Patent Publication Number: US-11028587-B2

Title: Concrete structure body and manufacturing method thereof

Description:
TECHNICAL FIELD 
     The present invention relates to a concrete structure body and a manufacturing method thereof. The present application claims priority based on Japanese Application No. 2017-162023, filed Aug. 25, 2017, the entire contents of which are incorporated herein by reference. 
     BACKGROUND ART 
     A precast concrete (Precast Concrete; PC) floor slab, which is a concrete member, is usable in, for example, construction of a floor slab of a bridge. Specifically, as a method of constructing a floor slab of a bridge, which is a concrete structure body, there is a known method in which, after a plurality of PC floor slabs are disposed adjacent to each other on a steel girder, the adjacent PC floor slabs are connected together with gaps therebetween filled with concrete (for example, refer to PTL 1). 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Unexamined Patent Application Publication No. 2012-62664 
     SUMMARY OF INVENTION 
     A concrete structure body according to the present invention includes: a first concrete member having a first facing surface; a second concrete member having a second facing surface and disposed such that the first facing surface and the second facing surface face each other; a connection portion that fills a gap between the first facing surface and the second facing surface; and a tendon disposed in the connection portion to extend along the first facing surface and the second facing surface and to which a tensile force is applied in a longitudinal direction. 
     A method of manufacturing a concrete structure body according to the present invention includes: a step of disposing a first concrete member having a first facing surface and a second concrete member having a second facing surface such that the first facing surface and the second facing surface face each other; a step of disposing a tendon so as to extend along the first facing surface and the second facing surface and, while holding the tendon with a holding member disposed to straddle on an external wall of the first concrete member and on an external wall of the second concrete member, applying a tensile force to the tendon in a longitudinal direction thereof; a step of filling a gap between the first facing surface and the second facing surface with a filling material that solidifies with a lapse of time; and a step of removing the holding member that holds the tendon extending in the filling material that has solidified. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic sectional view illustrating a structure of a floor-slab structure body according to a first embodiment. 
         FIG. 2  is a schematic sectional view illustrating a cross section of the floor-slab structure body at a face perpendicular to the longitudinal direction of a tendon. 
         FIG. 3  is a schematic sectional view illustrating a structure of the tendon. 
         FIG. 4  is a schematic sectional view illustrating a cross section of the floor-slab structure body perpendicular to the longitudinal direction of the tendon in a modification of the first embodiment. 
         FIG. 5  is a schematic sectional view illustrating a modification of the structure of the tendon. 
         FIG. 6  is a flow chart illustrating an outline of a method of manufacturing the floor-slab structure body according to the first embodiment. 
         FIG. 7  is a schematic sectional view for describing the method of manufacturing the floor-slab structure body according to the first embodiment. 
         FIG. 8  is a schematic sectional view for describing a modification of the method of manufacturing the floor-slab structure body according to the first embodiment. 
         FIG. 9  is a schematic sectional view illustrating a structure of the floor-slab structure body according to a second embodiment. 
         FIG. 10  is a schematic sectional view illustrating a cross section of the floor-slab structure body at a face perpendicular to the longitudinal direction of the tendon. 
         FIG. 11  is a flow chart illustrating an outline of a method of manufacturing the floor-slab structure body according to the second embodiment. 
         FIG. 12  is a schematic sectional view for describing the method of manufacturing the floor-slab structure body according to the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Problems to be Solved By Present Disclosure 
     In a floor slab (concrete structure body) of a bridge constructed by the aforementioned method, a connection portion that is formed as a result of solidification of concrete that fills gaps between adjacent PC floor slabs is inferior to the PC floor slabs in durability. Therefore, there is a problem that, even when PC floor slabs excellent in durability are employed, durability as the whole concrete structure body is not sufficiently improved due to the presence of the connection portion inferior in durability. 
     One object is to provide a concrete structure body improved in durability as a whole by improving durability of a connection portion. 
     Advantageous Effects of Present Disclosure 
     According to the concrete structure body and the method of manufacturing the concrete structure body mentioned above, it is possible to provide a concrete structure body improved in durability as a whole by improving durability of a connection portion. 
     DESCRIPTION OF EMBODIMENTS OF PRESENT INVENTION 
     First, embodiments of the present invention will be listed and described. A concrete structure body according to the present application includes: a first concrete member having a first facing surface; a second concrete member having a second facing surface and disposed such that the first facing surface and the second facing surface face each other; a connection portion that fills a gap between the first facing surface and the second facing surface; and a tendon disposed in the connection portion to extend along the first facing surface and the second facing surface and to which a tensile force is applied in a longitudinal direction. 
