JP7553015B2 - Split rigid culvert - Google Patents

Description

The present invention relates to a split-type rigid culvert.

Split rigid culverts are constructed by assembling unit blocks manufactured in a factory on-site. Patent Document 1 discloses a split rigid culvert (box culvert) in which an intermediate top plate and an intermediate bottom plate are sandwiched between left and right main body blocks, and the left and right main body blocks, intermediate top plate and intermediate bottom plate are connected by prestressing steel members passing through in the left-right direction (Patent Document 1, [Claim 1] [0018]). The split rigid culvert disclosed in Patent Document 1 passes the prestressing steel members straight through a linear sheath that passes through the middle position of the thickness of the intermediate top plate in the left-right direction, for example (Patent Document 1, [Figure 5]).

Patent Document 2 discloses a split rigid culvert (box culvert) in which a top block and a bottom block are sandwiched between left and right side wall blocks, and the top block and the bottom block are connected to the left and right side wall blocks by PC steel members passing through in the left-right direction (Patent Document 2, [Claim 1]). The split rigid culvert disclosed in Patent Document 2 has, for example, straight PC steel members passed through the top block that are inclined toward the left and right side wall blocks (Patent Document 2, [0031] [0042]). The PC steel members that are curved as a whole in this way are said to withstand the bending moment applied to the top block after construction (Patent Document 2, [0032]).

Japanese Patent Application Laid-Open No. 08-041842 JP 2009-097305 A

In a split-type rigid culvert, the prestressing steel members that pass through all the unit blocks are not only used as structural elements that connect the unit blocks to integrate them, but are also used as functional elements that are inserted laterally toward the top or bottom of the top block to resist the tensile forces that occur on the top or bottom due to the bending moment applied to the top block. As shown in Patent Document 1, there is no problem with the prestressing steel members as structural elements being straight. However, as shown in Patent Document 2, it is desirable to change the insertion position of the prestressing steel members as functional elements between the top block (the middle part) and the side wall blocks (the both end parts) depending on the bending moment applied to the top block.

In the split rigid culvert disclosed in Patent Document 2, the prestressing steel is inserted closer to the bottom of the top block in the middle section where bending moment acts mainly downward to resist the tensile force generated on the bottom surface, and the prestressing steel is inserted closer to the top of the side wall blocks at both ends where bending moment acts mainly upward to resist the tensile force generated on the top surface. Here, the prestressing steel passed through the top block and the side wall block is a single piece, so the prestressing steel inserted through the top block is bent upward before being inserted through the side wall block. Thus, in order to achieve the appropriate insertion position of the prestressing steel, it was necessary to snake the prestressing steel up and down.

Split rigid culverts are often large, and so the bending moment applied to the top, side or bottom plates is likely to be large. For this reason, the prestressing steel is expected to act as a functional element that resists the tensile force generated by the bending moment so as to suppress the effects of the bending moment. In this case, as seen in Patent Document 2, it is desirable to insert the prestressing steel in an appropriate position to resist the tensile force generated according to the distribution of the bending moment. However, it is difficult to insert the prestressing steel in a serpentine manner, which may increase the manufacturing costs of split rigid culverts.

The technology for tightly connecting the unit blocks of a split rigid culvert does not have to rely on prestressing steel, but can be substituted by other connecting means. Therefore, we investigated a simple and inexpensive structure for inserting prestressing steel into the top, side or bottom plates of a split rigid culvert in the appropriate position and direction, so that the prestressing steel acts solely as a functional element that resists the tensile force generated by bending moments.

As a result of the study, we developed a split-type rigid culvert with a top plate made up of two or more top plate unit blocks connected together, with linear prestressing steel members inserted into some or all of the top plate unit blocks in the horizontal direction near the bottom or the horizontal direction near the top, depending on the distribution of bending moment applied to the top plate. The top plate unit blocks are precast concrete blocks. The method of tensioning the top plate unit blocks with prestressing steel members may be either pretensioning or posttensioning. While the PC steel members are basically inserted into all top plate unit blocks, they may also be inserted into only some of the top plate unit blocks. Depending on the distribution of bending moment applied to the top plate, the PC steel members may be inserted laterally near the top of all top plate unit blocks, or conversely, inserted laterally near the bottom of all top plate unit blocks, or inserted in different positions in all top plate unit blocks.

