JP5064256B2 - Simple steel vertical telescopic device for road bridges - Google Patents

Description

  The present invention relates to a telescopic device installed between bridges of a road bridge or between a bridge and an abutment. In particular, the present invention relates to a simple steel vertical telescopic device used for a road bridge.

  In the simple steel vertical expansion and contraction device, for example, corrugated steel plates and comb steel plates are arranged vertically along the gap. The steel plate is fixed to a box opening portion provided at a floor slab end portion of a bridge girder or a parapet end portion of an abutment facing each other through an anchor member or the like, and then concrete is placed in the box opening portion. The steel plate plays the role of an inner mold on the idle side at the box opening, and the concrete is filled along the shape of the steel plate.

Although concrete shrinks when dried, it is constrained by an anchor member or the like embedded in the concrete. Therefore, when shrinkage progresses, tensile stress is generated inside, which causes cracks. In particular, since the concrete placement part is long in the road width direction, the tensile stress due to drying shrinkage is large in the road width direction. Furthermore, since the joint portion with the steel plate exhibits a waveform along the road width direction, stress concentration occurs at the peripheral portion of the recess, and cracks are likely to occur.
JP 59-0605102

  An object of the present invention is to prevent the occurrence of cracks in a simple steel vertical expansion and contraction device without using a reinforcing member.

  A simple steel vertical expansion / contraction device for road bridges according to the present invention is a simple steel vertical expansion / contraction device for road bridges using a smooth corrugated plate member as a vertical type, and the corrugated recess has a radius of curvature r. In addition to having an arc surface, r / t is 3.5 or more when the apex of the corrugated convex portion is arranged at a distance t away from the apex of the concave portion in the bridge axis direction.

  The opening angle β of the arc surface is preferably 60 ° or more, and more preferably 120 ° or more. Further, r / t is 3.5 or more and more preferably approximately 3.5.

  As described above, according to the present invention, it is possible to prevent the occurrence of cracks without using a reinforcing member in the simple steel vertical expansion and contraction device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partial plan view of a simple steel vertical telescopic device according to an embodiment of the present invention installed on a gap between road bridges, and FIG. 2 is a simple steel made on a gap between the gaps. It is a typical sectional side view of a vertical expansion-contraction apparatus. In FIG. 1, the right half shows the state after concrete placement, and the left half shows the state before concrete placement.

  The simple steel vertical expansion / contraction device 10 of the present embodiment includes vertical steel plates 11A and 11B that draw wavefront curved surfaces along a longitudinal direction that is a road width direction (a direction orthogonal to a bridge axis direction on a road surface). The vertical steel plates 11A and 11B are opposed to each other with a certain interval, and anchor members 15A to 17A are attached to box opening portions 14A and 14B provided at the end portions of the floor slabs 13A and 13B that are arranged to face each other with a gap. , 15B to 17B and the like.

  Bottom plates 19A and 19B are provided along the edges of the lower ends of the vertical steel plates 11A and 11B. The bottom plates 19A and 19B constitute the bottom surfaces of the vertical steel plates 11A and 11B protruding from the floor slabs 13A and 13B. When the simple steel vertical expansion and contraction device 10 is fixed to the boxing portions 14A and 14B, Together with the vertical steel plates 11A and 11B, it plays a role as a loose-side mold (left half in FIG. 1). In addition, concrete 20A, 20B is cast in the box opening portions 14A, 14B to the same height as the paved surface (the right half in FIG. 1). A flexible sealing member 18 is interposed between the vertical steel plates 11A and 11B.

  As shown in the right half of FIG. 1, the vertical steel plates 11A and 11B are made of plate members having a smooth corrugated vertical surface and include concave portions 21A and 21B and convex portions 22A and 22B. The shape of the vertical steel plate 11B will be described in the following description.

  The concave portion 21B of the vertical steel plate 11B is formed of an arc surface having a radius of curvature r, and the end point P1 on both sides of the arc of the concave portion 21B and the end point P2 on both sides of the arc of the convex portion 22B are smoothly connected to each other via a straight line portion. Is done. When the extension line connecting the end points P1 and P2 on one side is T1, and the extension line connecting the end points P1 and P2 on the other side is T2, the straight lines T1 and T2 are the sides containing the recess 21B. At the angle (opening angle) β. In this case, the end points P1 and P2 coincide with each other to become inflection points, and the straight lines T1 and T2 become tangent lines at the inflection points.

  Further, the arc surface of the convex portion 22B has a radius of curvature smaller than the radius of curvature r of the concave portion 21B by the distance between the vertical steel plates 11A and 11B, and the vertex Q2 of the convex portion 22B is relative to the vertex Q1 of the concave portion 21B. , And arranged at a distance t in the bridge axis direction. In addition, the vertex Q1 of the recessed part 21B is arrange | positioned along the edge | side which comprises an edge part on the box opening part 14B of the floor slab 13B, respectively.

  Next, the principle of the crack generation prevention method in the present embodiment will be described with reference to FIGS.

