JP2017119946A - Steel concrete sandwich structure and design method for steel concrete sandwich structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel concrete sandwich structure capable of appropriately calculating a deformation amount and satisfying a desired deformation amount, and a design method therefor.SOLUTION: A rotation angle λ is calculated from a sectional force generated in every concrete C surrounded by a connection main steel sheet 51s and a shear reinforcement steel sheet 52 but since a rotation angle generated at a position of the shear reinforcement steel sheet becomes a sum of halves of rotation angles of the neighboring concrete, a rotation angle θ at the position of the shear reinforcement steel sheet is represented like a mathematical expression 7 and by accumulating rotational deformation in every concrete like a mathematical expression 8, a distortion amount of a steel concrete sandwich structure is accurately calculated.SELECTED DRAWING: Figure 7

Description

  For example, the present invention relates to a steel-concrete sandwich structure for constructing a crossing structure under a track or a crossing structure under a road.

As a structure such as a box culvert as a crossing structure under the track, there are structures described in Patent Document 1 and Patent Document 2.
Such a structure using the structure described in Patent Document 1 and Patent Document 2 includes a main steel plate disposed at a predetermined interval, a plurality of shear-reinforced steel plates connecting the main steel plates, the main steel plate, A box culvert as shown in FIG. 1 can be constructed in the ground without cutting and comprising a steel-concrete sandwich structure member composed of concrete filled between the shear-reinforced steel plates.

  More specifically, the steel elements shown in FIG. 2 are connected to each other by a special meshing joint (connection joint) and inserted into the underground portion. This interlocking joint is provided with a gap in consideration of workability, and is filled with a cement grout material in order to transmit the stress of the steel plate and prevent water leakage. Thereafter, the steel element is filled with concrete to form a steel-concrete sandwich structure member, and a box culvert is constructed.

  Such a steel-concrete sandwich structure is generally evaluated as a composite structure in which two steel plates and the concrete sandwiched between them behave together, so that it is appropriate to ensure the integrity of the steel plate and concrete. Slip stoppers are provided at appropriate intervals. However, in the case of the structure for constructing the structure of Patent Document 1, the steel element and the concrete filled in the steel element are not integrated by a stopper such as a shear connector and are installed in a direction perpendicular to the member axis. The concrete filled with the shear-reinforced steel plate is separated into blocks.

  In the research on the bending characteristics of conventional steel-concrete sandwich structures so far, in the model experiment in which the stopper is attached, the deviation occurs between the steel plate and the concrete, and the amount of deflection is the general steel-concrete sandwich structure. It is known that it becomes larger than the calculated value by the beam theory. In particular, when an evenly distributed load is applied to a continuous member, the bending yield strength and the bending ultimate strength are equivalent to those calculated on the assumption that the flat surface is maintained, but the amount of deflection becomes considerably large. In any study, although it has been found that the actual deflection amount is larger than the calculated value for bending deformation, there is no method for quantitative evaluation, and a patent constructed by considering a general steel-concrete sandwich structure. The structure deflection described in Document 1 and Patent Document 2 is large, and there is a fear that the amount of deformation is larger than expected.

JP 2001-12182 A JP 2010-174542 A

  Accordingly, an object of the present invention is to provide a steel-concrete sandwich structure that can appropriately calculate the deformation amount and satisfy the desired deformation amount, and a design method thereof.

The present invention relates to a steel concrete comprising a main steel plate arranged at a predetermined interval, a plurality of shear-reinforced steel plates connecting the main steel plates, and concrete filled between the main steel plate and the shear-reinforced steel plate. Design method for sandwich structure and steel-concrete sandwich structure, with compressive stress σ ' _c (y) of concrete at position y away from neutral axis, member width b, compressive force T _c generated on compression side steel plate, tension For the tensile force T generated on the side steel plate, the ratio α of the crack depth to the cross section height of the concrete, the cross section height h, the compression deformation amount dx of the compression side concrete, and the rotation angle λ of the concrete, By the bending moment M generated in each of the block-shaped concrete surrounded by the main steel plate and the shear reinforced steel plate as expressed by Equation 2, and the axial force N generated in each concrete ,

The compressive strain ε ' _c (y) of concrete at a position away from the neutral axis by y, the edge strain ε' _{cm of} the concrete on the compression side, the distance y from the neutral axis, the interval L of the shear reinforced steel sheet, and the rotation angle λ It becomes the relationship of Formula 3 thru | or Formula 5,

Based on the crack depth ratio α, the cross-sectional height h, and the amount of compressive deformation dx, the rotation angle λ of the concrete that has the relationship of Equation 6 and the rotation angle θ of the adjacent concrete that has the relationship of Equation 7 Based on _n , the deformation amount δ shown in Formula 8 satisfies the desired deformation amount.