The present invention is used for split box culverts or split portal culverts. The split box culverts or split portal culverts may be of a multiple structure. The present invention is applicable to the top plate, even if the upper or lower surface is gently curved, as long as the PC steel can be inserted linearly into the top plate unit blocks. The top plate unit blocks are joined to each other by a conventionally known joint structure, for example, an indirect joint structure via a mechanical joint covered with a concrete-filled portion sandwiched between the top plate unit blocks, or a direct joint structure using a mechanical joint embedded in the end face by bringing the end faces of the top plate unit blocks into contact with each other.

The top plate unit block is exemplified by a configuration including a left-end top plate unit block and a right-end top plate unit block that protrude from the top of the side plate, and a middle top plate unit block sandwiched between the left-end top plate unit block and the right-end top plate unit block. In this case, the basic configuration is one middle top plate unit block, which is divided into three parts including the left-end top plate unit block and the right-end top plate unit block. There may be two or more middle top plate unit blocks. The multiple middle top plate unit blocks may have the same or different horizontal lengths and shapes. The left-end top plate unit block and the right-end top plate unit block may also have the same or different horizontal lengths and shapes.

"In accordance with the distribution of the bending moment applied to the top plate, straight prestressing steel members are inserted horizontally near the bottom surface into the top plate unit block" means that the prestressing steel members are inserted horizontally and linearly near the bottom surface of the top plate unit block to resist the tensile force on the bottom surface generated by the downward bending moment applied to the top plate. This applies, for example, to intermediate top plate unit blocks. Similarly, "In accordance with the distribution of the bending moment applied to the top plate, straight prestressing steel members are inserted horizontally and linearly near the top surface of the top plate unit block to resist the tensile force on the top surface generated by the upward bending moment applied to the top plate. This applies, for example, to the left end top plate unit block and the right end top plate unit block.

"Inserted laterally toward the bottom or toward the top" means that the prestressing tendons are inserted laterally at a vertical position that is biased toward either the bottom or top of the top plate unit block as a whole. The horizontal direction includes a direction that is slightly inclined relative to the horizontal direction, with the horizontal direction as the reference. For example, in the case of a top plate unit block that includes a portion where the direction of the bending moment applied to the top plate changes from top to bottom, the prestressing tendons may be inserted diagonally so that one side of the horizontal direction is closer to the bottom and the other side is closer to the top, sandwiching the portion where the direction of the bending moment applied to the top plate changes from top to bottom.

The present invention can also be applied to side slabs. In other words, the present invention also includes a split-type rigid culvert that has a side slab formed by connecting two or more side slab unit blocks, and in which linear PC steel members are inserted into some or all of the side slab unit blocks in the vertical direction near the inner surface or the vertical direction near the outer surface depending on the distribution of bending moment applied to the side slab. The side slab unit blocks are precast concrete blocks. The method of tensioning the side slab unit blocks with PC steel members may be either pretensioning or posttensioning. While the PC steel members are basically inserted into all side slab unit blocks, they may also be inserted into only some of the side slab unit blocks. In addition, the PC steel members may be inserted laterally near the inner surface of all side slab unit blocks, or conversely, horizontally near the outer surface of all side slab unit blocks, or in different positions in all side slab unit blocks depending on the distribution of bending moment applied to the side slab.

The present invention is used for split box culverts, split portal culverts, or split arch culverts. The split box culverts, split portal culverts, or split arch culverts may be of a multiple structure. The present invention is applicable to the side slabs, even if the inner or outer surface is gently curved, as long as the PC steel can be inserted linearly into the side slab unit blocks. The side slab unit blocks are joined to each other by a conventionally known joint structure, for example, an indirect joint structure via a mechanical joint covered with a concrete-filled portion sandwiched between the side slab unit blocks, or a direct joint structure using a mechanical joint embedded in the end face by bringing the end faces of the side slab unit blocks into contact with each other.

The side plate unit block is exemplified by a configuration including an upper end plate unit block that supports the top plate, a lower end plate unit block that supports the bottom plate, and a middle plate unit block sandwiched between the upper end plate unit block and the lower end plate unit block. In this case, the basic configuration is one middle plate unit block, and the upper end plate unit block and the lower end plate unit block are combined to divide it into three. There may be two or more middle plate unit blocks. The multiple middle plate unit blocks may have the same or different vertical lengths and shapes. The upper end top plate unit block and the lower end top plate unit block may also have the same or different vertical lengths and shapes.