     In the concrete structure body according to the present application, the tendon to which the tensile force is applied in the longitudinal direction is disposed in the connection portion to extend along the first facing surface and the second facing surface. Consequently, a compressive stress is applied to the connection portion. As a result, generation and propagation of cracks in the connection portion are suppressed, which improves durability of the connection portion. In addition, the improvement in the durability of the connection portion improves durability as the whole concrete structure body. Thus, according to the concrete structure body of the present application, it is possible to provide a concrete structure body improved in durability as a whole by improving durability of a connection portion. 
     In the aforementioned concrete structure body, the tendon may be a tendon that compresses the connection portion with an adhesion force with respect to the connection portion. Employing a structure in which the tendon is thus in direct contact with the connection portion and applies a compressive force thereto simplifies the structure of the concrete structure body according to the present application. 
     In the aforementioned concrete structure body, the tendon may include a twisted wire portion having a structure constituted by a plurality of steel wires that are twisted together, the twisted wire portion extending in the connection portion along the first facing surface and the second facing surface. The tendon that includes the twisted wire portion is suitable as a tendon of the concrete structure body according to the present application. 
     In the aforementioned concrete structure body, the tendon may include a cover layer that covers the outer circumference of the tendon. As a result of this, corrosion of the tendon due to, for example, infiltration of water is suppressed. The cover layer is preferably disposed to cover the outer circumference of the aforementioned twisted wire portion. 
     The aforementioned concrete structure body may include a plurality of tendons. Employing a plurality of tendons facilitates stable application of a compressive stress to the connection portion. 
     In the aforementioned concrete structure body, the connection portion may be made of concrete or mortar. Concrete and mortar are suitable as a material that constitutes the connection portion. 
     A method of manufacturing a concrete structure body according to the present application includes: a step of disposing a first concrete member having a first facing surface and a second concrete member having a second facing surface such that the first facing surface and the second facing surface face each other; a step of disposing a tendon so as to extend along the first facing surface and the second facing surface and, while holding the tendon with a holding member disposed to straddle on an external wall of the first concrete member and on an external wall of the second concrete member, applying a tensile force to the tendon in a longitudinal direction thereof; a step of filling a gap between the first facing surface and the second facing surface with a filling material that solidifies with a lapse of time; and a step of removing the holding member that holds the tendon extending in the filling material that has solidified. 
     In the method of manufacturing the concrete structure body according to the present application, the tendon to which a tensile force is applied in the longitudinal direction is disposed in the filling material that has solidified. Consequently, a compressive stress is applied to the connection portion that is obtained as a result of solidification of the filling material. As a result, generation and propagation of cracks in the connection portion are suppressed, which improves durability of the connection portion. In addition, the improvement in the durability of the connection portion improves durability as the whole concrete structure body. Thus, according to the method of manufacturing the concrete structure body of the present application, it is possible to manufacture a concrete structure body improved in durability as a whole by improving durability of a connection portion. 
     In the aforementioned method of manufacturing the concrete structure body, the step of filling the gap between the first facing surface and the second facing surface with the filling material may be performed after the step of applying the tensile force to the tendon in the longitudinal direction thereof. As a result of this, application of a compressive stress to the connection portion by a pre-tensioning method is achieved. 
     In the aforementioned method of manufacturing the concrete structure body, the tendon may include a twisted wire portion constituted by a plurality of steel wires that are twisted together. The tendon that includes the twisted wire portion is suitable as a tendon used in the method of manufacturing the concrete structure body according to the present application. 
     In the aforementioned method of manufacturing the concrete structure body, the tendon may include a cover layer that covers the outer circumference of the tendon. As a result of this, corrosion of the tendon due to, for example, infiltration of water is suppressed. The cover layer is preferably disposed to cover the outer circumference of the aforementioned twisted wire portion. 
     In the aforementioned method of manufacturing the concrete structure body, a plurality of the tendons may be disposed, and a tensile force may be applied simultaneously to the plurality of tendons in the longitudinal direction thereof in the step of applying the tensile force to the tendon in the longitudinal direction thereof. As a result of this, stable application of a compressive stress to the connection portion is facilitated. 
     In the aforementioned method of manufacturing the concrete structure body, the holding member may be disposed to be spaced from the filling material. As a result of this, the holding member and the filling material are suppressed from being joined together, which facilitates reuse of the holding member. 
     In the aforementioned method of manufacturing the concrete structure body, an intermediate member that impedes contact between the holding member and the filling material may be disposed between the holding member and the filling material. As a result of this, the holding member and the filling material are more reliably suppressed from being joined together, which further facilitates reuse of the holding member. 
     In the aforementioned method of manufacturing the concrete structure body, the holding member may include a wedge member that restricts the tendon, and a grip member that holds the wedge member. Employing the holding member having such a structure facilitates holding of the tendon by the holding member. 
     In the aforementioned method of manufacturing the concrete structure body, the filling material may be uncured concrete or uncured mortar. Uncured concrete and uncured mortar are suitable as the filling material. 
