JP5608054B2 - Precast reinforced concrete beam and floor assembly having the same - Google Patents

Description

The present invention relates to a precast reinforced concrete beam having a rectangular opening used as an air conditioning duct route or the like and a floor assembly having the same .

  Buildings are constructed by forming a column beam structure with columns and beams made of reinforced concrete or steel, and placing floor slabs on a floor set consisting of large beams and small beams. Since there are many ducts and piping for air conditioning, water supply / drainage, power supply, etc., these ducts and piping pass through the vertical wall (web) of the beam in order to avoid a low ceiling height. It is common to provide an opening (hereinafter referred to as a duct opening). Therefore, conventional office buildings use H-shaped steel with duct openings formed on the web as beams, and RC structures combined with steel structures (all S structures) combined with steel columns and RC (reinforced concrete) columns. In many cases, the beam S structure is used to suppress the strength reduction of the beam due to the duct opening.

  In recent years, it has superior vibration proofing performance compared to steel beams, construction costs are less susceptible to fluctuations in steel prices, and steel beams that require fireproof coating need to have a ceiling from a design standpoint. For reasons such as being bad, it has been studied to adopt precast prestressed concrete (PCaPC) beams, which are reinforced concrete beams, for office buildings.

  In addition, as a technique to provide openings through which ducts and pipes pass in reinforced concrete beams, upper and lower main bars are arranged in multiple stages on the upper and lower ends of the beam, and the upper and lower main bars are arranged. There has been proposed a structure in which the upper principal muscle group is constrained by the upper-end restraint muscle and the lower-end principal muscle group is restrained by the lower-end restraint muscle (see Patent Document 1). In this reinforced concrete beam, the upper end side virtual beam including the upper end main reinforcement group and the lower end side virtual beam including the lower end main reinforcement group can resist the shearing force. Thus, an opening can be easily provided between both virtual beams.

JP 2010-13797 A

  However, in the reinforced concrete beam of Patent Literature 1, the upper end side virtual beam and the lower end side virtual beam can resist the shearing force, but the upper end side virtual beam and the lower end side virtual beam are connected by an intermediate portion made of unreinforced concrete. And the handling of the intermediate portion where the shear stress in the horizontal direction due to the bending moment is maximum is ambiguous. In addition to the upper virtual beam and the lower virtual beam, which are stress bearing members against the shear force in the vertical direction, it has an intermediate part, so the weight of reinforced concrete beams that tend to be heavier than steel beams is reduced. It was hard to say that it was the optimal structure. In addition, since the reinforced concrete beam of Patent Document 1 has a plurality of circular openings of the same shape, the air conditioning duct having a large number of rectangular cross-sections is poorly fit, and depending on the shape and size of the duct, it can be passed through the openings. There is also a problem that it cannot be done.

  The present invention has been made in view of such a background, and provides a reinforced concrete beam capable of ensuring strength and reducing weight while providing a plurality of rectangular openings for passage through a duct or the like. Is its main purpose.

  In order to solve the above problems, the present invention is a rectangular shape in which an upper chord part (11) and a lower chord part (12) are connected by a plurality of bundle parts (13 to 16) and penetrate between the bundle parts in the beam width direction. A precast reinforced concrete beam (PCa beam) in which a plurality of openings (21 to 24) are formed, and the ratio of the bundle length and the opening length on the end side in the axial direction is the bundle length and the opening length on the central side in the axial direction. (A1 / B1> A4 / B4).

  According to this configuration, the reinforced concrete beam has a feelendel structure in which the upper chord part, the lower chord part, and the bundle part each bear a stress as a structural element, and the burden stress of each part can be obtained based on a clear structural calculation. Therefore, it is possible to flexibly correspond to the opening length according to the size and shape of the duct or the like. In addition, the load of the horizontal shearing force of the bundle portion increases as it approaches the end portion, but the ratio of the bundle portion length and the opening length on the end portion side in the axial direction is the ratio of the bundle portion length and the opening portion length on the central side in the axial direction By making it larger than the ratio, a mechanically rational structure can be achieved, and both the securing of strength and the weight reduction can be realized. In addition, because the bundle portion can bear a stress even with respect to the vertical direction shear force, the bundle portion is arranged in the vicinity of the end portion where the shear force is the largest, thereby reducing the weight of the reinforced concrete beam as a whole. . Furthermore, since the opening is rectangular, there is no surplus that does not contribute as a structural element, and an increase in weight can be suppressed.

  In addition, according to one aspect of the present invention, the lower part on the end side can be cut off obliquely. According to this structure, it becomes possible to arrange | position a duct etc. along the edge part of a reinforced concrete beam, ie, a big beam, and a pillar, and can raise the design freedom of equipment arrangement | positioning.

  Further, according to one aspect of the present invention, the beam width on the end side can be made larger than the beam width on the center side in at least one of the upper chord part and the lower chord part. According to this configuration, the strength on the end portion side where the shearing force is large can be improved, and the beam width on the center side having a relatively low required strength can be reduced, so that the reinforced concrete beam can be further reduced in weight. Moreover, when providing a notch in an edge part, it is suitable for reinforcement of an edge part.

  Moreover, according to one side of this invention, it can be set as the structure by which the prestress was provided to the lower chord part by PC steel wire (61, 62). According to this configuration, since the tensile strength of the lower chord portion is improved, it is possible to reduce the cross section and increase the span of the reinforced concrete beam. Moreover, since the PC steel wire is less expensive than the high-strength reinforcing bar, the manufacturing cost can be reduced. Furthermore, when a high-strength reinforcing bar is used, the manufacturing length is limited, but when a PC steel wire is used, there is no limitation on the beam manufacturing length.