  The steel-concrete sandwich structure described above includes a main steel plate arranged at a predetermined interval, a plurality of shear-reinforced steel plates connecting the main steel plates, and a concrete filled between the main steel plate and the shear-reinforced steel plate. It shall include the structural member which comprises and the structure using the said structural material.

  In addition, the steel concrete sandwich structure described above has an internal space formed by connecting a main steel plate arranged at a predetermined interval and a steel element composed of a plurality of shear reinforcing steel plates connecting the main steel plates, and forming an internal space. Steel-concrete sandwich structure constructed by filling the space with concrete, or steel-concrete sandwich constructed by placing multiple shear-reinforced steel plates on the main steel plate arranged at a predetermined interval and filling the interior space with concrete Includes structure.

According to the present invention, the deformation amount can be calculated appropriately.
More specifically, according to the results of the loading test performed on the steel-concrete sandwich structure of the present invention, the cracks concentrate near the shear-reinforced steel plate in the concrete filled in the internal space. The shear-reinforced steel plate and concrete do not adhere, and the curvature of the block-shaped concrete surrounded by the main steel plate and shear-reinforced steel plate is uniform. And the sum of rotational deformations that occur in block-shaped concrete surrounded by shear-reinforced steel sheets.

  In addition, since the shear-reinforced steel plate and concrete are not attached, the neutral axis in the crack cross section is the tip of the crack, the ratio of the crack depth to the cross section height is α, and the compression deformation amount of the compression edge is dx. The angle λ can be expressed as Equation 6.

  Note that the curvature of the block-shaped concrete surrounded by the main steel plate and the shear reinforced steel plate is uniform, and cracks due to rotational deformation are symmetrical on the left and right sides of the concrete, so the rotation angle of the crack generated on one side is λ / 2.

In addition, assuming that the strain is proportional to the distance from the neutral axis of the section, the stress-strain relationship of concrete is the curve shown in the concrete standard specifications, so that the compressive strain ε 'of the concrete at a position away from the neutral axis by y _c (y) and the deformation amount dx of the compression edge can be expressed as Equations 3 and 4, and the rotation angle λ can be expressed as Equation 5.
Furthermore, the relational expression of the balance of the force obtained from the cross-sectional force generated in the block-shaped concrete surrounded by the main steel plate and the shear reinforced steel plate can be expressed as Equation 1 and Equation 2.

  From the above relationship, the rotation angle λ is calculated from the cross-sectional force generated in each concrete surrounded by the main steel plate and the shear reinforced steel plate, but the rotation angle generated at the position of the shear reinforced steel plate is half of the rotation angle of the adjacent concrete. Therefore, the rotation angle θ at the position of the shear reinforced steel plate can be expressed as Equation 7.

  As described above, the amount of deflection of the steel-concrete sandwich structure can be accurately calculated by accumulating rotational deformation in each concrete as shown in Equation 8. Therefore, it is possible to construct a steel concrete sandwich structure that can satisfy a desired amount of deformation.

  The desired amount of deformation is, for example, that the amount of deformation at the center of the span of a structure composed of a steel-concrete sandwich structure satisfies a predetermined amount such as 1/100 of the span length of the structure. For example, it may be an amount that does not violate the building limit when the track is constructed below the structure constituted by the sandwich structure.

As an aspect of the present invention, the main steel plate can be constituted by a connected steel plate in which a partial main steel plate having a predetermined length is connected by a meshing joint capable of transmitting stress.
According to the present invention, since the partial main steel plates that are smaller than the main steel plates are connected by the meshing joint so that stress can be transmitted, the workability can be improved.

Further, as an aspect of the present invention, a steel element having a U-shaped cross section can be configured by the two partial main steel plates and the shear reinforced steel plate.
The above-described steel element having a U-shaped cross section only needs to constitute at least a part of the steel-concrete sandwich structure.

  According to the present invention, a steel element having a U-shaped cross-section is compared with a steel-concrete sandwich structure in which a main steel plate arranged at a predetermined interval and a plurality of shear-reinforced steel plates that connect the main steel plates are integrated. In the case of inserting into the middle part, the construction scale is reduced, and the workability can be further improved.