     Details of Embodiments of Invention of Present Application 
     Next, the concrete structure body and the manufacturing method thereof according to the present invention will be described below with reference to the drawings. Note that, in the following drawings, portions identical or corresponding to each other are given an identical reference number in the drawings, and description thereof will not be repeated. 
     First Embodiment 
     A floor-slab structure body, which is a concrete structure body according to a first embodiment, for an elevated road has a structure in which a plurality of PC floor slabs having the same shape are disposed adjacent to each other. Hereinafter, the floor-slab structure body according to the present embodiment will be described with reference to the drawings illustrating two adjacent PC floor slabs of the floor-slab structure body constituted by the plurality of PC floor slabs.  FIG. 1  is a schematic sectional view illustrating a structure of the floor-slab structure body according to the first embodiment.  FIG. 2  is a schematic sectional view illustrating a cross section of the floor-slab structure body at a face perpendicular to the longitudinal direction of the tendon.  FIG. 2  is a partial sectional view along the line A-A of  FIG. 1 . 
     1. Floor-Slab Structure Body 
     Referring to  FIG. 1  and  FIG. 2 , a floor-slab structure body  1  includes: a first floor slab  10 , as a first concrete member (PC floor slab), having a first facing surface  11 ; a second floor slab  20 , as a second concrete member (PC floor slab), having a second facing surface  21 , the second floor slab  20  being disposed such that the first facing surface  11  and the second facing surface  21  face each other; a connection portion  30  that fills a gap between the first facing surface  11  and the second facing surface  21 ; and a tendon  40  disposed in the connection portion  30  to extend along the first facing surface  11  and the second facing surface  21  and to which a tensile force is applied in a longitudinal direction. 
     The first floor slab  10  and the second floor slab  20  having various shapes are employable. In the present embodiment, the first floor slab  10  and the second floor slab  20  each have a rectangular parallelepiped shape. The first floor slab  10  and the second floor slab  20  are PC floor slabs that are obtained as a result of concrete (uncured concrete) in a state of having fluidity solidifying after being poured into a mold that has a predetermined shape. The first floor slab  10  has a first-floor-slab first face  18  and a first-floor-slab second face  19 . 
     The first facing surface  11  is a face that connects the first-floor-slab first face  18  and the first-floor-slab second face  19  to each other. The second floor slab  20  has a second-floor-slab first face  28  and a second-floor-slab second face  29 . The second facing surface  21  is a face that connects the second-floor-slab first face  28  and the second-floor-slab second face  29  to each other. 
     The first floor slab  10  and the second floor slab  20  are disposed such that the first-floor-slab first face  18  and the second-floor-slab first face  28  are flush with each other. In addition, the first-floor-slab second face  19  and the second-floor-slab second face  29  are also flush with each other. The first-floor-slab first face  18  and the second-floor-slab first face  28  are faces on a travelling surface side on which vehicles travel on an elevated road. In a direction (the thickness direction of the first floor slab  10  and the second floor slab  20 ) perpendicular to the first-floor-slab first face  18  and the second-floor-slab first face  28 , a recess is formed at a center portion of each of the first facing surface  11  and the second facing surface  21 . As a result, in the thickness direction of the first floor slab  10  and the second floor slab  20 , a distance between the first facing surface  11  and the second facing surface  21  is large at the center portions compared with at end portions (a region close to the first-floor-slab first face  18  and the second-floor-slab first face  28  and a region close to the first-floor-slab second face  19  and the second-floor-slab second face  29 ). 
     2. Connection Portion 
     The connection portion  30  is disposed to fill a space between the first floor slab  10  and the second floor slab  20 . The connection portion  30  is exposed on both the side of the first-floor-slab first face  18  and the second-floor-slab first face  28  and the side of the first-floor-slab second face  19  and the second-floor-slab second face  29 . The connection portion  30  is made of, for example, concrete or mortar. 
     3. Tendon 
     The tendon  40  is disposed in the connection portion  30  to extend parallel to the first facing surface  11  and the second facing surface  21 . The tendon  40  is disposed in a region at the center in the thickness direction of the first floor slab  10  and the second floor slab  20  and whose distance from the first facing surface  11  and distance from the second facing surface  21  are equal to each other. The tendon  40  extends through the connection portion  30 . Both end surfaces of the tendon  40  are exposed from the connection portion  30 . Both end surfaces of the tendon  40  and the surface of the connection portion  30  are flush with each other. 