  Moreover, according to one side of this invention, it can be set as the structure by which the main reinforcement is not arrange | positioned in the lower chord part, but the horizontal reinforcement (42) surrounding PC steel wire is arrange | positioned. According to this configuration, the lower chord can be reduced in cross section by using the PC steel wire. On the other hand, when a normal amount of rebar and PC steel wire are placed in the lower chord, the gap becomes smaller and the concrete can be filled. However, by omitting the main bars, the concrete filling property is improved, and the PC steel wires are restrained directly or through the concrete with the horizontal reinforcing bars to ensure the fixing of the PC steel wires. It is possible to realize both a small cross section and quality assurance.

  Moreover, according to one aspect of the present invention, the upper chord part, the lower chord part, and the bundle part are made of separate members that are individually precast, and are joined / integrated via PC steel bars or reinforcing bars. Can do. According to this configuration, it is possible to improve the productivity and reduce the manufacturing cost by facilitating the assembly of the mold, the assembly of the reinforcing bars, and the placement of the concrete.

  As described above, according to the present invention, it is possible to provide a reinforced concrete beam capable of ensuring strength and reducing weight while providing a plurality of openings for passage through a duct or the like.

The perspective view of the floor set to which the PCa beam according to the first embodiment is applied Front view of the PCa beam shown in FIG. Plan view of the PCa beam shown in FIG. Longitudinal section of the main part of the PCa beam shown in FIG. VV sectional view in FIG. VI-VI cross section in FIG. VII-VII sectional view in FIG. Side view of main part of PCa beam according to modification Explanatory drawing of the manufacturing procedure of the PCa beam shown in FIG. Explanatory drawing of the manufacturing procedure which concerns on the modification of the PCa beam shown in FIG. Explanatory drawing of the manufacturing procedure of PCa beam concerning a 2nd embodiment Explanatory drawing of the manufacturing procedure of PCa beam concerning a 3rd embodiment Explanatory drawing of the modification of the manufacturing procedure of the PCa beam shown in FIG. Explanatory drawing of the manufacturing procedure of PCa beam concerning a 4th embodiment Cross-sectional view of each part of PCa beam shown in FIG. Explanatory drawing of the manufacturing procedure of PCa beam concerning a 5th embodiment Cross-sectional view of the principal part of the PCa beam joint structure shown in FIG. Sectional drawing of the principal part of the joining structure which concerns on the modification of the PCa beam shown in FIG. Explanatory drawing of the manufacturing procedure of PCa beam concerning a 6th embodiment

  Hereinafter, several embodiments in which a reinforced concrete beam (hereinafter simply referred to as a PCa beam 1) of the present invention is applied to a floor set of a building for an office building will be described in detail with reference to the drawings. For the convenience of description, the PCa beam 1 is assumed to have the lower left diagonal in FIG. 1 as the left and the upper right diagonal as the right.

<< First Embodiment >>
As shown in FIG. 1, a PCa reinforced concrete beam (hereinafter simply referred to as a PCa beam 1) is a small beam made of PC concrete, and both ends are connected to a pair of large beams 2, and a floor slab 3 is formed on the upper part thereof. Has been built. As shown also in FIG. 2, the PCa beam 1 includes a pair of upper and lower chord portions 11 and 12 that extend in the left-right direction (axial direction), and a pair of left and right symmetrical portions to connect the upper chord portion 11 and the lower chord portion 12. It has the 1st-4th bundle parts 13-16 arranged.

  A rectangular first opening 21 is formed between the first bundle 13 and the second bundle 14, and a rectangular second opening 22 is formed between the second bundle 14 and the third bundle 15. A rectangular third opening 23 is formed between the third bundle portion 15 and the fourth bundle portion 16, and a rectangular fourth opening portion 24 is formed between the two fourth bundle portions 16. Is formed. In addition, these 1st-4th opening parts 21-24 are each formed in the aspect which penetrates the PCa beam 1 in a beam width direction.

  These openings 21 to 24 are piping routes such as air conditioning ducts of office buildings, and are large as RC beams, and a large number of rectangular openings 21 to 24 are provided. As shown, the piping route can be freely set, and a duct having a relatively large cross section can be used. It is also easy to change the piping route during renovation.

  A frame portion 2a is formed on the side surface of the large beam 2, and the PCa beam 1 is coupled to the large beam 2 with the upper chord portion 11 placed on the frame portion 2a. The PCa beam 1 has a substantially inverted trapezoidal shape in which the lower portions of the left and right end portions are obliquely cut out, and a substantially triangular gap 25 is formed between the PCa beam 1 and the large beam 2. Therefore, the lower chord part 12 is shorter than the upper chord part 11, and the 1st bundle part 13 arrange | positioned at the beam end part is also an inverted trapezoid whose one side is perpendicular | vertical.

  As described above, since the gap 25 is formed at the end of the PCa beam 1, it is possible to provide an air-conditioning duct or the like along the large beam 2 that has been considered difficult in the past. Is growing. In this embodiment, the PCa beam 1 is installed on the large beam 2. However, when the PCa beam 1 is installed on a column, an air conditioning duct or the like can be provided along the installed column.

  As shown in FIG. 3, the upper chord portion 11 has the smallest width at the central portion 11a, and the width increases toward the side portion 11c adjacent to the central portion 11a and the side end portion 11e adjacent to the side portion 11c. . In addition, connecting portions 11b and 11d whose widths are gradually changed are provided between the central portion 11a and the side portion 11c of the upper chord portion 11 and between the side portion 11c and the side end portion 11e, respectively. Yes.

  Further, the lower chord portion 12 also changes its width in the same manner as the upper chord portion 11 and is shorter than the upper chord portion 11, so that the width of the end portion is the same as the side portion 11 c of the upper chord portion 11. Similarly, the second to fourth bundle portions 14 to 16 arranged closer to the center also change the width in the same manner as the upper chord portion 11, while the first bundle portion 13 has the same width as the side portion 11 c of the upper chord portion 11. The cross section of the PCa beam 1 at the side end portion 11e of the upper chord portion 11 and the connecting portion 11d is T-shaped.