"In accordance with the distribution of the bending moment applied to the side slab, straight prestressing steel is inserted into the side slab unit block in a vertical direction near the inner surface to resist the tensile force on the inner surface generated by the inward bending moment applied to the side slab" means that the prestressing steel is inserted in a vertical direction near the inner surface of the side slab unit block, for example, to resist the tensile force on the outer surface generated by the outward bending moment applied to the side slab. This applies, for example, to the middle side slab unit block. Similarly, "In accordance with the distribution of the bending moment applied to the side slab, straight prestressing steel is inserted into the side slab unit block in a vertical direction near the outer surface" means that the prestressing steel is inserted in a vertical direction near the outer surface of the side slab unit block, for example, to resist the tensile force on the outer surface generated by the outward bending moment applied to the side slab. This applies, for example, to the upper end side slab unit block and the lower end side slab unit block.

"Inserted horizontally toward the inner surface or toward the outer surface" means that the prestressing tendons are inserted vertically at a left-right position that is biased toward either the inner surface or the outer surface of the side slab unit block as a whole. The vertical direction includes a direction that is slightly inclined relative to the vertical direction, with the vertical direction as the reference. For example, in the case of a top slab unit block that includes a portion where the direction of the bending moment applied to the side slab changes from inward to outward, the prestressing tendons may be inserted diagonally so that one vertical side is closer to the inner surface and the other vertical side is closer to the outer surface, sandwiching the portion where the direction of the bending moment applied to the side slab changes from inward to outward.

The present invention can also be applied to a base plate. That is, the present invention also includes a split-type rigid culvert having a base plate formed by connecting two or more base plate unit blocks, in which linear PC steel members are inserted into some or all of the base plate unit blocks in the horizontal direction near the bottom surface or the horizontal direction near the top surface depending on the distribution of bending moment applied to the base plate. The base plate unit blocks are precast concrete blocks. The tension of the base plate unit blocks by the PC steel members may be either pretensioned or posttensioned. While the PC steel members are basically inserted into all base plate unit blocks, they may also be inserted into only some of the base plate unit blocks. In addition, the PC steel members may be inserted into all base plate unit blocks in the horizontal direction near the top surface, or conversely, into all base plate unit blocks in the horizontal direction near the bottom surface, or into all base plate unit blocks at different positions depending on the distribution of bending moment applied to the base plate.

The present invention is used for split box culverts or split arch culverts. The split box culverts or split arch culverts may be of a multiple structure. The present invention is applicable to the base slab, even if the top or bottom surface is gently curved, as long as the PC steel can be inserted linearly into the base slab unit blocks. The base slab unit blocks are joined to each other by a conventionally known joint structure, for example, an indirect joint structure via a mechanical joint covered with a concrete-filled portion sandwiched between the base slab unit blocks, or a direct joint structure using a mechanical joint embedded in the end face by bringing the end faces of the base slab unit blocks into contact with each other.

An example of the bottom plate unit block is a configuration consisting of left and right end bottom plate unit blocks that protrude from the bottom of the side plate, and a middle bottom plate unit block sandwiched between the left and right end bottom plate unit blocks. In this case, the basic configuration is one middle bottom plate unit block, which is divided into three parts including the left end bottom plate unit block and the right end bottom plate unit block. There may be two or more middle bottom plate unit blocks. The multiple middle bottom plate unit blocks may have the same or different horizontal lengths and shapes. The left end top plate unit block and the right end top plate unit block may also have the same or different horizontal lengths and shapes.

"In accordance with the distribution of the bending moment applied to the base slab, straight prestressing steel members are inserted horizontally near the bottom surface into the base slab unit block" means that the prestressing steel members are inserted horizontally and linearly near the bottom surface of the base slab unit block to resist the tensile force on the bottom surface generated by the downward bending moment applied to the base slab. This applies, for example, to the left-end base slab unit block and the right-end base slab unit block. Similarly, "In accordance with the distribution of the bending moment applied to the base slab, straight prestressing steel members are inserted horizontally and linearly near the top surface of the base slab unit block to resist the tensile force on the top surface generated by the upward bending moment applied to the base slab. This applies, for example, to the middle base slab unit block.

"Inserted laterally toward the bottom or toward the top" means that the prestressing tendons are inserted laterally at a vertical position that is biased toward either the bottom or top of the base slab unit block as a whole. The horizontal direction includes a direction that is slightly inclined relative to the horizontal direction, with the horizontal direction as the reference. For example, in the case of a base slab unit block that includes a portion where the direction of the bending moment applied to the base slab changes from top to bottom, the prestressing tendons may be inserted diagonally so that one side of the horizontal direction is closer to the bottom and the other side is closer to the top, sandwiching the portion where the direction of the bending moment applied to the base slab changes from top to bottom.