     The tendon  40  includes a twisted wire portion having a structure constituted by a plurality of steel wires that are twisted together, the twisted wire portion extending in the connection portion  30  along the first facing surface  11  and the second facing surface  21 .  FIG. 3  is a cross section perpendicular to the longitudinal direction of the tendon  40 . Referring to  FIG. 3 , the tendon  40  according to the present embodiment is constituted by a twisted wire portion. The tendon  40  includes a core wire  41  that is a steel wire and a plurality (six, here) of circumference wires  42  that are steel wires. The circumference wires  42  are disposed in contact with the outer circumferential surface of the core wire  41  to surround the outer circumferential surface of the core wire  41 . The circumference wires  42  are wound in a spiral shape around the outer circumferential surface of the core wire  41 . A cross section of each of the core wire  41  and the circumference wires  42  is circular. 
     A tensile force is applied to the tendon  40  in the longitudinal direction. In other words, a tensile stress is applied in the longitudinal direction of the tendon  40 . The tendon  40  and the connection portion  30  are in contact with each other. As a result, the tendon  40  compresses the connection portion  30  with an adhesion force with respect to the connection portion  30 . In a state in which the tendon  40  is held by the holding member with a tensile force being applied to the tendon  40 , the connection portion  30  made of, for example, concrete or mortar is formed, and then, the holding member is removed, thereby maintaining the tensile force of the tendon  40 . In other words, a compressive force is applied to the connection portion  30  by a pre-tensioning method. A specific method of manufacturing the floor-slab structure body will be described later. 
     4. Modification of Floor-Slab Structure Body 
       FIG. 4  is a schematic sectional view illustrating a cross section of the floor-slab structure body perpendicular to the longitudinal direction of the tendon in a modification of the first embodiment. Referring to  FIG. 4 , in the present modification, the first floor slab  10  further includes a first reinforcing steel  12 . In addition, the second floor slab  20  further includes a second reinforcing steel  22 . The first reinforcing steel  12  and the second reinforcing steel  22  are disposed such that portions thereof are embedded in the first floor slab  10  and the second floor slab  20 , respectively, and loop portions, which are other portions thereof, project from the first facing surface  11  and the second facing surface  21 , respectively. The first reinforcing steel  12  projects toward the second facing surface  21 . The second reinforcing steel  22  projects toward the first facing surface  11 . In the longitudinal direction of the tendon  40 , the first reinforcing steel  12  and the second reinforcing steel  22  project, at positions that differ from each other, from the first facing surface  11  and the second facing surface  21 , respectively. In addition, the first reinforcing steel  12  and the second reinforcing steel  22  are disposed such that, in plan view in a direction along the longitudinal direction of the tendon  40 , the first reinforcing steel  12  and the second reinforcing steel  22  that respectively project from the first facing surface  11  and the second facing surface  21  overlap each other. 
     In the present modification, end portions of the first facing surface  11  and the second facing surface  21  on the side of the first-floor-slab second face  19  and the second-floor-slab second face  29  project. As a result, compared with on the side of the first-floor-slab second face  19  and the second-floor-slab second face  29 , a distance between the first facing surface  11  and the second facing surface  21  is large on the side of the first-floor-slab first face  18  and the second-floor-slab first face  28 . In a region in which the distance between the first facing surface  11  and the second facing surface  21  is large, the first reinforcing steel  12  and the second reinforcing steel  22  project from the first facing surface  11  and the second facing surface  21 , respectively. 
     In the present modification, the floor-slab structure body  1  includes a plurality (specifically, three) of the tendons  40  in the connection portion  30 . Among the three tendons  40 , two tendons  40  extend through inside the loop portions of the first reinforcing steel  12  and the second reinforcing steel  22 . Among the three tendons  40 , one tendon  40  extends through outside the loop portions of the first reinforcing steel  12  and the second reinforcing steel  22 . The tendon  40  may be disposed, as illustrated in  FIG. 4 , to be in contact with at least one of the first reinforcing steel  12  and the second reinforcing steel  22 . Employing the plurality of tendons  40  facilitates stable application of a compressive stress to the connection portion  30 . 
     In addition, the tendon  40  may further include, as illustrated in  FIG. 5 , a cover layer  43  that covers the outer circumference of the twisted wire portion constituted by the core wire  41  and the circumference wires  42 . The cover layer  43  surrounds the twisted wire portion constituted by the core wire  41  and the circumference wires  42  and fills a gap (a region between the outer circumferential surface of the core wire  41  and the outer circumferential surfaces of the circumference wires  42 ) of the twisted wire portion. The cover layer  43  is made of, for example, an epoxy resin. Including the cover layer  43  suppresses corrosion of the twisted wire portion due to infiltration of water and the like. 
     5. Effect of Floor-Slab Structure Body 
     In the floor-slab structure body  1 , which is the concrete structure body according to the present embodiment, the tendon  40  to which a tensile force is applied in the longitudinal direction is disposed in the connection portion  30  to extend along the first facing surface  11  and the second facing surface  21 . Consequently, a compressive stress is applied to the connection portion  30 . As a result, generation and propagation of cracks in the connection portion  30  are suppressed, which improves durability of the connection portion  30 . In addition, the improvement in the durability of the connection portion  30  improves durability as the whole floor-slab structure body  1 . As stated above, the floor-slab structure body  1  according to the present embodiment is a concrete structure body improved in durability as a whole by improving durability of the connection portion  30 . 
