KR20040055769A - Strengthening Method of Slab of Continuous Bridge by Inclining Tendons - Google Patents

Abstract

PURPOSE: A reinforcement method for a floor slab of a continuous bridge by an inclined tendon is provided to heighten the reinforcement effect of a girder by applying inclined tensile force on a floor slab and to execute works easily. CONSTITUTION: To resist the tensile stress added on a floor slab of an inner support by negative moment of external load added on a continuous bridge, the reinforcement method for a floor slab of a continuous bridge by an inclined tendon comprises the steps of arranging steel bar or strand shaped tendons(10) on the center height of a floor slab to be inclined in two ways to apply tensile force in the axial direction(27) and the horizontal direction(28) of a precast or cast-in-plate floor slab, and anchoring a tendon to the side of the floor slab at the same time.

Description

Strengthening Method of Slab of Continuous Bridge by Inclining Tendons

Multi-span bridges with simple supported girders are now avoided, where design technology is improved due to the use of expansion joints at relatively large cross sections and internal points and poor ride comfort. Figure 1 is a typical PS (prestressed) concrete girder bridge simply mounted PS concrete girder is generally continuous to the construction process of FIG. Recently, in order to improve the problem of simple girders, a strained carbon fiber is attached to the top of the girder (domestic application 20-2003-0040349) or the use of steel crossbeams (domestic application 20-2003-0026137) and the point rise and fall (domestic application 10- 1998-0001799) and the use of weights (domestic application 10-1998-0000421) have been tried.

However, when the external load 40 is applied to the continuous girder as shown in FIG. 2, a parent section section 42 is formed around the inner point 39 of FIG. 3, and the parent is formed on the bottom slab of the section. There is a fragility in cracking due to tensile stress caused by cement. The crack of the bottom plate due to the parent part of the inner branch part is caused by the outer and inner tension members 50 arranged in the axial direction on the bottom plate near the inner branch part 39 (Domestic Application 10-2000-0067723, 10-2002-0031034, 20). -2003-0040349). This method is effective when the bottom plate and the girder are synthesized after the tension is introduced to the bottom plate (domestic application 10-1998-0043606, 10-1998-00343608) like a precast bottom plate. However, when the composite is combined with the girder after the tension is introduced, the long-term deformation of the deck concrete is constrained to the relatively rigid girder, so it is necessary to accurately predict the residual tensile stress occurring after the tension is introduced.

Recently, after the bottom plate and the girder have been synthesized, it has been found that the introduction of the tension force into the composite section is more efficient than the introduction of the tension force independently into the girder or the bottom plate. 0019658, 10-1999-0043513, 20-2003-0031616) or a bottom plate (domestic application 10-2004-0024800, 10-2004-0034741) has been tried. After the bottom plate and the continuous girder are combined, when the tension force is introduced into the bottom plate in the axial direction, the secondary portion of FIG. 4 (e) at the inner point to restrain the displacement 53 due to the tension force in the simple supported case of FIG. The reaction force 54 and the secondary moment 55 are generated, and the moment distribution of the continuous compound girder is as shown in Fig. 4 (f). In this case, since a sudden change of moment occurs at the fixing position of the axial tension member, when the tension member is settled around the inflection point of the continuous girder where the stress is not generated by external load, it may cause a risk due to tension force. In addition, it is generally advantageous to install the middle bottom plate 35 and install or pour the point bottom plate 34 as shown in FIGS. 2 (b) and 2 (c). Or there is a disadvantage that the point bottom plate 34 must support the weight of the middle crossbeam 35 because it must be poured.

The most vulnerable part of the continuous composite girder bridge is the concrete deck of the inner branch, and the following supplements are necessary to ensure that the branch deck can fully support the parent moments caused by the external load acting after continuity.

1. The point bottom plate 34 should be able to be reinforced by the tension force introduced in the throttle direction.

2. The moment distribution of the continuous girder introduced by the tension force is to be the same as that of the moment distribution due to the external load in Fig. 3 and should be reversed in direction.