The split rigid culvert of the present invention inserts independent prestressing steel members into each of the top plate unit blocks, side plate unit blocks, and bottom plate unit blocks depending on the distribution of bending moments applied to the top plate, side plate, and bottom plate, respectively, allowing the prestressing steel members to efficiently perform their function of resisting the tensile force generated by the bending moment. For example, by changing the position where the prestressing steel members are inserted between the left-end top plate unit block and the right-end top plate unit block, it is possible to accommodate asymmetric bending moments. In addition, because the top plate unit blocks, side plate unit blocks, and bottom plate unit blocks only require the prestressing steel members to be inserted in a straight line, the structure is simple and can be manufactured inexpensively.

Depending on the distribution of bending moment applied to the top plate, the top plate unit block allows the prestressing steel to be inserted in a straight line laterally toward the bottom surface or the top surface, allowing the prestressing steel to efficiently resist the tensile force generated by the bending moment. The top plate unit block is a combination of a left-end top plate unit block, a middle top plate unit block, and a right-end top plate unit block, allowing the prestressing steel to be inserted in a straight line and laterally, simplifying the structure and allowing it to be manufactured inexpensively.

The side slab unit block allows the prestressing steel to be inserted in a straight line vertically toward the inner surface or vertically toward the outer surface depending on the distribution of bending moment applied to the side slab, allowing the prestressing steel to efficiently resist the tensile force generated by the bending moment. The side slab unit block is a combination of an upper end side slab unit block, a middle side slab unit block, and a lower end side slab unit block, allowing the prestressing steel to be inserted in a straight line vertically, simplifying the structure and allowing for inexpensive manufacture.

Depending on the distribution of bending moment applied to the base slab, the base slab unit block allows the prestressing steel to be inserted in a straight line either laterally toward the bottom or laterally toward the top, allowing the prestressing steel to efficiently resist the tensile force generated by the bending moment. The base slab unit block is a combination of a left-end base slab unit block, a middle base slab unit block, and a right-end base slab unit block, which allows the prestressing steel to be inserted in a straight line and laterally, simplifying the structure and allowing for inexpensive manufacture.

FIG. 1 is a front view showing an example (present example) of a split box culvert to which the present invention is applied. FIG. 2 is a plan view showing a split box culvert of this example. FIG. 2 is a left side view showing the split box culvert of this example. FIG. 2 is a front view showing the relationship between the split box culvert of this example and the bending moment. FIG. 1 is a front view showing an example (another example 1) of a split-type gate culvert to which the present invention is applied.

The following describes the embodiment of the present invention with reference to the drawings. The present invention is applied to a split box culvert 1, as shown in Figs. 1 to 3. The split box culvert 1 in this example is composed of eight components: the upper left corner block 11, the upper right corner block 12, the lower left corner block 13, the lower right corner block 14, the intermediate top plate unit block 15 sandwiched between the upper left corner block 11 and the upper right corner block 12, the left intermediate side plate unit block 16 sandwiched between the upper left corner block 11 and the lower left corner block 13, the right intermediate side plate unit block 17 sandwiched between the upper right corner block 12 and the lower right corner block 14, and the intermediate bottom plate unit block 18 sandwiched between the lower left corner block 13 and the lower right corner block 14.

The top plate in this example is divided into three parts: the left-end top plate unit block 111, which is the horizontal portion of the upper left corner block 11 that is L-shaped when viewed from the front and opens toward the bottom right; the right-end top plate unit block 121, which is the horizontal portion of the upper right corner block 12 that is L-shaped when viewed from the front and opens toward the bottom left; and the middle top plate unit block 15 that is sandwiched between the left-end top plate unit block 111 and the right-end top plate unit block 121. The upper left corner block 11, the upper right corner block 12, and the middle top plate unit block 15 are all precast concrete blocks (reinforcement is omitted in each figure).

The left side slab in this example is divided into three parts: upper left side slab unit block 115, which is the vertical portion of the upper left corner block 11 that is L-shaped when viewed from the front and opens toward the bottom right; lower left side slab unit block 135, which is the vertical portion of the lower left corner block 13 that is L-shaped when viewed from the front and opens toward the top right; and left intermediate side slab unit block 16, which is sandwiched between the upper left side slab unit block 115 and the lower left side slab unit block 135. The upper left corner block 11, the lower left corner block 13, and the left intermediate side slab unit block 16 are all precast concrete blocks (reinforcement is omitted in each figure).