     6. Manufacturing Method (Construction Procedure) of Floor-Slab Structure Body 
     Next, an outline of the construction procedure of the floor-slab structure body  1  will be described with reference to  FIG. 6  and  FIG. 7 . Referring to  FIG. 6 , in the construction of the floor-slab structure body  1  according to the present embodiment, a PC-floor-slab preparation step is first performed as a step (S 11 ). Referring to  FIG. 7 , in the step (S 11 ), the first floor slab  10  and the second floor slab  20  are prepared. The first floor slab  10  and the second floor slab  20  can be prepared by pouring uncured concrete (wet concrete) that has fluidity into a mold that has a predetermined shape and allowing the concrete to solidify. Then, the first floor slab  10  having the first facing surface  11  and the second floor slab  20  having the second facing surface  21  are disposed such that the first facing surface  11  and the second facing surface  21  face each other. 
     Next, a tendon disposing step is performed as a step (S 12 ). In the step (S 12 ), the tendon  40  is disposed, as illustrated in  FIG. 7 , so as to extend along the first facing surface  11  and the second facing surface  21  while the tendon  40  is held by a holding member  50  that is disposed to straddle on an external wall of the first floor slab  10  and on an external wall of the second floor slab  20 . As the tendon  40 , a tendon constituted by the twisted wire portion, described on the basis of  FIG. 3 , including the core wire  41  and the circumference wires  42 , which are steel wires, may be employed, or a tendon that further includes the cover layer  43 , described on the basis of  FIG. 5 , may be employed. The holding member  50  includes a base member  51 , a grip member  52 , a wedge member  53 , a jack  54 , and an anchor plate  55 . 
     The tendon  40  is disposed to extend through a space between the first facing surface  11  and the second facing surface  21  and to have, at both sides, excess length portions that project from the space. The base member  51  is made of a material, such as metal, having high strength, for example, steel. A pair of the base members  51  are disposed. One of the base members  51  is disposed to straddle on the external wall of the first floor slab  10  and on the external wall of the second floor slab  20  on one side where the tendon  40  projects. The other of the base members  51  is disposed to straddle on the external wall of the first floor slab  10  and on the external wall of the second floor slab  20  on the other side where the tendon  40  projects. The base members  51  each include a through hole  51 A. 
     On one of the base members  51 , the grip member  52  and the wedge member  53  are mounted. The grip member  52  has, for example, a cylindrical shape and is made of metal, such as steel. The grip member  52  is disposed such that one end surface thereof is in contact with a surface of the base member  51  on a side opposite to the side facing the first floor slab  10  and the second floor slab  20 . In the grip member  52 , a conical recess  52 A whose center axis coincides with the center axis of the grip member  52  is formed. The recess  52 A has a tapered shape having a diameter that decreases toward the base member  51 . The grip member  52  has a through hole that connects a pointed end of the recess  52 A and an end surface on the side in contact with the base member  51  to each other. 
     The wedge member  53  has a conical shape corresponding to the recess  52 A of the grip member  52  and is constituted by a plurality of members obtained by dividing a metal member in which a through hole is formed in a region that includes the center axis thereof in a circumferential direction along a plane including the center axis. The wedge member  53  is disposed by being fitted with respect to the grip member  52  so as to be in contact, at the outer circumferential surface, with an inner wall surface that surrounds the recess  52 A of the grip member  52 . The grip member  52  and the wedge member  53  are disposed such that respective center axes coincide with each other. In addition, the tendon  40  extends through the through holes  51 A of the base members  51 , the trough hole of the grip member  52 , and the through hole of the wedge member  53 . 
     On the other one of the base members  51 , the jack  54 , the anchor plate  55 , the grip member  52 , and the wedge member  53  are mounted by being stuck on each other in this order. As the jack  54 , for example, a center-hole type jack is employable. The anchor plate  55  is made of, for example, steel and has a disc shape having a through hole at a center portion. The grip member  52  and the wedge member  53  have the same structures as the structures of those disposed on the one of the base members  51  and are mounted on a surface of the anchor plate  55  on a side opposite to the side facing the jack  54 , in the same manner as with on the one of the base members  51 . Note that, until a step (S 13 ), which will be described later, is performed, the wedge member  53  on the side of the other one of the base members  51  is in a state of being detached from the grip member  52 . The tendon  40  is disposed so as to extend through the through hole of the anchor plate  55  and the through hole of the grip member  52  after passing through an inner portion of the jack  54 . 
