Prestressed concrete structure

Abstract

To provide a prestressed concrete structure capable of utilizing the advantage of an unbonded PC construction method by a construction method similar to a conventional bonded PC construction method.SOLUTION: This prestressed concrete structure 10 is formed with a column side unbonded part 31 having a column part outside sheath 30 arranged outside a sheath 16 arranged in a column member 11 and a sliding auxiliary body 31 interposed between the column part outside sheath 30 and the sheath 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a prestressed concrete structure in which prestress is introduced by a post-tensioning method. [Background technology]

[0002] One method of introducing prestress into concrete structures is the post-tensioning method, in which tension is applied to the PC steel members after the concrete has hardened.This post-tensioning method is classified into bonded PC method and unbonded PC method.

[0003] In the bonded PC method, PC steel strands or the like are inserted into a sheath embedded in the concrete structure to which prestress is to be introduced, the PC steel is tensioned, and the ends of the PC steel are fixed to the ends of the concrete structure. After that, PC grout such as cement milk is filled into the sheath through which the PC steel has been inserted, and the PC grout is cured and hardened, so that the PC steel is integrated with the concrete structure via the PC grout and sheath, and prestress is introduced into the concrete structure (see, for example, Patent Document 1).

[0004] In addition, when using a multi-cable with multiple PC steel strands inserted into a sheath, the general bonded PC construction method has the advantage that the ends of multiple PC steel strands can be fixed together using an anchoring device, allowing for flexible response to the tension required by the design.

[0005] Furthermore, the bonded PC construction method can also be applied to the PC pressure-bonding method, which integrates multiple precast concrete members using the tension of PC steel.

[0006] On the other hand, the unbonded PC construction method uses unbonded PC steel strands or other PC steel members, which have a sliding aid such as grease applied to the outer surface of the strands covered with a polyethylene film.The unbonded PC steel members are placed in a formwork in the same way as reinforcing bars, and concrete is poured into them.After the concrete hardens, prestress is introduced into the concrete structure by tensioning the unbonded PC steel members (see, for example, Patent Document 2).

[0007] In this unbonded PC construction method, a sliding aid such as grease is placed between the PC steel and the concrete, and the PC steel and concrete are not attached to each other. Therefore, even when the concrete hardens, the PC tendons can be tensioned without using a sheath, and the adhesive strength between the PC steel and the concrete can continue to be lost even after tensioning.

[0008] In addition, the unbonded PC method does not require a sheath, so there is no need to fill PC grout, simplifying construction, and is therefore widely used for floor slabs, etc.

[0009] Furthermore, when prestressed concrete members in which prestress has been introduced using the unbonded method (hereinafter referred to as "unbonded PC members") are used as earthquake-resistant elements such as the main beams of a building, a sliding aid such as grease is placed between the PC steel and the concrete, and the PC steel and the concrete are not attached to each other. As a result, the PC steel will not yield during an earthquake, and damage to the concrete is minor and concentrated at the ends of the member, and many studies have shown that these members have excellent reparability during earthquakes.

[0010] However, with the conventional technology described above, when conventional unbonded prestressing steel members are used, there is no bond strength to the concrete along the entire length of the prestressing steel members, so even if the building (concrete structure) is significantly deformed by an earthquake, the tensile force acting on the prestressing steel members hardly increases from normal levels, and compared to a concrete structure in which prestress has been introduced using a bonded method with the same amount of prestressing steel members, the strength of the structure is reduced by more than 30%.

[0011] In other words, the conventional unbonded method had the problem that if the same strength as a concrete structure prestressed by the bonded method was required, a large amount of prestressing steel would have to be used.

[0012] Furthermore, with conventional unbonded PC construction methods, even when multiple unbonded PC tendons are used, each unbonded PC tendon is embedded in concrete one by one, meaning that the ends of each unbonded PC tendon must be fixed. When a large number of unbonded PC tendons are used, it is often difficult to secure space to place equipment to fix each unbonded PC tendon.

[0013] Furthermore, with the conventional unbonded PC construction method, as the number of PC steel strands used increased, a corresponding number of anchoring devices had to be used, which resulted in increased costs in terms of materials and construction.