  According to the present invention, it is possible to provide a steel-concrete sandwich structure capable of appropriately calculating the deformation amount and satisfying the desired deformation amount and a design method thereof.

The schematic perspective view of the underground crossing structure constructed under a track. The schematic front view of the same state. Explanatory drawing about steel elements. The schematic longitudinal cross-sectional view of the same state. Explanatory drawing of the calculation model of a steel concrete sandwich structure. A calculation model for the amount of deflection due to rotation angle in steel-concrete sandwich structures. Explanatory drawing about the loading test body of a steel concrete sandwich structure. Explanatory drawing about the comparison with the loading test and calculation result of a steel concrete sandwich structure. Explanatory drawing about the test result of a loading test.

First, an underground underground structure 300 using the steel concrete sandwich structure S of the present invention will be described with reference to FIGS.
1 shows a schematic perspective view of an underground crossing structure 300 constructed below the track 200, FIG. 2 shows a schematic front view of the underground crossing structure 300 constructed below the track 200, and FIG. FIG. 4 shows an explanatory view of the square steel element 50 constituting the crossing structure 300, and FIG. In the description of the present specification, hatching showing a cross section of the concrete C filling the connection space 56 is omitted.

  The track 200, in which the square steel element 50 is inserted and the underground crossing structure 300 is constructed below, is constructed by embedding a road bed 401a and a roadbed 401b on an upper portion of a natural ground 400 to form a banking portion 401. The ballast 402 is compacted on the embankment 401, the sleepers 202 are placed at equal intervals in the length direction, and the rails 201 are fixed on the sleepers 202.

  The underground crossing structure 300 constructed in the direction crossing the track 200 (left-right direction in FIG. 4) is a rectangular section box constructed in the natural ground 400 at a position where the upper floor portion 300a becomes a predetermined earth covering. 1, 2, and 4, the underground crossing structure 300 with the connected square steel elements 50 exposed is illustrated, but depending on the use of the underground crossing structure 300, the underground crossing structure The underground crossing structure 300 is completed by constructing pavement and concrete in the internal space 300b and the end of the 300.

In this way, the underground crossing structure 300 is formed between the vertical shafts 420 (420a and 420b) constructed by dug down using earth retaining walls (not shown) built in advance on both sides in the transverse direction of the track 200 as shown in FIG. It is a structure that penetrates the natural ground 400 under the orbit 200 of the.
As shown in FIGS. 1 to 3, the underground underground structure 300 is constructed by connecting square steel elements 50 arranged in a rectangular shape in front view and excavating the inside thereof.

  As shown in FIGS. 2 and 3, the square steel element 50 is formed in a substantially rectangular shape, is configured to be connectable in the connecting direction Z <b> 1 by a connecting joint 53 described later, and is formed to a predetermined length. . Then, a plurality of square steel elements 50 formed to have a predetermined length are connected by connecting members (not shown) in the length direction (insertion direction) X to secure the length of the underground crossing structure 300. It is a configuration.

More specifically, as shown in FIG. 3, the square steel elements 50 constituting the underground underground structure 300 are arranged in two intersecting directions Z2 orthogonal to the connecting direction Z1 at a predetermined interval. The flange steel plate 51 and the shear reinforced steel plate 52 facing the crossing direction Z2 on both sides of the connecting direction Z1 in the flange steel plate 51 are configured to have a rectangular cross section.
In addition, since the length direction X of the above-mentioned square steel element 50 is a direction that coincides with the insertion direction X of the square steel element 50, it is indicated by the same symbol X in this specification.

  At both ends of the flange steel plate 51, a coupling joint 53 having a substantially C-shaped cross section is provided. Specifically, the base end side coupling joint 53 a disposed on the base end side in the connecting direction Z <b> 1 of the flange steel plate 51 is formed in a substantially inverted C shape in a protruding manner outside the flange steel plate 51 in the intersecting direction Z <b> 2. On the other hand, the distal end side coupling joint 53b disposed on the distal end side in the coupling direction Z1 of the flange steel plate 51 is formed in a substantially C shape in a protruding manner inside the intersecting direction Z2 from the flange steel plate 51. Therefore, the adjacent square steel elements 50 are connected to the distal end side coupling joint 53b of the already inserted square steel element 50 and the proximal end side coupling joint of the square steel element 50 to be inserted later. 53a is fitted and connected.

