Prestressed concrete beam and prefabricating method

Abstract

The invention relates to the technical field of prestressed structures, and discloses a prestressed concrete beam and a prefabricating method. The prestressed concrete beam comprises a prestressed tendon, a protective device and an anti-corrosion material; the prestressed tendon comprises a prestressed failure section and a prestressed effective section; the protective device comprises a protective sleeve and a spiral stirrup, wherein the protective sleeve sleeves the prestressed failure section, and the spiral stirrup sleeves the protective sleeve and part of the prestressed effective section; and the protective sleeve is filled with the anti-corrosion material. The prestressed concrete beam prefabricating method is used for prefabricating the prestressed concrete beam. According to the beam and the method, the prestressed failure section and concrete are isolated through the protective sleeve, so that the prestressed failure function is realized; meanwhile, the protective sleeve canserve as a common steel bar, the anti-cracking effect of the protective sleeve is exerted; and the spiral stirrup sleeves the prestressed effective section and spans the prestressed failure section and the prestressed effective section, so that the anti-cracking performance of a concrete stress mutation area is enhanced.

Description

technical field [0001] The invention relates to the technical field of prestressed structures, in particular to a prestressed concrete beam and a prefabrication method. Background technique [0002] During long-term use, transverse and oblique cracks gradually appear at the end of the prestressed concrete hollow slab beam and the lower surface of the beam bottom, and these cracks are just in the transition section between the prestressed effective area and the failure area of ​​the prestressed tendon. After peeling off the concrete protective layer in this cracked area, it was found that part of the prestressed tendons were corroded, the concrete burst, and more seriously, the prestressed tendons were corroded to fracture. The reason is that the prestressed failure measures of the prestressed tendons in the prestressed failure section at the end of the beam adopt the method of jacketing the PVC pipe and other methods, and there are the following defects: [0003] (1) When t...

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Problems solved by technology

[0003] (1) When the prestressed tendons are stretched and released, there is stress concentration in the prestressed tendons in the bottom plate in the transition section between the end prestressed effective area and the failure area, and the prestressed tendons and concrete in the prestressed failure section are used The outer PVC pipe is isolated, resulting in insufficient concrete reinforcement ratio in the prestressed failure area, and the concrete is cracked;

[0004] (2) The PVC pipe waterproof measures of the prestressed tendons in the prestressed failure section are flawed, resulting in the water on the bridge entering the PVC pipe, and the prestressed tendons in the PVC pipe have been eroded by accumulated water for a long time, and finally the prestressed tendons are corroded and broken, and the concrete protection Layer swelling and cracking;

[0005] (3) There are two types of prestressed tendons passing through the prestressed failure zone at the end of the prestressed concrete hollow slab beam, one is the prestressed tendons that artificially force prestressed failure, and the other is the prestressed tendon that must maintain the effective prestressed The prestressed tendons that fail to be artificially prestressed are corroded and broken due to defects in the PVC pipe, and the concrete cover is swollen and cracked. Another type of prestressed tendons that must maintain effective prestressing in this area is wrapped around the surface. The concrete is affected by the damage and is forced to crack and peel off. It is difficult to guarantee the effectiveness of the prestressing force. At the same time, there are large areas of cracks in the concrete in this area, and the durability of the prestressing tendons is reduced. Eventually, the two types of prestressing tendons will tend to corrode and break. The failure of the body's bearing capacity endangers the safety of the structure

This is not only a waste of resources, but also requires interruption of traffic, high cost and long construction period

Especially if this type of bridge crosses special structures, such as railways, military facilities, etc., it is more difficult to dismantle and rebuild, the cost is higher, and the construction period is longer

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