[0014] Furthermore, if the unbonded PC method can be applied to the PC pressure-bonding method, the PC steel will not yield during an earthquake, and damage to the concrete will be minor and concentrated at the ends of the material, making it possible to carry out post-earthquake repairs in the most efficient manner.

[0015] However, with the PC pressure-bonding method, it is necessary to embed a sheath in advance in each of the multiple precast concrete members (hereinafter referred to as PCa members) to be joined together, insert unbonded PC steel members so that they penetrate the sheaths of the multiple PCa members to be joined, and fill the sheaths with PC grout, so there was a problem that there was no structural meaning in using unbonded PC steel members.

[0016] Therefore, in recent years, a method has been developed that is based on the conventional bonded PC construction method, but involves providing an adhesive insulating layer between the sheath of a section that is grouted and an outer sheath placed on the outside of that section, creating a partial unbonded section in the concrete structure, and preventing the PC steel from yielding at the end of the beam in a rigid frame structure consisting of column members and beam members, even if large deformation occurs during an earthquake, thereby maintaining the resilience of the structure (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-137473 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-40052 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-90253 Summary of the Invention [Problem to be solved by the invention]

[0018] However, in the conventional technology disclosed in Patent Document 3 as mentioned above, in a rigid frame structure consisting of column members and beam members, deformation is concentrated at the ends of the beam members during an earthquake, causing large localized rotations, which causes interference between the sheath and the outer sheath and prevents the sheath, PC grout, and PC steel from slipping out as a unit.

[0019] One possible solution to this problem is to increase the thickness of the unbonded layer around the outer periphery of the sheath to ensure clearance between the sheath and the outer sheath. However, thickening the unbonded layer poses manufacturing problems and increases costs.

[0020] In addition, the wiring shape of the PC steel within the beam member is generally arranged in a straight line for about 100 to 200 mm from the boundary between the column and beam toward the center of the beam, and then in an arc near the center of the beam and toward the bottom end of the beam.

[0021] In this case, when the PC steel at the end of the beam is partially unbonded using the conventional technology disclosed in Patent Document 3, in order to avoid the bending rigidity of the PC grout restraining the PC steel, it is necessary to set up the unbonded section only in a limited section of a linear arrangement, and since high accuracy of linearity is required, there is a problem that this poses a major constraint on ensuring the unbonded section required for the design.

[0022] In view of the above-mentioned conventional problems, the present invention has been made with the aim of providing a prestressed concrete structure that can utilize the advantages of the unbonded PC method while following the same construction procedures as the conventional bonded PC method. [Means for solving the problem]

[0023] The invention as set forth in claim 1, which aims to solve the above-mentioned problems of the prior art, is characterized in that in a concrete structure in which concrete beam members are erected between concrete column members, prestressing is introduced by post-tensioning, with PC steel bars inserted into sheaths arranged across the column members and the beam members between the column members, a column-side unbonded section is formed which comprises a column outer sheath arranged outside the sheaths arranged on the column members, and a sliding aid interposed between the column outer sheath and the sheath.

[0024] The invention described in claim 2 is characterized in that, in addition to the configuration of claim 1, the column members are made of precast concrete members fabricated in advance in a factory or the like.

[0025] The invention as set forth in claim 3 is characterized in that, in addition to the configuration of claim 1 or 2, the sliding aid is a semi-solid or paste-like lubricant.

[0026] The feature of the invention described in claim 4 is that, in addition to the configuration of claim 1 or 2, a beam-side unbonded portion is formed continuously with the column-side unbonded portion, and the unbonded portion comprises a beam outer sheath arranged outside the sheath arranged at the end of the beam member and a sliding aid interposed between the beam outer sheath and the sheath.

[0027] The feature of the invention described in claim 5 is that, in addition to the configuration of claim 1 or 2, the sheath arranged on the column member and the sheath arranged on the beam member are connected through the joint between the column member and the beam member, and the joint is filled with non-shrinkage mortar.

