pc steel casing

Abstract

A casing for PC steel that stably transmits the compressive force of PC steel to the concrete structure while suppressing the occurrence of voids inside the casing by designing the shape of the casing for PC steel used in the construction of prestressed concrete structures things. The casing (1) for PC steel has a tubular body (10) in the shape of a helical wave. The volume of the cement slurry (4) embedded in the inner peripheral spiral groove (13) of the tubular main body (10) is larger than the volume of the concrete structure (2) embedded in the outer peripheral spiral groove (12) of the tubular main body (10). Increase the strength of the grout (4) side. Thus, even if the cement slurry (4) with low viscosity (good fluidity) is filled, the occurrence of voids inside the casing (1) is suppressed, and cracks and fractures are difficult to occur in the hardened cement slurry (4). The compressive force of the PC steel material (3) is stably transmitted to the concrete structure (2).

Description

technical field [0001] The present invention relates to a PC steel bushing for burying in a concrete structure and inserting PC steel (prestressed steel) for introducing prestress into the concrete structure. Background technique [0002] Generally, when using the post-tensioning method to construct prestressed concrete structures such as PC girder bridges, the PC steel is embedded in the concrete structure with a sleeve, and the PC steel inserted in the sleeve is stretched, and its reaction force is compressed. Force (prestress) is introduced into the concrete structure. In addition, the casing through which the PC steel is inserted is filled with cement slurry and hardened to maintain the corrosion resistance of the PC steel. At the same time, the concrete structure and the PC steel are integrated with the cement slurry to reduce the compression of the PC steel. The force imparts the concrete structure as a whole. [0003] In this case, as the sleeve, generally a tubular...

AI Technical Summary

Problems solved by technology

[0006] However, in the case of using a casing having the above-mentioned helically wave-shaped tubular body, when the cement slurry is filled in the tubular body, the inflow of the cement slurry in the inner peripheral spiral groove of the tubular body becomes poor, and there is a problem in the inside of the casing. Unfavorable conditions that are prone to voids

If voids are formed and air remains inside the bushing, condensation will easily occur in this part, which will cause rust and corrosion of PC steel.

[0007] If the cement slurry with low viscosity (good fluidity) is filled to suppress the occurrence of voids inside the casing, the compressive strength and shear fracture strength of the hardened cement slurry will decrease

In this case, there is a disadvantage that cracks and fractures are likely to occur in the hardened cement slurry (especially the hardened convex portion filled in the inner peripheral spiral groove)

If the hardened cement slurry cracks and breaks, the concrete structure and the cement slurry will move relative to each other, and the compressive force of the PC steel cannot be effectively transmitted to the concrete structure, which will significantly reduce the strength of the concrete structure.

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