JPH0467908A - Executing method for concrete lining synthetic steel pipe structure - Google Patents

Abstract

PURPOSE:To prevent the generation of tensile stress in a concrete part by a method wherein internal pressure is applied to a steel pipe having deviation preventing members arranged to the other peripheral surface thereof to generate tensile force in the steel pipe in the circumferential direction thereof and concrete is cast on the outer periphery of the steel pipe in this state and, after curing, the internal pressure is released to introduce compression stress into concrete. CONSTITUTION:Deviation preventing members 2 are arranged to the outer peripheral surface of a steel pipe 1 and pressure-resistant mirror plates 3 are attached to the opening surfaces of the steel pipe 1 and a pressure fluid is supplied into the steel pipe 1 through the pressure field supply pipes 4 connected to the mirror plates 3 to apply internal pressure (p) to the steel pipe 1. Whereupon, the steel pipe 1 expands and tensile force T is generated in the steel pipe 1 in the circumferential direction thereof. A retaining mold 5 is arranged to the outer periphery of the steel pipe 1 in this state while the internal pressure (p) is held and concrete 6 is cast on the steel pipe 1. When the internal pressure (p) is released at the point of time when concrete 6 is cured and required strength is developed, the steel pipe 1 is contracted so as to restore its original state over the circumferential direction and the tensile force generated in the steel pipe 1 in the circumferential direction thereof is also released.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of constructing a synthetic steel pipe structure such as an underwater tunnel whose outer periphery is lined with concrete.

(Prior Art) Fig. 11 shows a conventional synthetic steel pipe structure, in which concrete (C) is placed on the outer circumferential surface of a steel pipe (b) on which anti-slip (al) is provided. They are integrally layered with each other.

(Problems to be Solved by the Invention) In the conventional synthetic steel pipe structure, the outer peripheral concrete portion resists only compressive force, and the structure is rational for both uniformly distributed loads and concentrated loads against external forces. .

However, internal pressure is resisted by the steel pipe section, which has a high tensile resistance, but the concrete section cannot be expected to have tensile resistance, and the combined effect of the steel pipe and concrete cannot be exerted.

Therefore, even if a synthetic steel pipe structure is applied to a portion where internal pressure is dominant, there will be no economic advantage of using steel as a heavy source.

The present invention has been proposed in view of the problems of the prior art, and its purpose is to prevent tensile stress from occurring in the concrete part of a synthetic steel pipe structure due to internal pressure acting on the structure. The present invention provides a method for constructing a synthetic steel pipe structure without concrete lining.

(Means for Solving the Problem) In order to achieve the above-mentioned object, according to the method for constructing a concrete-lined synthetic steel pipe structure according to the present invention, internal pressure is applied to a steel pipe provided with a shear stopper on the outer peripheral surface. A tensile force is generated in the circumferential direction of the steel pipe, concrete is poured around the outer circumference of the steel pipe in this state, and after the poured concrete hardens,
The internal pressure between the two steel pipes is released to introduce compressive prestress into the concrete.

(Function) According to the present invention, as described above, by applying internal pressure to the steel pipe provided with the anti-slip on the outer circumferential surface, a tensile force (hoop tension) in the circumferential direction is generated in the steel pipe.

With the tensile force acting on the steel pipe in the circumferential direction, concrete is poured around the outer circumference of the steel pipe, and after the poured concrete hardens and develops the required strength, the internal pressure against the steel pipe is When the steel pipe is released, the steel pipe contracts in the circumferential direction in an attempt to return to its original state, and the tensile force generated in the circumferential direction of the steel pipe itself also tries to be released, but the outer circumference of the steel pipe Since concrete is anchored to the steel pipe through the shear stopper, the concrete restrains the deformation of the steel pipe in the circumferential direction, and as a result, the tensile force generated in the steel pipe is not released. As the force remains, compressive prestress will be introduced into the concrete.

Therefore, the tensile stress in the concrete generated by the internal pressure acting on the synthetic steel pipe structure according to the present invention and the compressive prestress introduced into the same portion are offset, and no tensile stress is generated in the concrete portion.

(Example) The present invention will be described below with reference to the illustrated embodiments.

1 to 6 show the steps of the embodiment, and FIGS. 7 to 10 are conceptual diagrams of the prestress introduction process based on the same steps.

Place the anti-slip (2) on the outer peripheral surface of the steel pipe (]),
(See Figures and Figure 7) Pressure-resistant end plate (
3) is attached, and when pressure fluid is supplied into the steel pipe (1) through the pressure fluid supply pipe (4) connected to the end plate (3) and an internal pressure p is applied, the steel pipe (1) expands and the steel pipe (1) A tensile force T is generated in the circumferential direction. (See Figures 2 and 8) In this state, while maintaining the internal pressure p, a formwork (5) is placed around the outer periphery of the steel pipe (1), and concrete (6) is poured.

(See Figure 3) The internal pressure P is maintained continuously while the poured concrete (6) is curing. (See Figures 4 and 9) When the concrete (6) hardens and develops the required strength. , when the internal pressure P is released, the steel pipe (1) contracts in an attempt to restore its original state across the circumference, and the tension T in the circumferential direction that has been generated in the steel pipe (1) is also released. However, the concrete (6) anchored to the outer periphery of the steel pipe (1) via the anti-slip (2) restrains the contraction of the steel pipe (1), and the tension generated in the steel pipe (1) The force T remains in the steel pipe (1) without being released, and compressive force acts on the concrete (6), introducing compressive prestress. (See Figure 10) After releasing the internal pressure p, the mold is removed and the gripping plate (3)
is removed to complete the construction of concrete-lined synthetic steel pipe structure A. (See Fig. 5) (Effects of the Invention) According to the present invention, as described above, internal pressure is applied to the steel pipe with the anti-slip disposed on the outer circumferential surface to generate a tensile force in the circumferential direction, and in this state, the steel pipe Concrete is poured around the outer periphery, and after the poured concrete has hardened, the internal pressure on the steel pipe is released, and compressive prestress is introduced into the concrete portion of the outer periphery of the steel pipe by utilizing elongation deformation in the circumferential direction of the steel pipe. By doing this, the tensile stress in the concrete part generated by the internal pressure acting on the synthetic steel pipe structure is offset, and the composite effect of the steel pipe and concrete part is suppressed against the internal pressure by canceling out the tensile stress generated in the concrete part. This is expected to result in the realization of an economical concrete-lined composite steel pipe structure that can reduce the weight of steel pipes.

[Brief explanation of the drawing]

1 to 5 are perspective views showing steps of an embodiment of the method for constructing a concrete-lined synthetic steel pipe structure according to the present invention, FIG. 6 is a longitudinal sectional view of FIG. 2, and FIGS. 7 to 10 The figure is a conceptual diagram showing the prestress introduction process, and FIG. 11 is a cross-sectional plan view of a conventional concrete-lined synthetic steel pipe structure. (1)...Steel pipe, (2)...Slip stopper, (6)...Concrete, (4)...Pressure fluid supply pipe.

Claims (1)

[Claims] Internal pressure is applied to a steel pipe with anti-slip devices installed on its outer circumferential surface to generate a tensile force in the circumferential direction of the steel pipe, concrete is poured around the outer circumference of the steel pipe in this state, and after the poured concrete hardens, A method for constructing a concrete-lined synthetic steel pipe structure, characterized in that compressive prestress is introduced into the concrete by releasing internal pressure to the steel pipe.