[0028] The invention described in claim 6 is characterized in that, in addition to the configuration of claim 1 or 2, an annular elastic member is fixed to the end face of the joint of the column member or the end face of the joint of the beam member, and the elastic member is sandwiched in a compressed state between the column member and the beam member so as to surround the outer edge of the beam side end of the column side unbonded portion. [Effects of the Invention]

[0029] By being equipped with the configuration described in claim 1, the prestressed concrete structure of the present invention can reliably secure the linear unbonded sections (unbonded sections) required in the design, and can prevent the PC steel from yielding at the beam ends of a rigid frame structure consisting of column members and beam members, even if large deformation occurs during an earthquake, thereby maintaining the resilience of the structure.

[0030] Furthermore, in the present invention, by providing the configuration described in claim 2, it is possible to prevent the bending and deformation of the outer sheath of the column section embedded in the column member due to the pressure when pouring concrete, and to prevent the PC steel strands from being bonded due to the PC steel strands being restrained by the bending and deformation of the outer sheath of the column section.

[0031] Furthermore, in the present invention, by providing the configuration described in claim 3, the sheath that houses the PC steel can be securely separated from the concrete at the unbonded portion, and the relative movement between the sheath and the concrete can be made smooth.

[0032] Furthermore, in the present invention, by providing the configuration described in claim 4, it is possible to extend the unbonded section as needed across the end of the beam member where deformation is concentrated during an earthquake and large local rotation occurs.

[0033] Furthermore, in the present invention, by providing the configuration recited in claim 5, the sheath in the pillar member and the sheath in the beam member can be suitably connected.

[0034] Furthermore, in the present invention, by providing the configuration recited in claim 6, the unbonded portion on the column member side and the unbonded portion on the beam member side can be connected without any gaps. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a longitudinal cross-sectional view showing an example of a prestressed concrete structure according to the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing a joint between the pillar member and the beam member of the same. [Figure 3] FIG. 10 is a cross-sectional view showing the state of the column-side unbonded portion of the same. [Figure 4] FIG. 10 is a cross-sectional view showing the state of the sheath portion of the bond portion of the beam member. [Figure 5] FIG. 2 is a cross-sectional view showing an example of the fixing device for PC steel bars of the same. [Figure 6] 10 is a cross-sectional view showing the steps of the method for constructing the prestressed concrete structure of the same as above, showing the state of the installation work of the beam member. FIG. [Figure 7] FIG. 2 is an enlarged cross-sectional view showing a joint between the pillar member and the beam member of the same. [Figure 8] FIG. 10 is a cross-sectional view showing the state in which the joints of the same have been filled with non-shrinkage mortar. [Figure 9] FIG. 4 is a cross-sectional view showing the state of the prestressing operation. [Figure 10]FIG. 10 is an enlarged cross-sectional view showing a joint portion between a column member and a beam member, illustrating another embodiment of a prestressed concrete structure according to the present invention. [Figure 11] FIG. 10 is an enlarged cross-sectional view showing a joint between a column member and a beam member, illustrating yet another embodiment of the prestressed concrete structure. DETAILED DESCRIPTION OF THE INVENTION

[0036] Next, an embodiment of the prestressed concrete structure according to the present invention will be described based on the examples shown in Figures 1 to 5. In the figures, reference numeral 1 denotes the prestressed concrete structure.

[0037] As shown in Figure 1, this prestressed concrete structure (hereinafter referred to as PC structure 10) comprises a concrete beam member 12 erected between a plurality of concrete column members 11, 11, with PC steel members 14 inserted through sheaths 16 arranged across the column members 11, 11 and the beam members 12, and prestress is introduced by the post-tensioning method. Note that in Figure 3 and other figures, the plurality of PC steel members 14, 14 are shown by a single dashed line for the convenience of drawing.

[0038] In addition, this PC structure 10 is formed with a column-side unbonded portion 32 comprising a column outer sheath 30 arranged outside the sheath 16 arranged on the column members 11, 11, and a sliding aid 31 interposed between the column outer sheath 30 and the sheath 16.

[0039] The column members 11, 11 are formed into a columnar shape such as a square column from precast concrete members fabricated in advance in a factory or the like, and are provided with a column-side unbonded portion 32 at a predetermined height position.