  Further, the shear reinforced steel plate 52 is arranged at an appropriate interval in the connecting direction Z1 from the connecting joint 53 on the distal end side and the proximal end side of the flange steel plate 51. Therefore, between the adjacent square steel elements 50, the shear-reinforced steel plate 52 of the inserted square-shaped steel element 50, the shear-reinforced steel plate 52 of the square steel element 50 to be inserted later, and the flange A connection space 56 surrounded by the connection joint 53 of the steel plate 51 is formed.

  The square steel element 50 configured in this way is not used as a temporary structure but is used as a structural member of the main body of the underground underground structure 300. Accordingly, the interval in the crossing direction Z2 of the flange steel plates 51, that is, the length in the crossing direction Z2 of the shear reinforced steel plate 52, together with the concrete C filling the connecting space 56, is the upper floor portion, lower floor portion or side wall of the underground crossing structure 300. As shown in FIG. Further, the width of the square steel element 50, that is, the length in the connecting direction Z1 of the flange steel plate 51 is determined by allocating according to the height and width dimensions of the underground underground structure 300 to be constructed.

  The proximal end side coupling joint 53a and the distal end side coupling joint 53b have the same cross-sectional shape, are arranged symmetrically with respect to each other, and can be engaged with the proximal end side coupling joint 53a and the distal end side coupling joint 53b. In addition, in the meshed state of the proximal end side coupling joint 53a and the distal end side coupling joint 53b, a clearance is provided in consideration of workability. Therefore, after the square steel element 50 is completely inserted into the ground, it is bitten. A cement grout material G (hereinafter referred to as grout G) for transmitting stress and preventing water leakage between the square steel elements 50 in a combined state is filled. Therefore, each of the proximal end side coupling joint 53a and the distal end side coupling joint 53b is provided with a grout steel plate 54 which covers the other in the meshed state and prevents leakage of the grout G to be filled. Further, a rust preventive sheet 55 is provided outside the base end side coupling joint 53a.

  Further, in the description of the square steel element 50 described above, the general element 50a of the general part constituting the underground crossing structure 300 has been described. However, as shown in FIGS. The reference element 50c, the corner element 50b constituting the corner of the underground crossing structure 300, and the adjustment element 50d inserted lastly and closed in an annular shape are the general elements of the above-described general part as described below. The configuration is slightly different from 50a.

  First, the reference element 50c to be inserted into the natural ground 400 connects the square steel elements 50 on the left and right sides with respect to the reference element 50c, and therefore, as shown in FIG. While providing the front end side coupling joint 53b, the shear reinforcement steel plate 52 is arrange | positioned at the both sides of the connection direction Z1 (illustration omitted).

  On the contrary, the adjusting element 50d inserted last and closed in an annular shape is connected to both inserted square steel elements 50 between the inserted square steel elements 50 inserted on the left and right sides. Therefore, as shown in FIG. 3D, the flanged steel plates 51 are provided with proximal end side coupling joints 53a on both sides, and shear reinforcing steel plates 52 are arranged on both sides in the coupling direction Z1 (not shown).

  As shown in FIG. 3 (b), the corner element 50 b has a connecting direction orthogonal to the base end side where the base end side connecting joint 53 a is located, so that the front end side connecting joint 53 b is an extension of the shear reinforced steel plate 52. Placed on top.

In the above description, the construction of the underground transverse structure 300 having a horizontally long rectangular cross-section with the general element 50a, the reference element 50c, the corner element 50b, and the adjustment element 50d in the general part is described. The element 50c and the corner element 50b are arranged in a single horizontal shape, or arranged in a vertical row, or the square steel element 50, the reference element 50c, and the corner element 50b are arranged in a T shape, a portal arrangement, or an L type. The underground crossing structure 300 may be constructed in the arrangement.
Furthermore, you may construct | assemble the underground crossing structure 300 of a circular cross section or an arc-shaped cross section using the trapezoidal cross section or the strip | belt-shaped arc shaped general element 50a, the reference | standard element 50c, and the adjustment element 50d.

  The square steel element 50 (50a, 50b, 50c, 50d) having such a configuration has a blade edge and a drilling device attached to the tip of the square steel element 50 in the longitudinal direction X, and the blade edge and the drilling device. While excavating the natural ground 400 at the front, the primary side pulling wire (not shown) is towed from the arrival side vertical shaft 420b, or pushed from the starting side vertical shaft 420a and inserted into the natural ground 400 to insert the underground crossing structure 300. To construct.

  Thus, the steel concrete sandwich structure S is comprised by connecting the some square steel element 50 which comprises the underground crossing structure 300 constructed | assembled in the natural ground 400. FIG.

