lower rolled shape steels of each set at load applying positions; enclosing the upper and lower rolled shape steels of all sets and the hydraulic jacks with a square frame; applying preflexion loads to the upper and lower rolled shape steels of all sets using the hydraulic jacks; and covering the upper flanges of the upper rolled shape steels and the lower flanges of the lower rolled shape steels with concrete.
[0021] In the same manner as that of the method of the first embodiment in which a square frame is not employed, the method for manufacturing preflex beams according to the second embodiment employs the positions of PS steel bars and the applying positions of the preflexion loads determined depending upon the use of beams and the length of the rolled shape steels, and further comprises the step of placing a plurality of upper supporting stands.
[0022] When the second set of upper and lower plate girders arranged in parallel with the first set of upper and lower rolled shape steels is plural, a plurality of preflex beams can be manufactured by one time application of preflexion loads.
[0023] In accordance with a third embodiment of the present invention, a method for manufacturing preflex beams, utilizing the way of connecting two dummy rolled shape steels to both ends of a non-cambered straight rolled shape steel, comprises the steps of connecting two dummy rolled shape steels to both ends of a non-cambered straight rolled shape steel by means of bolts into a rolled shape steel assembly; preparing a first set of non-cambered straight upper and lower rolled shape steel assemblies, and connecting the upper and lower rolled shape steel assembles of the first set to each other by a plurality of PS steel bars at both side ends of the rolled shape steels; preparing a second set of non-cambered straight upper and lower rolled shape steel assemblies, and connecting the upper and lower rolled shape steel assemblies of the second set to each other by a plurality of PS steel bars at both side ends of the rolled shape steel assemblies; arranging the first set of the upper and lower rolled shape steel assemblies and the second set of the upper and lower rolled shape steel assemblies in parallel while being spaced apart from each other by a predetermined interval; connecting the upper rolled shape steel assemblies of the first and second sets by a plurality of upper crossbeams spaced apart from one another by predetermined regular intervals, and connecting the lower rolled shape steel assemblies of the first and second sets by a plurality of lower crossbeams spaced apart from one another by predetermined regular intervals; placing a plurality of lower supporting stands under the lower crossbeams, respectively; placing a hydraulic jack between each connection portion of the upper rolled shape steel assembly of each set and each connection portion of the lower rolled shape steel assembly of each set at each load applying position, and applying preflexion loads to the upper and lower rolled shape steel assemblies using hydraulic jacks by plastic deformation; covering the upper flanges of the upper rolled shape steels except for the dummy rolled shape steels and the lower flanges of the lower rolled shape steels except for the dummy rolled shape steels, with concrete; placing a plurality of props on the lower rolled shape steel assemblies at predetermined positions; removing the PS steel bars and the hydraulic jacks; placing hydraulic jacks on the connection portions of the upper rolled shape steel assemblies of all sets or under the connection portions of the lower rolled shape steel assemblies of all sets; enclosing the upper and lower rolled shape steels of all sets and the hydraulic jacks with a square frame; applying preflexion loads to the rolled shape steel assemblies of all sets using the hydraulic jacks; covering the lower flanges of the upper rolled shape steels except for the dummy rolled shape steels and the upper flanges of the lower rolled shape steels except for the dummy rolled shape steels, with concrete; and dismounting the dummy rolled shape steels from the rolled shape steels covered with concrete.
[0024] When it is necessary to provide compressive stress to the web portions of the rolled shape steels, the method further comprises the step of providing compressive stress to the rolled shape steels using a pretension method after the web portions of the rolled shape steels are covered with concrete and PC steel wires are inserted into the web portions of the rolled shape steels.
[0025] When each of the manufactured preflex beams should have a relatively great length, the method further comprises the steps of enlarging the cross-sectional areas of the connection portions of the rolled shape steels so as to improve the strength of the connection portions; forming grooves for receiving male rolled shape steels on the female rolled shape steels, and connecting each of the male rolled shape steels and each of the female rolled shape steels to each other; and injecting a grouting agent into the grooves.
[0026] In this embodiment, in a case where the length of the rolled shape steels is 20 m or less, the lower supporting stands are placed at the applying positions of preflexion loads, and the method further comprises the step of respectively placing a plurality of upper supporting stands under the upper rolled shape steels at the same positions as those for the lower supporting stands after the step of placing the lower supporting stands.
[0027] In a case where the length of the rolled shape steels is 20 to 30 m, the lower supporting stands are placed at three positions respectively spaced inwardly apart from both side ends of the lower rolled shape steels by about 0.1 L and 0.5 L, and the method further comprises the step of respectively placing a plurality of upper supporting stands under the upper rolled shape steels at the same positions as those for the lower supporting stands after the step of placing the lower supporting stands.
[0028] In a case where the length of the rolled shape steels is 30 m or more, the lower supporting stands are placed at four positions respectively spaced inwardly apart from both side ends of the lower rolled shape steels by about 0.1 L and 0.3 L, and the method further comprises the step of respectively placing a plurality of upper supporting stands under the upper rolled shape steels at the same positions as those for the lower supporting stands after the step of placing the lower supporting stands.