     Next, a tensile force application step is performed as a step (S 13 ). In this step (S 13 ), a tensile force is applied to the tendon  40  by the jack  54 . Specifically, the tendon  40  is pulled in the longitudinal direction by the jack  54 . At this time, the wedge member  53  held by the grip member  52  on the base member  51  on the side opposite to the side where the jack  54  is mounted is pulled toward the base member  51 . Consequently, the wedge member  53  fastens the tendon  40  in a radial direction and restricts the tendon  40 . As a result, the tendon  40  enters a state of being elongated within a range of an elastic limit. Then, in this state, the wedge member  53  is pushed into a space between the tendon  40  and the grip member  52  on the base member  51  on the side where the jack  54  is mounted. Thereafter, when the tension applied to the tendon  40  by the jack  54  is released, the tendon  40  attempts to contract; however, the contraction is impeded by the restriction by the wedge member  53  and the grip member  52 , and the tensile force is maintained. 
     Next, a filling step is performed as a step (S 14 ). In the step (S 14 ), a gap between the first facing surface  11  and the second facing surface  21  is filled with a filling material  30  that solidifies with a lapse of time. As the filling material  30 , for example, uncured concrete (a mixture of cement, sand, gravel, and water) or uncured mortar (a mixture of cement, sand, and water) is employable. At this time, the holding member  50  is disposed so as to be spaced from the filling material  30 . In other words, a gap is formed between the base members  51  and the filling material  30 . Consequently, the base members  51  and the filling material  30  are suppressed from being joined together, and the filling material  30  is suppressed from adhering to base members  51 , which facilitates reuse of the holding member  50  that includes the base members  51 . 
     Next, a solidification step is performed as a step (S 15 ). In the step (S 15 ), the filling material  30  with which the gap between the first facing surface  11  and the second facing surface  21  is filled in the step (S 14 ) cures with a lapse of time. The filling material  30  becomes the connection portion  30  as a result of curing. 
     Next, a holding-member removal step is performed as a step (S 16 ). In the step (S 16 ), the holding member  50  that holds the tendon  40  extending in the filling material  30  (connection portion  30 ) that has solidified in the step (S 15 ) is removed. Specifically, the tendon  40  projecting from the connection portion  30  is cut and removed, and the holding member  50  is removed. Consequently, the method of manufacturing the floor-slab structure body  1  according to the present embodiment is completed. 
     In the method of manufacturing the floor-slab structure body  1  according to the present embodiment, the tendon  40  to which the tensile force is applied in the longitudinal direction is disposed in the filling material  30  that has solidified. Consequently, a compressive stress is applied to the connection portion  30  obtained as a result of the filling material  30  solidifying. As a result, the floor-slab structure body  1  improved in durability as a whole by improving durability of the connection portion  30  is easily manufactured. In addition, in the present embodiment, the gap between the first facing surface  11  and the second facing surface  21  is filled with the filling material  30  in a state in which the tendon  40  is tensed in advance, and the filling material  30  is allowed to solidify. In other words, the compressive stress is applied to the connection portion  30  by a pre-tensioning method. Consequently, quick application of the compressive stress to the connection portion  30  and at low costs is enabled. Moreover, in the present embodiment, the holding member  50  is disposed to be spaced from the filling material  30 . Consequently, reuse of the holding member  50  that includes the base members  51  is facilitated. 
     Note that, in the method of manufacturing the floor-slab structure body  1  according to the present embodiment, as illustrated in  FIG. 8 , an intermediate member  56  that impedes contact between the holding member  50  and the filling material  30  may be disposed between the holding member  50  (base members  51 ) and the filling material  30 . As the intermediate member  56 , for example, a wooden plate is employable. Consequently, the holding member  50  (base members  51 ) and the filling material  30  are suppressed from joining together, which further facilitates reuse of the holding member  50 . 
     In addition, when the floor-slab structure body  1  of the modification described on the basis of  FIG. 4  is to be manufactured, the first floor slab  10  and the second floor slab  20  including the first reinforcing steel  12  and the second reinforcing steel  22 , respectively, of the modification are prepared in the step (S 11 ), and a plurality of the tendons  40  are disposed between the first facing surface  11  and the second facing surface  21  in the step (S 12 ). In the step (S 13 ), a tensile force may be simultaneously applied to the plurality of tendons  40  in the longitudinal direction by the jack  54 . 
     Second Embodiment 
     Next, a second embodiment, which is another embodiment, will be described. The floor-slab structure body  1  according to the second embodiment has basically the same structure and exerts the same effects as with the case of the first embodiment. The floor-slab structure body  1  according to the second embodiment, however, differs from the case of the first embodiment in terms of the tendon being inserted into a sheath and the tendon being held by an anchorage. 
       FIG. 9  is a schematic sectional view illustrating a structure of the floor-slab structure body according to the second embodiment. In addition,  FIG. 10  is a schematic sectional view illustrating a cross section of the floor-slab structure body at a face perpendicular to the longitudinal direction of the tendon. 