  However, the steel-concrete sandwich structure S formed by connecting the square steel elements 50 constituted by the flange steel plate 51, the shear-reinforced steel plate 52 and the connection joint 53 and filling the connection space 56 with the concrete C is surrounded by the steel plates. In order to evaluate as a composite structure in which reinforced concrete behaves integrally with a steel plate, a general steel-concrete sandwich structure is provided with appropriate detents at appropriate intervals to ensure the integrity of the steel plate and concrete. The flange steel plate 51 or the shear reinforced steel plate 52 constituting the square steel element 50 and the concrete C are not provided with a slip stopper.

  As described above, in the case of a steel-concrete sandwich structure without a slip stopper, in the previous studies on the bending characteristics of a general steel-concrete sandwich structure, a deviation has occurred between the steel plate and the concrete, and the calculated deflection value is It is known that it is larger than the theoretically calculated value, and a steel-concrete sandwich structure of the underground transverse structure 300 constituted by connecting a plurality of square steel elements 50 and filling the connecting space 56 with concrete C. When S is structurally analyzed as a general steel-concrete sandwich structure, for example, the vicinity of the center of the upper floor portion 300a of the underground underground structure 300 is greatly bent, and there is a possibility that the deformation amount is larger than expected.

Therefore, a square steel element 50 having a U-shaped cross section composed of two flange steel plates 51 and a shear reinforced steel plate 52 is provided at both ends of the flange steel plate 51 and connected by connecting joints 53 capable of transmitting stress. The constructed steel concrete sandwich structure S is evaluated as follows.
In the steel-concrete sandwich structure S, a plurality of flange steel plates 51 that are connected by the connecting joint 53 so as to be able to transmit stress are referred to as a connected main steel plate 51s.

  First, FIG. 5A shows an outline of compression deformation and cracking due to rotational deformation of concrete C surrounded by the flange steel plate 51 and the shear reinforced steel plate 52. Here, since the shear reinforced steel plate 52 and the concrete C are not attached, the neutral axis in the crack cross section is the tip of the crack.

  At this time, if the ratio of the crack depth to the cross-sectional height is α, and the amount of compressive deformation of the compression edge is dx, the rotation angle λ can be expressed as Equation 6. Here, since it is assumed that the curvature of the concrete C surrounded by the flange steel plate 51 and the shear reinforced steel plate 52 is uniform, cracks due to rotational deformation are symmetric on the left and right of the concrete C, and thus occur on one side. The rotation angle of the cracks to be made is λ / 2.

Further, the strain distribution and the force balance of the concrete C surrounded by the flange steel plate 51 and the shear reinforced steel plate 52 are set as a model as shown in FIG. Here, it is assumed that the strain is proportional to the distance from the neutral axis of the cross section, and the stress-strain relationship of concrete C is based on the curves shown in the concrete standard specifications, as shown in FIGS. 8B and 8C. The compressive strain ε ′ _c (y) of the concrete C and the deformation dx of the compression edge at a position away from the neutral axis by y can be expressed as Equation 3 and Equation 4.

Further, based on Equation 6, Equation 3, and Equation 4, the rotation angle λ can be expressed as Equation 5.

Furthermore, the relational expression of the balance of forces obtained from the cross-sectional force generated in the concrete C surrounded by the flange steel plate 51 and the shear reinforced steel plate 52 can be expressed as Equation 1 and Equation 2.

From the above relationship, the rotation angle λ is calculated from the cross-sectional force generated in each concrete C surrounded by the flange steel plate 51 and the shear reinforced steel plate 52. Here, since the rotation angle generated at the position of the shear reinforced steel sheet 52 is the sum of the half of the rotation angles of the adjacent concrete C, the rotation angle θ at the position of the shear reinforced steel sheet 52 can be expressed as Equation 7. it can.

From the above, the rotational deformation of the concrete C surrounded by the flange steel plate 51 and the shear reinforced steel plate 52 is modeled as shown in FIG. 6 (a), and the rotational deformation in each concrete C as shown in Equation 8 is accumulated. The amount of deflection δ at the center of the span of the steel concrete sandwich structure S constituting the underground underground structure 300 can be accurately calculated.

Therefore, when structural analysis is performed on the underground crossing structure 300 configured by the steel-concrete sandwich structure S, the deformation amount δ calculated by Expression 8 satisfies the desired deformation amount that is the required performance of the underground crossing structure 300. The specifications of the square steel element 50 and the specifications of the underground underground structure 300 configured by connecting the square steel elements 50 are determined.