The right side slab in this example is divided into three parts, the upper right end slab unit block 125, which is the vertical portion of the upper right corner block 12 that is L-shaped when viewed from the front and opens toward the bottom left; the lower right end slab unit block 145, which is the vertical portion of the lower right corner block 14 that is L-shaped when viewed from the front and opens toward the top left; and the right middle slab unit block 17, which is sandwiched between the upper right end slab unit block 125 and the lower right end slab unit block 145, resulting in a top-to-bottom symmetrical structure. The upper right corner block 12, the lower right corner block 14, and the right middle slab unit block 17 are all precast concrete blocks (reinforcement is omitted in each figure).

The base slab in this example is divided into three parts: the left-end base slab unit block 131, which is the horizontal part of the lower-left corner block 13 that is L-shaped when viewed from the front and opens toward the upper right; the right-end base slab unit block 141, which is the horizontal part of the lower-right corner block 14 that is L-shaped when viewed from the front and opens toward the upper left; and the intermediate base slab unit block 18 that is sandwiched between the left-end base slab unit block 131 and the right-end base slab unit block 141. The lower-left corner block 13, the lower-right corner block 14, and the intermediate base slab unit block 18 are all precast concrete blocks (reinforcement is omitted from each figure).

As shown in Figure 4, the top plate pulls the bottom surface with the maximum near the center of the middle top plate unit block 15, and the left-end top plate unit block 111 and the right-end top plate unit block 121 are subjected to a bending moment M1 that pulls the top surface symmetrically. For this reason, the left-end top plate unit block 111 and the right-end top plate unit block 121 have the prestressing steel members 112, 122 inserted horizontally toward the top surface (e.g., toward the top in Figure 4), while the middle top plate unit block 15 has the prestressing steel member 151 inserted horizontally toward the bottom surface (e.g., toward the bottom in Figure 4). In this example, the prestressing steel members 112, 122, 151 are inserted in three pieces at equal intervals in the front-to-rear direction (see Figure 2). The prestressing steel members 112, 122, 151 may be steel wires or steel rods passed through a sheath, or unbonded steel wires.

As shown in Figure 4, the left side slab pulls the inner surface with the maximum near the vertical center of the left middle slab unit block 16, and the upper left end slab unit block 115 and the lower left end slab unit block 135 are subjected to a bending moment M2 that pulls the outer surface symmetrically from top to bottom. For this reason, the upper left end slab unit block 115 and the lower left end slab unit block 135 have the prestressing steel members 116, 136 inserted vertically toward the outer surface (e.g., toward the left in Figure 4), and the intermediate bottom slab unit block 16 has the prestressing steel member 161 inserted vertically toward the inner surface (e.g., toward the right in Figure 4). In this example, the prestressing steel members 116, 136, 161 are inserted two at the middle position of the three prestressing steel members 112. The prestressing steel members 116, 136, 161 may be steel wire or steel rods passed through a sheath, or unbonded steel wires.

As shown in Figure 4, the right-side slab is subjected to a bending moment M2 that is maximum near the vertical center of the right-side intermediate slab unit block 17 and convex inward, and is outwardly convex at the upper right-end slab unit block 125 and the lower right-end slab unit block 145, with the bending moment M2 acting vertically. For this reason, the upper right-end slab unit block 125 and the lower right-end slab unit block 145 have the prestressing steel members 126, 146 inserted vertically toward the outer surface (e.g., toward the right in Figure 4), and the intermediate bottom slab unit block 17 has the prestressing steel member 171 inserted vertically toward the inner surface (e.g., toward the left in Figure 4). In this example, the prestressing steel members 126, 146, 171 are inserted at two intermediate positions between the three prestressing steel members 122. The prestressing steel members 126, 146, 171 may be steel wires or rods passed through a sheath, or unbonded steel wires.

As shown in Figure 4, the bending moment M3 is applied symmetrically to the bottom slab, with the maximum near the center of the middle bottom slab unit block 18 and the left end bottom slab unit block 131 and the right end bottom slab unit block 141 being convex upward. For this reason, the left end bottom slab unit block 131 and the right end bottom slab unit block 141 have the prestressing steel members 132, 142 inserted horizontally toward the bottom (e.g., toward the bottom in Figure 4), while the middle bottom slab unit block 18 has the prestressing steel member 181 inserted horizontally toward the top (e.g., toward the top in Figure 4). In this example, the prestressing steel members 132, 142, 181 are inserted in three pieces at equal intervals in the front-to-rear direction, just like the top slab. The prestressing steel members 132, 142, 181 may be steel wires or steel rods passed through a sheath, or unbonded steel wires.