  The shearing force acting on the PCa beam 1 usually increases toward the end side. Therefore, the width of the upper chord portion 11 is maximized at the side end portion 11e in this way, so that the PCa beam 1 can resist the shearing force even at the connecting portion with the large beam 2. Moreover, even if the end portion of the PCa beam 1 is cut, the wide upper chord portion 11 suitably compensates for a decrease in shear strength due to the notch. On the other hand, by increasing the overall width of the PCa beam 1 including the upper chord part 11 and the lower chord part 12 toward the end side, the PCa beam 1 is reduced in weight while ensuring the strength to withstand shearing force. .

  As shown in FIG. 4 to FIG. 7, the main chord portion 11 has three main bars 31 arranged vertically in the vertical direction. In the PCa beam 1 in this embodiment, after the floor slab 3 is placed, a part of the floor slab concrete integrated with the PCa beam 1 constitutes a part of the small beam. For the PCa beam 1 before erection, only the lower two-stage main bars 31 function as main bars. Therefore, the upper main bar 31 exposed above the upper chord portion 11 at the time of erection to the large beam 2 is not originally included in the main bar of the PCa beam 1, but in the description related to the reinforcing bar, the upper main bar 31 including the upper main bar 31 is included. The main reinforcement 31 of the beam 1 will be described. In FIGS. 4 to 7, hatching is omitted in order to avoid complication of the drawings.

  As shown in FIG. 7, in the central portion 11 a of the upper chord portion 11, a plurality of main reinforcing bars 31 are arranged for each step, and a lateral reinforcing bar 41 that surrounds the main reinforcing bars 31 and a width stop bar 44 that straddles the middle main bar 31 is an axis It is provided at predetermined intervals in the direction. As shown in FIG. 6, in the side part 11c of the upper chord part 11, the number of main bars 31 in the lower stage and the middle stage is larger than the central part 11a (FIG. 7) in accordance with the increase in width, and is the same as the central part 11a in the upper stage. A number of main bars 31 are arranged, respectively, and horizontal reinforcing bars 41 surrounding the main bars 31 and width stopper bars 44 straddling the middle main bars 31 are provided at predetermined intervals in the axial direction. As shown in FIG. 5, at the side end portion 11e of the upper chord portion 11, the number of main bars 31 in the lower and middle tiers is larger than the side portion 11c (FIG. 6) as the width further increases. The same number of main bars 31 as the part 11c are arranged at the same position as the side part 11c, and the first horizontal reinforcing bars 41a surrounding all the lower and middle main bars 31 and the inner main bars 31 among the lower and middle stages. The surrounding second horizontal reinforcing bars 41b and the width stopping bars 44 straddling the pair of innermost main bars 31 arranged in the innermost stage are provided at predetermined intervals in the axial direction.

  As shown in FIG. 7, the lower chord portion 12 is not provided with a main bar, and a PC steel wire 61 that is pretensioned and extends over the entire length thereof has a plurality of stages (here, three stages) and Each stage is provided in a plurality (two in this case). The PC steel wire 61 is not necessarily inscribed in the lateral reinforcing bar 42 and does not need to be directly restrained by the lateral reinforcing bar 42, but is indirectly restrained by the lateral reinforcing bar 42 through concrete. What is necessary is just to be arrange | positioned inside 42. Also, as well shown in FIG. 4, the first chord part 12 and the first chord part 12 are arranged near the end of the lower chord part 12 in order to resist the bending moment (to resist the horizontal shearing force caused by the bending moment). In the two bundle portions 13 and 14, reinforcing bars 45 that are inclined upward toward the end portion and reach the upper chord portion 11 are appropriately arranged. On the other hand, lateral reinforcing bars 42 surrounding the PC steel wire 61 and the reinforcing bars 45 are provided at predetermined intervals in the axial direction.

  Since the PC steel wire 61 is arranged in the lower chord part 12 and prestress is applied in this way, the tensile strength of the lower chord part 12 is improved, so that the cross section can be reduced and the PCa beam 1 can have a large span. It has become.

  In addition, by arranging the PC steel wire 61 in the lower chord portion 12, it is possible to reduce the cross section of the lower chord portion 12. On the other hand, when a normal amount of rebar and the PC steel wire 61 are placed in the lower chord portion 12, the gap is reduced. The concrete fillability deteriorates, but by omitting the main bars, the concrete fillability can be secured even at the center side having the smallest cross section. In addition, by arranging the horizontal reinforcing bars 42 so as to surround the PC steel wire 61, the strength of the lower chord portion 12 is increased and the fixing of the PC steel wire 61 is ensured. The balance of securing is realized.

  In the bundle portions 13 to 16, as shown in FIG. 4, the horizontal reinforcing bar 41 of the upper chord part 11 and the horizontal reinforcing bar 42 of the lower chord part 12 are connected, and the main bar 31 of the upper chord part 11 and the PC steel wire of the lower chord part 12. One horizontal reinforcing bar 43 surrounding 61 is formed, and this horizontal reinforcing bar 43 functions as a shear reinforcing bar for increasing the bonding strength to the upper chord part 11 and the lower chord part 12 in the bundle parts 13 to 16.

  The PCa beam 1 configured as described above has a feelendel structure in which the upper chord part 11, the lower chord part 12 and the bundle parts 13 to 16 are rigidly coupled, and the stress applied to each part is based on a clear structural calculation. Can be sought.

Returning to FIG. 2, the length (axial length) A <b> 1 of the first bundle portion 13 taking the average value of the length of the upper end edge and the length of the lower end edge of the first bundle portion 13 exhibiting an inverted trapezoid, The relationship between the fourth bundle portions 14 to 16 and the lengths A2 to A4 is expressed by the following equation.
A1>A2>A3> A4 (1)

On the other hand, when the lengths (axial lengths) of the first to fourth openings 21 to 24 are B1 to B4, the lengths A1 to A4 of the bundle parts 13 to 16 and the opening 21 adjacent to the central part side. The ratio (A / B) to the lengths B1 to B4 of ˜24 has the relationship shown in the following formula.
(A1 / B1)> (A2 / B2)> (A3 / B3)> (A4 / B4) (2)
That is, the ratio of the bundle length and the opening length on the end side in the axial direction is larger than the ratio of the bundle length and the opening length on the central side in the axial direction.