  The desired amount of deformation is, for example, that the amount of deformation at the center of the span of the upper floor portion 300a formed of the steel-concrete sandwich structure S in the underground underground structure 300 satisfies a predetermined amount such as 1/100 of the span length of the upper floor portion 300a. Or an amount that does not violate the building limit when a track is constructed in the internal space 300b.

  In this way, the underground underground structure 300 of the steel-concrete sandwich structure S constructed by connecting the square steel elements 50 whose specifications are determined using the above Equations 1 to 8 has the desired required performance. Can be satisfied.

  The desired required performance refers to the upper floor portion 300a of the underground crossing structure 300, such as the amount of deformation such as deflection at the center of the span of the upper floor portion 300a constituted by the steel-concrete sandwich structure S and the shear strength. This is the required performance.

Next, a description will be given of a confirmation test performed in order to verify the calculation accuracy of the calculation results (hereinafter referred to as the present application calculation results) according to the above-described Equations 1 to 8.
In order to evaluate the steel-concrete sandwich structure S composed of the square steel elements 50, a loading test was performed using the test bodies S1 and S2 shown in FIG.

  More specifically, in order to conduct a loading test for the purpose of confirming the relationship between load and displacement, fracture mode, and bending strength of the steel concrete sandwich structure S in which the shear reinforcing steel plate 52 is disposed only in the direction perpendicular to the member axis, A static bending loading test was performed using a steel-concrete sandwich beam test body (test bodies S1, S2) simulating a plurality of square steel elements 50 connected by 53.

  The loading was a two-point monotonous loading by displacement control using a hydraulic jack with respect to two types of test bodies (test bodies S1, S2). Here, the specimens (S1, S2) used in the loading test faithfully reproduce the actual structure in order to avoid the influence of the dimensional effect, and the specimen S1 has the most standard shape of this construction method and has a high cross-sectional height. The test piece S2 has a cross-sectional height of 1000 mm and the interval between the shear reinforced steel plates 52 is 1160 mm, and the results of the test pieces S1 and S2 are as follows. A comparison was made.

  As shown in FIG. 7, the loading is provided with a loading point at a position where the section sandwiched between the shear-reinforced steel plates 52 in the center of the span becomes an equal bending section, and three joints at upper and lower positions between the loading point and the fulcrum. 53 was arranged. The shear span between the loading point and the fulcrum was set so that the shear span ratio at the member height was about 3.

The square steel element 50 constituting these test bodies (S1, S2) is filled with the connecting space 56 of the square steel element 50 using a standardly used SM400 material having a plate thickness of 16 mm. Normal concrete with a uniaxial compressive strength of about 30 N / mm ² is used as the concrete C, and all the connecting joints 53 are fitted in a state where the square steel element 50 is placed sideways. Was filled with cement milk (grout G) having a design standard strength of 30 N / mm ² .

  After the cement milk was hardened, concrete C was formed by placing ordinary concrete in the connection space 56 of the square steel element 50, and test specimens (S1, S2) were produced. The surface of the square steel element 50 in contact with the concrete C was not subjected to roughening or the like and was left untreated.

  FIG. 8B and FIG. 8C show the relationship between the load and displacement obtained from the loading test. All the test results showed a linear relationship up to the load load of about 1300 kN, and thereafter, the increasing tendency of the load became very gentle.

  The first cracks that occurred in the test specimens (S1, S2) occurred from the connection joint 53 on the tensile side that was closest to the loading point in any of the test specimens (S1, S2). Thereafter, unlike the bending crack of the reinforced concrete structure, it was confirmed that the crack was generated only in the vicinity of the shear reinforced steel plate 52 and was not spread without being dispersed with the increase of the load. Along with this, slip occurred between the square steel element 50 on the tension side and the concrete C, and the crack width in the vicinity of the shear reinforced steel plate 52 increased as shown in FIG.

  In the test body S1, when the loading load reaches 1431 kN, buckling of the compression side steel plate between the loading points occurs, and the load decreases rapidly. Thereafter, as shown in FIG. As it broke down, the load gradually decreased. On the other hand, the specimen S2 has a local buckling as shown in FIG. 9 (c) when the load on the compression side steel plate starts to yield at a load load of about 1450 kN and reaches about 1800 kN. After that, concrete C did not break down significantly and the load continued to increase slowly.