The split rigid culvert of the present invention can use conventionally known block structures and joint structures between blocks, other than the insertion of the unique PC steel. In the split box culvert 1 of this example, the upper left corner block 11, the upper right corner block 12, and the intermediate top slab unit block 15, the lower left corner block 13, the lower right corner block 14, and the intermediate bottom slab unit block 18 use a joint structure via mechanical joints covered with concrete filling parts 155, 185, and the upper left corner block 11, the lower right corner block 13, and the left intermediate side slab unit block 16, the upper right corner block 12, the lower right corner block 14, and the intermediate bottom slab unit block 18 use a direct joint structure in which the end faces are in contact with each other.

The joint structure of the top plate is explained with reference to Figure 2. The upper left corner block 11 in this example has a total of four reinforcing bars 114 protruding to the right in the vertical and front-to-back directions from the right end face of the left end top plate unit block 111, which is the horizontal part. Similarly, the upper right corner block 12 in this example has a total of four reinforcing bars 124 protruding to the left in the vertical and front-to-back directions from the left end face of the right end top plate unit block 121, which is the horizontal part. And the intermediate top plate unit block 15 has four reinforcing bars 153 protruding from the left end face in the same positional relationship as the reinforcing bars 114, and four reinforcing bars 153 protruding from the right end face in the same positional relationship as the reinforcing bars 124. Mechanical joints 154 are fitted around the reinforcing bars 153 so that they can move freely.

The upper left corner block 11, the upper right corner block 12, and the intermediate top plate unit block 15 are inserted and positioned between the upper left corner block 11 and the upper right corner block 12 located at the top ends of the previously installed left and right plates, for example by jacking up the intermediate top plate unit block 15, with the reinforcing bars 114 and 153 facing the reinforcing bars 124 and 153, respectively. Then, the mechanical joint 154 fitted to the outside of the reinforcing bars 153 is moved, and the reinforcing bars 114 and 153 and the reinforcing bars 124 and 153 are respectively joined to the mechanical joint 154, and the reinforcing bars 114 and 153 are respectively joined to the reinforcing bars 124 and 153 via the mechanical joint 154. The method of joining the reinforcing bars 114 and 153, or the reinforcing bars 124 and 153 to the mechanical joint 154 is a physical joining method such as fastening with a joining material (e.g., a grout material) or screwing or crimping with a screw.

Finally, with a temporary frame placed between the right end face of the left-end top plate unit block 111 and the left end face of the intermediate top plate unit block 15, and between the left end face of the right-end top plate unit block 121 and the right end face of the intermediate top plate unit block 15, the reinforcing bars 114, 124, 153, and mechanical joints 154 are filled with concrete filling sections 155 to complete the joint structure. The temporary frame is removed when the concrete filling sections 155 have solidified. The joint structure may be configured such that the reinforcing bars 114 or 124 and the reinforcing bars 153 are joined with mechanical joints 154 in this example, or the reinforcing bars 114, 124, and 153 may be joined with lap joints or loop joints.

The joint structure of the top plate in this example is an indirect joint structure in which the right end face of the left end top plate unit block 111 and the left end face of the middle top plate unit block 15, and the left end face of the right end top plate unit block 121 and the right end face of the middle top plate unit block 15 are not in direct contact with each other, and the mechanical joints 154 are covered with concrete filling sections 155. The joint structure of the top plate is not shown, but it may be a direct joint structure in which the end faces of the left end top plate unit block 111, the middle top plate unit block 15, and the right end top plate unit block 121 are in contact with each other, a rebar protruding from one end face is inserted into a mechanical joint embedded in the other end face, and the mechanical joint is filled with mortar (see the joint structure of the side plate in this example). The joint structure of the bottom plate is the same as that of the top plate, so a description is omitted.

The joint structure of the left side slab is explained with reference to Figure 3. The upper left corner block 11 of this example has four mechanical joints 119 embedded in the lower end surface of the upper left side slab unit block 115, which is the vertical part, from front to back and left to right. The lower left corner block 13 of this example has four reinforcing bars 139 protruding upward from the upper end surface of the lower left side slab unit block 135, which is the vertical part, from front to back and left to right. The left intermediate top slab unit block 16 has four reinforcing bars 164 protruding from its upper end surface in the same positional relationship as the mechanical joints 119, and four mechanical joints 165 on its lower end surface in the same positional relationship as the reinforcing bars 139. The upper left side slab unit block 115 and the left intermediate top slab unit block 16 are provided with filling holes for filling the mechanical joints 119 and mechanical joints 165 with mortar, but these are not shown in the figure.