       FIG. 10  is a partial sectional view along the line B-B of  FIG. 9 . 
     Referring to  FIG. 9  and  FIG. 10 , the floor-slab structure body  1  according to the second embodiment further includes, in addition to the floor-slab structure body  1  of the first embodiment, a sheath  61  and an anchorage portion  70 . The sheath  61  is disposed in the connection portion  30  along the first facing surface  11  and the second facing surface  21 , more specifically, disposed to extend parallel to the first facing surface  11  and the second facing surface  21 . The sheath  61  is disposed in a region at the center in the thickness direction of the first floor slab  10  and the second floor slab  20  and whose distance from the first facing surface  11  and distance from the second facing surface  21  are equal to each other. The sheath  61  extends through the connection portion  30 . Both end surfaces of the sheath  61  are exposed from the connection portion  30 . The sheath  61  has a tubular shape, more specifically, for example, a hollow cylindrical shape. The sheath  61  is made of, for example, a resin of polyethylene or the like. 
     The tendon  40  is inserted into the sheath  61  to extend through the entire length of the sheath  61 , and a tensile force is applied to the tendon  40  in the longitudinal direction. A region between the sheath  61  and the tendon  40  is filled with a grout material  62 . The tendon  40  is disposed to extend through the inside of the sheath  61  and to have, at both sides, excess length portions that project from both ends of the sheath  61 . 
     The anchorage portion  70  anchors the excess length portions of the tendon  40  exposed from the sheath  61  to the connection portion  30 . The anchorage portion  70  is disposed at each of both sides of the sheath  61 . The anchorage portion  70  includes a support plate  71 , a grip member  72 , a wedge member  73 , a cap  74 , and a cover portion  75 . In an extending direction of the tendon  40 , a recess having, for example, a disc shape is formed in each of both end surfaces of the connection portion  30 . In the recess, the support plate  71  that has a disc shape corresponding to the shape of the recess is fitted and mounted. In the support plate  71 , a through hole extending through a center portion in the thickness direction is formed. The support plate  71  is made of metal, such as steel. 
     The grip member  72  and the wedge member  73  are disposed on a surface of the support plate  71  on a side opposite to the side in contact with the connection portion  30 . The grip member  72  and the wedge member  73  have the same structures as those of the grip member  52  and the wedge member  53  employed in the aforementioned first embodiment. In other words, the anchorage portion  70  includes the wedge member  73  that restricts the tendon  40 , and the grip member  72  that holds the wedge member  73 . The cap  74  covers the grip member  72  and the wedge member  73 , and the tendon  40  projecting from the wedge member  73 . An inner portion of the cap  74  is filled with the cover portion  75 . The cap  74  has a shape of a hollow cylinder whose one end portion is closed by a wall portion and the other end portion opens. The cap  74  is in contact, at the end portion on the open side, with the support plate  71 , thereby covering the grip member  72  and the wedge member  73 , and the tendon  40  projecting from the wedge member  73 . The cap  74  and the cover portion  75  are made of, for example, a resin. 
     Even in such a structure, a compressive stress can be applied to the connection portion  30  of the floor-slab structure body  1 . In addition, employing such a structure enables application of the compressive stress to the connection portion  30  by a post-tensioning method that applies a tensile force to the tendon  40  after the connection portion  30  is formed. 
     Next, an outline of the construction procedure of the floor-slab structure body  1  according to the second embodiment will be described with reference to  FIG. 11  and  FIG. 12 . Referring to  FIG. 11 , in the construction of the floor-slab structure body  1  according to the present embodiment, first, the PC-floor-slab preparation step is performed as a step (S 21 ). The step (S 21 ) can be performed in the same manner as with the step (S 11 ) of the first embodiment. 
     Next, a sheath disposing step is performed as a step (S 22 ). Referring to  FIG. 12 , in the step (S 22 ), the sheath  61  is disposed so as to extend along the first facing surface  11  and the second facing surface  21 . Next, the filling step and the solidification step are performed as steps (S 23 ) and (S 24 ). The steps (S 23 ) and (S 24 ) are performed in the same manner as with the steps (S 14 ) and (S 15 ) of the first embodiment in a state in which the sheath  61  is disposed. The filling material  30  becomes the connection portion  30  by solidifying. Next, a tendon insertion step is performed as a step (S 25 ). In the step (S 25 ), the tendon  40  is inserted so as to extend through the entire length of the sheath  61  such that the excess length portions project from both ends of the sheath  61 . 