[0040] As shown in Figures 2 and 3, the column-side unbonded portion 32 comprises a cylindrical column outer sheath 30 that penetrates the column members 11, 11 in a direction perpendicular to the axial direction, and a cylindrical sheath member 16a that is concentrically arranged inside the column outer sheath 30 and forms the sheath 16 disposed on the column members 11, 11, with a sliding aid 31 interposed between the column outer sheath 30 and the sheath member 16a so that the column outer sheath 30 is maintained in a concentrically arranged state outside the sheath 16 disposed on the column members 11, 11.

[0041] Furthermore, when these pillar members 11, 11 are manufactured in a factory or the like, formwork is installed so that the pillar axis direction is horizontal (not shown), and concrete is poured into them, and after the concrete has hardened or has been transported to the construction site, the pillar members are raised so that the bridge axis direction is oriented vertically (up and down).

[0042] Furthermore, when pouring concrete, the column outer sheath 30 is placed with its axial direction facing vertically inside the formwork, which makes it difficult for pressure to act on the column outer sheath 30 when pouring concrete, thereby preventing deformation and bending of the column outer sheath 30.

[0043] The sheath member 16a constituting the sheath 16 is formed in a long cylindrical shape, and in addition to commonly used sheaths such as a steel spiral sheath or a resin spiral sheath, a polyvinyl chloride pipe or the like can also be used.

[0044] Furthermore, although not specifically shown, this sheath member 16a may be provided with an adhesion aid on either the inner or outer peripheral surface, or on either the inner or outer peripheral surface, to enhance adhesion to PC grout 23, concrete, etc.

[0045] The adhesion aiding portion may be, for example, a ring-shaped or spiral protrusion protruding from the inner or outer peripheral surface, such as a spiral sheath, or may be processed to increase the coefficient of friction of the inner or outer peripheral surface, such as an iris knurling.

[0046] The post outer sheath 30 is formed in a cylindrical shape with an outer diameter larger than that of the sheath 16, and is disposed outside the sheath 16 so as to cover part or all of the outer peripheral surface of the sheath 16.

[0047] The outer sheath 30 of the post portion is made of the same material as the sheath 16, for example, with an inner diameter larger than the outer diameter of the sheath 16, so that the sheath 16 and the outer sheath 30 of the post portion form a double-tube structure.

[0048] Furthermore, although not specifically shown, the outer sheath 30 of the column section may be provided with an adhesion aid on either the inner or outer peripheral surface, or on either the inner or outer peripheral surface, to enhance adhesion to the PC grout 23, concrete, etc.

[0049] The adhesion aiding portion may be, for example, a ring-shaped or spiral protrusion protruding from the inner or outer peripheral surface, such as a spiral sheath, or may be processed to increase the coefficient of friction of the inner or outer peripheral surface, such as an iris knurling.

[0050] The sliding aid 31 is made of a semi-solid or paste-like lubricant having a certain fluidity, such as grease, and is filled between the sheath member 16a and the outer post sheath 30.

[0051] The form of the sliding aid 31 is not limited to semi-solid or paste-like lubricating material having a certain degree of fluidity, such as the above-mentioned grease, and when the column outer sheath 30 and the sheath member 16a are made of the same material and form a double-tube structure, the air interposed in the gap between the column outer sheath 30 and the sheath member 16a may also be used as the sliding aid 31.

[0052] Furthermore, when the sliding aid 31 and the sheath member 16a are installed in advance in the outer sheath 30 of the pillar portion at a factory or the like using a sliding aid 31 with a certain degree of fluidity such as grease, it is desirable to seal the gap between the sheath member 16a and the outer sheath 30 of the pillar portion with a removable sealing material 33 or the like to prevent the sliding aid 31 from leaking out.

[0053] As shown in Figures 1 and 6, the beam member 12 is formed into a beam shape such as a square beam using precast concrete members fabricated in advance in a factory or the like, and a sheath body 16b that constitutes a sheath 16 through which PC steel 14 is inserted is arranged across both ends in the beam axial direction.