  As described above, when looking at the progress of these fractures, any specimen (S1, S2) does not disperse the bending cracks, and the deformation is increased by localizing the cracks in the vicinity of the shear reinforced steel plate 52. I understand that Further, in the vicinity of the shear reinforced steel plate 52, slip is generated between the square steel element 50 on the tension side and the concrete C, and it is considered that the plane holding is not established, and the bending deformation is assumed assuming the plane holding. It was confirmed that the deformation behavior was different from that of the reinforced concrete structure.

In comparing the above-described loading test result and the above-described calculation result of the present application, the elastic modulus of the square steel element 50 was set as follows.
As shown in FIG. 6 (b), the square steel element 50 constitutes a connected main steel plate 51 s that connects the flange steel plates 51 with connecting joints 53 and transmits stress. However, the flange steel plate 51 and the connection joint 53 constituting the connection main steel plate 51s are composite members obtained by connecting members having different tensile properties as shown in Table 1, and it is necessary to appropriately evaluate the tensile properties. is there. The characteristic values of the connecting joint 53 with the average value of the measured experimental results as 220 mm (L _j in FIG. 6 _(b)) between the gauge length.

Here, the elastic modulus of the square steel element 50 that is a composite member was calculated using Equation 10 from the average strain shown in Equation 9 with the average elastic modulus calculated using the elastic modulus of each material.

Table 2 shows the average elastic modulus of the square steel element 50 obtained from the above formulas 9 and 10. Here, the stress-strain relationship of the square steel element 50 is a bilinear relationship in which the secondary gradient ratio is 1/100 in consideration of strain hardening after the yield point. In addition, the square steel element 50 is a composite member having different yield strengths, and has a trilinear relationship with two yield points. However, the point at which the connecting joint 53 reaches the yield strength is dominant. Since the influence that 51 reaches the yield strength is very small, for the sake of simplification, when the connecting joint 53 reaches the yield strength, a linear relationship in which the secondary gradient ratio of the average elastic modulus becomes 1/100 is used. FIG. 8A shows the relationship between the stress and strain of the square steel element 50 in the body S1.
FIG. 8B shows the relationship between the load and displacement in the specimen S1, and FIG. 8C shows the relation between the specimen S2.

Here, Y ₁ points shown in the figure that the strain of the connecting joint 53 nearest the tension side span center has reached yield strain obtained from the yield strength of the connecting joint 53 shown in Table 1 (256N / mm ²⁾ , Y ₂ point is the point where the tensile strain of the flange steel plate 51 at the center of the span has reached the yield strain obtained from the yield strength (294 N / mm ² ) shown in Table 1, and M point is the compression edge strain at the center of the span reaches 3500 μm. The point is. These points were described in the figure by calculating the cross-sectional force using bending theory in the same manner as the reinforced concrete structure, assuming flat surface retention, and converting the cross-sectional force into a load.

  As shown in FIGS. 8 (b) and 8 (c), the relationship between the load and the displacement is linearly changed up to about half the stress region of the joint yield load. The calculation results of this application are considered to accurately approximate bending deformation.

Then with increasing displacement, load gradient obtained from the present calculated results whereas the linearly changes until _a point Y, the load gradient obtained from experiment the slope becomes loose as the displacement progresses The difference with the calculation result of this application came to be seen. It can be seen that the load gradient obtained from the experiment becomes very gentle as the displacement further increases. On the other hand, in the calculation result of the present application, the load gradient becomes very gentle after the yield point (Y ₁ point) of the coupling joint 53, and until the point (Y ₂ point) where the square steel element 50 at the center of the span yields. Since the load gradient can be regarded as the same as the experimental result, it is considered that the calculation result of this application was able to approximate the bending deformation in this range.

From the time since that midspan of the square steel elements 50 yield (Y ₂ points), which makes the load increases very slowly, which were obtained from the experiments, in particular specimens S1 the compression side concrete destroyed The load decreased gradually. On the other hand, the load gradient obtained from the calculation result of the present application shows a linear increasing tendency, and there is a slight deviation in the load gradient from the experimental result.

  From the above, with respect to the bending deformation of the steel-concrete sandwich structure S in which the shear reinforcing steel plate 52 is arranged in the direction perpendicular to the member axis, the initial bending rigidity and the bending deformation up to the vicinity where the center of the span yields are as follows. It was confirmed that can be evaluated with high accuracy.

In the correspondence between the configuration of the invention and the above-described embodiment, the main steel plate and the connecting steel plate of the invention correspond to the connecting main steel plate 51s,
Similarly,
The meshing joint corresponds to the coupling joint 53,
Although the partial main steel plate corresponds to the flange steel plate 51,
The present invention is not limited only to the configuration of the above-described embodiment, and many embodiments can be obtained.