     Next, the tensile force application step is performed as a step (S 26 ). In the step (S 26 ), a tensile force is applied to the tendon  40  that is inserted into the sheath  61  in the step (S 25 ). Specifically, referring to  FIG. 12 , the support plate  71  and the grip member  72  are disposed at portions of the connection portion  30  formed as a result of the filling material  30  solidifying, the portions corresponding to both ends of the sheath  61 . The tendon  40  extends through the support plate  71  and the grip member  72 . Then, the wedge member  73  is pushed into a space between the tendon  40  and the grip member  72  disposed on one end portion side of the sheath  61 . 
     On the other end portion side of the sheath  61 , a base member  76  made of, for example, steel is disposed. The base member  76  is disposed to straddle on the external wall of the first floor slab  10  and on the external wall of the second floor slab  20 . The base member  76  is disposed to straddle the grip member  72 . In the base member  76 , a through hole  76 A is formed. On a surface of the base member  76  on a side opposite to the side facing the connection portion  30 , a jack  77  is disposed. The tendon  40  passes through the through hole  76 A of the base member  76  and goes into the jack  77 . The jack  77  holds the tendon  40 . The base member  76  and the jack  77  constitute a holding member. 
     Then, a tensile force is applied to the tendon  40  by the jack  77 . Specifically, the tendon  40  is pulled in the longitudinal direction by the jack  77 . At this time, the wedge member  73  held by the grip member  72  on the support plate  71  on a side opposite to the side where the jack  77  is mounted is pulled toward the support plate  71 . Consequently, the wedge member  73  fastens the tendon  40  in the radial direction and restricts the tendon  40 . As a result, the tendon  40  enters a state of being elongated within a range of an elastic limit. Then, in this state, the wedge member  73  is pushed into a space between the tendon  40  and the grip member  72  on the support plate  71  on the side where the jack  77  is mounted. Thereafter, when the tension applied to the tendon  40  by the jack  77  is released, the tendon  40  attempts to contract; however, the contraction is impeded due to the restriction by the wedge member  73  and the grip member  72 , and the tensile force is maintained. 
     Next, the holding-member removal step is performed as a step (S 27 ). In the step (S 27 ), the jack  77  in the state of releasing application of the tensile force with respect to the tendon  40  and the base member  76  that supports the jack  77  are detached. Next, a grout-material injection step is performed as a step (S 28 ). In the step (S 28 ), the grout material  62  is injected into a space between the sheath  61  and the tendon  40  to which the tensile force is applied. The grout material  62  is made of a resin that cures with a lapse of time. The curing of the grout material  62  causes the tendon  40  and the connection portion  30  to be integrated. Thereafter, an excess portion of the tendon  40  projecting from the wedge member  73  is cut and removed. Then, with the cap  74  mounted to cover the grip member  72  and the wedge member  73 , and the tendon  40  projecting from the wedge member  73 , the inside of the cap  74  is filled with the cover portion  75 . Consequently, the method of manufacturing the floor-slab structure body  1  according to the present embodiment is completed. 
     In the method of manufacturing the floor-slab structure body  1  according to the present embodiment, the tendon  40  to which a tensile force is applied in the longitudinal direction is disposed in the filling material  30  that has solidified. Consequently, a compressive stress is applied to the connection portion  30  obtained as a result of the filling material  30  solidifying. As a result, the floor-slab structure body  1  improved in durability as a whole by improving durability of the connection portion  30  can be easily manufactured. In addition, in the present embodiment, the tendon  40  is tensed after the connection portion  30  is formed, and the compressive stress is applied to the connection portion  30 . In other words, in the present embodiment, the compressive stress is applied to the connection portion  30  by the post-tensioning method. 
     Note that the extending direction of the tendon  40  may be a direction along a bridge axis direction (travelling direction of vehicles and the like) and may be a direction (for example, a direction perpendicular to the bridge axis direction) intersecting the bridge axis direction. 
     The embodiments disclosed here are presented as examples in all respects and should be understood as nonrestrictive in any aspects. The scope of the present invention is prescribed by the claims not by the aforementioned description and intends to include meanings equivalent to the claims, and all changes within the scope. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  floor-slab structure body 
               10  first floor slab 
               11  first facing surface 
               12  first reinforcing steel 
               18  first-floor-slab first face 
               19  first-floor-slab second face 
               20  second floor slab 
               21  second facing surface 
               22  second reinforcing steel 
               28  second-floor-slab first face 
               29  second-floor-slab second face 
               30  connection portion (filling material) 
               40  tendon 
               41  core wire 
               42  circumference wire 
               43  cover layer 
               50  holding member 
               51  base member 
               51   a  through hole 
               52  grip member 
               52   a  recess 
               53  wedge member 
               54  jack 
               55  anchor plate 
               56  intermediate member 
               61  sheath 
               62  grout material 
               70  anchorage portion 
               71  support plate 
               72  grip member 
               73  wedge member 
               74  cap 
               75  cover portion 
               76  base member 
               76   a  through hole 
               77  jack