3. Tension force introduced into the floorboard should not interfere with the construction process of Figure 2, should be easy to settle, and should be re-tensionable.

4. After the girder and the bottom plate constitute a composite, tension should be available.

1 is a perspective view of a continuous PS concrete composite girder bridge

[Figure 2] Construction process diagram of the continuous PS concrete composite girder bridge

(a) Installation of PS concrete girder (b) Placing middle girder and middle floor plate

(c) Spotting robo and branch floor

3 is a moment distribution diagram due to external load acting on the continuous girder

[Figure 4] Moment due to the tension of the axial direction bottom plate introduced into the composite section

(a) Top view of continuous bridges with axial deck plate tension members

(b) Front view of continuous bridges with axial deck slabs

(c) moment distribution due to axial tension

(d) deflection due to tension and secondary reaction forces in the absence of internal points

(e) Secondary reaction forces and secondary moments required for the restraint of internal points

(f) Moment distribution chart generated in continuous composite girders by axial tension members

5 is a perspective view of a continuous bridge in which the inclined tension member of the present method is disposed

6 is a layout view and the introduced axial tension of the bottom plate tension material according to the present method

7 is a moment due to the inclined bottom plate tension force introduced into the composite section

(a) Top view of continuous bridges with inclined bottom plate tension members

(b) Front view of continuous bridges with inclined bottom plate tension members

(c) Average moment distribution by inclined tension

(d) Secondary reaction forces and secondary moments required for the restraint of internal points

(e) Moment distribution chart generated in continuous composite girders by inclined tension members

<Description of the symbols for the main parts of the drawings>

10. Tension material of the bottom plate disposed in the direction of inclination (27) and inclined direction

11. Tension material of bottom plate arranged in transverse direction (28)

12. Fixtures for tension members installed at the center height of the side plates

13. Segment of floor plate in which axial tension is introduced

14. Width of bottom plate 15. Spacing of tension material in axial direction (27)

16. Inclination length of the axial direction (27) of the inclined tension member (10)

17. Inclination angle of the inclined long tension member 10 in the transverse direction 28

20. Maximum compressive cross section force in the axial direction (27) of the inclined tension member (10)

21. Distribution of mean compressive sectional force in the axial direction (27) of the inclined tension member (10)

22. Moment distribution in composite section by average compressive section force (21)

23. Equivalent concentrated load for triangular moment distribution (22)

24. Secondary reaction force in the point of continuous girder by triangular moment distribution (22)

25. Distribution of Secondary Moments by Secondary Reaction Force (24)

26. Moment distribution of continuous girder by inclined tension member 10 of composite section

27. Axial direction 28. Lateral direction 29. Height direction

31.PS (prestressed) concrete or steel girders

32. Pier 33. Bridge system

34. Bottom floor plate 35. Middle floor plate

36. Branch street robo 37. Middle street robo

38. Outer Branches 39. Inner Branches

40. External load acting on continuous girder

41. Moment Distribution of Continuous Girder by External Load 40

42. Parent section of continuous girder by external load (40)

43. Central axis of composite section consisting of girder-floor plate

50. Bottom plate tension member disposed in the axial direction 27

51. Moment distribution by the axial tension member 50

52. Moment due to the axial tension member 50

53. Displacement by tension members (10,50) introduced into the composite section in the absence of internal points

54. Secondary reaction force at the point inside the continuous girder generated by the axial tension member 50

55. Distribution of Secondary Moments by Secondary Reaction Force (54)

56. Displacement due to secondary reaction forces (24, 54) without internal point

57. Moment distribution of continuous girder by axial tension member 50 of composite section

An example of the continuous PS concrete composite girder bridge to which the tensioning material of the present method disposed on the bottom plate is applied is shown in FIG. 5, and the plan view from above is illustrated in FIG. 5 and 6, the inclined tension member 10 according to the present method is disposed to be inclined in both the axial direction 27 and the transverse direction 28, and the tension member duct at the center height of the bottom plate according to the inclination direction of the tension member. It is positioned horizontally up and down by the diameter of), and is fixed 12 to the inclination angle 17 of the tension member at the side of the bottom plate.