In this example, the left side slab is constructed by transporting the lower left corner block 13, the left intermediate slab unit block 16, and the upper left corner block 11 to the installation location in that order, and stacking them up in that order. The lower left end slab unit block 135 and the left intermediate slab unit block 16 are joined by bringing the upper end face of the lower left end slab unit block 135 into contact with the lower end face of the left intermediate slab unit block 16, inserting reinforcing bars 139 into the mechanical joints 165, and filling the mechanical joints 165 with mortar. The left intermediate slab unit block 16 and the upper left end slab unit block 115 are joined by bringing the upper end face of the left intermediate slab unit block 16 into contact with the lower end face of the upper left end slab unit block 115, inserting reinforcing bars 164 into the mechanical joints 119, and filling the mechanical joints 119 with mortar.

In this example, the joint structure of the left side slab is such that the lower end surface of the upper left slab unit block 115 is in direct contact with the upper end surface of the left middle slab unit block 16, and the upper end surface of the lower left slab unit block 135 is in direct contact with the lower end surface of the left middle slab unit block 16. The lower end surface of the lower left slab unit block 135 is in contact with the foundation (not shown). From this, the anchoring fittings 117 that are joined to both ends of the tensioned PC steel 116, the anchoring fittings 137 that are joined to both ends of the tensioned PC steel 136, and the anchoring fittings 162 that are joined to both ends of the tensioned PC steel 161 are stored in the anchoring fitting recesses 118, 138, 163, respectively, and filled with mortar so that they do not protrude. The joint structure of the right side slab is the same as that of the left side slab, so a description will be omitted.

The present invention is also applicable to other rigid box culverts. As shown in Figure 5, the split-type portal culvert 2 of Alternative Example 1 is composed of seven parts: an upper left corner block 21, an upper right corner block 22, a lower left slab unit block 23, a lower right slab unit block 24, an intermediate top slab unit block 25 sandwiched between the upper left corner block 21 and the upper right corner block 22, a left intermediate slab unit block 26 sandwiched between the upper left corner block 21 and the lower left slab unit block 23, and a right intermediate slab unit block 27 sandwiched between the upper right corner block 22 and the lower right slab unit block 24.

The top plate of Alternative Example 1 is divided into three parts: left-end top plate unit block 211, which is the horizontal portion of the upper left corner block 21, which is L-shaped when viewed from the front and opens toward the bottom right; right-end top plate unit block 221, which is the horizontal portion of the upper right corner block 22, which is L-shaped when viewed from the front and opens toward the bottom left; and intermediate top plate unit block 25, which is sandwiched between the left-end top plate unit block 211 and the right-end top plate unit block 221. The upper left corner block 21, the upper right corner block 22, and the intermediate top plate unit block 25 are all precast concrete blocks (reinforcement is omitted in each figure).

The left side slab of Alternative Example 1 is a three-part structure with an asymmetrical top-bottom structure, consisting of an upper left slab unit block 215, which is the vertical portion of the upper left corner block 21 that is L-shaped when viewed from the front and opens toward the bottom right; a lower left slab unit block 23 with a footing 235 at its lower end; and a left intermediate slab unit block 26 that is sandwiched between the upper left slab unit block 215 and the lower left slab unit block 23. The upper left corner block 21, the lower left slab unit block 23, and the left intermediate slab unit block 26 are all precast concrete blocks (reinforcement is omitted in each figure).

The right side slab of Alternative Example 1 is a three-part structure with an asymmetrical top-bottom structure, consisting of an upper right corner block 225, which is the vertical portion of the upper right corner block 22 that is L-shaped when viewed from the front and opens toward the bottom left; a lower right corner block 24 with a footing 245 at its lower end; and a right middle block 27 that is sandwiched between the upper right corner block 225 and the lower right corner block 24. The upper right corner block 22, the lower right corner block 24, and the right middle block 27 are all precast concrete blocks (reinforcement is omitted in each figure).

The split gate culvert 2 of Alternative Example 1 also generates bending moments in the top plate, left plate, and right plate, similar to those in the split box culvert 1 of this example (see Figure 4). Therefore, the left end top plate unit block 211 and the right end top plate unit block 221 have the prestressing steel members 212, 222 inserted horizontally toward the top surface, and the middle top plate unit block 25 has the prestressing steel member 251 inserted horizontally toward the bottom surface. The upper left end side plate unit block 215 and the lower left end side plate unit block 23 have the prestressing steel members 216, 231 inserted vertically toward the outside surface, and the middle side plate unit block 26 has the prestressing steel member 261 inserted vertically toward the inside surface. The upper right end side plate unit block 225 and the lower right end side plate unit block 24 have the prestressing steel members 226, 241 inserted vertically toward the outside surface, and the middle side plate unit block 27 has the prestressing steel member 271 inserted vertically toward the inside surface. PC steel members 212, 216, 221, 226, 231, 241, 251, 261, and 271 may be steel wires or steel rods passed through a sheath, or unbonded steel wires.