  In the above description, the steel concrete sandwich structure S in which the square steel elements 50 are connected is constructed and the underground crossing structure 300 is constructed. However, the main steel plates arranged at a predetermined interval and the main steel plates are connected to each other. The underground crossing structure 300 may be formed of a steel-concrete sandwich structure including a plurality of shear-reinforced steel plates and a main steel plate and concrete filled between the shear-reinforced steel plates. However, the construction scale when the steel concrete sandwich structure S connected with the square steel elements 50 is inserted into the natural ground 400 is reduced, and the workability can be further improved.

DESCRIPTION OF SYMBOLS 50 ... Square steel element 51 ... Flange steel plate 51s ... Connection main steel plate 52 ... Shear reinforcement steel plate 53 ... Connection joint C ... Concrete S ... Steel concrete sandwich structure

Claims (6)

A steel-concrete sandwich structure comprising a main steel plate arranged at a predetermined interval, a plurality of shear-reinforced steel plates connecting the main steel plates, and concrete filled between the main steel plate and the shear-reinforced steel plate. And
The compressive stress σ ' _c (y) of the concrete at a position separated from the neutral axis by y, the member width b, the compressive force T _c generated on the compression side steel plate, the tensile force T generated on the tension side steel plate, the sectional height of the concrete The main steel plate and the shear reinforced steel plate in the relations of Equations 1 and 2 with respect to the ratio α of crack depth to thickness, the cross-sectional height h, the compression deformation dx of the compression side concrete, and the rotation angle λ of the concrete. By the bending moment M generated in each of the enclosed block-shaped concrete and the axial force N generated in each concrete,
The compressive strain ε ' _c (y) of concrete at a position away from the neutral axis by y, the edge strain ε' _{cm of} the concrete on the compression side, the distance y from the neutral axis, the interval L of the shear reinforced steel sheet, and the rotation angle λ It becomes the relationship of Formula 3 thru | or Formula 5,
Based on the crack depth ratio α, the cross-sectional height h, and the amount of compressive deformation dx, the rotation angle λ of the concrete that has the relationship of Equation 6 and the rotation angle θ of the adjacent concrete that has the relationship of Equation 7 Based on _n , the deformation amount δ shown in Formula 8 satisfies the desired deformation amount.
Steel concrete sandwich structure. The steel-concrete sandwich structure according to claim 1, wherein the main steel plate is composed of a connecting steel plate in which partial main steel plates having a predetermined length are connected by a meshing joint capable of transmitting stress. The steel-concrete sandwich structure according to claim 2, wherein a steel element having a U-shaped cross section is constituted by the two partial main steel plates and the shear-reinforced steel plate. Design of a steel-concrete sandwich structure composed of a main steel plate arranged at a predetermined interval, a plurality of shear-reinforced steel plates connecting the main steel plates, and concrete filled between the main steel plate and the shear-reinforced steel plate A method,
The compressive stress σ ' _c (y) of the concrete at a position separated from the neutral axis by y, the member width b, the compressive force T _c generated on the compression side steel plate, the tensile force T generated on the tension side steel plate, the sectional height of the concrete The main steel plate and the shear which have the relationship of Equation (1) and Equation (2) with respect to the ratio of crack depth to thickness α, section height h, compression deformation dx of compression side concrete, and rotation angle λ of concrete By the bending moment M generated in each of the block-shaped concrete surrounded by the reinforcing steel plate and the axial force N generated in each concrete,
The compressive strain ε ' _c (y) of concrete at a position away from the neutral axis by y, the edge strain ε' _{cm of} the concrete on the compression side, the distance y from the neutral axis, the interval L of the shear reinforced steel sheet, and the rotation angle λ While it becomes the relationship of Formula (3) thru | or Formula (5),
The cracking depth ratio α, the cross-sectional height h, and the compression angle d of the concrete based on the equation (6) based on the rotation angle λ of the concrete, and the adjacent concrete represented by the equation (7) The deformation amount δ shown in the equation (8) satisfies the desired deformation amount based on the rotation angle θ _n of
Design method for steel-concrete sandwich structure. 5. The method for designing a steel-concrete sandwich structure according to claim 4, wherein the main steel plate is a connected steel plate in which partial main steel plates having a predetermined length are connected by an interlocking joint capable of transmitting stress. The steel-concrete sandwich structure design method according to claim 5, wherein a steel element having a U-shaped cross section is configured by the two partial main steel plates and the shear-reinforced steel plate.