[0054] The sheath bodies 16b are arranged in two tiers, one above the other, on the beam member 12, and each sheath body 16b is arranged in a straight line for approximately 100 to 200 mm from each end face toward the center of the beam, and then arranged in an arc near the center of the beam toward the lower end of the beam.

[0055] In this embodiment, the sheaths 16, 16 are arranged in two tiers, one above the other, on the beam member 12, but the arrangement of the sheaths 16 is not limited to this embodiment and may be arranged in one tier or in multiple tiers of three or more tiers.

[0056] Furthermore, in this embodiment, the upper and lower two-tiered sheath bodies 16b are arranged linearly from both end faces of the beam toward the center of the beam for approximately 100 to 200 mm, and then are arranged in an arc toward the lower end near the center of the beam (hereinafter referred to as an arc-shaped arrangement). However, with regard to the sheath bodies 16b, only the upper tiered sheath body 16b may be arranged in an arc-shaped arrangement, or only any tier of the sheath bodies 16b, 16b arranged in multiple tiers may be arranged in an arc-shaped arrangement, or the sheath bodies 16b in the multiple tiered arrangement may be arranged in a straight line.

[0057] The sheath body 16b is formed in a long cylindrical shape with the same diameter as the sheath member 16a, and is made of a commonly used flexible sheath tube such as a steel spiral sheath or a resin spiral sheath.

[0058] Furthermore, although not specifically shown, the sheath body 16b may be provided with an adhesion aid on either the inner or outer peripheral surface, or on either the inner or outer peripheral surface, to enhance adhesion to the PC grout 23, concrete, etc.

[0059] The adhesion aiding portion may be, for example, a ring-shaped or spiral protrusion protruding from the inner or outer peripheral surface, such as a spiral sheath, or may be processed to increase the coefficient of friction of the inner or outer peripheral surface, such as an iris knurling.

[0060] The sheath body 16b arranged within the beam member 12 and the sheath members 16a arranged in the column members 11, 11 are connected to each other by a connecting member 34, and by connecting the sheath body 16b and the sheath members 16a, a sheath 16 is formed that extends across both ends of the concrete structure including the column members 11, 11 and the beam member 12.

[0061] In addition, in this PC structure 10, joint portions 35 are formed between the column members 11, 11 and the beam member 12, and the sheath member 16a arranged on the column members 11, 11 and the sheath main body 16b arranged on the beam member 12 are connected via the joint portions 35.

[0062] After the sheath 16 is connected, the joints 35 are filled with non-shrinkage mortar 36 so that the column members 11, 11 and the beam member 12 are joined without any gaps.

[0063] Furthermore, as shown in Figure 10, a ring-shaped elastic member 37 may be fixed to the end faces of the joints of the column members 11, 11, so that the elastic member 37 surrounds the outer edge of the beam-side end of the column-side unbonded portion 32 and is sandwiched in a compressed state between the joint end faces of the column member 11 and the beam member 12.

[0064] In this case, the elastic member 37 may be fixed to the joint end surface of the column member 11 or the beam member 12 in advance.

[0065] 3 and 4, the PC steel member 14 is composed of a PC steel strand in which a plurality of wires 14b, 14b... are arranged and twisted around a central core wire 14a, or a coated PC steel strand in which the outer periphery of a PC steel strand is coated with resin. Note that the PC steel member 14 can be any of the PC steel members 14 used in general bonded PC construction methods.

[0066] The PC steel members 14 are inserted into the sheaths 16, and as shown in Figure 9, the PC steel members 14 are pulled and tensioned by jacks 17, and the ends of each tensioned PC steel member 14 are fixed to the ends of the PC structure 10, i.e., the outer surface portions of the column members 11, 11, by fixing devices 18.

[0067] As shown in Figure 5, an anchoring device 18 compatible with multiple cables can be used, in which each prestressing steel member 14 is inserted into an insertion hole 20a formed in an anchoring block 20 that is in contact with a support plate 19 installed at the end of the pillar members 11, 11, and the end of the prestressing steel member 14 is gripped by a wedge-shaped anchoring tool (wedge) 21 driven into the insertion hole 20a from the outside. Note that reference numeral 22 in the figure denotes a grout injection port.