  By setting the lengths and the arrangement intervals of the bundle portions 13 to 16 in this way, it resists the shear force in the horizontal direction caused by the bending moment, which becomes larger at the end portion, with a mechanically rational structure. Therefore, both the securing of the strength of the PCa beam 1 and the weight reduction can be achieved. In addition, since the first bundle portion 13 that can be a stress bearing member for vertical shearing force is disposed at the end portion of the lower chord portion 12, the cross section of the upper chord portion 11 can be appropriately reduced above the first bundle portion 13. Therefore, weight reduction of the PCa beam 1 is achieved.

  In addition, since the openings 21 to 24 are rectangular, not only does the air conditioning duct fit in a large cross section with many rectangles, but there is also a surplus portion that does not contribute as a structural element that occurs when the circular opening is used. Since it does not occur, an increase in the weight of the PCa beam 1 is suppressed.

  On the other hand, as shown in FIG. 8, the PCa beam 1 can be configured by reducing the left and right end cutouts. In this way, the length of the portion of the lower chord portion 12 to which the first bundle portion 13 is connected is increased, so that the fixing length at the end of the PC steel wire 61 can be sufficiently secured, and the necessary prestress is achieved. Can be applied to the lower chord part 12. Further, as shown in FIG. 8, in the upper chord part 11, the connecting part 11d directly connects the center part 11a having the smallest width and the side end part 11e having the largest width without providing the side part 11c and the connecting part 11b. It is also possible to configure so as to. By doing in this way, an assembly of a reinforcing bar and a formwork can be made easy.

  Next, a procedure for manufacturing the PCa beam 1 having such a configuration with more rational and high quality will be described. FIG. 9 is an explanatory view of a rebar assembling procedure of the PCa beam 1, (A) is a front view, (B) is a BB cross-sectional view in (A), and (C) is in (A). CC sectional drawing is shown.

  When assembling the reinforcing bars of the PCa beam 1, first, as shown by solid and broken lines in FIG. 9, the main bars 31 of the upper chord part 11 and the setup bars 32 of the lower chord part 12 without considering the positions of the openings 21 to 24. Is disposed over the entire length of the PCa beam 1. Thereafter, in accordance with the positions of the openings 21 to 24, the central portion of the horizontal reinforcing bar 43 indicated by a broken line is cut and removed, and the width stop bars are respectively provided at the lower end of the main bar 31 of the upper chord part 11 and the upper end of the setup bar 32 of the lower chord part 12. 44, and a part of the horizontal reinforcing bar 43 remaining above and below becomes the side part of the horizontal reinforcing bar 41 of the upper chord part 11 and the side part of the horizontal reinforcing bar 42 of the lower chord part 12, respectively. The lateral reinforcing bars 41 and 42 surrounding the rim are formed.

  Alternatively, as in the modification shown in FIG. 10, the lateral reinforcement bars 41 that surround the horizontal reinforcement bars 41 of the upper chord part 11 and the horizontal reinforcement bars 42 of the lower chord part 12, and the main bars 31 of the upper chord part 11 and the setup bars 32 of the lower chord part 12. 43 are arranged over the entire length of the PCa beam 1 so as to be alternately arranged. Thereafter, in accordance with the positions of the openings 21 to 24, the central portion of the horizontal reinforcing bar 43 indicated by a broken line is cut and removed, and the width stop bars are respectively provided at the lower end of the main bar 31 of the upper chord part 11 and the upper end of the setup bar 32 of the lower chord part 12. 44 (not shown) are arranged, and a part of the horizontal reinforcing bar 43 left and right is a side part of the horizontal reinforcing bar 41 of the upper chord part 11 and a side part of the horizontal reinforcing bar 42 of the lower chord part 12. Alternatively, the lateral reinforcing bars 41 and 42 surrounding the setup bar 32 may be formed.

  By assembling the reinforcing bars of the PCa beam 1 in this way, it is not necessary to irregularly arrange the lateral reinforcing bars 41 to 43 according to the bundle portions 13 to 16 arranged at unequal lengths and at unequal intervals. Assembling work can be made efficient. Moreover, by assembling in such a procedure, it can be used as a general-purpose reinforcing bar for the PCa beam 1 having various forms with respect to the PCa beam 1 in which openings can be provided in various forms from a design viewpoint. Also, rebar assembly work can be made more efficient.

<< Second Embodiment >>
A second embodiment of a rational manufacturing method of the PCa beam 1 will be described with reference to FIG. In addition, the same code | symbol shall be attached | subjected to the member or site | part similar to the said embodiment, and the description which overlaps with the said embodiment is abbreviate | omitted. The same applies to the following embodiments.

  As shown in FIG. 11 (A), the upper member 51 constituting the central portion 11a, the connecting portion 11b and the side portion 11c, and the second to fourth bundle portions 14 in the upper chord portion 11 is precast-molded integrally with reinforced concrete. At the same time, the lower end member 52 constituting the side end portion 11e and the connecting portion 11d, the first bundle portion 13, and the lower chord portion 12 of the upper chord portion 11 is precast-molded integrally with reinforced concrete. The arrangement of the reinforcing bars of the upper member 51 and the lower member 52 is different from that of the above-described general configuration, but is substantially the same, and detailed changes are not related to the gist of the invention, so the description is omitted here. The same applies to the following embodiments.

  When the upper member 51 is precast-molded, it is preferable to assemble concrete with a reinforcing bar and a formwork so that the upper chord portion 11 is on the upper side, that is, the upper side of the paper surface of FIG. By placing the concrete in such a direction, it is possible to easily fill all parts with concrete, and it is possible to prevent the occurrence of construction defects such as so-called bean plates and jumpers.