The upper left corner block 21, the upper right corner block 22, and the intermediate top plate unit block 25 are joined by a joint structure via a mechanical joint 254 covered with a concrete filling section 255. For example, the upper left corner block 21 and the intermediate top plate unit block 25 are joined by a mechanical joint 254 between the reinforcing bar 214 protruding to the right from the right end face of the left end top plate unit block 211 and the reinforcing bar 253 protruding from the left end face of the intermediate top plate unit block 15, and the reinforcing bar 214, reinforcing bar 253, and mechanical joint 254 are filled with concrete filling section 255 to complete the joint structure. The joint structure of the top plate is not shown, but it may be a direct joint structure in which the end faces of the left-end top plate unit block 211, the middle top plate unit block 25, and the right-end top plate unit block 221 are brought into contact with each other, a rebar protruding from the other end face is inserted into a mechanical joint embedded in one of the end faces, and the mechanical joint is filled with mortar (see the side plate joint structure in Alternative Example 1).

The upper left corner block 21, the lower left side slab unit block 23, and the left middle side slab unit block 26, as well as the upper right corner block 22, the lower right side slab unit block 24, and the middle bottom slab unit block 27, are joined by a direct joint structure in which the end faces are in contact with each other. For example, the upper left corner block 21 and the left middle side slab unit block 26 are joined by inserting the reinforcing bar 264 protruding from the upper end face of the left middle side slab unit block 26 into the mechanical joint 219 provided on the lower end face of the upper left top slab unit block 215, and filling the mechanical joint 219 with mortar. The anchoring fittings 217, 262 joined to both ends of the tensioned PC steel members 216, 261 are stored in the anchoring fitting recesses 218, 263, respectively, and filled with mortar so that they do not protrude.

1. Split box culvert
11 Upper left corner block
112 PC steel
116 PC steel
12 Upper right corner block
122 PC steel
126 PC steel
13 Lower left corner block
132 PC steel
136 PC steel
14 Lower right corner block
142 PC steel
146 PC steel
15 Intermediate top plate unit block
151 PC steel
16 Left middle side plate unit block
161 PC steel
17 Right middle side plate unit block
171 Prestressing steel
18 Intermediate base plate unit block
181 PC steel material 2 Split type portal culvert
21 Upper left corner block
212 PC steel
216 PC steel
22 Upper right corner block
222 PC steel
226 PC steel
23 Lower left side plate unit block
231 Prestressing steel
24 Lower right side plate unit block
241 PC steel
25 Intermediate top plate unit block
251 Prestressing steel
26 Left middle side plate unit block
261 Prestressing steel
27 Right middle side plate unit block
271 PC steel M1 Bending moment of top plate M2 Bending moment of side plate M3 Bending moment of bottom plate

Claims (3)

A split rigid culvert having a top plate constructed by connecting a left-end top plate unit block and a right-end top plate unit block that protrude from the tops of the side plates, and an intermediate top plate unit block that is sandwiched between the left -end top plate unit block and the right-end top plate unit block, and depending on the distribution of bending moment applied to the top plate, the intermediate top plate unit block has straight PC steel inserted laterally near the underside , and the left-end top plate unit block and the right-end top plate unit block have straight PC steel inserted laterally near the top . A split rigid culvert having side panels connected together with an upper panel unit block supporting the top panel, a lower panel unit block supporting the bottom panel, and an intermediate panel unit block sandwiched between the upper panel unit block and the lower panel unit block, and in accordance with the distribution of bending moment applied to the side panels, the intermediate bottom panel unit block has straight PC steel inserted vertically near its inner surface , and the upper panel unit block and the lower panel unit block have straight PC steel inserted vertically near their inner surfaces . A split rigid culvert has a base plate composed of left and right end base plate unit blocks protruding from the bottom of the side plates and an intermediate base plate unit block sandwiched between the left and right end base plate unit blocks , and depending on the distribution of bending moment applied to the base plate, the intermediate base plate unit block has straight PC steel inserted horizontally near the top surface , and the left end base plate unit block and the right end base plate unit block have straight PC steel inserted horizontally near the bottom surface .

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