[0068] The fixing device 18 is not limited to the embodiment described above, and may be configured to fix each PC steel member 14 independently.

[0069] Then, as shown in FIGS. 2 and 5, the inside of the sheath 16 is filled with PC grout 23 made of mortar, cement paste, or the like, and the PC grout 23 is cured and hardened to integrate the PC steel member 14 and the sheath 16.

[0070] As a result, prestress is introduced into the PC structure 10 using the post-tensioning method, and the PC steel 14 and concrete are integrated together, but the column members 11, 11 have column-side unbonded sections 32, which are composed of sheath members 16a, column outer sheaths 30, and sliding aids 31, so the adhesion between the concrete and the PC steel 14 has been lost.

[0071] Therefore, in the column-side unbonded portion 32 of the column members 11, 11, the sheath 16 and the concrete are always able to move relative to each other via the sliding aid 31, achieving the same effect as the conventional unbonded PC construction method, and even if large stress acts on the PC steel 14 during an earthquake, the PC steel 14 will not yield, damage to the concrete can be suppressed, and the method has excellent repairability.

[0072] On the other hand, the beam member 12 is in a state where the PC steel member 14 and the concrete are adhered to each other via the PC grout 23 and the sheath 16 .

[0073] Therefore, under normal circumstances, prestress (compression force) from the PC steel 14 acts on the beam member 12, and when the beam member 12 is deformed due to earthquake motion or the like, the prestress from the PC steel 14 exerts its strength, while in the column members 11, 11, the sheath 16 and the outer sheath 30 of the column section held in the concrete can move relative to each other via the sliding aid 31, thereby achieving the same effect as the conventional unbonded PC construction method, whereby the PC steel 14 does not yield during an earthquake, damage to the concrete can be suppressed, and repairability is excellent.

[0074] Next, a method for constructing the above-mentioned prestressed concrete structure will be described with reference to Figures 6 to 9. Note that the same components as those in the above-mentioned embodiment will be given the same reference numerals and the description thereof will be omitted.

[0075] First, the pillar members 11, 11 that have been manufactured in advance in a factory or the like are carried to the construction site and erected at a predetermined interval with their axial directions facing up and down.

[0076] In this case, if the sliding aid 31 and the sheath member 16a are installed in advance in the outer sheath 30 of the column portion at a factory or the like, the gap between the sheath member 16a and the outer sheath 30 of the column portion is sealed with a removable sealing material 33 or the like to prevent the sliding aid 31 from leaking out.

[0077] Next, as shown in Figures 6 and 7, the beam member 12, which has been manufactured in advance at a factory or the like, is erected between the pillar members 11, 11 arranged at a distance from each other, at a predetermined height by aligning the positions of the sheath 16 member and the sheath main body 16b that constitute the sheath 16.

[0078] In this case, as shown in Figure 7, a joint portion 35 is provided at the joint between the column members 11, 11 and the beam member 12, and this joint portion 35 is used to connect the sheath member 16a arranged on the column members 11, 11 and the sheath main body 16b arranged on the beam member 12 using a connecting member 34 or the like, thereby forming a continuous sheath 16 arranged across both ends of the PC structure 10.

[0079] Next, as shown in FIG. 8, non-shrinkage mortar 36 is filled into the joints 35, and the non-shrinkage mortar 36 is cured and hardened to join the column members 11, 11 and the beam member 12 together.

[0080] Next, the PC steel members 14 are inserted into the sheaths 16 arranged across both ends of the PC structure 10, and the PC steel members 14 are tensioned while the ends of the PC steel members 14 are fixed to both ends of the PC structure 10, i.e., the outer surface portions of the column members 11, 11, using fixing devices 18.

[0081] Thereafter, similarly to the case shown in FIG. 8, the inside of the sheath 16 is filled with PC grout 23, and the column members 11, 11 and the beam member 12 are integrated with each other by the tension force of the PC steel members 14.

[0082] In a prestressed concrete structure configured in this manner, linear column member side unbonded sections (unbonded sections) 32 are provided within the column members 11, 11 arranged on both sides of the beam member 12, allowing the beam member 12 to behave partially as an unbonded PC member.