  Since the concrete 20A, 20B placed on the floor slabs 13A, 13B is restrained by the reinforcing bars or concrete anchor members 17A, 17B embedded in the concrete of the existing floor slab, and also shrinks dry as the moisture evaporates, During drying, a tensile stress σn is generated in the road width direction. At this time, stress concentration occurs in the recesses 21 </ b> A and 21 </ b> B, and cracks are likely to occur.

  FIG. 3 is a partial plan view of a plate member 24 provided with a notch 23, which is a model of the structure of the recesses 21A and 21B. The notch 23 is provided on one side of the plate member 24 so as to be bilaterally symmetric, and the tip of the recess is an arc 25 having a curvature r. Both ends of the arc 25 are smoothly connected to the straight portions 26, and each straight portion 26 reaches the side of the plate member 24 to form an opening. Further, the extended lines of the two straight portions 26 intersect at an angle β on the side containing the arc 25. Further, the depth of the notch 23 is represented by t.

  When a tensile stress σn is applied to the plate member 24 in a direction parallel to one side where the notch 23 is provided, stress concentration occurs at the tip of the recess of the notch 23. FIG. 4 shows changes in the value of the stress concentration coefficient α at the tip of the recess when the opening angle β is changed.

  In the graph of FIG. 4, the horizontal axis is the angle β (0 ° to 180 °), and the vertical axis is the stress concentration factor α. Each curve drawn in the graph shows the stress concentration coefficient α when the values of r / t are 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, and 3.5, respectively. Is a change with respect to the angle β.

  As shown in FIG. 4, the value of the stress concentration factor α decreases as the value of r / t increases, and decreases as the value of the angle β increases. In order to prevent the occurrence of cracks, it is required to reduce the value of the stress concentration factor α as much as possible.

  By the way, in the concrete in which the reinforcing bars are embedded, the problem of stress concentration similarly occurs around the reinforcing bars. In the conventional construction example, when the occurrence of cracks around the reinforcing bars in concrete with embedded reinforcing bars with a circular cross section is seen, the cracks do not occur around all the reinforcing bars, but only around some reinforcing bars. ing. Therefore, when it is considered that the state of the concrete at this time is substantially equal to the stress state of the plate member provided with the circular hole, the maximum value of the stress concentration coefficient α is at least the stress concentration around the circular hole in preventing cracking. It is considered desirable that α = 3 or less, which is the maximum value of the coefficient.

  However, even if the stress concentration factor α is 3 or less, cracks are generated around some reinforcing bars. From this, the maximum value of the stress concentration factor in the recesses 21A and 21B is 1 which is the minimum value of the stress concentration factor, the maximum value 3 of the stress concentration factor around the circular hole, and an intermediate value α = 2 or less. Is more preferable. Referring to FIG. 4, when r / t = 3.5 or more, the stress concentration coefficient α is 2 or less regardless of the value of the angle β, so that the shapes of the vertical steel plates 11A and 11B are, for example, r / t = 3. If it is set to .5 or more, the occurrence of cracks can be sufficiently suppressed regardless of the size of the opening angle β.

  On the other hand, from the viewpoint of running performance (noise prevention) of a vehicle running on the telescopic device, it is preferable that the value of r / t is small. Therefore, in this embodiment, for example, r / t is set to approximately 3.5. In addition, the stress concentration factor decreases as the opening angle β increases with respect to a predetermined value of r / t, and the angle β is preferably 60 ° or more, and more preferably 120 ° or more. Furthermore, if the opening angle β is too large, the running performance deteriorates in the same manner as when r / t is large, so the angle β is preferably 160 ° or less, for example.

  As described above, according to the present embodiment, it is possible to suppress the occurrence of cracks in the concave portion of the simple steel vertical expansion and contraction device without adding a crack prevention reinforcing bar or the like.

It is a partial top view of the simple steel vertical expansion-contraction apparatus which is one Embodiment of this invention. It is a typical sectional side view of the simple steel vertical expansion-contraction apparatus installed on the play. It is the elements on larger scale of a board member when modeling as a board member in which the notch of the crevice of a simple steel vertical expansion-contraction device was formed. It is a graph which shows the change with respect to the opening angle (beta) of the maximum stress concentration coefficient in the notch front-end | tip part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Simple steel vertical expansion / contraction apparatus 11A, 11B Vertical steel plate 13A, 13B Floor slab 14A, 14B Box opening part 15A-17A, 15B-17B Anchor member 18 Seal member 19A, 19B Bottom plate part 20A, 20B Concrete 21A, 21B Concave part 22A , 22B Convex

Claims (3)

  A simple steel vertical expansion and contraction device for a road bridge using a smooth corrugated plate member as a vertical type, wherein the corrugated recess has an arc surface with a radius of curvature r, and the apex of the corrugated convex portion is A simple steel vertical telescopic device for road bridges, wherein r / t is 3.5 or more when arranged at a distance t in the bridge axis direction with respect to the apex of the recess.   2. The simple steel vertical telescopic device for a road bridge according to claim 1, wherein an opening angle β of the arc surface is 60 ° or more.   The simple steel vertical telescopic device for a road bridge according to claim 2, wherein the opening angle β is 120 ° or more.

Images