  On the other hand, when the lower member 52 is precast-molded, the rebar and the formwork are assembled so that the lower chord 12 is on the upper side, that is, the lower side of the paper of FIG. Is preferred. By placing concrete in this direction, it is possible to easily fill all parts with concrete, as well as material separation by cross-flowing concrete and ridges on the lower finished surface due to the height difference of the finished surface. It is possible to prevent the occurrence of defects.

  Further, when the lower member 52 is precast-molded, it is strained through the PC steel wire 61 in the mold of the lower chord portion 12, and after high strength concrete is cast to express a predetermined strength, the tension is applied. Release and apply prestress to the lower chord part 12 over the entire length.

  From the end portion of the upper member 51, that is, the end surface of the side portion 11 c of the upper chord portion 11, the main bar 31 protrudes in order to join the upper chord portion 11 included in the lower member 52. In order to join the upper chord part 11, the place where the protruding main bar 31 is received is left in a state where the concrete is not placed.

  The part which comprises the 2nd-4th bundle parts 14-16 of the upper side member 51 is a rectangle which has a height dimension larger than the height h (refer FIG. 11 (B)) of actual 2nd-4th bundle parts. Is formed. On the other hand, the length of the second to fourth bundle portions 14 to 16 (the length in the axial direction of the PCa beam 1) is substantially equal to the portion of the lower member 52 that joins the second to fourth bundle portions 14 to 16. A recess 52a formed by cutting out the lower chord 12 over the same length is provided. Moreover, the part which comprises the 1st bundle part 13 is also formed so that it may have a height dimension larger than the actual height h of the 1st bundle part 13 (refer FIG. 11 (B)). On the other hand, in the portion of the upper member 51 that joins the first bundle portion 13, the upper chord portion 11 is cut out over the substantially same length as the length of the first bundle portion 13, and a recess 51 a is formed.

  Next, the upper member 51 and the lower member 52 are integrally joined as shown in FIG. 11B to form one PCa beam 1. Specifically, the portions constituting the second to fourth bundle portions 14 to 16 of the upper member 51 are respectively fitted into the corresponding concave portions 52 a of the lower member 52, and the first bundle portion 13 of the lower member 52 is moved. The portion to be configured is fitted into the concave portion 51a of the upper member 51, and the concrete is placed in a state where the projecting portion of the main reinforcement 31 of the upper member is disposed in the portion where the concrete of the lower member 52 is not placed. Integrate. By joining in this way, the upper member 51 and the lower member 52 are directly joined.

  In addition, between the part which comprises the 2nd-4th bundle parts 14-16 and the recessed part 52a, and the part which comprises the 1st bundle part 13, and the recessed part 51a, mortar etc. are spread | laid, both members It is good to make it adhere.

  In the PCa beam 1 manufactured in this way, at the stage shown in FIG. 11 (A), the upper member 51 has the upper edges 21u, 22u, 23u, 24u of the first to fourth openings 21 to 24u. The first opening 21 is formed so as to define a side edge 21sc on the beam center side and both side edges 22sc, 22se, 23sc, 23se, 24s of the second to fourth openings 22-24. The lower member 52 defines the lower edges 21l, 22l, 23l, and 24l of the first to fourth openings 21 to 24 and the side edge 21se on the beam end side of the first opening 21. It is formed. By splitting the upper member 51 and the lower member 52 separately in this way, the concrete filling property around the opening of each member can be ensured and the quality can be easily ensured. .

  In addition, since the weight of the member can be reduced by configuring the PCa beam 1 with a precast concrete member divided into a plurality of parts, if the upper member 51 and the lower member 52 are joined on site, the factory Can be easily handled and transported to the site. Even when prestress is applied to the PCa beam 1, by applying prestress using the PC steel wire 61, it becomes possible to manufacture in a normal PC factory, and handling is possible because the members can be small. Will also be easier.

  Furthermore, by applying prestress to the lower chord part 12 on which a tensile force acts, the member cross section can be effectively reduced. In addition, when prestress is applied to the PCa beam 1, it is necessary to use high-strength concrete with high compressive strength at the site where the prestress is applied. However, when the PCa beam 1 is molded as an integral part, However, the use of high-strength concrete even in areas where it is not necessary increases the cost. However, by splitting the PCa beam 1 into an upper member 51 and a lower member 52 and precast molding, expensive high strength It is possible to selectively use concrete and inexpensive ordinary concrete, and the material cost can be reduced.

  On the other hand, when the PCa beam 1 is integrated and prestress is applied, the prestress resultant force position is greatly decentered with respect to the center of gravity position in the beam cross section. Therefore, upward bending stress is generated in the entire PCa beam 1, and cracks due to excessive stress are likely to occur in the upper chord portion 11 and the bundle portions 13 to 16 during the construction. On the other hand, in this embodiment, since the PCa beam 1 is divided into the upper member 51 and the lower member 52 and formed, the prestress resultant force is applied at a position substantially the same as the center of gravity of the lower chord portion 12. it can. Therefore, the generation of cracks due to prestress can be prevented.

  On the other hand, when the upper member 51 is precast-molded, at least a part of the bundle portions (second to fourth bundle portions 14-16) are integrally molded, or when the lower member 52 is precast-molded, at least By integrally molding a part of the bundle portions (first bundle portion 13), the number of members and the joint locations can be reduced. Therefore, the assembly work of the PCa beam 1 can be facilitated.

  In addition, in this embodiment, the part which comprises the bundle parts 13-16 integrally molded by the upper side member 51 and the lower side member 52 respectively comprises the whole each bundle part 13-16, and the other member which is not integrally molded. The lower chord part 12 or the upper chord part 11 is divided so as to constitute a part (that is, the fitting convex part), but can be divided so as to constitute a part of each of the bundle parts 13 to 16, respectively. It is.

«Third embodiment»
Next, a third embodiment of a rational manufacturing method of the PCa beam 1 will be described with reference to FIG. In FIG. 12B, a plan view of the PCa beam 1 is also shown above the side view of the PCa beam 1.