[0083] Specifically, by designing the column members 11, 11 to have sufficient strength, deformation can be kept extremely small even during large deformations, the radial thickness of the sliding aid 31 of the unbonded portion 32 formed on the outside of the sheath 16 can be made significantly thinner than when it is provided at the end of the beam, and performance equivalent to that when a partial unbonded section is provided in the beam can be obtained at a low cost.

[0084] In addition, the tension within the column members 11, 11 of the PC steel 14 arranged at the upper and lower ends of the beam cross section remains constant until yielding after bending cracks occur at the beam end, thereby preventing plasticization due to partial yielding of the PC steel 14.

[0085] Therefore, stable and high recovery is achieved even during large deformations caused by earthquake motion, etc., and further, damage due to deterioration of the adhesion of the PC steel 14 in the column members 11, 11 during an earthquake is prevented, which also contributes to improving the continued usability of the building after an earthquake.

[0086] In the above-mentioned embodiment, the case where the unbonded portion is provided only on the column members 11, 11 has been described, but as shown in Fig. 11, a beam-side unbonded portion 41 comprising a beam-portion outer sheath 40 arranged outside the sheath 16 (sheath main body 16b) arranged at the end of the beam member 12 and a sliding aid 31 interposed between the beam-portion outer sheath 40 and the sheath 16 (sheath main body 16b) may be formed continuously with the column-side unbonded portion 32. Note that the same components as those in the above-mentioned embodiment are denoted by the same reference numerals and their description will be omitted.

[0087] The beam outer sheath 40 can be the same as the pillar outer sheath 30 described above.

[0088] The beam side unbonded section 41 has the beam outer sheath 40 arranged outside the linear arrangement section approximately 100 to 200 mm from each end face toward the center of the beam, and if necessary, the unbonded section can be extended across the end of the beam member 12 where deformation is concentrated during an earthquake and large local rotation occurs.

[0089] On the other hand, the unbonded portions of the column members 11, 11 always maintain linearity, so that the unbonded effect can be maintained even when the PC steel 14 is restrained at the beam-side unbonded portion 41. [Explanation of symbols]

[0090] 10 Prestressed and Concrete Structures (PC Structures) 11 Column members 12 Beam member 14 PC steel material 16 Sheath 17 Jack 18 Fixing device 19 Bearing plate 20 Fixation Block 21 Fixing device 22 Grout injection port 23 PC Grout 30 Pillar outer sheath 31 Sliding aid 32 Unbonded part on column side 33 Sealing material 34 Connecting member 35 Joint 36 Non-shrinkage mortar 37 Elastic member 40 Beam outer sheath 41 Unbonded beam part

Claims

1. A concrete structure in which concrete beam members are erected between concrete column members, and in which PC steel members are inserted into sheaths arranged across the column members and the beam members between the column members, and in which prestress is introduced by a post-tensioning method, A prestressed concrete structure characterized in that a column-side unbonded section is formed, which comprises a column outer sheath arranged outside the sheath arranged on the column member, and a sliding aid interposed between the column outer sheath and the sheath.

2. 2. A prestressed concrete structure according to claim 1, wherein the column members are precast concrete members fabricated in advance in a factory or the like.

3. 3. A prestressed concrete structure according to claim 1, wherein the sliding aid is a semi-solid or paste-like lubricant.

4. 3. A prestressed concrete structure as described in claim 1 or 2, wherein a beam-side unbonded portion is formed continuously with the column-side unbonded portion, the beam-side unbonded portion comprising a beam outer sheath arranged outside the sheath arranged at the end of the beam member and a sliding aid interposed between the beam outer sheath and the sheath.

5. 3. A prestressed concrete structure according to claim 1, wherein the sheaths arranged on the column members and the sheaths arranged on the beam members are connected through joints between the column members and the beam members, and the joints are filled with non-shrinkage mortar.

6. 3. A prestressed concrete structure according to claim 1, wherein an annular elastic member is fixed to the end face of the joint of the column member or the end face of the joint of the beam member, and the elastic member is sandwiched in a compressed state between the column member and the beam member so as to surround the outer edge of the beam-side end of the column-side unbonded portion.

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