[0029] In this embodiment, when the second set of upper and lower plate girders arranged in parallel with the first set of upper and lower rolled shape steels is plural, a plurality of preflex beams can be manufactured by one time application of preflexion loads.
[0030] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
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[0050] Hereinafter, embodiments of the present invention are described with reference to the accompanying drawings.
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[0057] The upper plate girders
[0058] In the methods shown in
[0059] Hereinafter, there is described a method for manufacturing preflex beams using non-cambered rolled shape steels and preflex beams used as piles and pillars in which both side flange concretes are compressively prestressed.
[0060] A conventional art causes considerable inconvenience in working because second load applying work have to be performed while rolled shape steels are turned upside down and placed on standing stands after first load application work is performed while rolled shape steels are placed on supporting stands so as to camber non-cambered rolled shape steels by plastic deformation or to give compressive stress to both flange portions of concrete. Accordingly, the below-described load applying method is to eliminate such inconvenience.
[0061] The above-mentioned method is described with reference to simple beams.
[0062] A plastic deformation theory that is concerned with the manufacture of non-cambered rolled shape steels is described with reference to the graph of
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[0065] Accordingly, the method for manufacturing preflex beams according to the present invention is to camber non-cambered rolled shape steels by plastic deformation through a manufacturing process, differently from a conventional art in which there occurs the difficulty and inconvenience of previously cambering steel girders to correspond to deflection due to dead loads.
[0066] Hereinafter, there is described a method for manufacturing preflex beams using non-cambered rolled shape steels with reference to the accompanying drawings.
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[0087] Hereinafter, there is described a process of manufacturing a preflex used as a pile or pillar in which compressive stress is given concrete that covers its both flanges.
[0088] The pile serves to transmit load, which is applied to upper and lower structures, to the ground. The pile should be dynamically stable and should not be partially displaced detrimentally. However, a conventional pile may be laterally and partially displaced by a horizontal load or an earthquake due to its structure, thus having low bearing capacity. Additionally, a plurality of piles are required to achieve sufficient bearing capacity, so that an excessive construction cost is necessary. Additionally, in a case where a pile is long, the connection portion of pile elements are weak, so that the use of a long pile is limited. In addition, in the case of a steel pile, reduction in strength due to corrosion is a major shortcoming. In the preflex beam manufacturing method of this embodiment of the present invention in which rolled shape steels are covered with concrete and compressive stress is given through the total cross sections, a horizontal load and an earthquake can be resisted sufficiently due to an increase in bending strength, corrosion is prevented, and bearing capacity can be increased by an increase in skin friction force due to the shapes of the cross sections of rolled shape steels. In the case of a pillar, reduction in cross-sectional area can be achieved due to an increase in bending strength for a pillar having great moment. This embodiment is illustrated in
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[0090] After loads P are applied to the rolled shaped steel assembly at positions spaced apart by about L/5 from both ends of the rolled shape assembly while the rolled shape steel assembly is placed on a support stand as shown in
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[0095] Though the above-mentioned processes, there can be manufactured in large quantities preflex beams used as piles and pillars, which have superior performance and uniform compressive stress through the total cross sections. The length of the preflex beam can be freely adjusted by the connection or cutting of the preflex beam.
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[0097] In addition, there is shown in
[0098] As described above, the present invention provides a method for manufacturing preflex beams in which preflexion loads are applied to plate girders or rolled shape steels while upper plate girders or rolled shape steels are supported by supporting stands in the form of tripods at fulcrum positions, upper and lower plate girders or rolled shape steels are all supported by supporting stands in the form of rigid frames at two, three or four positions, upper plate girders or rolled shape steels are supported by supporting stands in the form of rigid frames, or lower plate girders or rolled shape steels are supported by supporting stands in the form of tripods. In the preflex beam manufacturing method of the present invention, two or more preflex beams can be manufactured, that is, a great quantity of straight and curved preflex beams can be manufactured, by one time preflexion work. Accordingly, the working period for manufacturing beams can be reduced greatly.
[0099] In addition, a preflex beam can be manufactured using non-cambered rolled shape steel by means of a method for applying loads in a way of inwardly pulling upper and lower girders or rolled shape steels by the use of a square frame, so that there can be eliminated difficulty and inconvenience in which a cambering process is previously performed to correspond to deflection due to a dead load.
[0100] In addition, the preflex beam used as a pile or pillar in which compressive stress is given the total cross sections can be manufactured, so that horizontal load and earthquake can be resisted due to an increase in bending strength in the case of a preflex used as a pile, corrosion is prevented and bearing capacity is increased due to an increase in skin frictional force due the shape of the cross section of a rolled shape steel.
[0101] Furthermore, due to the great strength of the preflex beam of the present invention, desired bearing capacity can be obtained by a small number of piles in comparison with a conventional art. Additionally, in the case of the preflex beam used as a pillar, its bending strength is increased, so that the cross-sectional area of a pillar requiring great moment can be reduced.