  As shown in FIG. 8, the PCa beam 1 of this embodiment has a configuration in which the central portion 11a and the side end portion 11e are directly connected to each other at the upper chord portion 11 by the connecting portion 11d. The manufacturing procedure of this PCa beam 1 is as follows. First, as shown in FIG. 12 (A), the central part 11a of the upper chord part 11 and the upper member 51 constituting the second to fourth bundle parts 14 are precast-molded integrally with reinforced concrete, and the first bundle part 13 and The lower member 52 constituting the lower chord portion 12 is precast-molded integrally with reinforced concrete, and the side end portion 11e and the connecting portion 11d of the upper chord portion 11 and the end member 53 constituting the first bundle portion 13 are made of reinforced concrete. Precast molding as one piece.

  Also in this embodiment, when the upper member 51 is precast-molded, concrete is placed so that the upper chord portion 11 is on the upper side, and when the lower member 52 is precast-molded, the lower chord portion 12 is on the upper side. It is better to cast concrete so that In addition, when pre-casting the end member 53, it is preferable to cast concrete so that the upper chord portion 11 is on the upper side.

  Further, when the lower member 52 is precast-molded, it is strained through the PC steel wire 61 in the form of the lower chord portion 12, high-strength concrete is placed, and the tension is released after a predetermined strength is developed. Thus, prestress is applied to the lower chord portion 12 over the entire length, and the PC steel wire 61 is extended from the end surface of the lower chord portion 12 by a predetermined length or more.

  The end member 53 is formed with a protruding portion 53c that protrudes downward from the first bundle portion 13 and is joined to the side end surface of the lower chord portion 12, and the upper chord portion 11 from the joint surface with the lower chord portion 12 of the protruding portion 53c. A sheath tube (not shown) is embedded obliquely so as to reach the end of the steel plate so that the PC steel wire 61 extending from the end surface of the lower chord portion 12 can be inserted. Further, the end member 53 leaves a part of the concrete in an unplaced state so as to receive the main bar 31 protruding from the end face in order to join the upper chord portion 11 later.

  Next, the upper member 51 and the lower member 52 are integrally joined to form one PCa beam 1 as shown in FIG. Specifically, the portions constituting the second to fourth bundle portions 14 to 16 of the upper member 51 are respectively fitted into the corresponding concave portions 52a of the lower member 52, and the protruding portion 53c of the end member 53 is set to the lower member. 52, the portion constituting the first bundle portion 13 is fitted into the concave portion 51a of the upper member 51, the PC steel wire 61 is inserted into the sheath tube, and the tension and fixing work is performed. The concrete portion is placed by placing the protruding portion of the main reinforcement 31 of the upper member in the portion where is not placed. By joining in this way, the upper member 51 and the lower member 52 are joined directly by the second to fourth bundle parts 14 to 16 and indirectly by the end member 53 at the first bundle part 13. Is done.

  The PC steel wire 61 is used as a pre-tensioning method when the lower chord portion 12 is precast-molded, and then is endured obliquely upward as shown by the black arrow in the drawing when joining the end member 53. It is also used as a post-tension system that is fixed to the end portion of the upper chord portion 11 of the member 53 and applies prestress to the end member 53. That is, the PC steel wire 61 is used for both pre-tension and post-tension types.

  Here, the timing at which the post tension is applied to the PC steel wire 61 is not limited to the time of joining with the end member 53 as described above, and the PCa beam 1 is installed on the large beam 2 by joining the end member 53. It can be later. By performing at such a time, even when post tension is applied after the assembly of the PCa beam 1, it is possible to reliably avoid the occurrence of cracks and the like.

  In the PCa beam 1 manufactured as described above, at the stage shown in FIG. 12A, the upper member 51 is connected to the upper edges of the first to fourth openings 21 to 24 in the same manner as in the second embodiment. 21u, 22u, 23u, 24u, side edge 21sc on the beam center side of the first opening 21, and both side edges 22sc, 22se, 23sc, 23se, 24s of the second to fourth openings 22-24 are defined. Formed. The lower member 52 is formed so as to demarcate the lower edges 21 l, 22 l, 23 l, and 24 l of the first to fourth openings 21 to 24, and the end member 53 is a beam end of the first opening 21. It is formed so as to define a side edge 21se on the side.

  By dividing the upper member 51, the lower member 52, and the end member 53 separately by precast molding in this way, not only can the concrete fillability around the opening of each member be secured, but also the length of each member. Since the length can be made shorter than the length of the PCa beam 1, each member can be handled and transported more easily.

<Modification>
In the present embodiment, as in the modification shown in FIG. 13, the PC steel wire 61 provided inside the lower chord portion 12 is cut at the end portion of the lower chord portion 12, and the end portion of the lower chord portion 12 or the lower chord portion The main bar 31 is arranged over the entire length of the twelve part, and the main bar 31 is obliquely projected from the end surface of the lower chord part 12 so as to reach the upper chord part 11, and the upper member 51 and the lower member 52 are second to second. After arranging appropriately so that it may contact | abut with the 4 bundle parts 14-16, by placing concrete so that the main reinforcement 31 of the upper chord part 11 and the main reinforcement 31 of the lower chord part 12 may be wound, upper member 51 and lower member 52 of The end member 53 can also be precast molded after molding. Also by such joining, the upper member 51 and the lower member 52 are joined directly by the second to fourth bundle portions 14 to 16 and indirectly by the end member 53 at the first bundle portion 13. be able to.

<< Fourth Embodiment >>
As shown in FIGS. 14 and 15, the PCa beam 1 according to this embodiment includes an upper member 51, a lower member 52, and left and right end members 53, as in the third embodiment. In the present embodiment, the upper member 51 is precast-molded integrally with the central portion 11 a of the upper chord portion 11 and the upper half portions of the first to fourth bundle portions 13 to 16, and the lower member 52 is connected to the lower chord portion 12. The lower half of the first to fourth bundle parts 13 to 16 is precast-molded integrally, and the end member 53 includes the side end part 11e and the connecting part 11d of the upper chord part 11 and the side part of the first bundle part 13. It is precast molded integrally.