6, the inclination length 16 of the tension member is greater than half of the interval 13 in which the tension force is introduced and the interval of the tension member is greater than half of the interval 13 in which the tension force is introduced. 15) should be smaller than the sum so that more than one tension member is not settled in one anchorage. The inclination angle 17 of the tension member relative to the transverse direction 28 is determined from the inclination length 16 of the tension member and the width 14 of the bottom plate. The section 13 into which the axial tension is introduced does not need to coincide with the point bottom plate 34 and may extend to the span center as needed.

The lateral compression section force introduced by the inclined tension force of the present method is constant, while the axial compression force is distributed in a triangle as shown in the following figure of FIG. The axial compressive force in each cross section is proportional to the number of tension forces across the cross section and the sine of the tension force and the angle of inclination (17) in the transverse direction, and the maximum axial compressive force 20 in the axial direction is shown in FIG. To occur. The axial mean compressive force 21 of each cross section introduced by the inclined tension member 10 is such that a triangular distribution is symmetric about an internal point.

When the inclined tension member 10 of FIG. 7 (a) is disposed at the center height of the bottom plate as shown in FIG. For (43), it is distributed in a triangle that is maximum at an internal point as shown in FIG. The triangular moment distribution 22 may be replaced by the concentrated load and the point reaction force 23 acting on the intercenter of the simple beam, in which the section 13 into which the axial tension is introduced is interposed, and thereby the secondary reaction force 24. And the secondary moment 25 is shown in Figure 7 (d), the distribution of the moment 26 is introduced into the continuous compound girder can be represented by Figure 7 (e). The moment 26 of FIG. 7 (e) shows a distribution in the opposite direction to a shape similar to the moment 41 of FIG. 3 when the inclined tension member 10 is disposed over the entire span.

The expected effects of this method of introducing the tension member in the direction of throttling and inclining to the bottom plate near the inner point of the continuous girder are as follows.

1. Tension force can be introduced at the same time in the axial direction 27 and the transverse direction 28.

2. The introduction of the desired axial tension in the desired position can be freely controlled because the section 13 and the width 14 of the bottom plate into which the tension force is introduced and the interval 15 and the inclination angle 17 of the tension member and the magnitude of the tension force are freely controlled. It is possible.

3. If the tension force is introduced after the girder and the bottom plate form the composite section, the introduction of the moment to offset the moment of the external load acting on the continuous girder by adjusting the section 13 where the inclined tension member is arranged. It is possible to secure a larger eccentric distance than when the tension member is disposed on the girder because the tension member is disposed on the bottom plate.

4. The work is easy because the tension member is fixed 12 at the side of the bottom plate.

5. Since the tension member is placed in a straight line on the horizontal section of the center of the bottom plate, it can have the same effect as the parabolic arrangement of continuous girders without loss of friction. In particular, when the rust prevention treatment is sufficient, re-tensioning is possible because no grouting is required.

6. It is easy to install when rebuilding the bottom plate of the bridge being used for reinforcement purposes, and after the girder and the bottom plate are combined, the reinforcement effect on the girder as well as the bottom plate can be obtained.

Claims (1)

In order to resist the tensile stress generated in the bottom plate of the inner point section by the parent load 42 of the external load acting on the continuous bridge, The steel bar or strand-shaped tension member 10 is inclined in both directions so that tension can be introduced simultaneously in the axial direction 27 and the transverse direction 28 of the precast or cast-in-place floorboard. Placed at the center height of the plate, the tension member is settled on the side of the bottom plate, If necessary, the girder and the deck are introduced so that tension can be introduced before and after the composite section.