  One of the lower surface of the portion constituting the first to fourth bundle portions 13 to 16 of the upper member 51 and the upper surface of the portion constituting the first to fourth bundle portions 13 to 16 of the lower member 52 (here, the lower side) A convex portion 52b is formed on the member 52 side, and a concave portion 51a having a shape complementary to the convex portion 53b is formed on the other side (here, the upper member 51 side). Then, the upper member 51 and the lower member 52 are joined in a state where the convex portion 52b is fitted to the concave portion 51a in the first to fourth bundle portions 13 to 16, so that the fitting portion becomes a shear key. Thus, it can resist the horizontal shearing force caused by the bending moment. In addition, the first to fourth bundle portions 13 to 16 are joined in the vicinity of the center in the vertical direction, so that the joint portion is arranged at a position where the horizontal shearing force is minimized.

  In addition, the PCa beam 1 of the present embodiment has a PC steel wire 61 provided linearly over the entire length of the lower chord portion 12, and is located at the lower chord portion 12 in the central portion of the PCa beam 1, and the axial direction of the PCa beam 1 A PC steel wire 62 is provided over the substantially entire length of the PCa beam 1 in a gentle curve so as to be located at the upper chord 11 at the end. Therefore, the 1st opening part 21 is not a rectangle but trapezoid.

  The PC steel wire 61 is a pre-tension system in which tension is applied when the lower chord part 12 is precast-molded and pre-stress is applied to the lower chord part 12 by releasing the tension after curing for a predetermined period. Arranged in a straight line to be tense. On the other hand, in order to efficiently resist the bending moment, the PC steel wire 62 is arranged in a suspended curve shape such that the PC steel wire 62 is positioned on the lower side at the beam center and on the upper side at the beam end. Therefore, it is a post-tension method in which tension is applied after precast molding of the lower member 52 and the end member 53. The PC steel wire 62 may be tensioned when the lower member 52 and the end member 53 are joined, but after the PCa beam 1 is installed between the large beams 2 in order to prevent cracks and the like. It is preferable to be nervous.

  In this way, by using the pre-tension type PC steel wire 61 and the post-tension type PC steel wire 62 in combination, the PCa beam 1 can be effectively reduced in production cost by factory production and effectively strengthened by on-site construction. Can be achieved.

«Fifth embodiment»
Next, a fifth embodiment of the present invention will be described. As shown in FIG. 16 (A), the PCa beam 1 of this embodiment is composed of one upper member 51 in which most of the central portion 11a of the upper chord portion 11 is precast, and the lower chord portion 12 is large. The first part 13 and the upper chord part 11 are composed of end members 53, and the second to fourth bundle parts 14 to 16 are individually formed. It is comprised from the 2nd-4th bundle members 54-56 by which the precast formation was carried out, and as shown in FIG.16 (B), one each PCa beam 1 is comprised by integrating these members 51-56. Has been.

  As shown in FIG. 17 showing the periphery of the third bundle portion 15 as a representative example, recesses 51a and 52a are formed on the lower surface of the upper member 51 and the upper surface of the lower member 52, respectively, and the end member 53 and the second to second members are formed. Convex portions 53b, 54b, 55b, and 56b that are complementary to the concave portions 51a and 52a are formed on the upper surface and the lower surface of the four bundle members 54 to 56, respectively. The four bundle members 54 to 56 are joined to the upper member 51 and the lower member 52 in a state where the convex portions 53b, 54b, 55b, and 56b are fitted to each other, whereby the convex portions 53b, 54b, 55b, and 56b are joined. Becomes a shear key and can resist the horizontal shearing force caused by the bending moment.

  The upper member 51, the lower member 52, the end member 53, and the second to fourth bundle members 54 to 56 are each provided with a through hole 82 for inserting the PC steel rod 81, and the end member 53 and the second to fourth bundle members 54 to 56 are in a state where the convex portions 53b, 54b, 55b, and 56b are engaged with the corresponding concave portions 51a and 52a of the upper member 51 and the lower member 52, respectively. Are integrally joined by a plurality (two in this case) of PC steel bars 81 as tension members inserted into the straight through-holes 82.

  The procedure for manufacturing the PCa beam 1 is as follows. First, in parallel with the step of precast molding one upper member 51 with reinforced concrete, one lower member 52 is precast molded with reinforced concrete, and the end member 53 and the second to fourth bundle members 54 to 56 are formed. Precast molding with reinforced concrete. Thereafter, the PC steel rod 81 is inserted into the through hole 82 in a state where the end member 53 and the second to fourth bundle members 54 to 56 are disposed between the upper member 51 and the lower member 52, and the PC steel rod 81 is The upper and lower ends are locked to the upper member 51 and the lower member 52 while being tensioned by a jack or the like, so that the end member 53 and the second to fourth bundle members 54 to 56 are connected to the upper member 51 and the lower member 52. Crimp and bond to

  In this way, the PCa beam 1 separately precast-molds not only the upper member 51 and the lower member 52 but also the end member 53 and the second to fourth bundle members 54 to 56 constituting the bundle portions 13 to 16. The shape of each of the members 51 to 56 is simplified, the rebar and formwork assembly and concrete placement are facilitated, the concrete is more easily filled around the openings 21 to 24, and the quality is further secured. Making it easy. Further, since the PCa beam 1 is divided into a plurality of precast members, the weight of the members is further reduced, and handling at the factory and transportation to the site are further facilitated. As a result, productivity is improved and manufacturing costs can be reduced.

  In addition, by joining the end member 53 and the second to fourth bundle members 54 to 56 to the upper member 51 and the lower member 52 with the PC steel rod 81, the joining work is facilitated, and the curing period is increased at the time of joining. Since it is not necessary to take it, for example, after manufacturing each member 51-56 in a PC factory, it is also possible to join on-site. Therefore, even a large PCa beam 1 that is difficult to transport and handle after joining can be precast.

<Modification>
Next, a modification in which the configuration and the manufacturing method are partially different from those of the PCa beam 1 of the fifth embodiment will be described. The PCa beam 1 of this modification is configured by an upper member 51, a lower member 52, an end member 53, and second to fourth bundle members 54 to 56 having the basic configuration shown in FIG. It is manufactured by integrating. This is the same as the PCa beam 1 of the fifth embodiment.

  As shown in FIG. 18 showing the periphery of the third bundle portion 15 as a representative example, the upper member 51, the lower member 52, the end member 53 and the second to fourth bundle members 54 to 56 of this modification are also provided with through holes. 82 are respectively drilled, and the end member 53 and the second to fourth bundle members 54 to 56 are respectively provided with the convex portions 53b, 54b, 55b, and 56b corresponding to the concave portions 51a of the upper member 51 and the lower member 52, respectively. Reinforcing bar 83 and each member are inserted by inserting reinforcing bar 83 into each straight through-hole 82 in a state engaged with 52a, and further filling grout 84 as a filler in this through-hole 82. The end member 53 and the second to fourth bundle members 54 to 56 are integrally coupled to the upper member 51 and the lower member 52, respectively.

  The PCa beam 1 is constructed by integrating a plurality of precast members in this way, facilitating assembly of formwork, rebar assembly, and concrete placement, facilitating mass production and improving productivity. In addition, the manufacturing cost can be reduced. Moreover, since each member 51-56 can be joined only by the reinforcing bar 83 and the grout 84, joining work is also easy.

<< Sixth Embodiment >>
As shown in FIG. 19A, the PCa beam 1 of this embodiment is also composed of one upper member 51 in which most of the upper chord portion 11 is precast-molded, and most of the lower chord portion 12 is precast-molded. It is composed of a single lower member 52. On the other hand, as shown in FIG. 19B, concrete is cast with the upper member 51 and the lower member 52 facing each other, and the end member 53 and the second to fourth bundles are placed by the placement of the concrete. The members 54 to 56 are precast formed, and the upper member 51 and the lower member 52, the end member 53, and the second to fourth bundle members 54 to 56 are integrated to form one PCa beam 1. .

  That is, in order to manufacture the PCa beam 1, first, the upper member 51 is precast-molded so that the upper portion 43u of the lateral reinforcing bar 43 of the bundle portions 13 to 16 protrudes from the lower surface thereof, and the bundle portion from the upper surface thereof. The lower member 52 is precast-molded so that the lower portion 43l of the 13-16 horizontal reinforcing bars 43 protrudes. Next, the upper member 51 and the lower member 52 are juxtaposed, and the reinforcing bars of the bundle portions 13 to 16 in the state where the upper portion 43u of the lateral reinforcing bar 43 and the lower portion 43l of the lateral reinforcing bar 43 are overlapped, that is, By assembling the lateral reinforcing bars 43 and placing concrete so that the reinforcing bars of the bundle parts 13 to 16 are wound, the bundle parts 13 to 16 are precast-molded.

  By manufacturing the PCa beam 1 in this way, the upper member 51 and the lower member 52 can be joined by placing the bundle portions 13 to 16 into the concrete, so that a separate joining work can be eliminated.

  This is the end of the description of specific embodiments, but the present invention is not limited to these embodiments. The specific shape and arrangement of each member can be changed as appropriate without departing from the spirit of the present invention. It should be noted that the constituent elements of the PCa beam and the manufacturing steps of the PCa beam according to the present invention shown in the above embodiment are not necessarily all necessary, and can be appropriately selected as long as they do not depart from the gist of the present invention. Is possible.

DESCRIPTION OF SYMBOLS 1 PCa beam 11 Upper chord part 12 Lower chord part 13 1st bundle part 14 2nd bundle part 15 3rd bundle part 16 4th bundle part 21 1st opening part 22 2nd opening part 23 3rd opening part 24 4th opening part 42 Lateral reinforcement 61 PC steel wire 62 PC steel wire

Claims (6)

Both ends to a pair of girders are connected in a building, a pre-cast reinforced concrete beams supporting the floor slab that is built thereabove, and upper chord section, and the lower chord section, a plurality of connecting the lower chord section and the top chord section and a bundle portion, the opening of the rectangular penetrating the beam width direction between the bundle portion is formed with a plurality, the bundle length in the axial direction end portion side and the opening director Satono ratio axial direction at the center side precast reinforced concrete being greater than the length of the bundle length and aperture director Satono ratio much larger than the, and the axial direction of the arranged bundle portion on the end side length beam portion arranged in the center side Beams. The precast reinforced concrete beam according to claim 1 , wherein the lower chord portion is prestressed by a PC steel wire. The precast reinforced concrete beam according to claim 2 , wherein a main reinforcing bar is not arranged in the lower chord part, and a horizontal reinforcing bar surrounding the PC steel wire is arranged. The upper chord part, the lower chord part, and the bundle part are made of separate members that are individually precast, and are inserted into through holes that penetrate the upper chord part, the lower chord part, and the bundle part in the vertical direction. The precast reinforced concrete beam according to any one of claims 1 to 3 , wherein the precast reinforced concrete beam is joined / integrated via a reinforcing bar. A floor assembly comprising the precast reinforced concrete beam according to any one of claims 1 to 4 and the girder,
The precast concrete beam is cut at the bottom of the end portions at an angle, the floor assembly, which comprises forming voids substantially triangular between the girders. A pedestal is formed on the side of the large beam,
The precast reinforced concrete beam is coupled to the girder in a state where the upper chord part is placed on the gantry part,
The floor assembly according to claim 5 , wherein a beam width on the end side of the upper chord portion is made larger than a beam width on the center side.

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